| Due to complicated topographical and geological conditions as well as large numbers of mountainous areas, constructions of high-grade highway unavoidably meet with lots of tunnel works. As a result of special geological and topographical limitations, space of tunnels cannot satisfy with general technical codes. Therefore, such special structure shape as small spacing tunnel, twin-bore tunnel should be applied.Aiming at twin-bore tunnel with small spacing, this paper applied 2D and 3D FEM numerical analysis to study such key technologies as judging conditions of reinforcing middle rock pillars, reinforcing methods, design parameters of agent structures, reasonable construction methods.The paper at first studies on the stability of tunnel with no support by 2D FEM and draws the conclusion of what are the main factors effecting the it, stress distribution of surrounding rocks and deformation characters of middle rock pillars. Then by the simulation of the tunnel excavation after studying on the tunnel support especially for reinforcing middle rock pillars under the different condition of surrounding rocks we give some guidelines about how to decide the parameter of tunnel support and emphasize the that primary supports should be closed under the condition of weak surrounding rocks. Base on conclusion of before we put emphases on the construction methods of twin-bore tunnels with small spacing and then give some advices for choosing the reasonable construction methodsThe paper at first puts emphasis on studying the stability of tunnel with no support and draws the conclusion of what are the main factors effecting the it. Base on the conclusion of that we make a further study on the tunnel support and construction methods and give some guidelines about how to decide the parameter of tunnel support and the reasonable construction methods on the twin-bore tunnels with small spacing...
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