WELL BORING AT GREAT DEPTHS.
The first well that was executed of great depth, and which gave rise to
the adoption of tools which directed public attention to the art of well
boring, was that for the city of Paris by Mulot, at the Abattoir of
Grenelle. This was commenced in the year 1832; and after more than eight
years' incessant labour, water rose, on the 26th of February, 1842, from
the total depth of 1798 feet. Subsequent to this, many wells have been
sunk on the Continent, with the hope of attaining the brine springs so
often met with in the Rhine provinces, or the springs destined for the
supply of towns, and which are even deeper than the well of Grenelle,
reaching in some cases to the extraordinary depth of 2800 feet; but all
of them, like the Grenelle well, of small diameter. In their
construction, however, the German engineers introduced some important
modifications of the tools employed; and, amongst other inventions,
Euyenhausen imparted a sliding movement to the striking part of the tool
used for comminuting the rock, so as to fall always through a certain
distance; and thus, while he produced a uniform action upon the rock at
the bottom, he avoided the jar of the tools. Kind also began to apply
his system to the working of the large excavations for the purpose of
winning coal. Whilst the art was in this state, and when he had already
executed some very important works in Germany, Belgium, the North of
France, Creuzot, and Seraing, the Municipal Council of Paris determined
to entrust him with the execution of a new well they were about to sink
at Passy.
In sinking the well of Passy, the weight of the trepan for comminuting
the rock was about 1 ton 16 cwt., 1800 kilog.: the height through which
it fell was about 60 centimètres; and its diameter was 3 feet 3-7/16
inches, 1 mètre. The rods were of oak, about 8 inches on the side, and
the dimensions of the cutting tool were limited to 3 feet 3-7/16 inches
because it worked the whole time in water; but generally the class of
borings Kind undertook were of such a description as justified resorting
to tools of great dimensions. When sinking the shafts for winning coal,
his operations required to be carried on with the full diameters of 10
feet or 14 feet; and he then drove a boring of 3 feet 4 inches diameter
in the first instance, and subsequently enlarged this excavation. There
can be no objection to executing Artesian borings of this diameter,
other than the probable exhaustion of the supply; particularly as it is
now known that the yield of water by these methods is proportionate to
the diameter of the column; though, strange as it may appear, the first
opposition to Kind's plan of sinking the well of Passy was founded upon
the assumption that he would not meet with a larger supply of water from
the subcretaceous formations than had been met with at Grenelle, where
the diameter of the boring was at the bottom not more than 8 inches. It
is now, however, proved that there is a direct gain in adopting the
larger borings, not only as regards the quantity of water to be derived
from them, but also in their execution, arising from the fact that the
tools can be made more secure against the effects of torsion or of
concussion against the sides of the excavation, which is the cause of
the most serious accidents met with in well sinking.
The trepan of M. Kind contains some peculiar details, which are shown in
Figs. 97, 98. The trepan is composed of two principal pieces, the frame
and the arms, both of wrought-iron, with the exception of the teeth of
the cutting part, which are of cast steel. The frame has at the bottom a
series of holes, slightly conical, into which the teeth are inserted,
and tightly wedged up, Fig. 99. These teeth are placed with their
cutting edges on the longitudinal axis of the frame that receives them;
and at the extremity of the frame there are formed two heads, forged out
of the same piece with the body of the tool, which also carries two
teeth, placed in the same direction as the others, but double their
width, in order to render this part of the tool more powerful. By
increasing the dimensions of these end teeth, the diameter of the boring
can be augmented, so as to compensate for the diminution of the clear
space caused by the tubing, necessarily introduced for security in
traversing strata disposed to fall in, or for the purpose of allowing
the water from below to escape at an intermediate level.
[Illustration: The Trepan of M. Kind.
Figs. 97-99.]
Above the lower part of the frame of the trepan is a second piece
composed of two parts bolted together, and made to support the lower
portion of the frame. This part of the machinery also carries two teeth
at its extremities, which serve to guide the tool in its descent, and to
work off the asperities left by the lower portion of the trepan. Above
this, again, are the guides of the machinery, properly speaking,
consisting of two pieces of wrought-iron, arranged in the form of a
cross, with the ends turned up, so as to preserve the machinery
perfectly vertical in its movements, by pressing against the sides of
the boring already executed. These pieces are independent of the blades
of the trepan, and may be moved closer to it or farther away from it, as
may be desired. The stem and the arms are terminated by a single piece
of wrought-iron, which is joined to the frame with a kind of
saddle-joint, and is kept in its place by means of keys and wedges. The
whole of the trepan is finally jointed to the great rods that
communicate the motion from the surface, by means of a screw-coupling,
formed below the part of the tool which bears the joint; this
arrangement permits the free fall of the cutting part, and unites the
top of the arms and frame, and the rod, Fig. 100. It has been proposed
to substitute for this screw-coupling a keyed joint, in order to avoid
the inconvenience frequently found to attend the rusting of the screw,
which often interposes great difficulties in cases where it becomes
necessary to withdraw the trepan.
[Illustration: The Rod.
Fig. 100.]
The sliding joint is the part of Euyenhausen's invention most
unhesitatingly adopted by Kind, and it is one of the peculiarities of
his system as contrasted with the processes formerly in use. So long as
his operations were confined to the small dimensions usually adopted for
Artesian borings, he contented himself with making a description of
joint with a free fall; a simple movement of disengagement regulating
the height fixed by the machinery itself, like the fall of the monkey in
a pile-driving machine; but it was found that this system did not answer
when applied to large borings, and it also presented certain dangers.
Kind then, for the larger class of borings, availed himself of sliding
guides, so contrived as to be equally thrown out of gear when the
machinery had come to the end of the stroke, and maintained in their
respective positions by being made in two pieces, of which the inner one
worked upon slides, moving freely in the piece that communicated the
motion to the striking part of the machinery. The two parts of the tool
were connected with pins, and with a sliding joint, which, in the Passy
well, was thrown out of gear by the reaction of the column of water
above the tool unloosing the click that upheld the lower part of the
trepan, Figs. 101 to 103. The changes thus made in the usual way of
releasing the tool, and in guiding it in its fall were, however, matters
of detail; they involved no new principle in the manner of well boring:
and the modern authorities upon the subject consider that there was
something deficient in Kind's system of making the column of water act
upon a disc by which the click was set in motion. This system, in fact,
required the presence of a column of water not always to be commanded,
especially when the borings had to be executed in the carboniferous
strata.
[Illustration: Sliding Joints.
Figs. 101-103.]
[Illustration: wrought-iron Joints.
Fig. 104.]
[Illustration: Shell Elevation.]
The rods used for the suspension of the trepan, and for the transmission
of the blows to it, were of oak; and this alone would constitute one of
the most characteristic differences between the system of tools
introduced by Kind and those made by the majority of well-borers, but
which, like the disengagement of the tool intended to comminute the
rock, depended for its success upon the boring being filled with water.
The resistance that the wood offers, by its elasticity, to the effects
of any sudden jar, is also to be taken into account in the comparison of
the latter with iron, for the iron is liable to change its form under
the influence of this cause. The resistance to an effort of torsion need
not, however, be much dwelt on, for the turn given to the trepan is
always made when the tool is lifted up from its bed. For the purpose of
making the rods, Kind recommended that straight-grown trees, of the
requisite diameter, should be selected, rather than they should be made
of cut-timber, as there is less danger of the wood warping, and the
character of the wood is more homogeneous. He generally used these trees
in lengths of about 50 feet, and he connected them at the ends with
wrought-iron joints, fitting one into the other, Fig. 104. The ironwork
of the joints is made with a shoulder underneath the screw-coupling, to
allow the rods to be suspended by the ordinary crow's foot during the
operation of raising or lowering them. In the works executed at Passy
there was a kind of frame erected over the centre of the boring, of
sufficient height to allow of the rods being withdrawn in two lengths at
a time, thus producing a considerable economy of time and labour.
[Illustration: Shell Plan.
Figs. 105, 106.]
Nearly all the processes yet introduced for removing the products of the
excavation must be considered to be, more or less, defective, because
all are established on the supposition that the comminuting tool must be
withdrawn, in order that the shell, or other tool intended to remove the
products of the working of the comminutor, may be inserted. This remark
applies to Kind's operations at Passy and elsewhere, as he removed the
rock detached from the bottom of the excavation by a shell, Figs. 105,
106, which was a modification of the tool he invariably employs for this
purpose. It consisted of a cylinder of wrought-iron, suspended from the
rods by a frame, and fastened to it, a little below the centre of
gravity, so that the operation of upsetting it, when loaded, could be
easily performed. This cylinder was lowered to the level of the last
workings of the trepan, and the materials already detached by that
instrument were forced into the tool, by the gradual movement of the
latter in a vertical direction. Some other implements, employed by Kind
for the purpose of removing the products of the excavation in the shafts
for the coal-mines of the North of France, were ingenious, and well
adapted to the large dimensions of the shafts; but they were all, in
some degree, exposed to the danger of becoming fixed, if used in the
small borings of Artesian wells, by the minute particles of rocks
falling down between their sides and the excavation from above. Their
use was therefore abandoned, and the well of Passy was cleared out with
the shell, the bottom of which was made to open upwards, with a hinged
flap, which admitted the finer materials detached by the trepan. There
were also several tools for the purpose of withdrawing the broken parts
of the machinery from the excavation, or whatever substances might fall
in from above; and all were marked by a great degree of simplicity, but
they did not differ enough from those generally used for the same
purpose to merit further remarks. In fact, the accidents intended to be
guarded against or remedied are so precisely alike in all cases, that
there can be little variety in the manufacture of these instruments. But
there is no doubt that Kind deprived himself of a valuable appliance in
not using the ball-clack, _la soupape à boulet_, that other well-borers
employ, Fig. 107.
[Illustration: Ball-clack.
Fig. 107.]
At Passy great strength was given to the head of the striking tool, and
to the part of the machinery applied to turn the trepan, because the
great weight of the latter superinduced the danger of its breaking off
under the influence of the shock, and because the solidity of this part
of the machinery necessarily regulated the whole working of the tool.
The head of the boring arrangement was connected with the balance-beam
of the steam-engine by a straight link-chain, with a screw-coupling,
admitting of being lengthened as the trepan descended, Figs. 108, 109.
The balance-beam, in order to increase its elastic force in the upward
stroke, is in Kind's works made of wood, in two pieces; the upper one
being of fir and the lower one of beech. The whole of the machinery is
put in motion by steam, which is admitted to the upper part of the
cylinder, and presses it down, and thus raises the tool at the other end
of the beam to that part in connection with the cylinder. The
counterpoise to the weight of the tools is also placed upon the
cylinder-end of the beam. The cylinder receives the steam through ports
that are opened and closed by hand, like those of a steam-hammer; so
that the number of the strokes of the piston may be increased or
diminished, and the length of the strokes may be increased, as occasion
may require.
