| With the rapid development of economic construction and urbanization, the demand for all kinds of resources is increasing, the scope of the underground construction and infrastructure is widening, and more and more mixed ground engineering projects are encountered in the construction of TBM. As a means of the construction of the high degree of automation, the TBM construction method in mixed ground, compared with traditional rock burst construction method, still has a high economic security and many other advantages. However, many problems appeared in the construction of mixed ground shows that TBM construction method in mixed ground is not ripe. At present, most of the research and study on rock cutting mechanism is aimed at homogeneous strata, and it is not enough to understand the mechanism of rock breaking mechanism in composite strata, which is an important bottleneck to limit the development of the method. In this paper, based on discrete element software, the rock cutting mechanism of TBM disc in compound formation is studied. The main research contents are as follows:(1) by consulting a large number of literature, the domestic and foreign scholars on the disc cutter rock breaking theory research means, methods and theoretical results were summarized. Based on discrete element method, three dimensional numerical model of rock breaking is established, and the fracture process of rock under the action of single disc cutter and double disc cutter is simulated, and the feasibility and rationality of the numerical simulation is verified.(2) to simulate the cutter breaking process of rock in homogeneous strata under different geological parameters by double disc cutters,and studied the influence of the different parameter of joints, confining pressure and rock mass strength on rock breaking model by the disc cutter, crack model and the rock breaking efficiency and optimal cutter spacing effect. The results show that: joint parameters will influence the rock mass fragmentation pattern and joint attract cracks to internal development, blocking the crack piercing through a joint surface.In the range of 30 degree to 60 degree, the lateral crack is difficult to meet. With different joint parameters, according to the combination of joint angle and joint spacing,optimal cutter spacing exists. Confining pressure and rock strength have little influence on rock breaking mode, but it will affect the crack developing direction and the ability of crack propagation. The greater the confining pressure and the rock mass strength, the lower the rock breaking efficiency in term of energy consumption.(3) to simulate the mixed ground in different geological parameters of double disc cutter breaking process of rock and studied different parameters of joint, confining pressure and strength of rock mass with mixed ground disc cutter stress, crack development, crushing mode and the efficiency of rock breaking. Results show:the existence of an asymmetric breaking in mixed ground, the rock cutting efficiency in hard rock is lower than that of soft rock, as well as soft rock breaking volume, which is easy to "void",resulting to eccentric wearing. The joint parameter has great influence on the rock breaking mode, and the joints inclined to soft rock with high cutting efficiency. Confining pressure has little effect on the rock breaking mode, and the influence of the crack is the same as that of the homogeneous ground, and the hard rock is affected more obviously. Joint spacing and confining pressure are smaller, and the optimal cutter spacing of the composite strata tends to be consistent.The innovation of this paper mainly has the following several points: the three-dimensional model of the cutter broken rock is established by using the discrete element method, Interaction mechanism of double disc cutters under the different geological factors were in-depth analysis, Rock rupture characteristics by double disc cutters in mixed ground have been studied. |
