Effects of Soil Suction on Triaxial Shear Tests of Clay.

摘要

Construction of the Grand Coulee Third Powerplant required considerable alteration of existing slopes on the right (east) bank of the Columbia River just downstream from the original concrete dam. Overburden soils in this area are in the Nespelem formation; and the clay strata of this formation are preconsolidated, varved, and relatively dense. The clay strata are overlain and underlain by sand and gravel and also contain lenses of sand and gravel. Changing pore-water pressure in the clays was the source of slope instability, with the most recent extensive slope instability following high flooding in 1948. At that time, stability was restored by drilling drainage wells and placing riprap on a large area at the toe of the slope near the river's edge. An additional problem anticipated from construction of the third powerplant was the expected fluctuation of the river level, which was scheduled to be as much as 20 feet (6.1 m) during power generation operations.