Numerical Analysis Of Surrounding Rock Of Underground LPG Tunnel

Large-scale or super large-scale underground construction projects are the main developing trend in meeting the demands of energy, transportation and national defense system, especially the exploitation of hydro-electricity and other forms of natural energy. Recently-constructed underground plants and tunnels are characterized by large span, high sidewall, multiple crosses and complicated structure. Hence the technique of instability analysis and support design of enclosing rock of underground tunnels turns to be the most fundamental technique for underground construction projects. With the developing of computer science and technology, numerical simulation has been developed to a most advanced extent in instability analysis and support design of enclosing rock of underground tunnels. A variety of numerical methods and computational software have been proposed for analyzing the instability of enclosing rock of underground tunnels. Among them, finite element method (FEM), due to its characteristics, is more suitable for computing stress-strain problems of rock-soil materials. Based on FEM, PLAXIS is a kind of applied software internationally adopted in geo-technical computation as well as instability analysis of enclosing rock of underground tunnels.This paper is divided into three parts: Part One is theoretical preparation, in which geological conditions as well as factors of influencing stability of enclosing rock are introduced. Part Two is a detailed introduction of numerical computational theories and FEM theory. Currently in our country, there are no formed standard codes for support design in hydro-electricity construction projects. It is very hard to select anchorage parameters purely on the basis of engineering experience, for excavation of complicated large-scale underground tunnel-groups will lead to adjustment of displacement field and stress field of enclosing rock of the tunnel-groups, and excessive deformation and stress concentration will lead to damage or failure of enclosing rock consequently, which in turn will exert a great influence on the stability of the tunnels. In this paper, two-dimensional FEM PLAXIS is applied in simulation calculation of multiple engineering conditions of excavation and anchorage of underground tunnels, with anchor distance and length taken into consideration, and as a result, anchor and shotcrete support type is chosen as the most economically appropriate support scheme. Part Three is mainly about the discussion of temperature issues of underground LPG tunnel in extreme conditions such as earthquakes; moreover, the selected support type is confirmed as safe, reasonable and applicable. In a word, conclusions of this paper are somewhat meaningful in directing practical designs and constructions.