地铁盾构端头加固区水泥土服役性能不确定性研究

This project focuses on the uncertainties of working behavior of cement reinforced soil block adjacent to the metro shield end shaft. When metro shield is drilling through the reinforced block to approach the end shaft, it suffers from high construction risk. So far, researchers and practitioners have not yet adequately investigated the problem of uncertainties of working behavior in tunnel end reinforcement. It usually leads to over-conservative estimation of design values of relevant construction parameters. However, the construction risk level does not accordingly and proportionally drop. This project is based on the theory of random field to optimize the generation of multi-dimensional multivariate random field and derive the probabilistic distribution of the working behavior indexes to reveal the impact level and characteristics of spatial variability of soil-cement reinforcement at the shield end shaft influencing its working behavior. A series of large scale elastoplastic random finite element model is to be established to simulate the process of shield arrival. With practical case analysis, the study aim to clarify the mechanism of the construction risk attributable to the uncertain factors during shield arrival. Moreover, multi-risks coupled analysis is to be carried out, in which the uncertainty representation method is to be proposed and relevant countermeasures are to be discussed. This study, targeting a typical reinforcement method at metro work shaft in typical urban geological conditions, remains an intractable but urgent engineering problem in the current metro construction peak in China. It is of certain theoretical and engineering significance.

本项目针对地铁盾构端头加固水泥土在盾构接收中的服役性能不确定性展开研究。地铁盾构在经过加固区到达端头井时，施工风险很高。迄今，学术及工程界对端头水泥土加固体服役性能的不确定性研究得还不充分，这导致相关设计参数取值过份保守，而施工风险却并没有成比例地降低。本项目以随机场理论为基础，通过对多维多元随机场生成方法的优化，性能指标不同径向变化的单桩分析，揭示水泥土空间变异性对其性能的影响，推导其服役性能指标和盾构掘进误差的概率分布律，再对盾构接收过程进行大型三维弹塑性随机有限元模拟分析，辅以工程实例研究，尝试厘清由水泥土加固的不确定性因素导致的盾构接收施工风险机理，并对风险进行概率耦合分析，建立水泥土服役性能不确定性表征方法，探讨相应的风险对策。本研究以我国城市土质条件下的典型端头加固工法为研究对象，是我国正在经历的地铁建设高峰期不可避免又亟待改进的工程问题，具有较强的理论价值和工程指导意义。

地铁盾构始发与接收过程中在端头加固区，因水泥土加固体服役性能的不确定性，导致很高的施工风险。本项目针对盾构隧道端头软弱地层的水泥土加固区，着力研究了相关工法（深层搅拌deep mixing与高压旋喷jet grouting）的施工质量不确定性因素及加固质量的空间变异性机理。研究综合运用了理论分析、常规重力缩尺模型实验、离心机缩尺模型实验、常规有限元与三维超精细弹塑性随机有限元模型及工程现场实测等全面的研究手段，研究了用于模拟建筑材料随机性方法高斯静态随机过程的生成效率，提出了用于模拟统计均质建筑材料性能方法的修正形式；结合工程案例，检验了水泥土复合地基中粘结剂浓度与土体含水量空间变异性的耦合效应，考虑了两种主要不确定性因素：桩身位置不确定性和桩身内部水泥土强度不均匀性，建立水泥土服役性能不确定性表征模型，提出了工程勘测与设计修正方法。