[Illustration: Side Elevations on Balance-beam Connection.
Figs. 108, 109.]
The balance-beam is continued beyond the point where the piston is
connected with it, and it goes to meet the blocks placed to check the
force of the blow given by the descent of the tool. The guides of the
piston-head are attached to the part of the machinery that acts in this
manner; but at Passy, Kind made the balance-beam work upon two free
plummer-blocks, or blocks having no permanent cover, that they might be
more easily moved whenever it was necessary to displace the beam, for
the purpose of taking up or letting down the rods, or for changing the
tools; for the balance-beam was always immediately over the centre of
the tools, and it therefore had to be displaced every time that the
latter were required to be changed. This was effected by allowing the
beam to slide horizontally, so as to leave the mouth of the pit open.
The counter-check, above mentioned, likewise prevented the piston from
striking the cylinder cover with too great a force, when it was brought
back by the weight of the tools to its original position. The operation
of raising and lowering the rods, or of changing the tools, was
performed at Passy by a separate steam-engine, and the shell was
discharged into a special truck, moving upon a railway expressly laid
for this purpose in the great tower erected over the excavation. All
these arrangements were in fact made with the extreme attention to the
details of the various parts of the work which characterizes the
proceedings of foreign engineers, and conduces so much to their success.
The beating, or comminution of the rock, was usually effected at Passy
at the rate of from fifteen strokes to twenty strokes a minute. The rate
of descent, of course, differed in a marked manner, according to the
nature of the rock operated upon; but, generally speaking, the trepan
was worked for the space of about eight hours at a time, after which it
was withdrawn, and the shell let down in order to remove the _débris_.
The average number of men employed in the gang, besides the foreman, or
the superintendent of the well, was about fourteen: they consisted of a
smith and hammerman, whose duty it was to keep the tools in order; and
two shifts of men entrusted with the excavation, namely, an
engine-driver and stoker, a chief workman, or sub-foreman, and three
assistants. The total time employed in sinking the shafts executed upon
this system in the North of France, where it has been applied without
meeting with the accidents encountered in the Passy well, was found to
be susceptible of being divided in the following manner: from 25 per
cent. to 56 per cent. was employed in manoeuvring the trepan; from 11
per cent. to 14-1/2 per cent. in raising and lowering the tools; from 19
per cent. to 21 per cent. in removing the materials detached from the
rocks, and cleaning out the bottom of the excavation; and from 8 per
cent. to 10-1/2 per cent. was lost, owing to the stoppage of the
engines, or to the accidents from broken tools, or to other causes
always attending these operations. In the well of Passy there was, of
course, a considerable difference in the proportions of the time
employed in the various details of the work; and the long period
occupied in obviating the effects of the slips which took place in the
clays, both in the basement beds of the Paris basin and in the
subcretaceous strata, would render any comparison derived from that well
of little value; but it would appear that, until the great accident
occurred, the various operations went on precisely as Kind had
calculated upon.
KIND-CHAUDRON SYSTEM.
[Illustration: Section through Kind-Chaudron Well at Durham.
Fig. 110.]
In the year 1872 Emerson Bainbridge, C.E., drew attention to the
Kind-Chaudron system of sinking mine shafts through water-bearing
strata, without the use of pumping machinery, in a paper read before the
Institute of Civil Engineers. As the operation is almost identical with
that which would have to be carried through in the case of a well sunk
through an upper series of water-bearing strata, of minor importance or
of impure quality, past rock and into the lower water strata, as for
instance through tertiaries and chalk into the lower greensand, the
following extract from Bainbridge's paper may be read with interest.
In the first place, it may be desirable to describe briefly the system
of sinking hitherto pursued in passing through strata yielding large
quantities of water. The most important sinkings of this character have
been carried out in the county of Durham, to the east of the point at
which the Permian overlie the carboniferous rocks. In this district
there is a thin bed of sand between the Permian rock and the coal
measures. Towards this bed the feeders of water are generally found to
increase, and in the sand there is usually a large reservoir of water.
The mode of sinking will be understood by reference to Fig. 110. Whilst
sinking in hard rock, it has ordinarily been the custom to place iron
curbs, or cribs, wherever a bed of stone appeared to form a natural
barrier between two distinct feeders of water. Thus it has frequently
happened that important feeders have been tubbed back, rendering much
less pumping power necessary than would have been required had all the
feeders been allowed to accumulate in the shaft. As will be seen by Fig.
110, the number of wedging cribs employed is no less than thirteen in
250 feet. The cribs forming the foundation of each set of tubbing are
generally much more massive and costly than the segments of tubbing.
[Illustration: Cast-iron Tubbing.
Fig. 111.]
[Illustration: Wooden Tubbing.
Fig. 112.]
[Illustration: End Elevation showing Arrangement at Extensive Sinking.
Fig. 113.]
[Illustration: Side Elevation showing Arrangement at Extensive Sinking.
Fig. 114.]
[Illustration: Pass Pipe.
Fig. 115.]
[Illustration: Pass Pipe.
Fig. 116.]
[Illustration: Ball Type of Pressure Equalizer.
Fig. 118.]
The process of fixing the crib is as follows;--The diameter of the shaft
is made about 30 inches larger than that of the inside of the tubbing.
When a bed of rock, which may be considered sufficiently hard and close
to separate the feeders above and below it, is reached, the shaft is
contracted to the diameter of the tubbing, and a smooth horizontal face
is made on which to place the wedging crib. The wedging crib, which
usually consists of segments about 4 feet long by 6 inches high by 14
inches wide, is then placed on the bed. To give the crib a firm and
secure position, it is tightly wedged with wood, both behind and between
the joints; the tubbing is then built upon it to the next wedging crib,
which rests upon a bell-shaped section of rock. When the tubbing nearly
reaches this crib, the rock is removed piece by piece, and the top ring
of tubbing is placed close up against the crib. It will thus be seen
that the fixing of each crib is a costly process, often causing
considerable delay.
In some cases, where it has been difficult to find suitable foundations
for intermediate wedging cribs, the whole of the water-bearing rocks
have been sunk through without attempting to stop the feeders
separately, and no tubbing has been placed in the shaft till the wedging
crib could be fixed below the lowest feeder. This process is more
expeditious where there are small quantities of water; but where the
water is excessive greater delay is caused by contending with it than
from putting in numerous sets of tubbing to stop the feeders separately.
The tubbing used in England has almost invariably been of cast-iron; on
the Continent, till recently, tubbing of wood has chiefly been used.
Illustrations of both descriptions are shown by Figs. 111 and 112.
Figs. 113, 114, show, in elevation, the plant and the arrangements
generally in use at extensive sinkings. Where the water is in large
quantities it is usually pumped by an engine erected for the purpose,
assisted by the engine or engines intended to be employed to raise the
coal. A small capstan engine is used for passing the men and material up
and down the pit during the sinking, such engine being provided also
with a drum on slow motion, which is used for heavy weights. The
continual pumping, the placing of cribs, and the fixing of the tubbing
are proceeded with till the lowest feeder is reached, when a hard bed is
sought for on which to fix the lowest wedging crib. In all cases the
water has to be pumped out before the wedging crib, which forms the
foundation of each set of tubbing, can be placed.
From this description it will be understood that the sinkers, who number
from ten to twelve at one time, working four hours at a shift in a pit,
say, 14 feet in diameter, are compelled to work in water until all the
tubbing is fixed. This causes a serious obstacle to blasting, and in
other ways delays the progress of the work.
The tubbing used for damming back the water is generally in segments
from 1 foot to 3 feet high, and about 4 feet in length, the thickness
varying from half an inch to 3-3/4 inches. It is kept in position by
packing with wood behind the joints; and is made water-tight by placing
between the segments pieces of wood sheeting about half an inch thick,
which are wedged when all the tubbing is fixed, usually twice with wood,
and sometimes once with iron wedges.
[Illustration: Pressure Equalizing Valve in the Wedging Crib.
Fig. 117.]
To equalize the pressure of water and gas behind the different sets of
tubbing, pass pipes, Figs. 115 and 116, are sometimes used. Another
expedient to effect this is to have a valve, working upwards, placed in
the wedging crib, Fig. 117. A ball is also sometimes used, Fig. 118.
The various modes of piercing beds of quicksand are;--By hanging tubbing
to that already fixed, and adding fresh rings as the sand is removed.
This is only practicable when the quantity of sand is inconsiderable. By
heavily weighting a cylinder of iron of the same size as the shaft, and
thus forcing it down through the sand. By keeping back the sand by the
use of piles--a resource that can only be recommended when the bed of
sand is not of great thickness. When the water is excessive, by using
pneumatic agency. As these operations are apart from our immediate
subject we need not further discuss them.
M. Chaudron's system, which is a modification of Kind's, is divisible
into the following distinct processes, which consist of;--
The erection of the necessary machinery on the surface, and the opening
of the mine.
The boring of the pits to the lowest part of the water-bearing strata.
The placing of the tubbing.
The introduction of cement behind the tubbing to complete its solidity.
The extraction of the water from the pits, and the placing of the
wedging cribs, or "faux cuvelage," below the moss box.
[Illustration: Surface Plant Elevation.
Fig. 119.]
[Illustration: Surface Plant Elevation.
Fig. 120.]
[Illustration: Surface Plant Plan.
Fig. 121.]
Figs. 119 to 121 show in elevations and in plan the plant usually
employed on the surface. O is a small capstan engine, having a cylinder
20 inches in diameter and a stroke of 32 inches, working on the third
motion. Attached to this engine, and working in the small pit C, is a
counterbalance weight. This engine is used for raising and lowering
boring tools, and for lifting the _débris_ resulting from the boring. As
far as the platform, which is about 10 feet from the surface, the pit
has a diameter of 19 feet, or 4 feet more than the diameter of the pit
below. A at level of about 38 feet above this platform there is a
tramway on which small trucks run, carrying the _débris_ cylinder on one
side, and the boring tools on the other. At a level of 48 feet above the
platform are placed supports for the wooden spears to which the boring
tools are attached. The machinery for boring is worked by a cylinder,
which has a diameter of 39-1/3 inches, and a full stroke of 39-1/3
inches, the usual stroke varying from 2 feet to 3 feet. A massive beam
of wood transmits motion from this cylinder to the boring apparatus, the
connection between the beam and the piston-rod and the beam and the
boring tools being made by a chain. The engine-man sits close to the
engine, and applies the steam above the piston only. The down stroke of
the boring tools is caused by the sudden opening of the exhaust, and a
frame then prevents the shock of the boring rods from being too severe.
The engines work at speeds varying from 12 to 18 strokes a minute,
according to the character of the strata passed through.
[Illustration: The Small Trepan.
Fig. 122.]
[Illustration: The Small Trepan.
Fig. 123.]
[Illustration: The Small Trepan.
Fig. 124.]
