软土基坑引起下卧隧道隆起的非线性流变

摘要

Deep excavation in soft clay often brings soil stress disturbance and soil deformation,which would bring differential settlement and structural cracks.It probably brings safety problems to adjacent underground tunnels.Therefore,it is necessary to predict tunnel displacement induced by excavation for tunnel's security.A new method was proposed to estimate the heave of underlying tunnel induced by adjacent excavation verified by field measurements.The soil deformation by excavated soil gravity was analyzed by application of Boussinesq solution.The soil deformation by tunnel surface pressure was analyzed by Mindlin solution.The tunnel was assumed to be an elastic beam on foundation to simulate the tunnel,in which interaction analysis of tunnel and soil was employed.In consideration of rheologic soil,Viscoelastic model was employed to analyze soil nonlinear displacement with time in soft clay.Tunnel displacements were discussed by different excavation cases.A case study showed a good agreement between the results from the prediction and the measurement.%软土地区深基坑开挖改变了周边土体的初始应力,引起周边土体的位移,对周边构筑物造成不均匀沉降、混凝土开裂等不利的影响,并且可能危及临近地铁隧道的安全.对基坑开挖引起的下卧隧道的隆起变形进行了研究并提出了实用的预测方法.基坑开挖土体卸载引起的土体变形采用了Boussinesq应力解进行求解,隧道反力引起的土体变形采用了弹性半空间Mindlin应力解进行分析.隧道本身变形采用了弹性的地下连续梁进行分析,并且考虑隧道与土体的相互作用.通过引入软土的非线性流变模型,考虑了软土变形的时间效应,因此可以对复杂开挖过程进行模拟分析.还对基坑开挖对隧道隆起的效应进行了讨论,通过上海市某重点工程实例的隧道隆起量的预测结果与实测值对比分析,隧道隆起的监测结果证实了该方法的有效性.