| In recent years, with the continuous development of GuangZhou’s rail transit, more and more problems was encountered during the construction in Karst region, in addition, a large distribution of Karst region is the most of the history of the construction of urban rail. In general, the methods for construction of urban rail transit have Shallow Mining Method, Shield Method and open-cut method, this paper discusses the survey and plans for the Shield Method about construction in Karst region. On the one hand, for the problems of geological characteristics and shield construction in Karst region, the paper points out how to investigate and treatment, and how to handle the problems meet by the shield construction and selection, on the other hand, with the Three-dimensional finite element software, the paper recommendates for a cave principles of a typical project case in Guangzhou, forming a set of guiding engineering programs. The main research work and results are as follows:(1) By studying for four categories of disasters’ development mechanism in Karst regionrespectively, the paper points out four kinds of disaster how to survey and pretreatment before the shield construction in Karst region, and summarizes the existing investigation thinking and principles of treatment in Karst region, providing the technology to carry out the follow-up of shield construction.(2) Through the study in Karst region of shield construction often made three kinds of disasters(high pressure water, different forms cave, complex formation), according to the working mechanism of two types of shield machine, the paper pointed out how to select the construction method, handling disasters, processing for the shield knife exchange and selection for the shield machine, forming a Karst region of shield tunneling construction method.(3) Relying on Guangzhou typical engineering example, through the finite element numerical simulation analysis of existing caves with different case, shield construction impact the surrounding environment, putting forward to the diameter of the Karst cave and the tunnel between the net distance ratio K1(referred to as the hole distance ratio), cave diameter and tunnel diameter ratio K2(tunnel ratio) as to judge whether the cave treatment, thus making a optimized suggestion for the existing cave processing principle. |
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