Experimental investigation on the macro-mechanical behavior and micromechanical damage model of Xiyu conglomerate with pores and inclusions under triaxial compression

The complex and special mechanical properties of Xiyu conglomerate are of great significance to the construction of water conservancy and hydropower engineering. The crack characteristic stress, dilatancy behavior, and failure mechanism of Xiyu conglomerate collected from Momoke Water Control Project, southwestern China, were analyzed and discussed based on the experimental results of triaxial compression test and 3D X-ray computed tomography test. The results show that with increasing confining pressure, the deformation characteristics and all characteristic stresses increase monotonically, while the dilation angle and dilatancy index decrease, and exponential function model can accurately describe the evolution rule of dilatancy index with confining pressure. While the porosity is negatively correlated with confining pressure. The failure modes of Xiyu conglomerate include axial tensile cracks, shear cracks, local cross cracks and cracks around gravel. With increasing confining pressure, the failure modes transform from tension cracks to shear cracks. A non-associated micromechanical damage model considering pressure dependent matrix presenting tension-compression asymmetry is proposed and applied to Xiyu conglomerate with pores and a large number of gravels. By comparing numerical calculations and experimental results, the proposed micromechanical plastic damage model is able to describe the mechanical behavior of Xiyu conglomerate.