斜穿过砂卵石层地质构造隧道开挖的三维数值模拟分析

摘要

Aiming at a subway shallow tunnel construction,a three dimensional finite element numerical model is established for the oblique through the sand pebble bed geological structure tunnel excavation.Through the simulation,the tunnel excavation is analyzed in different supporting conditions of surrounding rock stress,displacement and plastic zone.The results show that the first step surrounding rock displacement is small after excavation,the second step has a sharp increasing displacement of the surrounding rock in sand pebble layer thickness,and the displacement becomes stable in the subsequent excavation process.The sand pebble structure bearing capacity is small,and its geological layer appears to be plastic zone.The role of bolt supporting is to improve the overall performance of surrounding rock,and reduces the internal stress of the surrounding vault top rock.Unloading action after the tunnel excavation makes the arching bear the most upper load of surrounding rock.In order to prevent tunnel collapse after the excavation,primary support and the second phase of lining should be applied.%以某地铁隧道浅埋暗挖法为研究对象,建立了斜穿过砂卵石地质构造隧道开挖的三维有限模型.通过模拟隧道开挖,分析了隧道在不同支护工况下的围岩应力、位移、塑性区.分析结果表明,在第一步开挖后围岩位移较小,第二步开挖后在砂卵石层最厚处的围岩位移急剧增大并在后续开挖过程中趋于稳定；开挖过程中砂卵石结构本身的性质使其承载力小,因此在其地质层处出现了塑性区；锚杆的支护作用提高了围岩的整体性能,减小了拱顶上部围岩的内应力；隧道开挖后的卸载作用使钢拱架承受上部围岩荷载且主要承受压应力.为防止隧道产生塌方开挖后应及时施做初期支护和二期衬砌.