Abstract
It is highly significant to theoretically assess the effect, under load, of initial stress and structure on the mass damage of rock mass. In this reported study, first a multi-factor coupling damage constitutive model under the action of joint-load was established by fully considering the non-uniformity, anisotropy and initial structure of a rock mass based on the Weibull distribution and D-P criterion. The relationship between the damage evolution and joint angle in the rock mass was elaborated. Then, a jointed rock mass strength criterion was built in line with the D–P criterion and the limit state of rock mass failure by the method of multivariate function total differential as based on the constitutive model. The results showed that the established constitutive model was in good agreement with the test results, which accurately reflected the damage characteristics of jointed rock mass during the entire loading process. The initial damage value of the rock mass increased with increasing joint dip angles, and the damage evolution of the jointed rock mass could be divided into the initial, stable, accelerated and failure damage stages. Comparing the results of this approach with other methods it was found that the strength criterion better reflected the effects of minimum principal stress σ3, volume stress σm, shear stress J21/2 and joint dip angle β on rock mass strength than other existing strength criteria, which showed that the proposed method offered important guiding principles for the engineering practice.
Highlights
It is highly significant to theoretically assess the effect, under load, of initial stress and structure on the mass damage of rock mass
Equation (35) is the strength criterion of rock mass we established considering the effect of joint dip angle based on D–P criterion and constitutive model combining with the extreme value condition at the peak point of the stress–strain curve, which can reflect the relation between the internal stress parameters under the ultimate state of rock mass with different joint dip angles
A constitutive model considering the effect of joint dip angle was established based on the Weibull distribution and D–P criterion, this represents the first attempt to model the effect of joints on rock mass damage under load
Summary
Dβ Joints damaged variable Ds Load damage variable Dt Total damage variable I1* First invariant of effective stress tensor J2* Second invariant of effective stress deviation I1 First invariant of nominal stress tensor a D–P criterion parameter εc Peak strain F1⁎ Axial distribution variable σ1 Nominal axial stress ε1 Nominal axial strain σ1* Effective stress σ2* Effective stress σ3* Effective stress β Joint dip angle. A joint-load multi-factor coupling damage constitutive model under the three-dimensional stress state was established based on the continuous distribution function of Weibull distribution and D–P criterion These were combined with the geometric conditions at the peak point of the stress–strain curve to describe the random damage process of rock mass under load by fully considering the influence of inhomogeneity, anisotropy and initial structure damage (joint) on the strength of rock mass. Previous research results[32,33] were used to analyze the influence of model parameters on the mechanical properties of rock mass with the joint angle of 15° and confining pressure of 3 MPa. Figure 3 shows the influence of m and F0 on the σ1–ε1 curve of rock mass according to Eqs.
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