Improved micro-elastoplastic constitutive model based on peridynamics and its numerical verification

This study proposes an improved micro-elastoplastic (IME) constitutive model within the bond-based peridynamic framework to tackle the challenges in characterizing the nonlinear mechanical behavior and fracture patterns of rock materials. Firstly, a statistical damage model based on the Weibull distribution was integrated to simulate the spatial distribution of natural microcracks. Moreover, a dual-parameter bond stiffness formulation was introduced to overcome the inherent limitation of the fixed Poisson’s ratio in conventional bond-based peridynamics. The validity and robustness of the proposed IME model were subsequently demonstrated through three representative numerical simulations: uniaxial compression of intact sandstone, cyclic loading–unloading of marble, and uniaxial compression of pre-fissured sandstone. The results show that the IME model can accurately reproduce the complete stress–strain responses of sandstone under uniaxial compression, including the elastic stage, strain hardening, and post-peak softening, while also capturing the characteristic hysteresis effect during cyclic loading and unloading of marble. Furthermore, the model effectively describes damage distribution in fractured rock under uniaxial compression and highlights the significant influence of fissure angle on peak strength. The simulation outcomes exhibit strong agreement with experimental results in terms of stress–strain relationships, crack propagation paths, and final failure patterns. Overall, the proposed IME model provides a solid theoretical framework and a reliable numerical tool for simulating the multi-scale mechanical behavior of rock materials.