A Numerical Study for Geomaterials Shear Strength Components Using Discrete Element Models

Geomaterials (ranging from clay to gravel) are usually composed of individual particles that have specific engineering properties. Those particles once packed to a certain density, exhibit a distinguished macromechanical behavior, which is a result of their micromechanical interactions at the contact levels. Soil masses are usually subjected to direct normal and indirect shear stresses; yet, they normally show shear type of failure as indicated by many researchers using experimental and numerical evidences. The shear strength concept of friction and cohesion is discussed in this paper. A Discrete Element Code (developed and owned by Caterpillar, Inc.) was used in this study to show that it is possible to drop the apparent cohesion portion and compensate for that with additional frictional resistance. Apparent cohesive bonds usually fail before mobilizing the fictional resistance and, therefore, we may not account on it to resist future stresses. The numerical simulations results for triaxial tests and excavation operations showed consistency regarding the proposed shear strength components. Triaxial simulations for fine-grained materials showed that it is possible for a numerical model to capture the stress–strain behavior if the cohesion component is dropped and, instead, additional frictional component is added to account for the dilation that many classical soil mechanics laws usually ignore. Likewise, excavation operations showed similar results using the same proposed theory. Some important observations regarding the apparent cohesion concept are discussed and shown in this paper