Finite Element Simulation Method And Engineering Application Of The Brittle Plastic Deformation And Failure Of Group Jointed Rock Mass

When the jointed rock mass is destroyed,the rock mass and joints will exhibit the characteristics of strain softening or brittle plasticity.Studying the finite element simulation method of jointed rock mass and correctly analyzing the deformation and damage situation and safety of the rock mass structural engineering are urgently needed in the project.Based on the analysis of surrounding rock stability of the underground powerhouse caverns of the Kabangbo Hydropower Project in Zambia,this paper studies the finite element simulation of the deformation and failure of group jointed rock masses,considers the brittle plastic failure effect of rock mass and joint,and establishes the elastoplastic constitutive model of the jointed rock mass deformation failure,and the realizes it`s finite element simulation.This model can correctly reflect the characteristics and state of group jointed rock mass deformation and failure.It can be widely used in deformation and failure analysis of jointed rock mass structure engineering.The main contents and results of this paper are as follows:(1)Analysis of numerical solution methods for the deformation and failure of rock mass and jointAnalyze the yield criterion and its characteristics used in numerical calculation of rock mass and joints.The implicit constitutive integral algorithm is used to discuss the elastoplastic stress correction method after rock mass and joint yielding respectively.Based on the brittle plasticity theory,the calculation method of stress drop in brittle failure of the joint and rock mass are discussed separately.(2)Studying on the constitutive model of brittle plastic deformation and failure of group jointed rock massConsidering the brittle plastic deformation and failure of rock mass and joint,combined with engineering practice and experimental results,the three basic failure modes of equivalent continuous jointed rock mass are studied.The mechanical properties of jointed rock mass under different failure modes are analyzed,and corresponding treatment methods of numerical calculations are proposed.The brittle-plastic deformation failure process of jointed rock mass is analyzed,and the elastoplastic incremental constitutive model corresponding to the process is established to determine the elastoplastic stress correction method of jointed rock mass.(3)Finite element simulation studying on the brittle plastic deformation failure of group jointed rock massBased on the constructed constitutive model of jointed rock mass,the UMAT calculation subroutine is programmed by the secondary development function of finite element software ABAQUS to realize the finite element simulation of the brittle plastic deformation and failure of jointed rock mass.The numerical simulation test results and the physical test results of the jointed rock mass specimens were compared and analyzed to verify the correctness of the constructed constitutive model.The model is applied to the numerical simulation of the hydraulic tunnel excavation project.It is proved that compared with the ideal plastic jointed rock mass model,the model constructed in this paper can correctly reflect the deformation and failure of the jointed rock mass.(4)Engineering application studyingApplying the constructed rock mass model to the rock mass in the underground powerhouse of Kabangbo Hydropower Station in Zambia,according to the joint connectivity rate provided by the engineering data,firstly take 20% joint connectivity rate to carry out the finite element simulation calculation of the excavation support of the powerhouse.The result is used to analyze the deformation and failure of the surrounding rock and the yield and stress of the anchor,and evaluate the stability of the surrounding rock.Then,the surrounding rock stability analysis and calculation are carried out for the 40% joint connectivity condition,and the calculation results of the two working conditions are compared and analyzed to evaluate the influence of the change of joint connectivity rate on the stability of surrounding rock.And the optimization recommendations for the spray anchor support program are provided.