注浆加固对盾构施工沉降控制成效的概率评估

Probabilistic Evaluation of Grouting Reinforcement on Settlement Control Effectiveness in Shield Tunneling Construction

[目的]为了减少盾构隧道下穿建筑物时的地层扰动,有必要研究盾构隧道下穿建筑物过程中注浆加固的沉降控制效果。[方法]以杭州地铁12号线下沙路某区段盾构隧道下穿桩基建筑物为例,基于FLAC 3D有限差分软件,分别采用确定性分析与可靠度分析两种方法,评估了注浆加固措施对盾构施工引起的基础沉降控制成效。[结果及结论]在确定性分析中,现场实测数据和数值分析结果均表明,建筑物基础的最大沉降发生在先开挖隧道一侧;注浆加固技术能够有效降低盾构开挖引起的建筑物基础沉降,使建筑物沉降值满足规范设计要求。在可靠度分析中,以黏聚力和内摩擦角为随机变量,采用拉丁超立方抽样-响应面-有限差分法评估注浆加固的控制效果,发现注浆加固可以有效提高建筑物基础的结构可靠度,以及显著降低计算沉降值的不确定性。与确定性分析方法相比,可靠度分析方法由于考虑了参数的不确定性,在描述建筑物基础结构安全性方面更为合理,能够用于评估复杂盾构隧道开挖工程的控制措施有效性。

[Objective]In order to reduce the ground disturbance when the shield tunnel underpasses buildings,it is necessary to study the settlement control effect of grouting reinforcement during shield tunneling under the buildings.[Method]Taking the shield tunnel of Hangzhou Metro Line 12 passing under the pile foundation building in a certain section of Xiasha Road as an example,and based on the FLAC 3D finite difference software,two methods of deterministic analysis and reliability analysis are adopted respectively to evaluate the effectiveness of grouting reinforcement measures in controlling foundation settlement caused by shield construction.[Result&Conclusion]In the deterministic analysis,both the on-site measured data and the numerical analysis results show that the maximum building foundation settlement occurs on one side of the tunnel that is first excavated;grouting reinforcement technology can effectively reduce the building foundation settlement caused by shield excavation,making the building settlement value meets the specification design requirements.In the reliability analysis,the cohesion and internal friction angle are used as random variables,and the Latin hypercube sampling-response surface-finite difference method is adopted to evaluate the control effect of grouting reinforcement.It is found that the grouting reinforcement can effectively improve the structural reliability of the building foundation and significantly reduce the uncertainty of the calculated settlement value.Compared with the deterministic analysis method,the reliability analysis method is more reasonable in describing building foundation structure safety by taking the uncertainty of the parameters into account,and can be used to evaluate the effectiveness of control measures in complex shield tunnel excavation projects.