渗流侵蚀下含粉砂土地层中盾构隧道结构性态演化及可恢复性控制

Many in-situ measurements on operating shield tunnels show a significant effect of tunnel leakage-induced erosion on the tunnel performance during their service life in saturated silty soils. Leakage-induced erosion around shield tunnels can decrease the resistance of soils, and thus cause the excessive settlements and convergence of tunnels, which may ultimately threaten the structural safety of the tunnels. Many researches have been carried out to study the behavior of tunnels due to leakage of groundwater into the tunnel. However, the leakage-induced erosion was often ignored in most previous studies. The objective of this research is to study the tunnel behavior caused by leakage-induced erosion. This research will starts with the experimental investigation and CFD-DEM simulation to reveal the mechanism of tunnel leakage-induced erosion. The influence of erosion on soil properties can be studied using the results of laboratory erosion tests. Based on the experimental results, the erosion law will be developed in terms of the fluid velocity and fine particle loss. Based on the erosion law and critical state based constitutive model of soils, the hydraulic-geomechanical erosion model can be proposed and compiled into software of ABAQUS. Therefore, the erosion can be coupled with geomechnical analysis in the numerical simulation. The small scale model test of tunnel leakage-induced erosion will also be carried out to study the impact of leakage-induced erosion on tunnel behavior and validate the numerical simulation. The effect of leakage-induced erosion on the tunnel behavior can be numerically simulated. The safety state of shield tunnel due to the leakage-induced erosion is evaluated based on the serviceability and safety limit state of shield tunnel. Finally, the resilience engineering measures to control the effect of leakage-induced erosion on tunnel performance is investigated using numerical simulation.

盾构隧道运营维护实践表明，富水含粉砂土地层中隧道渗流侵蚀引起的周围水土流失是影响隧道结构安全的关键因素之一。其最直接的影响是降低隧道周围土层抗力，引起隧道过量沉降和变形，威胁隧道结构安全。现有研究多针对隧道渗漏水影响展开，关于土体流失影响的考虑较少。鉴于此，本项目以含粉砂土地层中运营盾构隧道结构安全为目标，旨在揭示渗流侵蚀影响下隧道结构性态演化规律。基于渗流侵蚀单元试验和CFD-DEM耦合数值试验，揭示隧道局部渗漏条件下渗流侵蚀发展机理，建立土体侵蚀控制方程，分析渗流侵蚀对土体力学特性的影响；基于土体临界状态面方程，构建能综合考虑渗流侵蚀发展过程和土体特性变化的渗流侵蚀水力-土力学耦合模型，实现模型的二次开发，建立隧道渗流侵蚀三维精细化有限元模拟方法；利用数值模拟结合隧道局部渗流侵蚀模型试验，分析渗流侵蚀对隧道结构性态的影响规律；提出隧道结构变形可恢复性控制方法；保障运营盾构隧道结构安全。

随着沿海及富水地区轨道交通的发展，盾构隧道频繁发生渗流侵蚀问题，严重威胁结构安全。然而，目前隧道渗流侵蚀机理尚不明确，缺乏针对性的分析方法，导致渗流侵蚀对隧道结构的影响机理不明，无法实现结构安全的科学评价与可恢复控制。以渗流侵蚀影响条件下盾构隧道结构安全控制为目标，本项目首先设计并开展了隧道渗流侵蚀室内物理模型试验，研究了不同初始和边界条件下隧道渗流侵蚀的时空发展特征，分别从宏观和细观角度揭示了隧道渗流侵蚀的发生机理与演化规律；在模型试验的基础上，建立了隧道渗流侵蚀控制方程与渗流-土力学耦合本构方程，利用Abaqus UEL进行软件开发，实现了隧道渗流侵蚀的有限元模拟；同时，基于计算流体力学、离散单元法与有限差分方法，建立了渗流-土体-结构耦合数值模拟方法，实现了隧道渗流侵蚀多尺度分析；结合模型试验，采用多尺度分析方法，考虑渗漏位置、水位高度、隧道埋深、流失缝尺寸等因素，从宏观和细观尺度，分析了隧道渗流侵蚀对土体特性、地层环境及隧道结构力学性态的影响规律；基于渗流侵蚀条件下隧道结构力学性态的演化规律，建立了盾构隧道安全评价指标体系及评价等级，提出了考虑隧道结构多指标动态综合评价方法，该方法具有广泛的通用性；采用数值模拟方法，研究了隧道结构不同控制措施的变形恢复效果，以结构剩余性能为可恢复性指标，考虑渗流侵蚀引发的钢筋和螺栓锈蚀的结构劣化影响，评估了不同加固措施下隧道结构的可恢复性，提出了隧道结构可恢复性优化控制方法。解决了渗流侵蚀对隧道结构影响预测、评价及控制等关键技术难题，研究成果在工程实践中得到应用和完善，为富水含粉砂地层中渗流侵蚀引起结构安全控制提供了坚实的理论基础。