Simulation Of Creep Process Of Heterogeneous Rock Based On Viscoelastic-plastic Damage Coupling

The creep properties of the rock may cause underground engineering local damage then collapse during the long-term operation.In order to explore the creep mechanism of rock,this paper considering the viscoelastic-plastic damage coupling on the basis of elasto-viscoplastic theory of Perzyna,and the creep damage characteristics of rock under the influence of heterogeneity and initial crack of rock matrix materials are studied.Revealing the creep failure mechanism and mesoscopic evolution mechanism of heterogeneous rocks from mesoscopic.The main research work and results of this paper as follows:(1)On the basis of elasto-viscoplastic theory of Perzyna,A mesoscopic coupled elasto-viscoplastic damage model which can describing the whole creep process,is constructed by introducing a mesoscopic unit strength damage model based on strain energy theory,and considering the creep rate variation with time during rock creep.(2)The model established in this paper was verified by the experimental data and then applied to the numerical experiments of uniaxial and biaxial compression creep process under different axial stresses,confining pressures,homogeneity coefficients and macroscopic fracture angle.The results showed that,First,the increased axial stress can improve the creep rate,which reduces the creep failure time.Second,the increased confining pressure and homogeneity coefficient can reduce the creep rate and lead to the extend of creep failure time.Third,The increase of the macroscopic crack dip angle prolongs the time when the wing crack propagates to the boundary of the rock sample,indicating that the influence on the rock strength is decreasing.(3)A true triaxial Mogi-Coulomb yield criterion is introduced,and the true triaxial model was verified by the experimental data and then applied to the numerical experiments of true triaxial compression creep process under different maximum principal stress and intermediate principal stress.The results showed that,on one hand,the increased maximum principal stress can improve the creep rate,which reduces the creep failure time and increasing the damage area of rock.On the other hand,the increased intermediate principal stress can reduce the creep rate and lead to the extend of creep failure time and reduces the damage degree of rock.(4)The model is applied to simulate the creep failure process of tunnel surrounding rock under the influence of lateral pressure coefficient and homogeneity coefficient.The results showed that,on one hand,with the increase of the side pressure coefficient,the convergence displacement of the left and right side wall gradually increases,and the closing displacement between the top and bottom of the cave is reduce.The creep damage mode of the tunnel surrounding rock gradually transitions from the compression shear failure of the left and right side wall to tensile failure of the top and bottom of the cave.On the other hand,the homogeneity coefficient has little effect on the creep damage mode of tunnel surrounding rock.With the increase of the homogeneity coefficient,the convergence displacement of the left and right side wall and the closing displacement of the top and bottom of the cave are decreasing,but the damage time of tunnel surrounding rock is increasing.(5)The model is applied to numerically simulate the creep-induced rock burst failure process of coal-rock roadway.From the accumulation and release of elastic strain energy of coal mass angle better explains the mechanism of creep-induced rock burst.