| With the development of infrastructure construction in China,there are more and more construction scenes of tunnel engineering.As an advanced equipment of tunnel excavation,TBM needs to adapt to more complex engineering geological conditions,and the relevant parameters of cutter should also adapt to geological conditions.The spacing of cutter arrangement affects the crack propagation mode and rock breaking efficiency in rock mass.Therefore,it is of great theoretical and practical significance to study the optimization scheme of cutter spacing in jointed strata under different joint conditions for clarifying the rock breaking mechanism of jointed rock mass and the evolution law of rock breaking efficiency of cutter with geological conditions.In this paper,based on the shear rheometer,the cutter head and confining pressure loading die are designed independently.Combined with the subject of "Research on Macro-and Micro-breaking Mechanism and Rock-breaking Efficiency of Jointed Rock Mass under Cutter Action",the rock-breaking experiment of rock mass with different joint orientations and joint spacing is carried out by using the four-in-one method of "data investigation,laboratory test,numerical simulation and model prediction".Combined with digital image technology,the information such as strain field and displacement field of rock mass cracking is monitored,and the interaction mechanism between rock mass and cutter,the relationship between rock breaking efficiency and cutter spacing,and the optimization mode of cutter spacing are studied.Then,the failure process of rock mass with different cutter spacing and penetration depth is simulated by PFC 2D discrete element software,and the specific energy of crack propagation is predicted by simulation results and experimental data,which can be used as a reference for optimizing the efficiency of tunnel construction in jointed strata.The main research contents are as follows:(1)The rock mass with different joint orientations and joint spacing was prepared,and the vertical intrusion force and confining pressure were applied by the modified shear rheometer.The process of crack initiation-propagation-penetration and the evolution of strain displacement of rock mass were observed by DIC equipment,and the failure properties of cracks were counted.The rock mass failure forms and corresponding intrusion force curve characteristics under different cutter spacing and joint conditions were summarized.The influence of cutter spacing and joint conditions on rock breaking effect was analyzed,and the interaction between jointed rock mass and cutter was revealed.(2)The rock-breaking efficiency of cutter is discussed according to the fluctuation of invasion force of cutter,rock slag particle size,specific energy consumption and crack propagation specific energy,and the influence of cutter spacing,joint orientation and joint spacing on rock-breaking specific energy of cutter is analyzed.The influence of joint conditions on the optimal cutter spacing is studied,and the optimal cutter spacing under different joint conditions is determined by fitting method.(3)The failure process of rock mass under different cutter spacing and penetration depth is simulated by using the discrete element software PFC 2D,and the obtained crack propagation specific energy data is combined with the experimental data as a sample database.the multiple nonlinear regression model is used to predict the crack propagation specific energy under the influence of four independent variables,namely cutter spacing,penetration depth,joint orientation and joint spacing,and the obtained prediction model has high correlation coefficient and good fitting effect. |
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