复杂环境与盾构隧道结构变形性能耦合作用动态演化机理

As the mileage of operated tunnels increases, the possibility for accidents of urban shield tunnel might become larger than ever. Intensive focus thus has been placed on the safety of operated shield tunnels. It is generally recognized that the high complex ground condition are twofold, i.e., one is due to the spatial variation of soils and the other is due to the aggressive nearby underground constructions. The surrounding ground could produce both the active loading and the passive reaction. Hence, lots of research emphasis have been placed on an accurate description of confining effect of subgrade and a precise quantification of long-term performance of segmental lining. However, a large vagueness exists in the study on the coupling interactions between structural performance and the subgrade reaction of surrounding ground, in particular with the evaluation and distribution of subgrade reaction and long-term effect of the interaction. This potentially could induce an unsafe assessment for structural performance. In view of the situation, this project emphasizes on the coupling interactions among the three parts including the surrounding environments, the subgrade reaction and the shield tunnel linings. By applying the mobilized strength design (MSD) method, an explicit nonlinear curve of subgrade reaction varying with the lining convergence will be presented. Then the distribution of subgrade reaction in spatially varied ground will be proposed by using the Markov chain theory. Finally, the time series analysis will be utilized to derive a joint evolution model for subgrade reaction and lining deformations. This evolution model could precisely quantify the effect of subgrade on the structural performance of shield tunnel lining in complex ground conditions. It could help to establish a general frame for safety control from the subgrade reaction point of view and eventually support the safe operation and preventive maintenance for urban shield tunnel lining structures.

近年来我国城市盾构隧道大规模建设运行以及各类结构损坏事故频发引起了各界对隧道结构运行安全问题的高度关注。盾构隧道结构赋存的复杂环境（包括地层条件和外界扰动）一方面是荷载作用，同时也是结构变形的约束条件。国内外学者十分重视研究地层约束抗力、隧道结构变形及其性能耦合作用机理问题，现有地层抗力分析限于简化的力学模型和经验方法，无法考虑其中的耦合机制及结构长期服役性态变化，因此，对复杂环境中的盾构隧道结构安全运行状态及失效机理缺乏准确的判断。本项目将围绕工程环境-地层抗力-隧道结构三者耦合作用机理问题，利用调用强度设计方法建立复杂环境中地层抗力与结构变形的非线性显式映射关系，应用Markov链理论研究单元地层抗力的空间场分布特性，建立地层抗力与结构变形在时空域内的联合概率演化模型，精确量化各类复杂环境中地层抗力对隧道结构力学行为影响规律，为我国城市盾构隧道结构运维安全提供基础理论支持。

盾构隧道结构赋存的复杂环境（包括地层条件和外界扰动）一方面是荷载作用，同时也是结构变形的约束条件。现有地层抗力的取值无法考虑复杂环境与管片结构的耦合机制及结构长期服役性态变化，导致隧道安全运行状态和失效机理缺乏准确判断。本项目围绕工程环境-地层抗力-隧道结构三者耦合作用机理问题，在以下2个方面取得突出成果：.1）利用调用强度设计（MSD）方法建立复杂环境中地层抗力与结构变形的非线性显式映射关系：. 提出以隧道圆形均匀收缩、隧道椭圆化变形的两种基本结构变形模式条件下地层位移场函数，构建隧道结构断面水平收敛位移δ与地层应变ε的映射关系。另一方面，对应均匀收缩变形场函数、椭圆化变形场函数，引入均匀分布抗力与椭圆化余弦函数分布抗力两种模式，通过场内能量平衡原理建立抗力pk与调用强度su,mob之间关系，考虑土体复杂应力应变关系曲线（硬化土体模型），构建抗力pk与结构水平收敛位移δ之间的非线性关系，提出复杂环境中地层抗力与盾构隧道结构变形非线性映射关系模型，为软土盾构隧道性能化设计提供关键参数。.2）应用随机场理论研究单元地层抗力的空间场分布特性，建立结构变形在时空域内的联合概率演化模型，精确量化各类复杂环境中地层抗力对隧道结构力学行为影响规律：. 提出以有限地质钻孔作为先验数据以及Hidden Markov随机场更新的地层空间分布模型，基于该模型采用Monte Carlo进行地层随机模拟，提取地层空间随机分布条件下隧道开挖前后衬砌结构作用的径向土压力，建立以径向土压力系数表征的地层抗力空间分布模型(系数<1则地层抗力为正，系数>1则地层抗力为负），分析显示隧道拱顶和拱底位置处抗力受地层变异条件影响较小，而在隧道两侧拱腰位置处的影响较大。进一步提出基于实测结构变形数据更新的隧道结构变形安全概率密度演化模型，为隧道结构变形长短期时空域内的安全性能预测提供依据。. 依托以上内容，共发表学术论文20篇，包括SCI检索10篇（含1篇ESI高被引论文），申请专利著作权3项，培养硕博士研究生5名。成果为软土盾构隧道结构性能演化机理以及加固维护决策提供必要的理论支撑与实操指南。