Numerical Simulation Study Of Rock Fragmentation Mechanism And Effect By TBM Disc Cutter

The tunnel boring machine(TBM)is widely used to the engineering project of trasportation and Hydro-Power,because it has obvious advantages of high efficiency,good security,good working environment.The engineering environment of TBM is complicated and TBM involves lots of mechanical parameters,so the rock fragmentation effect under the different factors and the rock fragmentation mechanism are not still clear.In this paper,the change rules of the crack propagation and the forces on disc cutter are analyzed.For the high rock-breakingefficient,the rock fragmentation mechanism and effect also are researched deeply.The primary contents of this paper are as follows:(1)Analyzing the rock fragmentation mechanism and the different factors.The major estimate formulas of the disc cutter cutting forces are elaborated and analyzed,which are verified by practical engineering to analyze their characteristics.This work can guide the calculation of disc cutter cutting forces and the design of the cutterhead.(2)Based on method of the distinct element code,the numerical model of the interaction between the single disc cutter and rock mass has been established.From the microscopic view,the the change rules of the crack propagation and the forces on disc cutter are analyzed The rock-breaking pattern is composite pattern,which is composed of tension failure and shear failure.The vibratory vertical thrust indicates the jump-breaking phenomenon.By changing the different factors,including rock strength,confining stress,joints strength,effecting the rock fragmentation are discussed to improve the high rock cutting efficiency.Simulation results indicate that the increase of the rock strength and the confining stress can restrain the radial crack propagation and need to increase vertical thrust to break rock.The joint planes control the propagation process of cracks and obstruct the cracks spread to the underside of joint planes.(3)For the purpose of analyzing the cooperative action of TBM disc cutters,the numerical model of the interaction between the double TBM disc cutters and rock mass has been established.Based on the numerical model,that the cutter space effects the rock fracture process is analyzed.The optimum cutter space is evaluated quantitatively to gain the good rock cutting effect by the SE(specific energy)theory.The numerical models of the interaction between the double disc cutters and rock mass under different sequences are established.Through the comparison with simultaneous rock-breaking,the simultaneous rock-breaking is found better than the serial rock-breaking under the same condition.