Unsteady Creep Damage Model of Rock Considering Acid Solution Corrosion

This study investigates the triaxial creep mechanical behavior of Carboniferous surrounding rock under acidic solution corrosion with different pH values and establishes a novel viscoelastoplastic creep damage constitutive model considering pH-time coupling effects. Experimental results quantitatively indicate that acid corrosion significantly weakens the long-term bearing capacity of the rock. With the solution pH decreasing from 7 to 4, the peak bearing stress of rock declines from 50 to 30 MPa, representing a 40% reduction in the long-term bearing strength. Meanwhile, the maximum creep strain increases by 62.4%, and the steady-state creep rate rises obviously, accompanied by an earlier occurrence of accelerated creep. The experimental data fully validate the proposed model with all fitting correlation coefficients higher than 0.94. The theoretical curves precisely reproduce the full creep stages including instantaneous elastic deformation, decelerating creep, steady-state creep, and accelerated creep, which demonstrate that the established model can accurately characterize the time-dependent deformation and damage evolution of corroded rock. This model provides a reliable theoretical basis for the long-term stability evaluation of deep underground engineering under water-chemical coupling conditions.