[Illustration: Plan of Guide B.
Fig. 125.]
[Illustration: Swivelled Ring Front Elevation.
Fig. 126.]
[Illustration: Swivelled Ring Side Elevation.
Fig. 127.]
[Illustration: Large Trepan Front Elevation.
Fig. 128.]
[Illustration: Large Trepan Side Elevation.
Fig. 129.]
[Illustration: Large Trepan Component,
Fig. 130.]
[Illustration: Trepan Teeth.
Figs. 131-134.]
After the working platform is fixed, the first boring tool applied is
the small trepan, Figs. 122 to 125. This tool is attached to the wooden
beam by the same arrangement shown by Fig. 109. The boring tools can be
lowered at pleasure by means of an adjusting screw. Next in order comes
the handle for boring. This is worked by four men on the platform, and
is turned by the aid of a swivel. Attached to the handle-piece are
wooden rods, made from Riga pitch pine. These rods are 59 feet in length
and 7-3/4 inches square. A swivelled ring, Figs. 126, 127, is attached
to the rope when raising and lowering the boring rods. The small trepan
cuts a hole 4 feet 8-3/4 inches in diameter, and has fourteen teeth,
fitted in cylindrical holes and secured by pins entering through
circular slots. The teeth are steeled. At a distance of 4 feet 4 inches
above the main teeth of the trepan there is an arm, with a tooth at each
end. This piece answers the purpose of a guide, and at the same time
removes irregularities from the sides of the hole. At a distance of 13
feet 6 inches above the main teeth are the actual guides, consisting of
two strong arms of iron fixed on the tool, and placed at right-angles to
each other. The hole made by the small trepan is not kept at any fixed
distance in advance of the full-sized pit, but the distance generally
varies from 10 to 30 yards. With the small trepan, which weighs 8 tons,
the progress varies from 6 to 10 feet a day.
The large trepan, Figs. 128 to 130, weighs 16-1/2 tons, is forged in
one solid piece, and has twenty-eight teeth. A projection of iron forms
the centre of this trepan, and fits loosely into the hole made by the
small trepan, acting as a guide for the tool. At a distance of 7 feet 6
inches above the teeth, a guide is sometimes fixed on the frame, but is
not furnished with teeth. At a distance of 13 feet 3 inches from the
teeth are two other guides at right-angles to each other. These guides
are let down the pit with the boring tool, the hinged part of the guides
being raised whilst passing through the beams at the top of the pit,
which are only 6 feet 7 inches apart. When the tool is ready to work,
the two arms are let down against the side of the pit, and are hung in
the shaft by ropes, thus acting as a guide for the trepan, which moves
through them. To provide against a shock to the spears when the trepan
strikes the rock on the down stroke, at the upper part of the frame a
slot motion is arranged, the play of which amounts to about half an
inch. The teeth of the large trepan are not horizontal, but are deeper
towards the inside of the pit, the face of the inside tooth being 3-3/4
inches lower than the outside. The object of this is to cause the
_débris_ to drop at once into the small hole, by the face of the rock at
the bottom of the pit being somewhat inclined. The teeth used, Figs. 131
to 134, are the same both for the large and the small trepan, and weigh
about 72 lb. each. As a rule, only one set of teeth is kept in use, this
set working for twelve hours, the alternate twelve hours being employed
in raising the _débris_. This time is divided in about the following
proportions;--Boring, twelve hours; drawing the rods, one hour to five
hours, according to depth; raising the _débris_, two hours; and lowering
the rods one hour to five hours. The maximum speed of the larger trepan
may be taken at about 3 feet a day. The ordinary distance sunk is not
more than 2 feet a day, and in flint and other hard rocks the boring has
proceeded as slowly as 3 inches a day.
[Illustration: Tools used in Boring.
Figs. 135, 136.]
[Illustration: Epicycloidal Hook.
Figs. 137, 138.]
[Illustration: Rod Disconnection Key.
Figs. 139, 140.]
[Illustration: Connections to the Trepan and Spears or Rods.
Fig. 141, 142.]
The _débris_ in the small bore-hole contains pieces of a maximum size of
about 8 cubic inches. In the large boring, pieces of rock measuring 32
cubic inches have been found. As a rule, however, the material is beaten
very fine, having much the appearance of mud or sand. In both the large
and the small borings the _débris_ is raised by a shell, similar to
Figs. 105, 106, and in this system consisting of a wrought-iron
cylinder, 3 feet 3 inches in diameter by 6 feet 9 inches long, and
containing two flap-valves at the bottom, through which the excavated
material enters. This apparatus is passed down the shaft by the
bore-rods, and it is moved up and down through a distance varying from 6
to 8 inches, for about a quarter of an hour, and is then drawn up and
emptied. In some cases where the rock is hard, three sizes of trepan are
used consecutively, the sizes being 5 feet, 8 feet, and 13 feet.
The several other tools and appliances used during the boring operations
are shown, Figs. 135 to 140, including the key, Figs. 139, 140, used at
the surface to disconnect the rods, the hook on which each rod is hung
after being raised to the high platform and there detached, the bar upon
which the hooks are moved, and the fork for suspending the rods or
tools from the rollers when it is desired to move the rods or tools from
above the shaft.
[Illustration: Connections to the Trepan and Spears or Rods.
Figs. 143-146.]
Figs. 141 to 146 are of the connections to the trepan and spears or
rods.
Should broken tools fall into the shaft, several varieties of apparatus
are used for their recovery. In case of broken rods of any kind having a
protuberance that can be clutched, a hook or crow, Figs. 137, 138, of an
epicycloidal form, enables the object to be taken hold of very readily.
Where the broken part has no shoulder which can be held, but is simply a
bar, the apparatus shown by Figs. 147, 148, is employed. This is
composed of two parts. The rods, the bottom of which have teeth inside,
are prevented from diverging by the cone and slide on the main rods.
When passed over a rod or pipe, they clutch it by means of the teeth,
and draw it up. Chaudron has, by this tool, raised a column of pipes 295
feet in length and 8 inches in diameter. An instrument, called a
"grapin," Figs. 149, 150, is used for raising broken teeth or other
small objects which may have fallen into the bottom of the shaft. This
tool also has one part sliding in the other, and is lowered with the
claws closed. The parts are moved by two ropes worked from the surface.
By weighting the cross-bar, which is attached to the moving parts, the
pressure desired can be exerted on the claws. The weight is then lifted,
the claws are opened, and are made to close upon the substance to be
raised. This instrument is now seldom required.
[Illustration: Pipe or Rod Recovery Tool.
Figs. 147, 148.]
[Illustration: Grapin.
Figs. 149, 150.]
In boring shafts in the manner described, without being able to prove in
the usual way the perpendicularity of the shaft, it might be feared that
the system would be open to objection on this account. It appears,
however, that in all cases where Chaudron has sunk shafts by this system
he has succeeded in making them perfectly vertical. This is ensured by
the natural effect of the treble guide, which the chisels and the two
sets of arms attached to the boring tools afford, and by the fact that
if the least divergence from a plumb-line is made by the boring tool,
the friction of the tool upon one side of the shaft is so great as to
cause the borers to be unable to turn the instrument.
Boring alternately with the large and the small instrument, the shaft is
at length sunk to the point at which the lowest feeder of water is
encountered. In a new district this has to be taken, to some extent, at
hazard; but where pits have been sunk previously, it is not difficult to
tell, by observing the strata, almost the exact point at which the
bottom of the tubbing may be safely fixed. This point being ascertained,
the third process is arrived at.
[Illustration: Hydraulic Test Apparatus.
Fig. 151.]
As the object of placing tubbing in a shaft is effectually to shut off
the feeders, which for water supply may have some bad qualities, and to
secure a water-tight joint at the base, it is important that the bed on
which the moss box has to rest should be quite level and smooth. This is
attained by the use of a tool, termed a "scraper," attached to the
bore-rods, the blades being made to move round the face of the bed
intended for the moss box. The tubbing employed is cast in complete
cylinders. At Maurage each ring has an internal diameter of 12 feet and
is 4 feet 9 inches high. Each ring has an inside flange at the top and
bottom, and also a rib in the middle, the top and bottom of the ring
being turned and faced. The rings of tubbing are attached to each other
by twenty-eight bolts 1·1 inch in diameter, passed through holes bored
in the flanges. The tubbing is suspended in the pit by means of six
rods, which are let down by capstans placed at a distance of 30 feet
above the top of the pit. These machines work upon long screws. When a
new ring of tubbing is added, the rods are detached at a lower level,
and are hung upon chains, thus leaving an open space for passing it
forward. Before each ring is put into the pit it is tested by hydraulic
apparatus, Fig. 151. The tubbing is usually proved to one-half more
pressure than it is expected to be subjected to. At Maurage, where a
length of 550 feet of tubbing has to be put in, the chief particulars
respecting it are;--
+-----------+---------+------------+--------------+--------------+
| | | | | Pressure |
| | | | Pressure | at which |
| | Length. | Thickness. | expected. | Tubbing is |
| | | | | proved. |
+-----------+---------+------------+--------------+--------------+
| | | | lbs. a | lbs. a |
| | feet. | inches. | square inch. | square inch. |
| | | | | |
| Top | 130 | 1·17 | 30 | 45 |
| | 60 | 1·31 | 60 | 90 |
| | 60 | 1·57 | 90 | 135 |
| | 60 | 1·76 | 120 | 180 |
| | 60 | 1·96 | 150 | 225 |
| | 60 | 2·16 | 180 | 270 |
| | 60 | 2·35 | 210 | 315 |
| Bottom | 60 | 2·55 | 240 | 360 |
+-----------+---------+------------+--------------+--------------+
The joints between the rings of tubbing are made with sheet lead
one-eighth of an inch thick, coated with red-lead. The lead is allowed
to obtrude from the joint one-third of an inch, and is wedged up by a
tool which has a face one-twelfth of an inch thick. The mode of
suspending the tubbing to the rods will be understood by referring to
Figs. 152 to 154. The rods are attached to a ring by the bolts
connecting one ring of tubbing with another. The bottom ring of tubbing
and the ring carrying the moss box have their top flange turned inwards,
but their bottom flange outwards. A strong web of iron, forming the
base of a tube 16-1/2 inches in diameter, is attached to the tubbing.
The object of this tube is to cause the water in the shaft to ease the
suspension rods, by bearing part of the weight of the tubbing. Cocks to
admit water are placed at intervals up the tube, by which means the
weight upon the rods can be easily regulated, so that not more than
one-tenth to one-twentieth of the weight of the tubbing is suspended by
the rods at one time. The ring holding the moss box is hung from the
bottom joint in the tubbing by sliding rods.
[Illustration: Mode of Suspending the Tubbing to the Rods.
Figs. 152-154.]
