砂卵石地层盾构隧道施工超挖土对地表沉降影响研究

Study on the influence of ground settlement affected by over-excavation of shield tunnel in sandy cobble stratum

为解决盾构超挖土缺少行之有效的理论支撑和数值模拟手段的问题,本文研究了超挖土和滞后沉降工况对盾构隧道施工沉降的影响规律。借助数值模拟方法,通过对扩大某一开挖环半径的方式来模拟盾构超挖施工,通过挖除不同埋深的土体单元来演示盾构超挖引起的空洞往地表延伸的施工模拟过程。结果表明,当空洞发生在偏离隧道轴线的位置时,其空洞与地表间距对地表轴线位置沉降的影响规律不与间距的大小成正比例关系;给出了因盾构隧道在砂卵石地层中施工导致的地表瞬间塌陷时的空洞埋深与隧道顶部埋深的比值,并总结了盾构超挖时现场处置措施,可供类似工程参考。

In order to solve the problem of lack of effective theoretical support and numerical simulation means of shield over excavation,the influence of over excavation and hysteretic settlement conditions on shield tunnel construction settlement is studied in this paper.With the help of numerical simulation method,the shield overexcavation construction is simulated by expanding the radius of a certain excavation ring,and the construction simulation process of the cavity extending to the surface caused by the shield overexcavation is demonstrated by excavating soil elements with different buried depths.The results show that the influence of the distance between the cavity and the surface on the settlement of the surface axis is not directly proportional to the distance when the cavity occurs at the position deviated from the tunnel axis.The ratio of the buried depth of the cavity formed when the ground surface collapsed instantly due to shield tunneling construction in sandy cobble stratum to the buried depth of the tunnel top is given.In addition,the on-site disposal measures of shield tunneling are summarized,which can be used as reference for similar projects.