Hasty Demolition. Gunpowder. Dynamite. How Used in Blasting.
Guncotton. Rack-a-rock. Handling, Transportation, and Storage of
High Explosives. Charges for Hasty Demolition. Where and How to
Place Charges.
GUNPOWDER.
Gunpowder is a very intimate mixture of potassium nitrate (nitre),
charcoal, and sulphur, and generally consists of the following
proportions:
Nitre, 75 parts; charcoal, 15 parts; sulphur, 10 parts.
The following processes are used in its manufacture:
(1) Mixing the ingredients; (2) incorporating or "milling"; (3)
breaking down the mill-cake; (4) pressing; (5) granulating; (6)
dusting; (7) glazing; (8) second dusting; (9) stoving or drying; (10)
finishing.
Good gunpowder should be composed of hard angular grains which do not
soil the fingers, and should have a perfectly uniform dark-gray color.
When new, it should be free from dust, and a gramme of it flashed on a
copper or porcelain plate should leave no residue or foulness.
It should give the required initial velocity to the projectile, and
produce not more than the maximum strain upon the gun.
When exposed to air of average dryness, it should not absorb more
than 0.5 to 1.5 per cent of water. In damp air it absorbs more and
deteriorates. Its exploding-point is 560° F.
DYNAMITE.
Dynamite is composed of a particularly porous siliceous earth
(Keiselguhr) impregnated with about 70 or 75 per cent of
nitro-glycerine. True dynamite resembles in appearance moist brown
sugar. It takes fire at 350° F., and freezes.
MATERIALS IN USE FOR BLASTING.
=Cartridges.=--The regular sizes are from four to eight inches long
and from three fourths of an inch to two inches in diameter. They are
furnished to order of any required size, packed in boxes containing 25
or 50 pounds, the layers of cartridges being separated by sawdust. To
use a small cartridge in a large hole, slit it on the side and press
it down into the drill-hole with a wooden tamping-rod. Cartridges may
be readily cut into desired lengths. _In tamping powder or explosives
always use a wooden rammer, never an iron or steel bar._
=Caps.=--The regular cap or exploder is employed. It consists of a
hollow copper cylinder about ¼ inch in diameter and from one to two
inches long, and contains 15 to 20 per cent or more of fulminate of
mercury mixed with other ingredients into a cement, which fills the
closed end of the cap.
=Fuzes.=--The double-tape fuze is the best. Single-tape fuze may be
used when the ground is only a little wet.
=Nippers and Pincers.=--For cutting the fuze, and after it is inserted
in the cap for squeezing the cap tightly around the fuze.
=Funnel.=--Used in charging with loose powder.
DRILL-HOLES.
As a general rule drill-holes and charges for dynamite should be
comparatively small. In heavy work the holes should be large in size
and less in number, and the amount of dynamite should be in proportion
to the work done.
=Charging with Cartridges.=--The charge must fit and fill the bottom of
the bore, and be packed solid. Take a cartridge as nearly as possible
of the same size as the bore, and cut it into sections of about twice
or three times the diameter. With a hard-wood rammer, as large as
will run freely in the hole, press these sections into the bore-hole
one by one with sufficient force until each section is driven to
the bottom and expanded laterally so as to fill the hole solidly in
every direction. If the cartridge is smaller than the hole, slit it
lengthwise. _Metallic rammers must not be used._
=Priming.=--Cut off squarely the end of the fuze and thrust it into
the cap up to the fulminate. If the fuze is too large, scrape it down,
and if too small wind it with paper. Then clamp the cap to the fuze
with the nippers, being careful not to disturb the fulminate in the
cap. If for a wet hole, smear the junction of the fuze and the cap
with bar-soap or the like, to make it water-tight. Now open the end of
the cartridge, and with a pointed stick make a hole in the explosive
and insert the cap (with the fuze attached) the full length of the
cap, and press the explosive firmly about the cap. Next gather the
cartridge-paper about the fuze and tie it there strongly with a string,
so that the cap cannot be withdrawn from the explosive. Cut off so much
of the cartridge as is not needed, and the primer is complete. Thus
prepared, place it in the drill-hole and press it with a wooden rod
into contact with the charge.
=Tamping.=--This is of great importance. Always tamp if you can, and
with the best materials and in the strongest manner. In deep and down
holes water is good. A shallow tamp of water amounts to very little.
A shallow tamp of sand or clay is better. In driving and packing the
tamp next to the primer be careful not to explode the cap; the first
handful of tamp should always be pressed down gently. In fissures or
artificial cracks surround the charge with mud, clay, sand, or water,
if possible.
