THE COLLIERY GUARDIAN

AND

JOURNAL OF THE COAL AND IRON TRADES.

Vol. CVII.	FRIDAY APRIL 3, 1914.	No. 2779.

Cement Grout in Water-Bearing Fissures.

(From the “Transactions” of the American Institute of Mining Engineers.)

By FRANCIS

The direct injection of cement grout into water-
bearing fissures as a means of checking or stopping
the flow of water into shafts and tunnels has been
experimented with for a decade or longer, and seems to
have been first attempted in Europe.

It is only lately, however, that the process has been
entirely successful. This success has been accomplished
on the Catskill aqueduct, now under construction by
the city of New York. This aqueduct in-
cludes a number of deep-pressure tunnels,
reached by shafts for both waterway
and construction purposes. In portions
of these shafts and tunnels considerable
underground water was met. The contract
for the first of these deep-pressure tunnels
was let to the T. A. Gillespie Company.
This section is known as the Rondout
siphon. It leads under the Rondout Valley
at a depth of from 400 to 800 feet, and is
about 5 miles long. The engineers expected
that considerable water would be encoun-
tered, but fortunately this was not the case
except at one shaft, known as No. 4, which
penetrated the rock at a junction between
limestone and conglomerate. Water-
bearing fissures were encountered almost
immediately. At a depth of about 200 ft. a
flow of 1,500 gallons per minute was struck.
The shaft then contained as many pumps
as could be used, and it seemed impossible
to sink it further. After vain efforts had
been made to proceed, John P. Hogan, a
division engineer of the Board of Water
Supply, suggested that cementation of the
fissures be tried. The process was attempted
for the first time in America. Since
the shaft was partly full of water it was
necessary to drill grout holes with a
diamond drill. Platforms were placed on
the timbers at the water level, the diamond
drill was installed, and six 90 ft. holes were
drilled in the bottom of the shaft. Several
carloads of cement were pumped through
these holes into the fissures, the drill
casings being used for grout pipes. This
largely cut off the flow of water from the
bottom, and sinking could then proceed.
After that, water-bearing seams were
grouted as soon as encountered, and the
contractor was able to finish the shafts and
tunnel within the contract time. No. 4 was
a rectangular, timbered shaft, with no
concrete lining; consequently it was im-
possible to cut off any of the water coming
in from above the point where grouting was
first attempted. On this account large
volumes of water had to be pumped until
the tunnel was finally sealed.

At the next wet shaft the writer had to
do with, advantage was taken of the
experience gained at shaft No. 4. At this
second shaft—No. 4 of the New York City siphon—
good progress was made until a depth of about 100 ft.
was reached. The first hole drilled in the bottom
below this depth struck a stream of water. The flow
amounted to about 150 gallons per minute. This was
plugged. It was found that each of the 12 holes in the
sump cut encountered the same stream of water.

As soon as each hole cut the water-bearing seam
it was plugged with a tapered wooden plug. After all
the holes in the sump had been drilled and plugged in
this way, the grout connections were made one at a

DONALDSON.

time, so as to restrict the flow of water into the shaft.
Each connection was made with a piece of 2 in. or
2'5 in. iron pipe about 3 ft. long, threaded at one end
and given a long taper at the other. The tapered
portion was made rough on the outside by nicking it
with a chisel. A heavy iron stop-cock was screwed to
the pipe, the tapered end wrapped in several thicknesses
of burlap, the wooden plug removed from the drill hole

Photo by Beresford.

