Hoek-Brown Elastoplastic Damage Multi-Field Coupling Model And Algorithm Of Rock And Its Engineering Application

With the increase of the construction scale of rock mass engineering,various engineering safety problems are becoming more and more prominent.Rock mass engineering has the characteristics of elastoplastic,timeliness,multi-field coupling,anisotropy,etc.And it is affected by complex factors such as construction disturbance,freeze-thaw and so on.In the stability evaluation,the traditional ideal elastoplastic model and general elastoplastic damage model could not reflect the above problems accurately,which leads to a large deviation between the calculated results and the actual.It is of great scientific and engineering value to study the rock damage constitutive model and algorithm which can reflect the characteristics of the above complicated factors.Therefore,the Hoek-Brown(H-B)elastoplastic multi-factor damage coupling model is established in this paper based on rock elastoplastic theory,continuous damage mechanics,rock seepage theory and finite element algorithm.The model could take into account the complex factors of rock mass characteristics and engineering influence.In particular,the Hydraulic-mechanical-damage(HMD)coupling model of rock based on H-B elastoplastic criterion is established.The corresponding solving algorithm was established and the solving program is written.The preliminary engineering application is carried out.Specifically,the main research work is as follows:(1)In order to overcome the problem that the general elastoplastic damage model could not reflect the influence of rock mass structure,rock strength,stress state and the nonlinear failure characteristics,the elastoplastic damage constitutive model of rock mass based on the H-B yield criterion was established.The model could consider the damage caused by the coupling effect of stiffness degradation and the plastic flow.Meanwhile,the modified principle of effective stress is introduced to consider the effect of pore water pressure.And the damage variable evolution equation is given.Aiming at the singularity problem in the numerical solution process of the model,a completely implicit return mapping algorithm for elastoplastic damage model is derived from the principal stress space.Fortran language is used to write the numerical algorithm of the model.The accuracy of the model and the robustness of the numerical solution process are verified by laboratory single and triaxial compression tests.The model is used to analyze the excavation stability of submarine shield tunneling,and the influence of pore water on excavation damage and displacement of surrounding rock is revealed.The influence of different support pressures on excavation disturbance is compared,and reasonable construction suggestions are put forward according to the simulation results.(2)Aiming at the disturbance damage of rock mass caused by cyclic freeze-thaw or cyclic blasting during construction and the inherent fatigue mechanism,the evolution equation of fatigue damage variable was derived based on the rock fatigue damage theory.The disturbance damage is coupled with H-B elastoplastic damage.The H-B elastoplastic fatigue damage coupling model is established,and the numerical algorithm of the model is given.The model is applied to load-freeze thaw damage coupling problem and load-blasting disturbance damage coupling problem respectively.And the relevant verification and engineering application are carried out.The parameters of the evolution equation of fatigue damage variable are determined through the indoor uniaxial compression test of freeze-thaw rock and the acoustic test of tunnel blasting site.The good verification and engineering application results are obtained,which shows the rationality of the model.(3)In order to reveal the long-term stability evolution mechanism of rock mass engineering,a microscopic H-B elastoplastic damage model is established which can reflect the time effect.First,the Weibull distribution was used to express the probability of the microscopic unit parameters of H-B damage model.Then,the evolution formula of long-term strength is introduced to describe the change rule of rock mechanical parameters with time.The fatigue damage variables mentioned above are introduced to establish the relevant solving algorithm.Finally,the numerical simulation of the long-term stability of a slope engineering is carried out by using the model,and the aging deformation characteristics of the rock slope with different degrees of non-uniformity and different freeze-thaw times are analyzed.Based on the calculation results,reasonable construction suggestions are put forward.(4)Aiming at the problem of multi-field coupling of HMD in the process of rock loading,the seepage characteristics tests of quartz sandstone in the process of full stress-strain are carried out by using the transient permeability test method with the help of the multi-function RLW-2000 rock triaxial instrument.Secondly,based on the experimental results,an isotropic H-B elastoplastic HMD coupling model for rock is proposed by introducing the evolution equation of permeability coefficient.And the corresponding numerical solution algorithm is given.Finally,the model was applied to the stability analysis of cross-sea karst tunnel and high side wall of railway station of Dalian subway.The simulation results verified the reasonability and engineering applicability of the HMD coupling model,and provided a theoretical basis for the design of construction parameters of the project.(5)In order to reflect the influence of rock anisotropy on HMD coupling fields,a H-B elastoplastic damage constitutive model for anisotropic rock was established based on the elastic constitutive theory of layered rock and Pietruszczak microstructure tensor theory.On this basis,the evolution equation of the permeability coefficient of anisotropic rock is introduced,and the H-B elastoplastic HMD coupling model of anisotropic rock is established,and the numerical solution algorithm of the model is given.The accuracy of the model in strength prediction is verified by indoor bedding slates compression test,and the influence of anisotropic parameters on rock strength is analyzed.Finally,the model is applied to a tunnel project with small clear distance,and the effects of bedding angle on the damage zone,displacement field,stress field and pore water pressure distribution of surrounding rock are compared,which provides a theoretical basis for the safety design of similar projects.