Investigation into the Influence of Stress Conditions on the Permeability Characteristics of Weakly Cemented Sandstone

This study, conducted in the geological context of the Yixin coalfield, systematically performed indoor mechanical tests to analyze the impact of different stress conditions on the permeability of weakly cemented sandstone. The results were used to establish numerical simulations of permeability curves, revealing the following key findings. (1) After saturation, weakly cemented sandstone transitions from brittle to plastic failure. Numerical simulations closely matched experimental results, ensuring the accuracy of subsequent permeability simulations using the Hoek-Brown method. (2) Indoor permeability experiments identified a unique "root" shaped permeability curve for weakly cemented sandstone, differing from traditional sandstone. Numerical simulations confirmed this pattern and provided a basis for modeling weakly cemented strata under varying confining pressures. (3) The mesoscopic analysis of numerical simulation shows that that confining pressure limits the expansion of microcracks, while pore pressure causes cracks to develop from high- to low-pressure areas. Increasing pore pressure gradually raises permeability, and elevated confining pressure initially reduces, then increases permeability. (4) A damage parameter "D" was introduced to monitor fractures during compression simulations, showing that with increasing confining pressure, the damage parameter decreases and then sharply increases. Hydraulic pressure differentials directly correlated with the damage. This comprehensive study enhances our understanding of weakly cemented sandstone's hydrological behavior under varying stress conditions and parameters.