Extension of discontinuous deformation analysis and application in cohesive-frictional slope analysis

This paper extends the discontinuous deformation analysis (DDA) by using an additional evaluation of edge-to-edge contact, with the aim that it can be used to accurately model the failure behaviour of joints dominated by both cohesion and interface friction angle. The original DDA can deal well with the effects of interface friction angle. However, when cohesion exists, DDA results often show an inscrutable behaviour, i.e. a slope may be unstable even if the cohesion is much greater than the theoretical value required for its critical stability. After many detailed investigations and validations, joint contact treatment was found to be the key reason why the original DDA cannot simulate the cohesive material accurately, in which every edge-to-edge contact is treated as two vertex-to-edge contacts that may have different contact states associated with different cohesion treatments. In order to solve this problem, an additional contact type determination process for an edge-to-edge contact was added into the original computer code to avoid the unreasonable situation when two contact states exist in one joint. Several examples were performed to illustrate the accuracy of the modified code and a real landslide case was analysed by using the improved DDA to estimate the shear strength on the interface. Our results show that the improved DDA can simulate the failure of cohesive-frictional material accurately.

• Improve the DDA so that it can accurately simulate the failure of c–φ joint.
• Conservative results and unreasonable phenomena of the original DDA were presented.
• Edge-to-edge contact was used to judge the failure behaviour of joints.
• Calculated critical shear strengths were almost identical to the analytical ones.
• The improved DDA can be used to estimate the residual shear strength of landslides.