THE EARL OF CRAWFORD AND BALCARRES,

who was last week elected president of the Mining Association of Great
Britain, is a member of an ancient family that has been closely associated
with the coalmining industry of Lancashire for many years. Like his
father, the 26th Earl, his lordship, who was born in 1871, is a man of high
attainments, and is a recognised authority on art and architecture. He is
a trustee of the National Portrait Gallery, hon. secretary of the Society
for the Protection of Ancient Buildings, and vice-chairman of the National
Trust. As Lord Balcarres, he sat for several years in the House of
Commons as Conservative member for the Chorley Division of Lancashire,
and was a Junior Lord of the Treasury from 1903 to 1905. Last year he
succeeded to the earldom on the death of his father. One of the largest
royalty owne'S in the Wigan district, his lordship is chairman of the
Wigan Coal and Iron Company Limited, and resides at Haigh Hall, Wigan.
It is safe to say that his personality will add still further distinction to the
important office which he has now been called upon to fill.

and the tapered pipe driven in, the stop-cock being left
open. This was the most exciting and the wettest part
of the job. After the pipe had been driven in hard the
stop-cock was closed.

In this case connections were placed in all the wet
holes before grouting. The grouting machine or tank
used on the aqueduct was the Caniff machine, in which
the grout is mixed by air. It is built like an air lock
with a door on the top through which cement, sand and
water are introduced, and has a 2 in. discharge opening
in the bottom and air connections top and bottom. The

discharge opening is connected to the grout hole by a
heavy rubber hose. Another 2 in. stop-cock is placed
at the outlet of the tank and a 2 in. by 1 in. T is placed
between the hose and the cock attached to the pipe in
the drill hole. Into the side opening of this T a 1 in.
stop-cock is screwed.

The machine is installed at the bottom of the shaft,
and is connected to one of the holes and also to the
high-pressure air supply. The 2 in. stop-cock on the
machine is closed and the other is opened. The door in
the top is opened, a sack of cement, three or four buckets
of water, and (if the cavity to be filled is large) a sack of
fine sand are poured in, the air connection at the bottom
is opened and the air allowed to bubble through and mix
the grout. Then very quickly the door is closed, the
lower air connection is closed, and the
discharge connection and the upper air
connection are opened, and the air enters
and drives the grout into the cavity. A
man stationed at the 1 in. stop-cock keeps
opening it a crack ; when air shows instead
of grout he closes the 2 in. stop-cock and
the machine is recharged. If the cavity is
open the charge is pushed in in three or
four seconds. By working continuously
more than 1,000 batches can be placed in
24 hours.

The grouting of the fissure was successful
and sinking was resumed. About 50 ft.
further down another water-bearing fissure
was drilled into, and this, instead of being
open, was filled with sand formed by the
crushing of metamorphic gneiss due to
folding. This sand was carried up out of
the drilled holes in large quantities by the
water. Grout will not permeate sand, and
it was necessary to continue drilling holes
and pumping in grout, increasing the
pressure at the end from 100 lb. to 400 lb.
and 500 lb. to the square inch. The sand
was tamped so full of cement that when
cut through it was compacted like sand-
stone, and contained balls of grout from
the size of a fist to as large as a man’s
head.

The most difficult grouting on the
aqueduct was done on the Hudson Siphon,
which is a deep siphon tunnel under the
Hudson River, at a depth of 1,000 ft. below
tide-water. The shafts were sunk by the
city forces, after which the contract for the
driving and lining of the tunnel and lining
the shafts was let. About 150 ft. from the
foot of the east shaft the heading cut a
water-bearing fissure which flowed about
300 gallons per minute. The full flow did
not develop until the cut was blasted. The
problem then was to grout this flow against
a hydrostatic pressure of 500 lb. per square
inch, with no solid rock to which to make
grout-pipe connections. This problem was
finally solved by the construction of a
concrete bulkhead 8 ft. thick across the full
section of the head. The concrete was
mixed in proportion of 1:2:4, and was
heavily reinforced with rails set into holes
drilled laterally into the sides, roof and
floor of the tunnel. Grout pipes leading
into the fissure were set through the bulkhead. After
the concrete had set for a week, grout was forced into
the fissure—first by the pneumatic process with a high-
pressure air compressor, and finally by means of a high-
pressure plunger pump, which forced water instead of
air into the grout tank. Pressures were reached in this
way up to 1,0001b. per square inch.

In driving or sinking through rock containing a large
number of seams carrying small quantities of water it is
not practicable to stop and grout each seam as described
above. In this case it is advisable to increase the section