The arrangement of the moss box which forms the base of the tubbing is
one of the most important points requiring attention in this system of
sinking. Ordinary peat moss is used. It is enclosed in a net, which,
with the aid of springs, keeps it in its place during the descent of the
tubbing. When the moss box, which hangs on short rods fixed to the
tubbing, reaches the face of rock, it is dropped gently upon it, and the
whole weight of the tubbing is allowed to rest upon the bed. This
compresses the moss, the capacity of the chamber holding it is
diminished, and the moss is forced against the sides of the shaft, thus
forming a water-tight joint, past which no water can escape. This
completes the third process.
It may be noted that up to this point the following important
differences between this and the ordinary system of placing tubbing are
to be observed;--The tubbing, on reaching its bed, bears the aggregate
pressure of all the feeders of water which have been met with in the
shaft. The tubbing, having been passed down the shaft in the manner
described, no wedging behind, or other modes of consolidating it in the
shaft, have been carried out. The connection between each ring of
tubbing is so carefully made, that the repeated wedging of the joints,
as in the ordinary system, is rendered unnecessary. The pit is still
full of water up to the ordinary level.
Under these conditions the next process is;--The introduction of cement
behind the tubbing to complete its solidity.
[Illustration: Close Ladle,
Figs. 155, 156.]
Before the water is removed, the annular space between the tubbing and
the sides of the shaft is filled with hydraulic cement, to render the
tubbing impermeable, by a process of consolidation, less liable to the
effect of any pressure of water or gas which may be exerted towards the
centre of the shaft. The cement is inserted behind the tubbing by close
ladles, Figs. 155, 156, capable of holding 44 gallons, and consisting of
two iron plates, one-eighth of an inch thick, fixed on two wooden
uprights 3-1/8 inches square. This apparatus is curved to suit the mean
circumference of the space to be concreted. A piston is placed at the
top of the ladle, and to this piston is attached a rod, which can be
moved from the surface; a door is also attached to the piston. The ladle
containing the concrete is passed down behind the tubbing by means of a
windlass at the surface, and when it reaches the lowest point, the
piston is pushed down and the cement allowed to escape from the chamber.
The weight of the cement and the ladle is sufficient with a little
ballast to enable it to descend easily.
A number of experiments have been made to discover a cement which will
not harden too quickly, and which, when hardened, will form a perfectly
compact and solid mass. A composition having the following proportions
has been found the best;--Hydraulic lime, from the lias near Metz,
slaked by sprinkling, 1 part; picked sand, from the Vosges sandstone, 1
part; trass, from Andernacht on the Rhine, 1 part; cement from Ropp
(Haute Saone), 1/4 part.
Six men are employed in putting in the cement;--two at the windlass for
letting down the ladle, two for working the rods attached to the piston,
and two on the working platform. The rods referred to have been found
such an inconvenience, that lately a rope on another windlass has been
used, and an appliance arranged for dropping the piston by moving the
rope.
[Illustration: Sectional Elevation showing Base to the Tubbing.
Fig. 157.]
When a sufficient time has elapsed for the cement to harden, the water
within the tubbing, now effectually separated from the feeders, is drawn
out by a bucket worked by the crab engine,--an operation which occupies
from one to three weeks, according to circumstances. When concluded, the
joint between the moss box and the rock bed can be examined. In some
cases this joint is considered sufficient; but it is generally thought
desirable to form a base to the tubbing by building a few feet of
brickwork in cement on a ring or crib of wood, as in Fig. 157. Another
wooden crib is then placed on the top of this brickwork, and above
this, two cast-iron segmental wedging cribs with a broad bed also wedged
perfectly tight. On the base so prepared, four or more rings of tubbing
in segments are fixed, the top ring coming close against the bottom of
the moss box. This being done the work is completed, and the sinking of
the shaft is continued in the ordinary way.
The application of the boring trepan is not to be recommended in the
sinking of the dry part of the shaft. The use of the tool would cause
the sinking to extend over a longer period, since the breaking of the
rock passed through into such minute particles would lead to loss of
time.
DRU'S SYSTEM.
[Illustration: Dru's System.
Sectional Elevation showing Surface Arrangement.
Fig. 158.]
The system applied by Dru is worthy of attention, not so much on account
of the novelty of the invention, or of any new principle involved in it,
as on account of the contrivances it contains for the application of the
tool, "_à chute libre_," or the free-falling tool, to Artesian wells of
large diameters. It has been already explained that under Kind's
arrangements the trepan was thrown out of gear by the reaction of the
water which was allowed to find its way into the column of the
excavation; but that it is not always possible to command the supply of
the quantity necessary for that purpose; and even when possible, the
clutch Kind adopted was so shaped as to be subject to much and rapid
wear. Dru, with a view to obviate both these inconveniences, made his
first trepan similar to that shown in Fig. 101, in which it will be seen
that the tool was gradually raised until it came in contact with the
fixed part of the upper machinery, when it was thrown out of gear. The
bearings of the clutch were parallel to the horizontal line, and were
found in practice to be more evenly worn, so that this instrument could
be worked sometimes from eight days to fourteen days without
intermission; whereas, on Kind's system, the trepan was frequently
withdrawn after two days' or three days' service.
We take the following complete account of the system from a paper read
by M. Dru at the Conservatoire des Arts et Métiers, Paris, 6th June,
1867.
It will be seen from Figs. 158, 159, that the boring rod A is suspended
from the outer end of the working beam B, which is made of timber hooped
with iron, working upon a middle bearing, and is connected at the inner
end to the vertical steam cylinder C, of 10 inches diameter and 39
inches stroke. The stroke of the boring rod is reduced to 22 inches, by
the inner end of the beam being made longer than the outer end, serving
as a partial counterbalance for the weight of the boring rod. The steam
cylinder is shown enlarged in Fig. 160, and is single-acting, being used
only to lift the boring rod at each stroke, and the rod is lowered
again by releasing the steam from the top side of the piston; the stroke
is limited by timber stops both below and above the end of the working
beam B.
The boring tool is the part of most importance in the apparatus, and the
one that has involved most difficulty in maturing its construction. The
points to be aimed at in this are,--simplicity of construction and
repairs; the greatest force of blow possible for each unit of striking
surface; and freedom from liability to get turned aside and choked.
[Illustration: Elevation showing Beam connected to Rods,
Fig. 159.]
[Illustration: Steam Cylinder.
Fig. 160.]
[Illustration: Single Chisels.
Figs. 161, 162.]
The tool used in small borings is a single chisel, as shown in Figs.
161, 162; but for the large borings it is found best to divide the
tool-face into separate chisels, each of convenient size and weight for
forging. All the chisels, however, are kept in a straight line, whereby
the extent of striking surface is reduced; and the tool is rendered less
liable to be turned aside by meeting a hard portion of flint on a single
point of the striking edge, which would diminish the effect of the blow.
[Illustration: Tools for Large Borings.
Figs. 163-169.]
The tool is shown in Figs. 163 to 169, and is composed of a wrought-iron
body D, connected by a screwed end E to the boring rod, and carrying the
chisels F F, fixed in separate sockets and secured by nuts above; two
or four chisels are used, or sometimes even a greater number, according
to the size of the hole to be bored. This construction allows of any
broken chisel being easily replaced; and also, by changing the breadth
of the two outer chisels, the diameter of the hole bored can be
regulated exactly as may be desired. When four chisels are used, the two
centre ones are made a little longer than the others, as shown in Fig.
167, to form a leading hole as a guide to the boring rod. A cross-bar G,
of the same width as the tool, guides it in the hole in the direction at
right-angles to the tool; and in the case of the larger and longer tools
a second cross-bar higher up, at right-angles to the first and parallel
to the striking edge of the tool, is also added.
[Illustration: Free-falling tools.
Figs. 170-173.]
If the whole length of the boring rod were allowed to fall suddenly to
the bottom of a large bore-hole at each stroke, frequent breakages
would occur; it is therefore found requisite to arrange for the tool to
be detached from the boring rod at a fixed point in each stroke, and
this has led to the general adoption of _free-falling tools_. M. Dru's
plan of self-acting free-falling tool, liberated by reaction, is shown
in side and front view in Figs. 170 to 173. The hook H, attached to the
head of the boring tool D, slides vertically in the box K, which is
screwed to the lower extremity of the boring rod; and the hook engages
with the catch J, centred in the sides of the box K, whereby the tool is
lifted as the boring rod rises. The tail of the catch J bears against an
inclined plane L, at the top of the box K; and the two holes carrying
the centre-pin I of the catch, are made oval in the vertical direction,
so as to allow a slight vertical movement of the catch. When the boring
rod reaches the top of the stroke, it is stopped suddenly by the tail
end of the beam B, Fig. 159, striking upon the wood buffer-block E; and
the shock thus occasioned causes a slight jump of the catch J in the box
K; the tail of the catch is thereby thrown outwards by the incline L, as
shown in Fig. 172, liberating the hook H, and the tool then falls freely
to the bottom of the bore-hole, as shown in Fig. 173. When the boring
rod descends again after the tool, the catch J again engages with the
hook H, enabling the tool to be raised for the next blow, as in Fig.
171.
[Illustration: Self-acting Free-falling Tools.
Figs. 174-178.]
Another construction of self-acting free-falling tool, liberated by a
separate disengaging rod, is shown in side and front view in Figs. 174
to 178. This tool consists of four principal pieces, the hook H, the
catch J, the pawl I, and the disengaging rod M. The hook H, carrying the
boring tool D, slides between the two vertical sides of the box K, which
is screwed to the bottom of the boring rod; and the catch J works in the
same space upon a centre-pin fixed in the box, so that the tool is
carried by the rod, when hooked on the catch, as shown in Fig. 175. At
the same time the pawl I, at the back of the catch J, secures it from
getting unhooked from the tool; but this pawl is centred in a separate
sliding hoop N, forming the top of the disengaging rod M, which slides
freely up and down within a fixed distance upon the box K; and in its
lowest position the hoop N rests upon the upper of the two guides P P,
Fig. 174, through which the disengaging rod M slides outside the box K.
In lowering the boring rod, the disengaging rod M reaches the bottom of
the bore-hole first, as shown in Figs. 174, 175, and being then stopped
it prevents the pawl I from descending any lower; and the inclined back
of the catch J sliding down past the pawl, the latter forces the catch
out of the hook H, as shown in Fig. 176, thus allowing the tool D to
fall freely and strike its blow. The height of fall of the tool is
always the same, being determined only by the length of the disengaging
rod M.
The blow having been struck, and the boring rod continuing to be lowered
to the bottom of the hole, the catch J falls back into its original
position, and engages again with the hook H, as shown in Fig. 177, ready
for lifting the tool in the next stroke. As the boring rod rises, the
tail of the catch J trips up the pawl I in passing, as shown in Fig.
176, allowing the catch to pass freely; and the pawl before it begins to
be lifted returns to the original position, shown in Fig. 177, where it
locks the catch J, and prevents any risk of its becoming unhooked either
in raising or lowering the tool in the well.
