Mechanical damage constitutive model of geotechnical materials subject to confining pressure

Modeling the full deformation response of geotechnical materials under loading is crucial in engineering practice because this response is complex. A mechanical constitutive model can provide a theoretical basis for deformation calculations in geotechnical engineering. Existing models cannot capture the entire response, creating an urgent need for suitable predictive models. First, a new method for calculating the strain difference curve was introduced to examine the simulation of initial compaction stage. Damage mechanics and Weibull distribution theories were adopted to develop a novel constitutive model for the entire deformation process. The model was validated and discussed using triaxial compression test results for rock-like materials, aggregate concrete, and rock material. The relative error coefficient method was used to quantify the agreement between the theoretical and experimental curves. The error correlation coefficients exceeded 0.970 for all material types, verifying the applicability of the new model, which reproduced the experimental response more accurately than existing models. Linear regression provided a good representation of plastic softening. The physical significance of model parameters η and β corresponded to the strength and deformation characteristics in geotechnical engineering, respectively. Increasing η and β produced pronounced changes in the peak strength and post-peak stress-strain response, respectively, across the different material types. These findings provide a theoretical basis for deformation calculations during the construction and operation of geotechnical engineering projects.