Study on the influence of non-homogeneous pore morphology on the extension path and mechanical properties of sandstone fractures

Abstract

Sandstones in karst regions often form multi-scale non-homogeneous pores of different sizes and shapes due to dissolution, and their morphological differences lead to the complexity of fissure expansion paths, which affects the mechanical properties of the rock body. However, the quantitative relationship between pore geometries and fissure dynamics and strength deterioration is not clear, which limits accurate prediction of the stability of the rock body in karst regions. Therefore, in this study, the effects of different pore morphologies on the extension paths and mechanical properties of sandstone fractures were analyzed by theoretical analysis, uniaxial compression test, discrete element numerical simulation and CT scanning. The experimental results show that the crack initiation position of the circular hole specimen is located in the diagonal quadrant, the crack initiation position of the square hole specimen is located in the left tip position, and the crack initiation position of the triangular hole specimen is located in the midpoint of the bottom edge and the right tip position. When the defect morphology is constant, increasing size has a deteriorating response on rock mechanical properties; whereas under equal-size defect conditions, squares trigger the greatest loss of strength, followed by circles, and triangular defects exhibit optimal strength retention properties. With the increase of hole size, the volume of the plastic zone shows an increasing trend, under the same size conditions, the development of the plastic zone of the rock expanding then round > triangle > square. The research results can provide theoretical references for rock stability assessment and disaster prevention and control in karst areas.