Study On Rock Mass And Rock Burst Mechanism Of Deep Tunnel

The construction of a large underground tunnel is a necessary requirement for the future social development.At the same time,the high burial depth of the rock and the nature of the rockburst disaster to the underground engineering construction and safety has brought serious impact.In this paper,the mechanical properties of the granitic granite and the rockburst mechanism of the surrounding rock of the diversion tunnel are studied by means of indoor physical test and numerical simulation.This paper mainly analyzes the mechanical properties of rock,the influence of minimum confining pressure on rockburst,the influence of different lateral pressure coefficients and different excavation shapes on the rock burst,and provides some reference for practical engineering.The main contents and achievements are as follows:?1?The uniaxial compression test,the Brazilian splitting test and the conventional triaxial test were carried out on the standard samples of the Qirehataer gneiss granite.The mechanical behavior of rock is measured,and the rock burst tendency and brittleness characteristic are analyzed by combining failure modes and stress-strain curves.The linear relationship between mechanical properties and confining pressure is obtained.The results show that the measured rock has a large brittle hardness,tension and compression ratio and a higher rockburst tendency.?2?Combined with the sample parameters,failure phenomena and crack propagation in the physical experiment,the bonded constitutive model in PFC^2D is compared and analyzed.The more suitable Flat-Jointed model is used to carry out the parameter inversion and indoor rockburst test simulation.The parameters are retrieved from the three aspects of crack number,fracture mode and stress-strain curve,and the comparison of indoor test shows the reliability of the model.The results show that the confining pressure is more serious when the confining pressure is within a certain range,but the rockburst is more serious when the confining pressure is smaller or larger.?3?The simulation of the excavation of the caverns was carried out after the reduction of the meso-gravitational strength was carried out in combination with the actual situation of the project.The rockburst failure process of the different caverns under different excavation shapes and different lateral pressure coefficients was studied.This paper analyzes the development situation and types of crack initiation,the distribution of force chain and the displacement state of excavation.The results show that the lateral pressure coefficient has some influence on the stress redistribution after excavation,but the stress distribution area and the crack generation trend are similar under different lateral pressure coefficients.The circular cavern is more stable than the gates of the gates,but the construction process is more complicated.There are relatively weak areas in the junction of the side wall and the floor,but the excavation process is simple.