Statistical Damage Model for Whole Deformation and Failure Process of Rock Considering Initial Void Closure

In order to establish a constitutive model that can accurately simulate the whole deformation and failure process of rock, a deep analysis is made of the limitations of the existing statistical damage models incapable of well describing the initial nonlinear phase of rock deformation. Considering the deformation mechanism of rock comprehensively, the intact rock is abstracted as a material composed of rock skeleton and voids. Based on the analysis of the deformation relationships among the whole rock, rock skeleton and voids, the concept of rock void strain ratio K is proposed; the calculation methods of rock skeleton strain and voids strain are presented using triaxial test results to derive the evolution equation of K. By introducing the statistical damage theory, the rock is regarded as being composed of many micro elements whose strength obeys the distribution of Weibull function. Finally, a new constitutive model is established to describe the whole rock deformation process, and the determination methods of relevant model parameters are given. Compared with other model calculations and test results, this constitutive model can better simulate the five phases of the whole rock deformation and failure process under load, and the correlation coefficients are all larger than 0.92 for different confining test results. It also well explains the mechanical behavior characteristics that the larger the confining pressure, the shorter the initial void closure phase, and the larger the elastic modulus, peak strength and peak strain.