=Explosion of Blast.=--In most cases it is better not to cut off the
required length of fuze until the hole is tamped. Then cut off at a
safe length and fire by igniting with a match or fuzee. If it misses
fire, be careful in taking out the tamping not to approach nearer the
cap than within two or three inches; then put in another cartridge and
fire it. _Never pick out the charge._ After inserting the primer it is
well to put a ball of newspaper or some substance readily recognized on
top of it and then the tamping. If then the tamping has to be removed,
warning will be given on approaching the primer.
=To Insure Explosion.=--The dynamite must not be frozen; the fuze must
be good and kept in the cap; the cap must be dry and not withdrawn from
the explosive.
=Frozen Dynamite.=--Dynamite freezes more easily than water, becomes
hard and cannot be properly loaded into bore-holes, and is more
difficult of explosion. Keep it where it will not freeze if possible.
_It must not be thawed by a fire_, but by hot water in an apparatus
like a common glue-pot, the dynamite being in the inner vessel and hot
(not boiling) water in the outer. Eissler states that there is but one
safe way of thawing it, which is to keep it in a kitchen or other room
at summer heat, and away from the fire, until it is soft. It is then
ready for use.
=Precautions.=--Never attempt to thaw frozen dynamite by _roasting_,
_toasting_, or _baking_ it. Never put it in heated vessels, or in
boilers, or before fires or heated metals. _It must not be thawed or
heated rapidly._
Never put a cap into a charge or primer until you are ready to use it.
After it is made never let a primer leave your hands until it is in
the hole. Keep the caps away from the dynamite. Never let them come
near each other except when used.
Never allow smoking or other fire near the powder or explosive,
as it burns rapidly, and especially when loose, and may fire caps
incautiously left near by, and thus bring on an explosion.
Never use a metallic rammer.
Do not get nitro-glycerine on your fingers. It will be absorbed by
the skin and give you a headache. Invariably prepare your primer at a
distance from your explosive.
RACK-A-ROCK.
This powerful explosive, composed of a solid and a liquid ingredient,
entirely inexplosive when separate, but easily and quickly combined,
seems to present undoubted advantages for use in the military service.
The solid is potassium chlorate, and the liquid is either "dead oil,"
or dead oil and bisulphide of carbon in equal volumes, or bisulphide of
carbon with 3 per cent of carbon added, or mono-nitro-benzine.
General Abbot considered the following the best:
Potassium chlorate, 79 parts; mono-nitro-benzine, 21 parts.
The potassium chlorate is put up in the form of a cartridge enclosed in
a bag made of cotton or other suitable material.
In preparing the charge for use the cartridges are placed in a wire
frame, which is suspended from a spring-balance, and dipped in the
liquid until a proportion of 3 to 4½ parts of solid to 1 part of liquid
is shown by the balance; this requires from 3 to 6 seconds.
Or, place the cartridges in a pan containing cells (each cartridge
having a corresponding cell and cup) and then pour in each cell its
cupful of liquid. As soon as it has all been absorbed remove the
cartridges and in ten minutes they are ready for use.
If the cartridges be kept, they appear to tend to increased sensibility
to friction or percussion.
GUNCOTTON.
=Compressed Guncotton.=--Clippings and other waste from cotton-mills
are thoroughly purified from oil and fatty matters by treatment with
alkali and extraneous substances removed. The material is then opened
up by a carding-machine and cut into suitable lengths. After thorough
drying and when quite cold small quantities at a time are immersed in
a cool mixture of 1 nitric acid (s. g. 1.52) and 3 sulphuric acid (s.
g. 1.85). The excess of acid is then removed and the cotton carefully
washed, reduced to pulp, purified, and compressed into given weights
and shapes by a powerful hydraulic press, and weighs 60 lbs. per cubic
foot.
The disks or slabs can be cut into smaller sizes with a sharp saw or
knife without danger, care being taken to press them between boards
while so doing to prevent their falling to pieces.
It has from 2 to 2½ times the strength of gunpowder for equal weights
when the charges are well tamped, and 4 times the strength of gunpowder
when the charges are untamped; it ignites at a lower temperature than
gunpowder, as it may explode at 277° F. and must explode at 400° F.;
it is comparatively insensible to shocks--caissons containing dry
guncotton have been frequently inflamed by the penetration of a bullet
from a military rifle, but never exploded,[11] while wet guncotton in
a condition for service cannot possibly be ignited by the same means
even at the shortest ranges.
Wet guncotton is not easily ignited, burns up quietly in the open
air, is not sensitive to friction; but if fired by a strongly charged
percussion-cap it will explode with great violence. It does not
deteriorate when wet and is then perfectly safe to handle. It is
therefore stored in a wet state (as it cannot be exploded except by
the detonation of other disks of dry guncotton); but it should not
be exposed to a temperature that will freeze the water in the cakes,
if possible. While frost has no effect on dry guncotton, it causes a
mechanical disintegration of the wet compressed variety.
