Stability of Steep Slopes on Hard Unweathered Rock

Synopsis This Paper contains a discussion of the factors which determine the degree of stability of steep slopes on hard unweathered rock. These factors include the angle of shearing resistance of the jointed rock, the effective cohesion, and the seepage pressures exerted by the water percolating through the joints of the rock. The Paper also deals with concealed sources of instability which may exist beneath slopes in deep valleys located between high mountains. The angle of shearing resistance can be estimated on the basis of the results of a joint survey. The effective cohesion cannot be determined by any of the presently available procedures of rock exploration, but its influence on the stability of slopes on jointed rock is commonly much less important than that of the angle of shearing resistance. The most unpredictable factor determining slope stability is the hydrostatic pressure in the water flowing out of a reservoir or a leaking pressure tunnel through the joints towards a slope, because this p...