Research On Interaction With Soil Of TBM Cutting-Wheel Tools And Their Type Selection Design In Gravel Stratum

Based on the MPB shield construction of Sections 14 and 4 in Beijing Metro No.4 and the slurry balance tunneling of Nanjing Weiqi Road River-crossing Project and the summary of such related cases as metro tunneling in gravel stratum in Chengdu and Shenyang in China, the approaches like theoretic analysis, field tests and shield model experiments are employed to make systematic and profound research on the design of TBM cutting-wheel tools for gravel stratum and their interaction with soil, with a series of findings beneficial for theory and practice achieved.1) The design flow of cutting wheel is summarized and put forward as the principal line in fully discussing all the links of cutting-wheel design, for which, the theoretical frame of cutting-wheel design is established by extracting and summarizing the rational design of cutting-wheel tool parameters and the selection of material technology;2) The mechanism of tool abrasion is summarized and put forward, it is firstly indicated that the working condition of alloy cracks will be categorized as abrasion and defined as unusual abrasion;3) Using the operational principle of plough-loosening rock fragmentation in strip coal mine, the author brings forward the mechanism of tool cutting and names it as "plough-loosening principle":for gravel stratum, the fishtail tools are used together with overcutting tools primarily for plough-loosening of the original stratum, added by stripping with scrapers, and the tool cutting torque equals to the sum of the torques of fishtail and overcutting tools; the proposed mechanism of cutting is verified in combination with the field tests and indoor model experiments;4) Research is made on the mechanism of accidental shutdown caused by excessive wear on cutting tools. The findings indicate:the sharp increase of torque before shutdown is not resulted from the rise of cutting torque but from the fast increase of squeezing and friction torque between the cutting wheel and stratum; the squeezing effect impacts little on the pushing force of TBM but much on the torque of cutting wheel;5) According to the research and analysis on project cases by comparison and field test, the principle for type selection and configuration of cutting-wheel & tools is put forward, and also following is pointed out:type selection of cutting-wheel is more important than configuration of cutting tools, EPB shield mechine with spoke type cutting-wheel has most powerful adaptability for sandy pebble stratum, large diametered slurry balanced shield mechine to install spoke & faceplate style cutting-wheel is feasible and rational, pre-cutting bits in cutting tool configuration is utmost important, cutter bits is only playing auxilliary function of peeling and cutter bits shall adopt "blunt type" with powerful impact resistance without affecting boring efficiency, which is worth promotion and extensive application;6) Technical measures like theoretical analysis, field tests and indoor model experiments are used to make research on the impact given by EPB cutting wheel structure, tool configuration and scraper parameters on cutting torque, based on which, the torque calculation model T=1250D_e³Â·Î¼Â·P_m·[(Ï€/12)·k·(1-η)+0.5π·ζ] is set up for EPB shield cutting wheel and may be taken as the theoretical verification of Japanese scholar's empirical formula on statistics of cutting-wheel torque;7) The technological measures such as field experiments is are taken to make research on the impact given by slurry mix-shield cutting wheel structure, scraper parameters, nature of slurry, advancing parameters on cutting torque and cutting-wheel torque, based on which, the calculation model for cutting torque and cutting-wheel torque is established:cutting torque:T_cut=0.25k_cut(?)D_e²p, cutting-wheel torque: T=K{(13G_s-mud-13)[(1-η)D_e/12+0.5b_{刀盘}]Ï€D_e²P_f+0.25k_cutD_e²(?)p+k_sealD_e³},(G_s-mud≤1.4).