On the 11th of January (says the _Liverpool Daily Post_) will be
opened for traffic the new station of the Mersey Tunnel Railway at the
bottom of Bold Street. With the completion of the station at Bold
Street the scheme may be said to have been brought successfully to a
conclusion. It was not until 1879, after the expenditure of
125,000_l._ upon trial borings, that the promoters ventured to appeal
to the public for support, and that a company, of which the Right Hon.
H. Cecil Raikes, M.P., was chairman, was formed for carrying the
project of the Mersey Railway into effect. The experience of the
engineers in the construction of the tunnel is not a little curious.
It was proved by the borings that the position in which the tunnel was
proposed to be bored was not only the most important from the point of
view of public convenience, and therefore of commercial advantage, but
was from the point of view of engineering difficulty decidedly the
most preferable. In this position the cuttings passed through the
sandstone rock, although on the Liverpool side the shafts were sunk
through a considerable depth through "made" ground, the whole of Mann
Island and the Goree being composed of earth and gravel tipped on the
old bank of the river. Indeed the miners passed through the cellars of
old houses and unearthed old water pipes; excavated through a depth of
tipped rubbish on which these houses had evidently been built; and
then came upon the former strand of the river, beneath which was the
blue silt usually found; then a stratum of bowlder clay; and finally
the red sandstone rock. Once begun, the works were pushed forward
night and day, Sundays excepted, until January, 1884, when the last
few feet of rock were cleared away by the boring machine, and the
mayors of Liverpool and Birkenhead met in fraternal greeting beneath
the river. The operations gave employment to 3,000 men working three
shifts of eight hours each, but were greatly accelerated by the use of
Colonel Beaumont's boring machine, on which disks of chilled iron are
set in a strong iron bar made to revolve by means of compressed air.
This machine scooped out a tunnel 7 feet in diameter; and by
successive improvements Colonel Beaumont attained a speed of 150 feet
per week, leaving the old method of blasting far behind. As the
machine moved forward the rock behind was broken out to the size of
the main tunnel and bricked in in short lengths. One remarkable
circumstance in connection with the work is that the boring from the
Birkenhead side and the boring from Liverpool were found, when they
were completed and joined, to be out of line by only 1 inch.
This excellent result was attained by careful calculations and
experiments with perpendicular wires kept in position by weights,
which, to avoid oscillation, were suspended in buckets of water. From
shaft to shaft the tunnel is 1,770 yards in length and 26 feet in
diameter; but for a length of 400 feet at the James Street and
Hamilton Square stations the arch is enlarged to 50½ feet. The tunnel
is lined with from six to eight rings of solid brickwork embedded in
cement, the two inner rings being blue Staffordshire or Burnley
bricks. For the purpose of ventilation a smaller tunnel, 7 feet in
diameter, was bored parallel with the main tunnel, with which it is
connected in eight places by cross cuts, provided with suitable doors.
Both at Liverpool and at Birkenhead there are two guibal fans, one 40
feet and the other 30 feet in diameter. The smaller, which throw each
180,000 cubic feet of air per minute, ventilate the continuations of
the tunnel under Liverpool and Birkenhead respectively, and the larger
tunnel under the river. The fans remove together 600,000 cubic feet of
air per minute, and by this combined operation the entire air in the
tunnel is changed once in every seven minutes. By the use of
regulating shutters the air passes in a continuous current and the
fans are noiseless. The telegraph and telephone wires pass through the
tunnel, thus avoiding the long detour by Runcorn. Probably, as a feat
of engineering, the construction of the new station at Bold Street is
not inferior to any part of the scheme advanced. Under very singular
and perplexing difficulties it could only be proceeded with in its
first stages from midnight until six o'clock the following morning, it
being of course essential that the traffic at the Central Station
should not be interfered with. During these hours, night after night,
trenches were cut at intervals of 10 feet across the roadway
connecting the arrival platforms at the station, and into these were
placed strong balks of timber, across which planks were laid as a
temporary roadway. Beneath these planks, which were taken up and put
down as required, the rock was excavated to a depth of 9 feet, and the
balks supported upon stout props. Then from the driftway or rough
boring beneath well holes were bored to the upper excavation, and
through them the strong upright iron pillars designed to support the
roof of the new tunnel station were passed, bedded and securely fixed
in position. No sooner were they _in situ_ than the most troublesome
part of the task was entered upon, for the balks had then to be
removed in order to allow to be placed in position the girders running
the length of the new station, and resting on the tops of the upright
pillars. From these longitudinal girders cross girders of great
strength were placed, and between these were built brick arches,
packed above with concrete. This formed the roof of the new station.
One portion of it passed under the rails in the station above, and had
to be constructed without stoppage of the traffic. The rails had
consequently to be supported on a temporary steel bridge of ingenious
design, constructed by Mr. C.A. Rowlendson, the resident engineer and
manager of the company, under whose personal supervision, as
representing Sir Douglas Fox, the work has been carried out. With this
device the men were enabled to go on in safety although locomotives
were passing immediately above their heads. After the completion of
the roof the station below was excavated by what is technically called
"plug and feather" work--that is to say, by drilling holes into which
powerful wedges are driven to split the rock.
* * * * *