An Improved Damage–Plasticity Constitutive Model Capturing Rock Softening Behavior Under Various Confining Pressures

With the gradual depletion of shallow high-grade mineral resources, global mining activities are shifting toward deeper regions with more complex geological conditions. Rocks exhibit significantly different mechanical responses under high confining pressure environments, posing new challenges to deep mining safety. To address this, this study proposes an optimized rock damage constitutive model that characterizes the influence of confining pressure on rock mechanical behavior, incorporating its peak strength enhancement effect and regulatory mechanism on post-peak softening behavior. The core innovation lies in establishing an inverse relationship between softening parameters and confining pressure, as confining pressure increases, softening parameters decrease. This inverse relationship enables the model to reasonably reflect the inhibitory effect of confining pressure on the rock softening process, meaning that under higher confining pressure, the material exhibits slower stress decay and more pronounced ductile characteristics. This model can consistently describe brittle responses under low confining pressure and ductile responses under high confining pressure. The findings provide reliable theoretical support for predicting rock mass failure and conducting stability analysis under deep mining conditions.