复杂渗漏条件下软土盾构隧道结构性态演化规律及控制

Leakage of groundwater is one of the key factors causing the settlement and deformation of operating tunnels, which may ultimately threaten the structural safety of the tunnels. Many researches have been carried out to study the soil movement due to leakage of groundwater into the tunnel, where the permeability of tunnel was often described using the relative permeability between tunnel and soil in most studies. Thus, the permeability of tunnel was simplified to be uniform. The leakage-induced surface settlements were then calculated with consolidation theory considering the steady leakage of tunnels. In reality, the grouting is often carried out during tunneling. The hardened grout and the non-uniform tunnel leakage boundary have great influence on the evolution of pore pressure and movement of surrounding soils during the tunnel leakage. However, the hardened grout around the tunnel was often ignored and the tunnel leakage was assumed to be uniform in most previous studies. As such，the real tunnel behavior due to leakage could be very different from the previous studies because of the interaction between shield tunnel and soils. The objective of this research is to study the leakage induced tunnel behavior and soil movements considering the effect of the hardened grout and non-uniform tunnel leakage boundary. This research will starts with inverstiagion of the permeability and micro-structure of hardened grout. Then, model tests will be carried out to sort out the influence of thickness as well as permeability of hardened grout on the tunnel leakage in terms of the evolution of pore pressure and soil movements. The influence of hardened grout on tunnel leakage could then be discovered with the results from micro-tests and model tests. Based on knowledge learned from the model tests results, numerical methods will be developed to simulate the effect of leakage on soil movement considering the hardened grount, based on which the leakage induced tunnel settlement and deformation as well as and soils movement could be investigated further. Thereafter, parametric study will then be conducted to investigate the relationship between tunnel deformation and factors affecting tunnel leakage. The effect of tunnel deformation on the tunnel performance will be evaluated in terms of the tunnel joint opening, the stress sates of the concrete and bolts. Indexes that can reflect the well-being of tunnels will also be suggested together with their threshold values for safety evaluation of tunnels. Finally, engineering measures and their effectiveness for controling the safety of tunnels against leakage induced hazards will also be studied.

建造在富水软土地层中的盾构隧道，渗漏水是诱发隧道长期沉降和变形，进而影响其结构安全的关键因素之一。由于软土盾构隧道注浆层和隧道渗漏非均匀性的影响，使隧道周围地层不同区域孔隙水压力发展规律、土层变形机理存在差异，在隧道和土层共同作用下，隧道结构性态发展规律也更加复杂。目前研究一般将其简化为隧道和土层均匀渗流条件下的固结问题，忽略了注浆层和隧道渗漏非均匀性复杂渗漏条件的影响，不能合理反映隧道结构性态的发展。因此，综合考虑注浆层和隧道渗漏非均匀性的复杂渗漏条件的影响，以渗漏水对隧道结构安全影响为目标，首先通过试验揭示注浆层对盾构隧道渗漏水发展的影响规律；提出隧道-注浆层-地层耦合条件下隧道渗漏模拟方法，揭示复杂渗漏条件下隧道变形的发展规律；提出隧道结构性态评价指标，研究隧道变形对隧道结构性态的影响，揭示隧道结构性态演化规律，提出隧道结构性态控制标准和控制方法。为运营盾构隧道结构安全提供依据。

盾构隧道结构性能随着运营时间不断演化，而渗漏水作为影响隧道长期结构性态演化的重要因素之一，越来越引起人们的重视。隧道所处环境复杂，周围为土体-注浆层-衬砌三重介质，但是，目前研究没有充分考虑隧道周围的介质特点。本项目从室内试验、理论解析和数值模拟等多角度开展复杂渗漏条件下盾构隧道长期受力性能的演化研究。研究成果对评价和维护运营盾构隧道结构安全提供了技术支撑。.具体的研究内容和研究成果如下：（1）注浆体渗透性能试验研究。通过室内实验得到了不同浆液在不同固结压力和龄期下的渗透系数。（2）建立了隧道均匀渗漏条件下考虑注浆层影响的盾构隧道渗流场解析解，可以用于预测均匀渗水时隧道周围的孔隙水压力分布、地层沉降及隧道的沉降、受力和变形等长期性态。提出了能完整反映注浆层和衬砌渗透系特性影响的参数RPg，并能依据RPg进行渗水影响预测。（3）通过数值模拟揭示了局部渗水时地层及隧道横向长期性态的发展及注浆层的影响。渗水位置越靠下，渗水引起的地表沉降越小，而隧道沉降、内力及变形均越大，单侧渗水还引起隧道的侧移，渗水位置越靠下，隧道侧向位移越大，对隧道结构越不利。（4）揭示了渗透系数不均匀性对隧道结构性能的影响。渗水时，地层渗透系数各向异性对隧道纵向受力和变形越有利，最大竖向和水平变形曲率和弯矩越小，但是，地层渗透系数各向异性导致隧道横断面水平向拉伸和竖向压缩显著增大，对隧道结构非常不利。（5）基于隧道结构受力特点，建立了隧道直径变化和混凝土受力、螺栓受力以及接头张开量之间的关系，提出了以隧道直径变化作为评价隧道横向结构性态的判定指标。（6）揭示了隧道横向变形注浆控制机理，注浆初期，注浆对隧道的影响以管片转动为主，该阶段隧道接头张开量减小显著，而隧道收敛减小则相对缓慢；随注浆量的增加，注浆引起的管片运动以刚体平动位移为主，该阶段隧道横向收敛显著减小，但注浆引起的接头错台量和隧道侧向位移则不断增加。