The boring tool shown in Figs. 163, 164, which was employed for boring a
well of 19 inches diameter, weighs 3/4 ton, and is liberated by
reaction, by the arrangement shown in Figs. 170 to 173; and the same
mode of liberation was applied in the first instance to the larger tool,
shown in Figs. 166 to 169, employed in sinking a well of 47 in. diameter
at Butte-aux-Cailles. The great weight of the latter tool, however,
amounting to as much as 3-1/2 tons, necessitated so violent a shock for
the purpose of liberating the tool by reaction, that the boring rods and
the rest of the apparatus would have been damaged by a continuance of
that mode of working; and M. Dru was therefore led to design the
arrangement of the disengaging rod for releasing the tool, as shown in
Figs. 174, 175. In this case the cross-guide G fixed upon the tool is
made with an eye for the disengaging rod M to work through freely. For
borings of small diameter, however, the disengaging rod cannot supersede
the reaction system of liberation, as the latter alone is able to work
in borings as small as 3-1/4 inches diameter; and a bore-hole no larger
than this diameter has been successfully completed by M. Dru with the
reaction tool to a depth of 750 feet.
The boring rods employed are of two kinds, wrought-iron and wood. The
wood rods seen in Figs. 159, 179, are used for borings of large
diameter, as they possess the advantage of having a larger section for
stiffness without increasing the weight; and also when immersed in water
the greater portion of their weight is floated. The wood for the rods
requires to be carefully selected, and care has to be taken to choose
the timber from the thick part of the tree, and not the toppings. In
France, Lorraine, or Vosges, deals are preferred.
[Illustration: Lantern.
Fig. 179.]
[Illustration: Boring Rod Sockets.
Figs. 180-182.]
The boring rods, whether of wood or iron, are screwed together either by
solid sockets, as in Fig. 181, or with separate collars, as in Figs.
180, 182. The separate collars are preferred for the purpose, on account
of being easy to forge; and also because, as only one half of the collar
works in coupling and uncoupling the rods, while the other half is
fixed, the screw-thread becomes worn only at one end, and by changing
the collar, end for end, a new thread is obtained when one is worn out,
the worn end being then jammed fast as the fixed end of the collar.
The boring rod is guided in the lower part of the hole by a lantern R,
Fig. 159, shown to a larger scale in Fig. 179, which consists of four
vertical iron bars curved in at both ends, where they are secured by
movable sockets upon the boring rod, and fixed by a nut at the top. By
changing the bars, the size of the lantern is readily adjusted to any
required diameter of bore-hole, as indicated by the dotted lines. In
raising up or letting down the boring rod, two lengths of about 30 feet
each are detached or added at once, and a few shorter rods of different
lengths are used to make up the exact length required. The coupling
screw S, Fig. 158, by which the boring rod is connected to the working
beam B, serves to complete the adjustment of length; this is turned by a
cross-bar, and then secured by a cross-pin through the screw.
[Illustration: Conical Socket.
Fig. 183.]
[Illustration: Crow's Foot.
Fig. 184.]
In ordinary work, breakages of the boring rod generally take place in
the iron, and more particularly at the part screwed, as that is the
weakest part. In the case of breakages, the tools usually employed for
picking up the broken ends are a conical screwed socket, shown in Fig.
183, and a crow's foot, shown in Fig. 184; the socket being made with an
ordinary V-thread for cases where the breakage occurs in the iron; but
having a sharper thread, like a wood screw, when used where the breakage
is in one of the wood rods. In order to ascertain the shape of the
fractured end left in the bore-hole, and its position relatively to the
centre line of the hole, a similar conical socket is first lowered,
having its under surface filled up level with wax, so as to take an
impression of the broken end, and show what size of screwed socket
should be employed for getting it up. Tools with nippers are sometimes
used in large borings, as it is not advisable to subject the rods to a
twist.
When the boring tool has detached a sufficient quantity of material, the
boring rod and tool are drawn up by means of the rope O, Fig. 158,
winding upon the drum Q, which is driven by straps and gearing from the
steam-engine T. A shell is then lowered into the bore-hole by the
wire-rope U, from the other drum V, and is afterwards drawn up again
with the excavated material. A friction break is applied to the drum Q,
for regulating the rate of lowering the boring rod down the well. The
shell shown in Figs. 186, 187, consists of a riveted iron cylinder, with
a handle at the top, which can either be screwed to the boring rod or
attached to the wire-rope; and the bottom is closed by a large valve,
opening inwards. Two different forms of valve are used, either a pair of
flap-valves, as shown in Fig. 186, or a single-cone valve, Fig. 187; and
the bottom ring of the cylinder, forming the seating of the valve, is
forged solid, and steeled on the lower edge. On lowering this cylinder
to the bottom of the bore-hole, the valve opens, and the loose material
enters the cylinder, where it is retained by the closing of the valve,
whilst the shell is drawn up again to the surface. In boring through
chalk, as in the case of the deep wells in the Paris basin, the hole is
first made of about half the final diameter for 60 to 90 feet depth, and
it is then enlarged to the full diameter by using a larger tool. This is
done for convenience of working; for if the whole area were acted upon
at once, it would involve crushing all the flints in the chalk; but, by
putting a shell in the advanced hole, the flints that are detached
during the working of the second larger tool are received in the shell
and removed by it, without getting broken by the tool.
[Illustration: Shells.
Figs. 185-187.]
The resistance experienced in boring through different strata is
various; and some rocks passed through are so hard, that with 12,000
blows a day of a boring tool weighing nearly 10 cwt., with 19 inches
height of fall, the bore-hole was advanced only 3 to 4 inches a day. As
the opposite case, strata of running sand have been met with so wet,
that a slight movement of the rod at the bottom of the hole was
sufficient to make the sand rise 30 to 40 feet in the bore-hole. In
these cases Dru has adopted the Chinese method of effecting a speedy
clearance, by means of a shell closed by a large ball-clack at the
bottom, as shown in Fig. 186, and suspended by a rope, to which a
vertical movement is given; each time the shell falls upon the sand a
portion of this is forced up into the cylinder, and retained there by
the ball-valve.
Borings of large diameter, for mines or other shafts, are also sunk by
means of the same description of boring tools, only considerably
increased in size, extending up to as much as 14 feet diameter. The well
is then lined with cast-iron or wrought-iron tubing, for the purpose of
making it water-tight; and a special contrivance, invented by Kind, and
alluded to at p. 110, has been adopted for making a water-tight joint
between the tubing and the bottom of the well, or with another portion
of tubing previously lowered down. This is done by a stuffing-box, shown
in Fig. 188, which contains a packing of moss at A A. The upper portion
of the tubing is drawn down to the lower portion by the tightening
screws B B, so as to compress the moss-packing when the weight is not
sufficient for the purpose. A space C is left between the tubing and the
side of the well, to admit of the passage of the stuffing-box flange,
and also for running in concrete for the completion of the operation.
The moss-packing rests upon the bottom flange D; but this flange is
sometimes omitted. The joint is thus simply made by pressing out the
moss-packing against the sides of the well; and this material, being
easily compressible and not liable to decay under water, is found to
make a very satisfactory and durable joint.
[Illustration: Stuffing-box.
Fig. 188.]
M. Dru states that the reaction tool has been successfully employed for
borings up to as large as about 4 feet diameter, witness the case of the
well at Butte-aux-Cailles of 47 inches diameter; but beyond that size he
considers the shock requisite to liberate the larger and heavier tool
would probably be so excessive, as to be injurious to the boring rods
and the rest of the attachments; and he therefore designed the
arrangement of the disengaging rod for liberating the tool in borings of
large diameter, whereby all shock upon the boring rods was avoided and
the tool was liberated with complete certainty.
In practice it is necessary, as with the common chisel, to turn the
boring tool partly round between each stroke, so as to prevent it from
falling every time in the same position at the bottom of the well; and
this was effected in the well at Butte-aux-Cailles by manual power at
the top of the well, by means of a long hand-lever fixed to the boring
rod by a clip bolted on, which was turned round by a couple of men
through part of a revolution during the time that the tool was being
lifted. The turning was ordinarily done in the right-hand direction
only, so as to avoid the risk of unscrewing any of the screwed couplings
of the boring rods; and care was taken to give the boring rod half a
turn when the tool was at the bottom, so as to tighten the
screw-couplings, which otherwise might shake loose. In the event of a
fracture, however, leaving a considerable length of boring rod in the
hole, it was sometimes necessary to have the means of unscrewing the
couplings of the portion left in the hole, so as to raise it in parts
instead of all at once. In that case a locking clip was added at each
screwed joint above, and secured by bolts, as shown at C in Fig. 180, at
the time of putting the rods together for lowering them down the well to
recover the broken portion; and by this means the ends of the rods were
prevented from becoming unscrewed in the coupling sockets, when the rods
were turned round backwards for unscrewing the joints in the broken
length at the bottom of the bore-hole.
When running sands are met with, the plan adopted is to use the Chinese
ball-scoop, or shell, Fig. 186, described for clearing the bottom of the
bore-hole; and where there is too much sand for it to be got rid of in
this way, a tube has to be sent down from the surface to shut off the
sand. This, of course, necessitates diminishing the diameter of the hole
in passing through the sand; but on reaching the solid rock below the
running sand, an expanding tool is used for continuing the bore-hole
below the tubing with the same diameter as above it, so as to allow the
tubing to go down with the hole.
In the case of meeting with a surface of very hard rock at a
considerable inclination to the bore-hole, M. Dru employs a tool, the
cutters of which are fixed in a circle all round the edge of the tool,
instead of in a single diameter line; the length of the tool is also
considerably increased in such cases, as compared with the tools used
for ordinary work, so that it is guided for a length of as much as 20
feet. He uses this tool in all cases where from any cause the hole is
found to be going crooked, and has even succeeded by this means in
straightening a hole that had previously been bored crooked.
The cutting action of this tool is all round its edge; and therefore in
meeting with an inclined hard surface, as there is nothing to cut on the
lower side, the force of the blow is brought to bear on the upper side
alone, until an entrance is effected into the hard rock in a true
straight line with the upper part of the hole.
Although as regards diameter, depth, and flow of water in favourable
localities, some extraordinary results have been obtained with this
system of boring by rods worked by steam power, yet, as Dru himself
observes, "in some instances his own experience of boring had been, that
owing to the difficulties attending the operation, the occurrence of
delays from accidents was the rule, while the regular working of the
machinery was the exception." A further disadvantage to be noticed is
that, owing to the time and labour involved in raising and lowering
heavy rods in borings of 10 inches diameter and upwards, there is a
strong inducement to keep the boring tool at work for a much longer
period than is actually necessary for breaking-up fresh material at each
stroke. The fact is that after from 100 to 200 blows have been given,
the boring tool merely falls into the accumulated _débris_ and pounds
this into dust, without again touching the surface of the solid rock. It
may therefore be easily understood how much time is totally lost out of
the periods of five to eight hours during which with the rod system the
tool is allowed to continue working.
