紧邻深开挖下盾构隧道水土压力及承载机制研究

Due to the rapid development of urban underground space, more and more excavation activities are conducted nearby the metro lines, which will inevitably threaten the serviceability and safety of running metro tunnels. Excavation induces ground deformation and alters the groundwater seepage filed, which will have adverse effects on the serviceability of tunnel structures. The change of contacted water and earth pressure on shield tunnel due to adjacent excavation is the main factor that affects the tunnel structures bearing capacity. However, few researches focused on the tunnel structures deformation mechanism and bearing capacity due to adjacent excavation, considering the water and earth pressure on the tunnel. This study plans to conduct shield tunnel-excavation interaction laboratory experiment and fluid-solid coupling numerical simulation to reveal the mechanism and model of water-earth pressure interaction on tunnel. Segmental ring model experiment and finite-element simulation are further carried out, based on the water and earth pressure acting model, to analyze the deformation mechanism and bearing capacity characteristics of segmental ring. Then, the design calculation method of segmental ring subjected to excavation is to be established. Finally, based on the relationship of earth pressure and displacement, the analytical method for longitudinal deformation of shield tunnel due to adjacent excavation is to be proposed by considering the seepage force. The conclusions of this study could provide theoretical basis for tunnel protection and reinforce.

随着我国城市地下空间开发利用的速度加快，地铁隧道沿线深开挖工程日益增多，严重威胁地铁隧道的服役性能和运营安全。深开挖引起地层变形与地下水渗流场的改变，将对处于服役状态的既有隧道结构产生不利的影响。深开挖下水土接触压力的改变是影响隧道结构承载能力的主要因素。前人研究缺乏从水土接触压力方面，探究在深开挖下隧道结构受力与承载特性。本项目通过深开挖隧道变形室内物理试验与流固耦合数值模拟，揭示在深开下隧道水土压力作用规律与模式；基于水土压力作用模式，进一步开展管片模型试验与有限元仿真分析，探究在深开挖下管片的受力变形特征与承载性能，构建管片受力变形设计计算方法。最后，基于土压力-位移函数关系，考虑渗流力的作用，采用梁-弹簧模型，推导在深开挖下盾构隧道纵向变形预测计算方法。研究成果可为我国在深开挖工程影响下地铁盾构隧道的保护与加固提供理论依据。

随着我国城市建设的发展，地铁沿线深开挖工程日益增多，严重威胁地铁隧道的服役性能和运营安全，然而目前对于深开挖下水土接触压力和隧道结构承载性能的研究还不完善。因此本项目通过对两个紧邻既有盾构隧道基坑工程开挖过程中地层和隧道的综合监测与分析，结合室内缩尺模型试验和流固耦合数值模拟等手段，对水土压力、地层位移和隧道变形等进行了分析，探究了深开挖下隧道水土压力的作用规律和盾构隧道变形规律。接着通过模型管片承载性试验和精细化数值建模分析，进一步探究了盾构隧道的承载性能和深开挖下盾构隧道结构的受力变形特征，特别是管片衬砌结构和接头部位的受力和变形特点，并建立了管片受力变形计算方法。然后基于土压力-位移函数关系，建立隧道-土体非线性相互作用理论。接着在建立的非线性地基模型的基础上，形成深开挖下盾构隧道纵向受力变形预测方法。最后分析了关键参数特别是基坑规模、基坑与隧道相对位置、地层土体特性和既有盾构隧道承载性能等因素对既有盾构隧道受力变形特性的影响。形成的主要成果有：①盾构隧道精细化建模的数值分析方法；②隧道-土体非线性相互作用理论；③深开挖下盾构隧道纵向受力变形预测方法；④围绕模型试验装置的专利。本项目的研究成果可以为紧邻地铁隧道的基坑工程施工和地铁隧道的保护提供合理的理论指导，也能为相关地下工程的进一步研究提供新的思路和方法。