A design method coupling block theory and three-dimensional discontinuous deformation analysis (3D DDA) has been developed. In this paper, two field case histories involving rock slopes are used to test the method. The stability analysis of and stabilization design for rock slopes in two case histories are performed using the coupled method. The results are presented and compared with those from limit equilibrium analysis methods. For the first case history, the factors of safety from a limit equilibrium analysis that assumes a failure surface through the rock mass are larger than those given by the coupled method, which considers rock block failures only. Therefore, for the original slope, the block failure mechanism should control the design. However, the stabilization design should be satisfactory with respect to all failure mechanisms, and for the modified slope, the block failure mechanism may or may not remain the controlling mechanism. For the second case history, rock block failures are analyzed using both limit equilibrium-based block theory and the coupled method. Both methods give about the same factor of safety, with the factor of safety from block theory being slightly higher than that from the coupled method.
Block theory, developed by Goodman and Shi [1], has some limitations. The mode and stability analyses consider only sliding modes and some special rotational modes and cannot handle general modes of simultaneous sliding and rotation. Furthermore, they do not consider dynamic equilibrium. To overcome these limitations, block theory.s removability analysis is coupled with three-dimensional discontinuous deformation analysis (3D DDA) single block analysis. 3D DDA single block analysis is used to perform the mode and stability analyses, because DDA considers dynamic equilibrium and can handle general modes of failure including simultaneous sliding and rotation. In this way, the advantages of both block theory and DDA can be combined.
A design method coupling block theory and 3D DDA has been developed [2]. To test the computer program that carries out the required analyses, the coupled method has been applied to one case history involving a rock slope in the Three Gorges Reservoir area in China [2]. In this subsequent paper, the same case history is revisited to compare results obtained from the coupled method to results of conventional limit equilibrium analyses. As a part of the continuing effort to test and validate the coupled method, another case history involving some rock slopes in Macau, China, is presented in which results from the coupled method and limit equilibrium analyses are again compared.
