基坑对称开挖引起下穿隧道竖向变形解析解初探

深基坑施工引起的邻近地铁隧道变形是我国城市轨道交通施工安全控制和风险评估中较为关心的一类问题。目前针对该问题的理论研究,大都采用Mindlin解求基坑开挖作用在地铁隧道上的附加应力;然后基于Winkler地基模型求解隧道的变形;该方法没有考虑软土的流变性以及地基变形的连续性。根据弹性理论的经典解答Mindlin公式,同时考虑软土的非线性流变性,推导出基坑对称开挖引起下方隧道附加应力的简化计算公式。采用Pasternak双参数地基模型,建立隧道竖向变形的平衡微分方程,得到两侧深基坑开挖引起下穿地铁隧道竖向变形和内力的实用计算表达式。通过将某市深基坑工程下方的隧道变形监测结果与Pasternak地基和Winkler地基计算结果进行对比,验证了采用Pasternak地基的优越性和提出的理论计算方法的有效性。

DEFORMATION CALCULATION OF SUBWAY-TUNNEL UNDER SYMMETRICAL DEEP EXCAVATION

The deformation of metro tunnel caused by near deep excavation is hot issue in the underground transportation construction safety control and risk assessment. Previous researches are basically concentrated on calculating the additional stress due to adjacent foundation pit excavation based on the Mindlin solution , then the tunnel deformation is calculated based on Winkler model. But the rheological of soft soil and continuity of foundation are not considered in this method. According to Mindlin solution of elasticity theory and considering the nonlinear rheology of soft soil , the simplified calculation formula of the additional stress of tunnel is deduced. The governing differential equation of vertical deformation for tunnel is built up based on Pasternak foundation model, then we can get the practical calculation of vertical deformation and internal force of tunnels by deep excavation in both sides. Finally,based on a deep foundation pit case, the result of monitoring are compared with the calculation results of Pasternak and Winkler,the validity of the theory presented in this paper and the superiority of Pasternak foundation are verified.