The fundamental objective in designing most slopes is to achievethe steepest slope possible consistent with knowledge of material properties, site constraints, external loads, required safety factors, and so on. Most traditional design methods for slopes in jointed media involve two-dimensional limit equilibrium analyses. All limit equilibrium analyses are restricted to predefined failure modes and assume that failure occurs along the failure surface according to a perfectly plastic shear force law (i.E, shear force is independent ofdisplacement). Such approaches may yield reasonable results for situations in which the failure mode is readily identifiable and involves only translation or rotation. However, for more complicated problems or problems in which displacement estimates are important, limitequilibrium methods may not be appropriate. For example, in analysis of slopes composed of distinct rock blocks, analysis based on the distinct element method may be more appropriate. The results of several slope stability analyses are presented, including one actual problem in which limit analysis falsely predicts stable equilibrium anda distinct element kinematic analysis correctly predicts instability. Such false predictions can arise from the assumption of an inappropriate failure mode in limit equilibrium analysis. The distinct element method was developed specifically to study the behavior of jointed rock. Failure modes are not prescribed using this method but evolve naturally as the solution progresses. The method models a rock mass as an assemblage of blocks, not as an equivalent continuum. Discontinuities are regarded as distinct interactions between blocks with joint behavior prescribed for these interactions. A description ofthe fundamentals of the distinct element method relevant to slope stability analysis is included. Extensions of the method that allow practically meaningful problems to be addressed are also described. All of the features are described through illustrative examples. Thispaper appears in transportation research record no. 1330, Behavior of jointed rock masses and reinforced soil structures 1991
Samenvatting