特大跨隧道在双侧壁岛坑法施工下的数值模拟

Numerical Simulation of Super-long Span Tunnel under Construction of Double-side Drift Method

依托实际项目,运用FLAC3D进行后处理,模拟双侧壁导坑法用于V级围岩的施工,全面展示了暗挖隧洞右洞的分步开挖对左洞初期支护应力、右洞周围围岩变形的变化规律。结果表明:对于开挖洞在既有洞初期支护上产生的支护轴向应力规律,双侧壁导坑法和全断面开挖理论规律基本一致。开挖洞在双侧壁导坑工法下,地表沉降会出现下导坑较上导坑对地表沉降影响更大的规律。在偏压工况下,开挖对于地面沉降量在大偏压侧较小偏压侧更明显。导坑法对地面沉降会产生peck曲线的叠加效应,但最终沉降曲线满足peck沉降理论。

Relying on an actual project, FLAC3D is used for post-treatment to simulate the construction of Class V surrounding rock by double-side drift method, which comprehensively shows the variation law of staged excavation of the right tunnel of the underground excavated tunnel on the initial support stress of the left tunnel and the deformation of surrounding rock around the right tunnel. The results show that the axial stress law of the excavation tunnel on the initial support of the existing tunnel by the double-side drift method is basically consistent with the whole section excavation theory law. By the construction method of double-side drift method, the effect of the lower drift heading on the surface settlement of the excavation tunnel is greater than that of the upper drift heading. Under the condition of bias pressure, the ground surface settlement caused by excavation is smaller on the large bias pressure side and more obvious on the bias pressure side. The drift heading method will produce the superposition effect of peck curve on ground settlement, but the final settlement curve meets the peck settlement theory.