Investigation of the mechanical characteristics of limestone after high-temperature treatment and the T-M coupling constitutive model based on statistical damage

Thermal damage induces changes in the mechanical properties of rock, making it crucial to clarify the thermal damage characteristics of rock and describe the thermo-mechanical coupling behavior of thermally damaged rock. Limestone samples were heat-treated at 100–600 °C, followed by triaxial compression tests on the thermally damaged samples. Scanning electron microscopy (SEM) was used to observe their microscopic thermal damage characteristics. Based on the micro-element concept, a pore compaction coefficient was defined. Integrating the Hooke-Brown strength criterion and the micro-element cumulative damage parameter, a Weibull distribution-based thermo-mechanical coupling statistical damage constitutive model for limestone was established. The coefficient of determination (R 2 ) between the model-calculated results and the experimental stress-strain curves reached 0.98. Microscopically, high-temperature-induced rock damage is characterized by crack propagation and pore erosion. As temperature increases, the elastic modulus decreases nonlinearly, while the peak compressive strength first increases and then decreases. Under compressive loading, the total pore closure strain increases with the heat-treatment temperature. The proposed constitutive model effectively captures the nonlinear deformation characteristics during the initial compaction stage. • Below and above 100 °C, the peak strength of limestone increases first and then decreases. • Microscopic thermal damage of limestone is characterized by cracking and pore erosion. • Pore compaction coefficient can reflect the closure degree of pores under compression load. • Constitutive model can reflect the nonlinear deformation in initial compaction stage.