Study On The Wear Mechanism Of TBM Disc Cutter And Boring Efficiency During TBM Rock Breaking Process In Mixed Face Ground Conditions

With the development of large-scale infrastructure construction in China, more and more tunnels are needed to build, while the TBM can complete the excavation of tunnel with faster speed, higher quality and lower cost, therefore, the application of TBM will become more and more widely and TBM advancing will encounter the mixed ground excavation. In the TBM tunneling process, the working environment of the TBM cutter head is very complex, especially in mixed ground, disc cutter forces which acting on the cutter head directly affect the tunneling direction in the process of disc cutter rock breakage, the effect of the disc cutter breaking rock are different with different geological conditions and different construction parameters, and the wear of disc cutter is very serious in TBM tunneling process, moreover the disc cutter may occur abnormal wear in mixed ground, which can affect the construction progress and cost directly. So, the studies of the rock breaking mechanism and wear situation of disc cutter are very important. The study of this issue adopts methods of theoretical research and numerical simulation. The main contents of this paper are as follows:Firstly, based on the analysis of disc cutter wear factors, the methods for quantitative calculating the wear of the disc cutter by taking the cutter structure parameters and the boring parameters into account is introduced. The critical conditions are set up by studying eccentric wear of disc cutter in mixed ground, and the eccentric wear extent of disc cutter is also analyzed. Then, the methods for predicting the normal wear extent and the eccentric wear extent are proposed.Secondly, according to the analysis of the disc cutter rock breaking movement, based on the single-point and double-angle variant theory, the TBM disc cutter rock breaking three-dimensional mechanical model is established, and by the corresponding study deducing the numerical model of the normal force, rolling force and lateral force of the disc cutter, and combined with the existing theoretical models to verified the feasibility of the three-dimensional mechanical model.Thirdly, the three-dimensional rock breaking mechanical model is applied to the mixed ground, the disc cutter cutting force and the rock mass stress field when the cutter broken rock are discussed and analyzed, then the failure zone and damage zone of rock under the action of disc cutter are obtained, the rock damage zone is not symmetrical and it is divided into two parts: left damage region and right damage region.Fourth, the disc cutter eccentric wear under the mixed ground geological condition is analyzed, and the risk factors of disc cutter eccentric wear in soft and hard mixed ground is studied. In addition, the effect of cutter penetration depth and installing radius on the cutter eccentric wear are also studied.At last, the rock stress field and failure characteristic under the action of disc cutter is analyzed by using the finite program ANSYS/LS-DYNA, and the force variation of disc cutter and the failure process of rock in the rock breaking progress are discussed. Moreover, the cutting forces are studied in the uniform ground and mixed ground geological condition, and the boring efficiency of disc cutter in mixed ground is also analyzed.