MATHER AND PLATT'S SYSTEM.
In the most recent method of boring adopted in England, the rope
employed in the Chinese system has been reverted to, in place of the
iron or wood rods used on the Continent. A flexible rope admits of being
handled with greater facility than iron rods, but wants the advantage of
rigidity: in the Chinese method it admitted of withdrawing the chisel or
bucket very rapidly, but gave no certainty to the operation of the
chisel at the bottom of the hole. The rods on the other hand enable a
very effective blow to be given, with a definite turning or screwing
motion between the blows according to the requirements of the strata;
but the time and trouble of raising heavy rods from great depths on each
occasion of changing from boring to clearing out the hole form a serious
drawback, which makes the stoppages occupy really a longer time than the
actual working of the machinery.
[Illustration: Elevation of Mather and Platt Apparatus.
Fig. 189.]
[Illustration: Small Boring Machine.
_Side Elevation._]
[Illustration: Small Boring Machine.
_Plan._
Figs. 190, 191.]
The method invented by Colin Mather, and manufactured by Mather and
Platt, of Oldham, employed largely in England for deep boring, seems to
combine the advantages of the systems hitherto used, and to be free from
many of their disadvantages. The distinctive features of this plan,
which is shown in Figs. 189 to 195, are the mode of giving the
percussive action to the boring tool, and the construction of the tool
or boring-head, and of the shell-pump for clearing out the hole after
the action of the boring-head. Instead of these implements being
attached to rods, they are suspended by a flat hemp-rope, about 1/2 inch
thick and 4-1/2 inches broad, such as is commonly used at collieries;
and the boring tool and shell-pump are raised and lowered as quickly in
the bore-hole as the bucket and cages in a colliery shaft.
[Illustration: LARGE BORING MACHINE.
_Longitudinal Section._
Fig. 192.]
The flat rope A A, Fig. 189, from which the boring-head B is suspended,
is wound upon a large drum C driven by a steam-engine D with a reversing
motion, so that one man can regulate the operation with the greatest
ease. All the working parts are fitted into a wood or iron framing E E,
rendering the whole a compact and complete machine. On leaving the drum
C the rope passes under a guide pulley F, and then over a large pulley G
carried in a fork at the top of the piston-rod of a vertical
single-acting steam cylinder.
[Illustration: _Large Boring Machine._
_Transverse Section._
Fig. 193.]
This cylinder, by which the percussive action of the boring-head is
produced, is shown to a larger scale in the vertical sections, Figs.
192, 193; and in the larger size of machine here shown, the cylinder is
fitted with a piston of 15 inches diameter, having a heavy cast-iron rod
7 inches square, which is made with a fork at the top carrying the
flanged pulley G of about 3 feet diameter and of sufficient breadth for
the flat rope A to pass over it. The boring-head having been lowered by
the winding drum to the bottom of the bore-hole, the rope is fixed
secure at that length by the clamp J; steam is then admitted underneath
the piston in the cylinder H by the steam valve K, and the boring tool
is lifted by the ascent of the piston-rod and pulley G; and on arriving
at the top of the stroke the exhaust valve L is opened for the steam to
escape, allowing the piston-rod and carrying pulley to fall freely with
the boring tool, which falls with its full weight to the bottom of the
bore-hole. The exhaust port is 6 inches above the bottom of the
cylinder, while the steam port is situated at the bottom; and there is
thus always an elastic cushion of steam retained in the cylinder of that
thickness for the piston to fall upon, preventing the piston from
striking the bottom of the cylinder. The steam and exhaust valves are
worked with a self-acting motion by the tappets M M, which are
actuated by the movement of the piston-rod; and a rapid succession of
blows is thus given by the boring tool on the bottom of the bore-hole.
As it is necessary that motion should be given to the piston before the
valves can be acted upon, a small jet of steam N is allowed to be
constantly blowing into the bottom of the cylinder; this causes the
piston to move slowly at first, so as to take up the slack of the rope
and allow it to receive the weight of the boring-head gradually and
without a jerk. An arm attached to the piston-rod then comes in contact
with a tappet which opens the steam valve K, and the piston rises
quickly to the top of the stroke; another tappet worked by the same arm
then shuts off the steam, and the exhaust valve L is opened by a
corresponding arrangement on the opposite side of the piston-rod, as
shown in Fig. 193. By shifting these tappets the length of stroke of the
piston can be varied from 1 to 8 feet in the large machine, according to
the material to be bored through; and the height of fall of the
boring-head at the bottom of the bore-hole is double the length of
stroke of the piston. The fall of the boring-head and piston can also be
regulated by a weighted valve on the exhaust pipe, checking the escape
of the steam, so as to cause the descent to take place slowly or
quickly, as may be desired.
The boring-head B, Fig. 189, is shown to a larger scale in Figs. 194,
195, and consists of a wrought-iron bar about 4 inches diameter and 8
feet long, to the bottom of which a cast-iron cylindrical block C is
secured. This block has numerous square holes through it, into which the
chisels or cutters D D are inserted with taper shanks, as shown in Fig.
195, so as to be very firm when working, but to be readily taken out for
repairing and sharpening. Two different arrangements of the cutters are
shown in the elevation, Fig. 194, and the plan, Fig. 196. A little above
the block C another cylindrical casting E is fixed upon the bar B, which
acts simply as a guide to keep the bar perpendicular. Higher still is
fixed a second guide F, but on the circumference of this are secured
cast-iron plates made with ribs of a saw-tooth or ratchet shape,
catching only in one direction; these ribs are placed at an inclination
like segments of a screw-thread of very long pitch, so that as the
guide bears against the rough sides of the bore-hole when the bar is
raised or lowered they assist in turning it, for causing the cutters to
strike in a fresh place at each stroke. Each alternate plate has the
projecting ribs inclined in the opposite direction, so that one half of
the ribs are acting to turn the bar round in rising, and the other half
to turn it in the same direction in falling. These projecting spiral
ribs simply assist in turning the bar, and immediately above the upper
guide F is the arrangement by which the definite rotation is secured. To
effect this object two cast-iron collars, G and H, are cottered fast to
the top of the bar B, and placed about 12 inches apart; the upper face
of the lower collar G is formed with deep ratchet-teeth of about 2
inches pitch, and the under face of the top collar H is formed with
similar ratchet-teeth, set exactly in line with those on the lower
collar. Between these collars and sliding freely on the neck of the
boring bar B is a deep bush J, which is also formed with corresponding
ratchet-teeth on both its upper and lower faces; but the teeth on the
upper face are set half a tooth in advance of those on the lower face,
so that the perpendicular side of each tooth on the upper face of the
bush is directly above the centre of the inclined side of a tooth on the
lower face. To this bush is attached the wrought-iron bow K, by which
the whole boring bar is suspended with a hook and shackle O, Fig. 192,
from the end of the flat rope A. The rotary motion of the bar is
obtained as follows: when the boring tool falls and strikes the blow,
the lifting bush J, which during the lifting has been engaged with the
ratchet-teeth of the top collar H, falls upon those of the bottom collar
G, and thereby receives a twist backwards through the space of half a
tooth; and on commencing to lift again, the bush rising up against the
ratchet-teeth of the top collar H receives a further twist backwards
through half a tooth. The flat rope is thus twisted backwards to the
extent of one tooth of the ratchet; and during the lifting of the tool
it untwists itself again, thereby rotating the boring tool forwards
through that extent of twist between each successive blow of the tool.
The amount of the rotation may be varied by making the ratchet-teeth of
coarser or finer pitch. The motion is entirely self-acting, and the
rotary movement of the boring tool is ensured with mechanical accuracy.
This simple and most effective action taking place at every blow of the
tool produces a constant change in the position of the cutters, thus
increasing their effect in breaking the rock.
[Illustration: _Boring Head._
_Elevation._
Fig. 194.]
[Illustration: _Boring Head._
_Sectional Elevation._
Fig. 195.]
[Illustration: _Plan at Bottom, Inverted._
Fig. 196.]
[Illustration: Shell Pump.
Figs. 197, 198.]
The shell-pump, for raising the material broken up by the boring-head,
is shown in Figs. 197, 198, and consists of a cylindrical shell or
barrel P of cast-iron, about 8 feet long and a little smaller in
diameter than the size of the bore-hole. At the bottom is a clack A
opening upwards, somewhat similar to that in ordinary pumps; but its
seating, instead of being fastened to the cylinder P, is in an annular
frame C, which is held up against the bottom of the cylinder by a rod D
passing up to a wrought-iron bridge E at the top, where it is secured by
a cotter F. Inside the cylinder works a bucket B, similar to that of a
common lift-pump, having an indiarubber disc valve on the top side; and
the rod D of the bottom clack passes freely through the bucket. The rod
G of the bucket itself is formed like a long link in a chain, and by
this link the pump is suspended from the shackle O, Fig. 192, at the end
of the flat rope, the bridge E, Fig. 197, preventing the bucket from
being drawn out of the cylinder. The bottom clack A is made with an
indiarubber disc, which opens sufficiently to allow the water and
smaller particles of stone to enter the cylinder; and in order to enable
the pieces of broken rock to be brought up as large as possible, the
entire clack is free to rise bodily about 6 inches from the annular
frame C, as shown in Fig. 197, thereby affording ample space for large
pieces of rock to enter the cylinder, when drawn in by the up stroke of
the bucket.
The general working of the boring machine is as follows. The winding
drum C, Fig. 189, is 10 feet diameter in the large machine, and is
capable of holding 3000 feet length of rope 4-1/2 inches broad and 1/2
inch thick. When the boring-head B is hooked on the shackle at the end
of the rope A, its weight pulls round the drum and winding engine, and
by means of a break it is lowered steadily to the bottom of the
bore-hole; the rope is then secured at that length by screwing up tight
the clamp J. The small steam jet N, Figs. 192, 193, is next turned on,
for starting the working of the percussion cylinder H; and the
boring-head is then kept continuously at work until it has broken up a
sufficient quantity of material at the bottom of the bore-hole. The
clamp J which grips the rope is made with a slide and screw I, Fig. 192,
whereby more rope can be gradually given out as the boring-head
penetrates deeper in the hole. In order to increase the lift of the
boring-head, or to compensate for the elastic stretching of the rope,
which is found to amount to 1 inch in each 100 feet length, it is simply
necessary to raise the top pair of tappets on the tappet rods whilst the
percussive motion is in operation. When the boring-head has been kept at
work long enough, the steam is shut off from the percussion cylinder,
the rope unclamped, the winding engine put in motion, and the
boring-head wound up to the surface, where it is then slung from an
overhead suspension bar Q, Fig. 189, by means of a hook mounted on a
roller for running the boring-head away to one side, clear of the
bore-hole.
