Abstract
The hydraulic efficiency of a double-wall cutoff built through 126 m (420 ft) of pervious alluvial deposit filling a V-shaped canyon and under a 107 m (350 ft) high earthfill dam is discussed. The cutoff walls are made up of cast-in-place concrete interlocking piles and panels and are intended primarily to minimize the danger of piping, by controlling the pore pressures in the downstream zone of the dam. The behaviour of the cutoff, monitored by a comprehensive instrumentation program, indicated after [Formula: see text] years a relatively high hydraulic efficiency (over 92%). During this period the cutoff has exhibited a very slight decrease in its efficiency (less than 1%), probably due to leaching of the grout at the rock-wall contact in the grout curtain, and probably also due to some removal of the bentonite from between the piles and panels. The analysis of the efficiency of each wall considered individually (using Casagrande's latest recommendation) indicates a lower efficiency for the upstream wall as compared to that of the downstream wall, probably because of the migration of bentonite particles downstream under the hydraulic gradient. The double-wall cutoff exhibits an efficiency about 18–30% higher than that for a similar single-wall cutoff.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
