Prevention of slope failure during the construction of hydraulic-fill, fine sand structures on impermeable foundations

Abstract

1. The measures for preventing slope failure and organizing evacuation of the seepage water permitted constructing a hydraulic-fill dam having a compact section, close to the section of an earth-fill dam. 2. In hydraulic-fill dams and piles of fine sands with steep slopes, the initial fill must be constructed of gravel, in the form of gravel toes. 3. The construction of gravel toes, to serve as drainage zones during construction, or as strengthening masses for the slopes, is economically justified, since it permits increasing the intensity of the hydraulic-filling work, prevents swelling of the slopes, increases the coefficient of utilization of the equipment by reducing delays, and permits combining the hydraulic-filling operations with other construction work (slope protection, permanent drainage, etc.). 4. The specific cost of a drainage gravel toe is extremely low. The volume of gravel for each cubic meter of hydraulic fill is 0.01 m3. 5. At the downstream slope, the drainage gravel toes must be constructed in such a manner that in the future they may become a part of the permanent horizontal drainage; in this manner, their cost practically does not increase the over-all cost of the hydraulic fill. In such a case it is necessary to select carefully the drainage layers for the gravel toe.