The shell-pump is next lowered down the bore-hole by the rope, and the
_débris_ pumped into it by lowering and raising the bucket about three
times at the bottom of the hole, which is readily effected by means of
the reversing motion of the winding engine. The pump is then brought up
to the surface, and emptied by the following very simple arrangement: it
is slung by a traversing hook from the overhead suspension bar Q, Fig.
189, and is brought perpendicularly over a small table E in the waste
tank T; and the table is raised by the screw S until it receives the
weight of the pump. The cotter F, Fig. 197, which holds up the clack
seating C at the bottom of the pump, is then knocked out; and the table
being lowered by the screw, the whole clack seating C descends with it,
as shown in Fig. 198, and the contents of the pump are washed out by the
rush of water contained in the pump cylinder. The table is then raised
again by the screw, replacing the clack seating in its proper position,
in which it is secured by driving the cotter F into the slot at the top;
and the pump is again ready to be lowered down the bore-hole as before.
It is sometimes necessary for the pump to be emptied and lowered three
or four times in order to remove all the material that has been broken
up by the boring-head at one operation.
The rapidity with which these operations may be carried on is found in
the experience of the working of the machine to be as follows. The
boring-head is lowered at the rate of 500 feet a minute. The percussive
motion gives twenty-four blows a minute; this rate of working continued
for about ten minutes in red sandstone and similar strata is sufficient
for enabling the cutters to penetrate about 6 inches depth, when the
boring-head is wound up again at the rate of 300 feet a minute. The
shell-pump is lowered and raised at the same speeds, but only remains
down about two minutes; and the emptying of the pump when drawn up
occupies about two or three minutes.
[Illustration: Accident Tools.
Figs. 199-204.]
In the construction of this machine it will be seen that the great
desideratum of all earth boring has been well kept in view; namely, to
bore-holes of large diameter to great depths with rapidity and safety.
The object is to keep either the boring-head or the shell-pump
constantly at work at the bottom of the bore-hole, where the actual work
has to be done; to lose as little time as possible in raising, lowering,
and changing the tools; to expedite all the operations at the surface;
and to economize manual labour in every particular. With this machine,
one man standing on a platform at the side of the percussion cylinder
performs all the operations of raising and lowering by the winding
engine, changing the boring-head and shell-pump, regulating the
percussive action, and clamping or unclamping the rope: all the handles
for the various steam valves are close to his hand, and the break for
lowering is worked by his foot. Two labourers attend to changing the
cutters and clearing the pump. Duplicate boring-heads and pumps are
slung to the overhead suspension bar Q, Fig. 189, ready for use, thus
avoiding all delay when any change is requisite.
As is well known by those who have charge of such operations, in well
boring innumerable accidents and stoppages occur from causes which
cannot be prevented, with however much vigilance and skill the
operations may be conducted. Hard and soft strata intermingled,
highly-inclined rocks, running sands, and fissures and dislocations are
fruitful sources of annoyance and delay, and sometimes of complete
failure; and it will therefore be interesting to notice a few of the
ordinary difficulties arising out of these circumstances. In all the
bore-holes yet executed by this system, the various special instruments
used under any circumstances of accident or complicated strata are fully
shown in Figs. 199 to 207.
[Illustration: Grapnel for Stiff Clay.
Fig. 207.]
[Illustration: Straightening Plug for Tubes.
Fig. 205.]
[Illustration: Grapnel for Cores.
Fig. 206.]
The boring-head while at work may suddenly be jammed fast, either by
breaking into a fissure, or in consequence of broken rock falling upon
it from loose strata above. All the strain possible is then put upon the
rope, either by the percussion cylinder or by the winding engine; and if
the rope is an old one or rotten it breaks, leaving perhaps a long
length in the hole. The claw grapnel, shown in Fig. 199, is then
attached to the rope remaining on the winding drum, and is lowered until
it rests upon the slack broken rope in the bore-hole. The grapnel is
made with three claws A A centred in a cylindrical block B, which slides
vertically within the casing C, the tail ends of the claws fitting into
inclined slots D in the casing. During the lowering of the grapnel, the
claws are kept open, in consequence of the trigger E being held up in
the position shown in Fig. 199, by the long link F, which suspends the
grapnel from the top rope. But as soon as the grapnel rests upon the
broken rope below, the suspending link F continuing to descend allows
the trigger E to fall out of it; and then in hauling up again, the
grapnel is lifted only by the bow G of the internal block B, and the
entire weight of the external casing C bears upon the inclined tail ends
of the claws A, causing them to close in tight upon the broken rope and
lay hold of it securely. The claws are made either hooked at the
extremity or serrated. The grapnel is then hauled up sufficiently to
pull the broken rope tight, and wrought-iron rods 1 inch square with
hooks attached at the bottom are let down to catch the bow of the
boring-head, which is readily accomplished. Two powerful screw-jacks are
applied to the rods at the surface, by means of the step-ladder shown in
Fig. 201, in which the cross-pin H is inserted at any pair of the holes,
so as to suit the height of the screw-jacks.
If the boring-head does not yield quickly to these efforts, the attempt
to recover it is abandoned, and it is got out of the way by being broken
up into pieces. For this purpose the broken rope in the bore-hole has
first to be removed, and it is therefore caught hold of with a sharp
hook and pulled tight in the hole, while the cutting grapnel, shown in
Fig. 200, is slipped over it and lowered by the rods to the bottom. This
tool is made with a pair of sharp cutting jaws or knives I I opening
upwards, which in lowering pass down freely over the rope; but when the
rods are pulled up with considerable force, the jaws nipping the rope
between them cut it through, and it is thus removed altogether from the
bore-hole. The solid wrought-iron breaking-up bar, Fig. 203, which
weighs about a ton, is then lowered, and by means of the percussion
cylinder it is made to pound away at the boring-head, until the latter
is either driven out of the way into one side of the bore-hole, or
broken up into such fragments as that, partly by the shell-pump and
partly by the grapnels, the whole obstacle is removed. The boring is
then proceeded with again, the same as before the accident.
The same mishap may occur with the shell-pump getting jammed fast in the
bore-hole, as illustrated in Fig. 208; and the same means of removing
the obstacle are then adopted. Experience has shown the danger of
putting any greater strain upon the rope than the percussion cylinder
can exert; and it is therefore usual to lower the grapnel rods at once,
if the boring-head or pump gets fast, thus avoiding the risk of
breaking the rope.
[Illustration: Shell-pump Jammed in the Bore-hole.
Fig. 208.]
The breaking of a cutter in the boring-head is not an uncommon
occurrence. If, however, the bucket grapnel, or the small screw grapnel,
Fig. 202, be employed for its recovery, the hole is readily cleared
without any important delay. The screw grapnel, Fig. 202, is applied by
means of the iron grappling rods, so that by turning the rods the screw
works itself round the cutter or other similar article in the bore-hole,
and securely holds it while the rods are drawn up again to the surface.
The bucket grapnel, Fig. 206, is also employed for raising clay, as well
as for the purpose of bringing up cores out of the bore-hole, where
these are not raised by the boring-head itself in the manner already
described. The action of this grapnel is nearly similar to that of the
claw grapnel, Fig. 199; the three jaws A A, hinged to the bottom of the
cylindrical casing C, and attached by connecting rods to the internal
block B sliding within the casing C, are kept open during the lowering
of the tool, the trigger E being held up in the position shown in Fig.
206, by the long suspending link F. On reaching the bottom, the trigger
is liberated by the further descent of the link F, which, in hauling up
again, lifts only the bow G of the internal block B; so that the jaws A
are made to close inwards upon the core, which is thus grasped firmly
between them and brought up within the grapnel. Where there is clay or
similar material at the bottom of the bore-hole, the weight of the heavy
block B in the grapnel causes the sharp edges of the pointed jaws to
penetrate to some depth into the material, a quantity of which is thus
enclosed within them and brought up.
Another grapnel that is also used where a bore-hole passes through a bed
of very stiff clay is shown in Fig. 207, and consists of a long
cast-iron cylinder H fitted with a sheet-iron mouthpiece K at the
bottom, in which are hinged three conical steel jaws J J opening
upwards. The weight of the tool forces it down into the clay with the
jaws open; and then on raising it the jaws, having a tendency to fall,
cut into the clay and enclose a quantity of it inside the mouthpiece,
which on being brought up to the surface is detached from the cylinder H
and cleaned out. A second mouthpiece is put on and sent down for working
in the bore-hole while the first is being emptied, the attachment of the
mouthpiece to the cylinder being made by a common bayonet-joint L, so as
to admit of readily connecting and disconnecting it.
[Illustration: Tubing for Bore-hole.
Fig. 209.]
A running sand in soft clay is, however, the most serious difficulty met
with in well boring. Under such circumstances the bore-hole has to be
tubed from top to bottom, which greatly increases the expense of the
undertaking, not only by the cost of the tubes, but also by the time and
labour expended in inserting them. When a permanent water supply is the
main object of the boring, the additional expense of tubing the
bore-hole is not of much consequence, as the tubed hole is more durable,
and the surface water is thereby excluded; but in exploring for mineral
it is a serious matter, as the final result of the bore-hole is then by
no means certain. The mode of inserting tubes has become a question of
great importance in connection with this system of boring, and much time
and thought having been spent in perfecting the method now adopted, its
value has been proved by the repeated success with which it has been
carried out.
The tubes used by Mather and Platt are of cast-iron, varying in
thickness from 5/8 to 1 inch according to their diameter, and are all 9
feet in length. The successive lengths are connected together by means
of wrought-iron covering hoops 9 inches long, made of the same outside
diameter as the tube, so as to be flush with it. These hoops are from
1/4 to 3/8 inch thick, and the ends of each tube are reduced in
diameter by turning down for 4-1/2 inches from the end, to fit inside
the hoops, as shown in Fig. 209. A hoop is shrunk fast on one end of
each tube, leaving 4-1/2 inches of socket projecting to receive the end
of the next tube to be connected. Four or six rows of screws with
countersunk heads, placed at equal distances round the hoop, are screwed
through into the tubes to couple the two lengths securely together. Thus
a flush joint is obtained both inside and outside the tubes. The lowest
tube is provided at the bottom with a steel shoe, having a sharp edge
for penetrating the ground more readily.
In small borings, from 6 to 12 inches diameter, the tubes are inserted
into the bore-hole by means of screw-jacks, by the simple and
inexpensive method shown in Figs. 210, 211. The boring machine
foundation A A, which is of timber, is weighted at B B by stones, pig
iron, or any available material; and two screw-jacks C C, each of about
10 tons power, are secured with the screws downwards, underneath the
beams D D crossing the shallow well E, which is always excavated at the
top of the bore-hole. A tube F having been lowered into the mouth of the
bore-hole by the winding engine, a pair of deep clamps G are screwed
tightly round it, and the screw-jacks acting upon these clamps force the
tube down into the ground. The boring is then resumed, and as it
proceeds the jacks are occasionally worked, so as to force the tube if
possible even ahead of the boring tool. The clamps are then slackened
and shifted up the tubes, to suit the length of the screws of the jacks;
two men work the jacks, and couple the lengths of tubes as they are
successively added. The actual boring is carried on simultaneously
within the tubes, and is not in the least impeded by their insertion,
which simply involves the labour of an additional man or two.
