Experimental Study On Failure Mechanism And Stability Of Soft Surrounding Rock Of Deep Underground Cavern

Since entering the 21 st century,with the gradual development of underground engineering construction in China towards the direction of "long,large and deep",the scale,quantity and complexity of rock mass engineering have increased significantly,especially the geological disaster of large deformation of soft rock.By means of indoor similar model test and numerical simulation,this paper studies the deformation,failure evolution process,stress and strain variation law of cavern surrounding rock under different working conditions.The research content of this paper mainly includes the following aspects:(1)A similar material with iron sulfide sand and barite powder as aggregate,rosin and alcohol as cementitious material and mudstone as binder is studied.This type of material has the advantages of simple composition,short curing cycle and recyclable utilization of materials with the same ratio.On this basis,the proportioning test is carried out in combination with the principle of orthogonal test,the variation law and sensitive factors of various physical quantities of similar materials are deeply discussed,the optimal proportioning of similar materials is determined by fuzzy mathematical analysis method,and the quantitative relationship between material control factors and mechanical parameters is established based on multiple regression analysis,so as to provide reference and basis for the relevant research of similar material proportioning of mudstone.(2)The overload tests of the cavern under rough tunnel and different support conditions were carried out on a multi-functional model testing machine.During the test,the whole failure evolution process of the surrounding rock of the tunnel is recorded,and the displacement sensor is used to monitor the displacement of the tunnel wall with different buried depths,so as to determine the deformation characteristics and crack evolution characteristics of the tunnel under the condition of high stress;The pressure sensor and strain brick are embedded in the surrounding rock around the cavern for measurement,and the variation law of stress and strain field of surrounding rock with buried depth is analyzed.(3)Using the same boundary conditions as the model test,the numerical simulation of Maodong tunnel and overload under different support conditions is carried out.The plastic zone,stress field and displacement of surrounding rock mass are studied.The numerical calculation results are compared with the model test.The results show that the model test results are consistent with the numerical calculation.The influence of excavation loading steps on the test results is verified by numerical simulation.The results show that different test steps have an influence on the test results,but the influence is within an acceptable range.(4)Based on the M3 model,the numerical simulation method is used to explore the best support form of the surrounding rock of the cavern under the condition of high ground stress(simulated buried depth of 1800m).The results show that the support capacity of surrounding rock support system can be effectively improved by adjusting the spacing of steel arch frames and the anchorage range of anchor cables.