Environmental Engineering Reference
In-Depth Information
FIGURE 3.8
Sheet piles installation. (Reproduced with permission from Robertson GeoConsultants Inc.)
PRB (Figure 3.8) (Gavaskar 1999). Before driving the sheet into the subsurface
by a drop hammer or vibrating hammer, the sheet piles are connected at
their interlocking edges to form a cutoff wall. The installation of the sheet
pile is relatively easy and quick. The University of Waterloo, Canada, has pat-
ented a technique for sealing adjoining sheet piles by pouring grout into the
joints. The integrity of the sheet piles can be maintained to depths of about
15 m. Use of sheet piles generates much less soil than other methods and is
a very useful construction technique when the barrier has to be installed
where there are horizontal space limitations.
3.3.1.5 Slurry Wall
Slurry wall installation is generally used to construct the impermeable
funnel of the funnel-and-gate PRB. Soil/bentonite, cement/bentonite, and
composite slurry walls are most commonly used (Meggyes 2005), with soil/
bentonite being the most common (Figure 3.9). A slurry trench is gener-
ally excavated with a backhoe, a modified backhoe, or a clamshell digger,
depending on the required depth. Backhoes are used extensively in North
America for PRB installation whereas in Europe a hydraulic grasp and crane
is the most popular method. Appropriate slurry is placed in the trench to
maintain its stability. As the slurry permeates into the sides of the excavation
depending on the slurry used, a fully hydrated filter cake of bentonite or
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