The Main Engineering Geological Problems Related To Tbm Study

As the most advanced tunnel excavation method in the world, TBM excavation technique has been applied extensively in tunnel construction of energy source, traffic, water conservancy and national defence in many countries. However, because of TBM's poor applicability for complicated engineering geologic condition, many problems occur in TBM excavation, even cause serious accident, resulted in great economics loss. So, it is very important to have an all-sided and objective evaluation of TBM's applicability, and study the genesis, rule, prediction methods and countermeasures of main engineering geologic hazards occurred in TBM excavation.First of all, the author take an all-sided and objective analysis of primary two tunnel excavation techniques - TBM excavation and drill-blasting method from the points of economy and technology. Then, aimed at rock classification of TBM tunnels, pointed out that rock classification of TBM tunnels should contrapose drillability of rock, and adequately consider the primary geologic factors which affect TBM driving efficiency. Claimed that classifying wall rock into three category on the basis of 'engineering rock mass classification standard', according to uniaxial compressive strength, wear resistance and integrity of rock mass. By applying it to TBM engineering practice of Shanggongshan tunnel, the result indicated this means can really reflect drillability of rock and possess preferable use value, and are feasible in engineering practice.After summing up a great deal of TBM engineering examples, pointing out that large deformation of weak rock, sudden water inflow, rock burst and gas projection are primary engineering geologic hazards which affect TBM driving, above all large deformation of weak rock and sudden water inflow. Taken apart of formation mechanism and orderliness of all kinds of engineering geologic hazards, and brought forward relevant prediction methods and countermeasures.Finally, established engineering geologic model using advanced FLAC^3D according to engineering geologic condition of Shanggongshan tunnel, and modeled the influence to TBM driving of buried depth, hypsography and faults fractured zone. Studied the rule of stress redistribution and distortion after tunnel excavation.The research can offer reference for great decision of tunnel projects planning and construction scheme selection. It has very important significance for shortening time limit, reducing investment outlay, improving economic and social benefit, increasing tunnel construction level and so on.