Time-Dependent Damage to the Surrounding Rock in Underground Chambers Considering Stress Release

In the construction of underground chambers, damage to the surrounding rock will cause a series of potential safety hazards. To investigate the damage behavior of the chamber from the beginning of the original stress redistribution to achieve the final stable state, an elastoplastic double-scalar damage model defines damage in terms of elastic and shear moduli using continuum thermodynamics and describes the rock damage evolution with time under different stress release conditions based on the Drucker–Prager yielding criterion and energy evolution mechanisms. A numerical simulation of a deeply buried circular chamber, with a lateral pressure coefficient of λ, was carried out to quantify the dynamic stress adjustment process, and a time variable was introduced to analyze the damage evolution and elastic constants from the kinetic to potential energy conversion relationship of the releasable elastic strain energy. The simulation results reveal two distinct types of damage: triangular damage at the top and bottom of the chamber, which is the initial stage of destruction, and flanking ear damage at the shoulder of the chamber, caused by compression and shear forces, which extends from the center to the deeper part of the formation. Accumulation of plastic strains is identified as the primary driver of the damage, and one of the key reasons for the radiating expansion of shoulder damage is the high shear stresses. The model describes the damage from both mechanical and energy evolution perspectives and can be combined with the elastic wave detection technology to obtain the temporal pattern of surrounding rock damage development by inversion of elastic constants.