The Pacific commercial advertiser. [volume] (Honolulu, Hawaiian Islands) 1885-1921, 1899-03-23
The Work Of Blasting Rock Be-
meath The Water.
GREAT VALUE OF DYNAMITE
He'll Gate EnterprIse-A Reef Tha.
was Moved-Just How X .lihi
May be Reached.

Extensive rock blasting under
water was first made possible by the
invention OF dynamite. y great scns,-
ton was caused in 1S69-lS7G by the
work done by Gen. Newton in re.nov-
ing the reef of rocks a. Hell Gaze In
The East River. which connects Ne1v
York HarbOr with Long Island Sound
This reef consisted OF 4 mass OF rock
about 1868 feet long. 9Si feet wide. and
was covered by an average OF 6 feet to
8 feet Of water, which was to be deem
ened to about % feet The rock was
honeycombed by about 1855 feet of
radial and 5S39 feet OF concentric GAL
leries, which varied in width from Il
feet to Il fee, and were about II feet
3 inches high. The average thickness
OF the roof left was . feet. 1t took sew
en- years to blast out these galleries. AZ
first the work was done by hand. bu,
later by steam-driven machines. In this
way 1914 cubic yards of stone were
detached and carried out. while the
mass left in the pillars and roof
amounted TO about 1926 cubic yards.
which was blasted away on the 9th OF
September. 1876. by means OF 1000
mines that We're exploded simultan-
eously by electricity. Before blasting
the galleries were filled with water
The vibration caused by the
explosion was perccptible in the
water only for distance of
about 1910 feet. but the water
was thrown to a height OF about -
feet and the mass of water thrown up
was about 295 feet in diameter.
Where an isolated block OF stone
under water is to be removed. Il Is
broken to pieces by means OF dynamite
cartridges and the debris Is raised by
divers or by using grippers. In Ger
tain cases rock has been surrounded
by a wall of piles or beton and then re-
moved dry. Rock is sometimes de-
stroyed withou; previous drilling by
simply placing dynamite cartridges on
IL. In such cases the rock Is broken in
away by the current or are raised by
dredges. Since the introductioU OF
bucket chain dredges these have been
used not only for the removal OF brok-
en- pieces, but also for removing hard
rock that is formed in nearly hor,zont-
al strata (even when the some is II
inches thick alternating with strata
of soft material. In this way the banks
of limestone alternating with strata OF
clay were removed from the harbur %
Boulogne-sur-Mer.
Sometimes rocks are broken up by
heavy rams provided with iron points
or by machine-operated Chisels. The
latter method was used in the cons; rue
ton of the SueZ Canal and also in the
work on the cataractS OF the Danube.
where three apparatus OF this kind
were used. Such an apparatus con-
sists of 4 large. heavy iron chissl.
which, with the necessary machinery.
! is placed in the center OF a boat built
| specially for II. The machinery may
be divided into two essential parts. the
| tripod frame on which the chisel is
| raised to the water level by means OF
! lifting devices and the arrangements
for moving the host forward. back
ward, or sidewise. The operation l.
very simple. The boat is anchored by
one chain from the bow. four from the
sides and one from the stern. and after
the rock has been destroyed for n dis
lance CT about half n yard. the boat Is
moved forward a corresponding dis
lance by pulling on the chain NJ the
bow, and then work is begun anew.
The debris Is removed by means 81
! dredgers.
During the operations on The Danube
IN 1893, $3.50 cubic yards OF stone
! We're loosened by $4,000 blows % the
chisels in 52l working days. Each ap-
paratus destroyed SIS cubic yards per
( day. or 0.05 cubic yard at each blow.
( Besides these apparatus seven floating
+, drilling machines were employed iu
/ breaking the rock in the Danube. such
as had already been tested on the
| Rhine. and later in blasting ont a
canal 10 feet : inches deep in the =.
/ Lawrence River near Montreal In
order TO hold a boat in the rapid cur
rent OF the river II is supported ~ four
movable pillars. the ends OF which are
pressed firmly into the bed Of the river
so that the boa. itself is raised some
/ what from the water. The process q
+ rs follows: After a boat is IN place
and the chains have l0eu stretched che