Study On Tunnel Mechanical Behavior In Plane Bifurcate Section

Traffic tunnel often need to build a variety of contact channels and branch tunnels, thus forming various types of bifurcate tunnel, plane bifurcate tunnel is a special tunnel form. However, the design theory and construction methods of plane bifurcate tunnel is not yet perfect until now because the researches and applications of the bifurcate tunnel are still in the exploratory stage, lacks a systematic and completely study.In this paper, the MIDAS-GTS finite element software was adopted to deepth study the mechanical behavior of the Lishuwan tunnel with different surroundingrocks grade, bifurcate angle and section size, and the major conclusions were drawn as follows:①according to studies, it can obtained the stress-affected area of plane bifurcate tunnel under different influencing factors in bifurcate part. The influencing factors of tunnel contain surroundingrocks grade (Ⅲ,Ⅳ,Ⅴ), bifurcate angle (45°, 60°, 90°) and main tunnel section size (two-lane, three-lane) . This paper only carried out separate analysis of each factor because the impact will become obscured if simultaneous change all factors. Therefore, the other influencing factor should keep invariant when study the stress concentration range of main tunnel which is affected by one factor. In this paper, several tunnel conditions were studied, On the one hand, longitudinal influencing range along the bifurcate section of three-lane tunnel with different surrounding rocks grade and bifurcate angle. On the other hand, the stress concentration range in bifurcate part of the tunnel with 60°bifurcate angle, different surrounding rocks grade and section size. Finally, the stress concentration range in bifurcate part of the tunnel with surrounding rocks gradeⅣ, different bifurcate angle and section size.②The stress and deformation variation raw in bifurcate section of main tunnel with bifurcate tunnel excavated are obtained according to separately study on the stress and deformation of main tunnel with bifurcate tunnel excavated and not excavated, including the stress field, the stress and displacement change curve of surrounding rocks and supporting structure in main tunnel.③The practical reinforced supporting range was proposed according to the mechanical behavior in bifurcate section of plane bifurcate tunnel. The corresponding suggestions of improvment and optimization are put forward according to depth study on the bifurcate part of Lishuwan tunnel. It shows that the research results can provide some useful references for the design and construction of bifurcate tunnel.