Civil Engineering Reference
In-Depth Information
Method
Soils suitable for treatment
Uses
Comments
Sump pumping
Clean gravels and coarse sands
Open shallow excavations
Simplest pumping equipment. Fines easily removed
from the ground. Encourages instability of forma-
tion. See Fig. 12.4
Well-point system with
Sandy gravels down to fine sands
Open excavations including
Quick and easy to install in suitable soils. Suction
suction pump
(with proper control can also be
utility trench excavations
lift limited to about 18 ft (5.5 m). If greater lift
used in silty sands)
needed, multistage installation is necessary. See
Fig. 12.3
Deep wells with electric
Gravels to silty fine sands, and water-
Deep excavation in, through,
No limitation on depth of drawdown. Wells can
submersible pumps
bearing rocks
or above water-bearing
be designed to draw water from several layers
formations
throughout its depth. Wells can be sited clear of
working area
Jetting system
Sands, silty sand, and sandy silts
Deep excavations in confined
Jetting system uses high-pressure water to create
space where multistage well
vacuum as well as to lift the water. No limitation
points cannot be used
on depth of drawdown
Sheet piling cutoff wall
All types of soil (except boulder beds)
Practically unrestricted use
Tongue-and-groove wood sheeting utilized for
shallow excavations in soft and medium soils.
Steel sheet piling for other cases. Well-understood
method and can be rapidly installed. Steel sheet
piling can be incorporated into permanent works
or recovered. Interlock leakage can be reduced by
filling interlock with bentonite, cement, grout, or
similar materials
Slurry trench cutoff wall
Silts, sands, gravels, and cobbles
Practically unrestricted use;
Rapidly installed. Can be keyed into impermeable
extensive curtain walls
strata such as clays or soft shales. May be imprac-
around open excavations
tical to key into hard or irregular bedrock surfaces,
or into open gravels
