Investigating the shear strength of infilled rock discontinuity replicas

Abstract

Understanding shear strength of discontinuities is essential when assessing the stability of excavations or slopes in fractured rock masses. Challenges are seen in Malta where clay-filled joints are present in fractured limestone formations. This study investigates the shear strength of infilled rock discontinuities by replicating these joints in a controlled laboratory setup. The focus is placed on the effect of Blue Clay, used as the infill material, on the mechanical behaviour of the joint. To isolate the influence of clay infill thickness, the study uses 3d printed moulds which were used to cast plaster specimens of consistent geometry. Test were conducted on specimens with different thicknesses. Results indicate that infill thickness significantly influences shear strength. The smallest clay volume (1mm) retained asperity interlock, leading to higher peak shear stress. In contrast, shearing the clay alone showed the lowest strength. These findings demonstrate how geometry and infill material affect shear response, and the relevance of infill thickness in predicting failure mechanisms in real life scenarios.