Control of Internal Erosion and Piezometric Pressure in the Rock Foundation of Revelstoke Dam

The Revelstoke Project is located on the Columbia River in southeastern British Columbia. The main dam of this project is a 166 m high gravity dam which extends across the river gorge (Figure 1). The dam is founded on metamorphic rock of the Monashee Complex which has shears and jointed, crushed zones that are susceptible to internal erosion. Seepage through the foundation erodes the fine material from these features and transports the fines to the drains. If the migration of fines is not controlled the seepage flows could increase to excessive levels and higher pressures could result. However, when filters are installed in the foundation drains to limit the fines migration, these filters become clogged by fines and this has led to high piezometric pressures in the foundation. Since the reservoir was filled in 1983, there have been repeated remedial programs to control the internal erosion and piezometric pressures in the foundation. Cont.