[Illustration: Tube-forcing Apparatus with Screw-jacks.
Fig. 210, 211.]
A more perfect and powerful tube-forcing apparatus is adopted where
tubes of from 18 to 24 inches diameter have to be inserted to a great
depth, an illustration of which is afforded by an extensive piece of
work at the Horse Fort, standing in the channel at Gosport. This fort is
a huge round tower, as shown in Fig. 212; and to supply the garrison
with fresh water, a bore-hole is sunk into the chalk. A cast-iron well
A, consisting of cylinders 6 feet diameter and 5 feet long, has been
sunk 90 feet into the bed of the channel in the centre of the fort, and
from the bottom of this well an 18-inch bore-hole B is now in progress.
The present depth is 400 feet, and the bore-hole is tubed the whole
distance with cast-iron tubes 1 inch thick, coupled as before described.
[Illustration: _Horse Fort, Spithead._
_Section shewing Bore-hole._
Fig. 212.]
[Illustration: Tube-forcing Apparatus with Hydraulic Presses.
Fig. 213.]
The method of inserting these tubes is shown in Fig. 213. Two
wrought-iron columns C C, 6 inches diameter, are firmly secured in the
position shown, by castings bolted to the flanges of the cylinders A A
forming the well, so that the two columns are perfectly rigid and
parallel to each other. A casting D, carrying on its under side two
5-inch hydraulic rams I I of 4 feet length, is formed so as to slide
freely between the columns, which act as guides; the hole in the centre
of this casting is large enough to pass a bore-tube freely through it,
and by means of cotters passed through the slots in the columns the
casting is securely fixed at any height. A second casting E, exactly the
same shape as the top one, is placed upon the top of the tubes B B to be
forced down, a loose wrought-iron hoop being first put upon the shoulder
at the top of the tube, large enough to prevent the casting E from
sliding down the outside of the tubes; this casting or crosshead rests
unsecured on the top of the tube and is free to move with it. The
hydraulic cylinders I, with their rams pushed home, are lowered upon the
crosshead E, and the top casting D to which they are attached is then
secured firmly to the columns C by cottering through the slots. A small
pipe F, having a long telescope joint, connects the hydraulic cylinders
I with the pumps at the surface which supply the hydraulic pressure. By
this arrangement a force of 3 tons on the square inch, or about 120 tons
total upon the two rams, has frequently been exerted to force down the
tubes at the Horse Fort. After the rams have made their full stroke of
about 3 feet 6 inches, the pressure is let off, and the hydraulic
cylinders I with the top casting D slide down the rams resting on the
crosshead E, until the rams are again pushed home. The top casting D is
then fixed in its new position upon the columns C, by cottering fast as
before, and the hydraulic pressure is again applied; and this is
repeated until the length of two tubes, making 18 feet, has been forced
down. The whole hydraulic apparatus is then drawn up again to the top,
another 18 feet of tubing added, and the operation of forcing down
resumed. The tubes are steadied by guides at G and H, Fig. 213, shown
also in the plans.
The boring operations are carried on uninterruptedly during the process
of tubing, excepting only for a few minutes when fresh tubes are being
added. It will be seen that the cast-iron well is in this case the
ultimate abutment against which the pressure is exerted in forcing the
tubes down, instead of the weight of the boring machine with stones and
pig iron added, as in the case where the screw-jacks are used; the
hydraulic method was designed specially for the work at Gosport, and has
acted most perfectly. Both the cast-iron well and the bore-hole are
entirely shut off from all percolation of sea-water, by first filling up
the well 30 feet with clay round the tubes, and making the tubes
themselves water-tight at the joints at the time of putting them
together.
In the event of any accident occurring to the tubes while they are being
forced down the bore-hole, such as requires them to be drawn up again
out of the hole, the prong grapnel, Fig. 204, is employed for the
purpose, having three expanding hooked prongs, which slide down readily
inside the tube, and spring open on reaching the bottom; the hooks then
project underneath the edge of the tube, which is thus raised on hauling
up the grapnel. In case the tubes get disjointed and become crooked
during the process of tubing, the long straightening plug, Fig. 205,
consisting of a stout piece of timber faced with wrought-iron strips, is
lowered down inside them; above this is a heavy cast-iron block, the
weight of which forces the plug past the part where the tubes have got
displaced, and thereby straightens them again.
Although there are few localities where the geological formation is not
favourable to the yield of pure water if a boring be carried deep
enough, yet it rarely happens that free-flowing wells such as those in
Paris and Hull are the result. Generally after the water-bearing strata
have been pierced, the level to which the water will rise is at some
depth below the surface of the ground; and only by the aid of pumps can
the desired supply be brought to the surface. Various pumping
arrangements have therefore been adopted to suit the different
conditions that are met with.
It is not the object of the present work to treat of the forms and
fittings of pumps, and the following details are only given as
completing Mather and Platt's system.
It is always desirable to sink a cast-iron well, such as that at the
Horse Fort, as nearly as possible down to the level at which the water
stands in the bore-hole. The sinking of such a well is rendered an easy
and rapid operation, with the aid of the boring machine in winding out
the material from the bottom, and keeping the sinkers dry by the use of
the dip-bucket, shown in Figs. 214 to 216, which will lift from 50 to
100 gallons of water a minute, for taking off the surface drainage. A
well having thus been made down to the level of the water in the
bore-hole, the permanent pumps are then applied to the bore-hole as
follows, the size of the pumps varying according to the diameter of the
bore-hole. Taking the case of a 15-inch bore-hole, a pump barrel
consisting of a plain cast-iron cylinder, say 12 inches diameter and 12
feet long, as shown in section in Fig. 219, is attached at the bottom of
cast-iron or copper pipes, which are 1/4 inch larger in diameter than
the pump barrel, and are coupled together in lengths by flanges, Fig.
217. By adding the requisite number of lengths of pipe at the top, the
pump barrel is lowered to any desired depth down the bore-hole: the
nearer to the depth of the water-bearing strata the better. The topmost
length of pipe has a broad flange at its upper end, which rests upon a
preparation made to receive it on the cast-iron bottom of the well, as
at C in Fig. 219.
[Illustration: Dip Bucket.
Figs. 214, 215.]
[Illustration: Sectional Plan.
Fig. 216.]
[Illustration: Joint of Copper Tubes.
Fig. 217.]
[Illustration: Couplings of Pump Rods.
Fig. 218.]
A pump bucket D, Fig. 219, with a water passage through it and a clack
on the top side, is then lowered into the barrel, being suspended by a
solid wrought-iron pump-rod E, which is made up of lengths of 30 feet
coupled together by right-and-left-hand screw-couplings, as in Fig. 218.
A second bucket F of similar form is also lowered into the pump barrel,
above the first bucket, and is suspended by hollow rods G coupled
together in the manner just described; the inside diameter of the hollow
rods G being such that the couplings of the solid rods E may pass freely
through. The pump-rods are carried up the well A to the surface, where
the hollow rod of the top bucket is attached to the horizontal arm of a
bell-crank lever H, Fig. 219; and the solid rod of the bottom bucket,
passing up through the hollow rod of the top bucket, is suspended from
the horizontal arm of a second reversed bell-crank lever K, facing the
first lever H. As the extremities of the horizontal arms of the levers
meet over the centre of the well, one of them is made with a forked end
to admit of the other passing it. The vertical arms of the two levers
are coupled by a connecting rod L, and a reciprocating motion is given
to them by means of an oscillating steam cylinder M, the piston-rod of
which is attached direct to the extremity of one of the vertical arms; a
crank and flywheel N are also connected to the levers, for controlling
the motion at the ends of the stroke. With the proportion shown in the
Figure of 3 to 4 between the horizontal and vertical arms of the
bell-crank levers, the stroke of 5 feet 4 inches of the steam piston
gives 4 feet stroke of the pump. The reciprocating motion of the
reversed bell-crank levers causes the two buckets to move always in
opposite directions, so that they meet and separate at each stroke of
the engine. A continuous flow of water is the result, for when the top
bucket is descending, the bottom bucket is rising and delivering its
water through the top bucket; and when the top bucket rises, it lifts
the water above it while the bottom bucket is descending, and water
rises through the descending bottom bucket to fill the space left
between the two buckets. In this way the effect of a double-acting pump
is produced.
[Illustration: Pumping Engine and Bore-hole.
Fig. 219.]
Although a continuous delivery of water is thus obtained of equal amount
in each stroke, it is found in practice that a heavy shock is occasioned
at each end of the stroke, in consequence of both the buckets starting
and stopping simultaneously, causing the whole column of water to be
stopped and put into motion again at each stroke. As an air-vessel for
keeping up the motion of the water is inapplicable in such a situation,
a modified arrangement of the two bell-crank levers has been adopted,
which answers the purpose, causing each bucket at the commencement of
its up stroke to take the lift off the other, before the up stroke of
the latter is completed. By this means all shock is avoided, as the
first bucket gently and gradually relieves the second, before the return
stroke of the second commences.
[Illustration: Pumping Engine and Double-acting Pump with Improved
Motion.
Fig. 220, 221.]
In this improved pumping motion, which is shown in Figs. 220, 221, the
two bell-crank levers H and K, working the pump buckets, are centred one
above the other, the upper one being inverted; the vertical arms are
slotted, and are both actuated by the same crank-pin working in the
slots, the revolution of the crank thus giving an oscillating movement
to the two levers through the extent of the arcs shown by the dotted
lines in Fig. 220. The solid pump-rod E suspending the bottom bucket D
is attached to the upper bell-crank lever K, and the hollow rod G of the
top bucket is suspended from the lower lever H; the crank-shaft J
working the levers is made to revolve in the direction shown by the
arrow in Fig. 220, by means of gearing driven by the horizontal
steam-engine P.
The result of this arrangement is, that in the revolution of the crank
the dead point of one of the levers is passed before that of the other
is reached; so that the bucket which first comes to rest at the end of
its stroke is started into motion again before the second bucket comes
to rest. Thus in the lifting stroke of the bottom bucket worked by the
upper lever K, the bucket in ascending has only reached the position
shown at D in Fig. 220, at the moment when the top bucket worked by the
lower lever H arrives at the bottom extremity of its stroke, and the
bottom bucket D, which is still rising, continues to lift until it
reaches its highest position, by which time the top bucket has got well
into motion in its up stroke, and is in its turn lifting the water.