Research On Time-space Effect And Selection Of Preliminary Support For Tunnel In Soft Rock With High Ground-stress

ABSTRACT:Recently, tunnels in soft rock with high ground-stress appear frequently among the railway and road tunnel engineerings under construction in our country. Problems, such as large deformation, supporting damage, etc, seriously affect the normal construction of these tunnels. On the background of the construction of Daliang tunnel in LXS-7of Lanzhou-Xinjiang double line Railway, the time-space effect and selection of steel frame for tunnels in soft rock with high ground-stress were mainly discussed. The main work and the results were as follows:1. Based on the construction of Daliang tunnel, engineering properties of tunnels with weak surrounding rocks in high ground-stress region were researched by several aspects. Characteristics of large deformation in these tunnels were illustrated and extrusion index for the quantitative analysis of it was introduced.2. Use ANSYS/FLAC3D numerical analysis software to simulate excavation process of Daliang tunnel, analyse the temporal and spatial effect of these tunnels. Besides supporting structure internal force, contrast surrounding rock plastic deformation range, heterotaxy of different sequence of excavation.3. On the background of the construction of Daliang tunnel, the different application effect of steel frame and steel grid frame in high ground-stress region were mainly discussed. The Daliang tunnel is taken as the experimental section in which the section steel and steel grid of20meters in length are set respectively. The main comparison included the settlement of tunnel crown and arch foot, horizontal convergence, surrounding rock pressure, stress of initial supporting steel framework, etc. By practice proving that multiple support runs effectively.4. According to the surrounding rock-support characteristic curve theory, different forms of tunnel supports with varied stiffness were applied to the tunnel, and their deformation mechanisms and mechanical responses were also investigated. Based on the surrounding rock-support characteristic curve theory, several possible rock-support characteristic curves, which may be used as theoretical evidences, were attained for the tunnels in high ground-stress soft rock. Furthermore, the support form suitable for large-deformation rock was proposed.