In the field the slabs are carried _wet_; the disks _dry_ and packed
in hermetically sealed tins. These disks are used as primers, and have
attached to them, when used, a fulminate fuze.
=To Fire Guncotton=, the fuze is cut to the required length and
inserted in the hollow end of the detonator, especial care being taken
to push it down so as to rest on the quick-match; the tube is then
slightly bent to prevent the fuze from being withdrawn. The small end
of the detonator is then gently inserted into the primer (the dry disk)
so as to fill the entire length of the hole in the latter. If it is
loose, a piece of paper or grass must be wrapped round to make it fit
tight. The primer must be placed in close contact with the charge to be
fired. Care must be taken that no sparks from the fuze can fall on the
charge, which might then burn instead of exploding. Bear in mind that a
moist primer is certain to cause failure.
The charge should be in close contact with the object to be demolished.
=Transportation.=--The handling of high explosives should be done
under the immediate supervision of persons thoroughly familiar with
the proper methods to be pursued and who will exercise great care
and judgment. High explosives should be packed in light wooden boxes
properly marked. The French have a wagon containing about 350 lbs.
attached to a horse-battery accompanying the cavalry division, acting
independently, and two such wagons with the artillery-park. Care is
taken that they are not placed too near the other ammunition and are in
the safest place under careful observation.
On a steamer place the explosives in a well-ventilated place remote
from the engine.
On railways, if the weather be hot, there should be good ventilation
and ice in the car, so placed that water cannot reach the explosives.
In winter protect from freezing if possible. Packing in straw or
sawdust may be useful. Under no circumstances should cases of fuzes be
in the same car, or in the vicinity of the explosive. The packages of
guncotton should not be exposed to the sun--cover with paulins, put
under shade-trees.
=Storage.=--At military posts, in ordinary service magazines over
which are erected light wooden roofs, so as to insure a draught during
hot weather.
The usual precautions against fire and for storage of ordinary powder
must be taken; and neither fuzes, caps, nor detonators of any kind
should ever be allowed in the magazine containing the explosives. Dry
guncotton should not be stored in the same magazine with wet guncotton.
Before being placed in the magazine the boxes should be given a coat of
paint or shellac, to protect them from moisture. They should also be
placed on skids and the space between the skids partially filled with
sawdust, to absorb any exuding nitro-glycerine. If any powder should be
spilled on the floor, or nitro-glycerine exude and be absorbed by the
sawdust, it should be removed at once and burned. The boxes should be
turned over every month or two, and if kept long on hand they should be
opened and the explosive tested from time to time.
When guncotton is received, pour into each package enough water to
cover it, or otherwise immerse it. Let the water remain for 15 minutes;
then pour it off and hermetically close the box. This should be done
every three months.
Packages of guncotton stained brown or yellow, giving off nitric fumes,
or showing other signs of decomposition, should be removed and immersed
in water. If decomposition be far advanced, they should be removed to a
safe place and burned.
WHERE AND HOW TO PLACE CHARGES.
=Masonry or Brick Arch.=--Attack the haunches of the arch or the
piers. In bridges of a single arch the haunches are the best points,
two trenches being dug across the width of the roadway down to the
back of the arch. When there is no time for this, the charge should
be placed along the crown of the arch. With guncotton untamped use
¾_T²_ × _B_; if tamped with a depth of earth equal to the thickness
of the arch, use ⅜_T²_ × _B_.
With gunpowder, if over crown of arch, use 3/2_T²_ × _B_; if behind
haunch, ⅔_T²_ × _B_. In the former case use tamping if possible
equal to the thickness of the arch, and in the latter case equal to
twice the thickness. The quantity of powder obtained by these rules
should be divided into two or more charges placed across the arch.
When the bridge consists of a series of arches, and the piers are short
and thick, the haunches should be attacked by the rules given in table
on next page.
If the piers be high and thin, it is better to place the charges
against them, as the fall of one pier will involve the destruction of
two arches. The charge should be slightly greater than for a wall of
the same thickness.
RULES FOR CALCULATING CHARGES FOR HASTY DEMOLITIONS BY GUNCOTTON OR
GUNPOWDER.
Charges are in lbs.; _B_ and _T_ are in feet; _t_ is in inches. _B_ is
length of breach to be made; _T_ or _t_ is thickness of object to be
demolished.
Gunpowder is assumed to be roughly tamped with sand-bags, guncotton
untamped. If the guncotton is tamped, the charges may be reduced one
half. Charges of guncotton must be equal in length to the breach which
is to be made.
---------------------+-----------+------------+------------------------
Object Attacked. |Gunpowder. | Guncotton. | Remarks.
---------------------+-----------+------------+------------------------
Brick arch. |} {| ¾_BT²_ }|The length of breach,
Brick wall 2 ft. or |} {|2 lbs. per}}|_B_, should not be less
less. |}3/2_BT²_ {| foot run }|than the height of the
Brick wall over 2 ft.|} {|½_BT²_ }|wall to be brought
Brick piers. |} {|⅔_BT²_ }|down.
| | |
Hard wood in any | 40 to 100 | 3_BT²_ |In a concentrated
form, stockade, | lbs. for | |charge, or for trees
palisade, single | stockade | |not over 12 in. in
timbers, trees, etc. | | |diameter in a necklace.
| | |
Do., do. | | ⅜_T²_ |In auger-hole; when
| | |the timber is not
| | |perfectly round, _T_
| | |smaller axis.
| | |
Soft wood. { | Half the charges |
{ | for hard wood |
| | |
Breastwork of | 60 to 80 |4 lbs. per |
horizontal balks, | lbs. per | foot |
or earth between | 5 feet | |
sleepers up to | | |
3½ ft. thick. | | |
| | |
Heavy rail stockade. | | 7lbs. |
| | per ft. |
| | |
Fortress gate. | 200 lbs. | 50 lbs. |
| | |
Iron plate. | |3/2_Bt²_ |
| | |
Field- or siege-guns.| | 1½ lbs. |On chase near muzzle.
| | |
Heavier guns. | | 4 lbs. |In bottom of bore,
| | |tamped with water or
| | |sand.
| | |
First-class iron rail| | 2/8 lb. |Touching web of rail
| | |and near a chair.
| | |
" steel " | | 4 oz. |Four rails placed around
| | |the charge will be cut
| | |simultaneously by it.
---------------------+-----------+------------+------------------------
In the presence of an enemy increase above charges
50% to allow for contingencies.
=House with Moderately Thick Walls.=--Attack portions of walls between
the windows, the charges being tamped, and inside the house if
possible. Otherwise place outside, or one or two large charges inside
untamped.
To demolish a building, a sufficient height of wall must be brought
down to insure the arches over the doors and windows falling. The
length of breach must be equal to this height. With very thick walls
cut grooves.
=To Cut Down Trees.=--Place charge in an auger-hole bored horizontally
into the tree at desired height. If tree be 1½ to 2 feet in diameter,
use two holes. With a little care they can be bored so as to meet
in the centre, in which case one detonator will suffice to fire the
charge; with plenty of detonators it may be better to fire one hole
first and then a second hole in the uninjured part of the tree, and so
on.
The tree may be made to fall in any required direction by attaching a
rope to the upper branches, and taking the strain on it before firing.
The guncotton may be hung around the tree, but this often fails with
trees over 12 inches in diameter.
A hole may be dug under the roots. Dig down by the side of the tree and
then horizontally under the bottom close to the wood, the hole being
just large enough for the cartridge.
The rules for felling trees apply to timbers of wooden bridges, the
uprights of the piers being the best point to attack.
=To Blow Down a Stockade 12″ × 12″.=--Use 3 lbs. of guncotton per
running foot. The slabs should be threaded together, so as to be in
contact, and hung or laid against the timbers at the required level.
If gunpowder be used, a charge of 80 lbs. should be allowed for the
same stockade when the charge is not tamped; when tamped by having a
few sand-bags piled on top, the charge may be reduced to 60 lbs. This
would probably make a breach about 6 feet wide.
=To Demolish a Gate.=--Fifty pounds of guncotton hung against the gate
by a nail or pickaxe or laid on the ground will suffice.
The charge of gunpowder should be 200 lbs., covered with sand-bags if
possible.
=Destruction of Iron Bridges.=--Place charge on lower girders near an
abutment, and at a point where the thickness of the plates is least.
If sections are uniform throughout the length of the bridge, place
charge at centre of a span between two piers. When the bridge plate is
entirely of iron, place charge on top of beams.
=Destruction of Railroad Tracks.=--To destroy heavy iron rails, a
charge of six 2-ounce disks (including primer) should be used.
=To Destroy a Tunnel.=--The crown of the arch or the side-walls should
be attacked. The points selected should be some distance inside the
tunnel.
=To Destroy Field-and Siege-guns.=--Detonate 1½ lbs. of guncotton on
the outside near the muzzle. In heavier wrought-iron guns detonate 4
lbs. in the bottom of the bore, tamping with sand.
Heavy cast-iron guns can be burst by firing 1 lb. of guncotton in the
same position and tamping with sand.