基于周期性薄片模型的软土直线及曲线地铁盾构隧道车致长期变位研究

The train-induced long-term position change of metro shield tunnel in soft soils is an important realistic problem related to the safety of tunnel structure and metro operation, therefore studying on it has very important significance. However, there are currently many deficiencies in the calculation theory for the train-induced long-term position change of shield tunnel, and there is not yet an effective analysis method for the curved shield tunnel. In addition, the influences of some key factors on the train-induced long-term position change of shield tunnel are also not clear. In this context, this project will study on the periodic slice models for analyzing the train-induced dynamic responses of both the straight and the curved track-shield tunnel-soil coupling systems, and explore the cumulative deformation characteristics of soft soil under cyclic loads. After that, the project will establish the effective prediction algorithms for the train-induced long-term position changes of both the straight and the curved metro shield tunnels in soft soils, and will then analyze the influences of some important factors such as line type and fastener type on the train-induced position change of shield tunnel based on these established algorithms. Through theoretical and test researches, three key and difficult problems will be addressed: (1) the high efficiency and high precision simulation for train-induced dynamic response of the track-tunnel-soil system; (2) the cumulative deformation characteristics in different directions of soft soil under cyclic loads and their differences; (3) the position change pattern of the curved shield tunnel under the long-term effects of train load. This project will play an important role in promoting and guiding the analysis and the treatment of related problems in the engineering practice in our country.

软土地铁盾构隧道车致长期变位是关系到隧道结构和运营安全的重要实际问题，对其进行研究具有十分重要的意义。然而，目前盾构隧道车致长期变位的计算理论还存有较多不足，尚无针对曲线隧道段的有效方法，且一些关键因素对盾构隧道车致变位的影响也不明确。在此背景下，本项目将研究直线及曲线段轨道-盾构隧道-地层耦合系统车致动响应分析的周期性薄片模型，探索循环荷载作用下软土的累积变形特性，进而建立直线及曲线两种线型软土地铁盾构隧道车致长期变位的有效预测算法，并以此分析线型及扣件类型等重要因素对隧道车致变位的影响及程度。通过理论和试验研究，拟解决3个关键难点问题：（1）列车荷载引起轨道-隧道-地层系统动响应的高效、高精度模拟；（2）软土在不同方向上的动力累积变形特性及差异；（3）曲线盾构隧道在列车荷载长期作用下的变位模式。本项研究将对我国工程实践中盾构隧道车致长期变位问题的分析及处理起到较大推动和指导作用。

软土地区大量地铁盾构隧道在列车荷载的长期作用下出现了严重的长期变位问题，这对地铁隧道的安全运营产生了极大的危害。为了研究这一问题，本项目首先从列车荷载作用下轨道-隧道-地层耦合系统动力响应的分析入手，分别针对地铁直线段及曲线段建立了相应的周期性薄片模型，实现了轨道-隧道-地层耦合系统动力响应问题的高效、高精度计算。项目随后通过开展动三轴试验，系统研究了循环荷载作用下软土在不同方向上的累积变形特性，明确了软土循环累积变形的特征。在这些研究的基础上，项目进一步构建了地铁直线段及曲线段车致长期变位的预测算法，分析了软土地铁直线段及曲线段车致长期变位的演变特征，揭示了地铁隧道线型及扣件类型等因素对隧道变位的影响及程度。通过项目的研究，主要得到了如下结论：1）项目所建立的轨道-隧道-地层系统车致动力响应分析的周期性薄片模型及隧道长期变位的预测算法具有较高的计算效率及计算精度，因而具有较高的工程应用价值；2）软土在垂向及水平方向上的循环累积变形特征具有显著差异；3）软土地铁盾构隧道的车致长期变位在地铁运营初期发展较为迅速，但在运营1~2年后，发展逐步趋缓，变位量值也会逐步趋于稳定；4）在列车荷载的长期作用下，软土曲线地铁盾构隧道不仅会产生一定量值的沉降，还会产生一定量值的朝向曲线隧道外侧的侧移，但通常侧移量值小于沉降量值；5）地质条件是决定软土地铁盾构隧道车致长期变位的主要因素，轨道扣件类型及列车运营速度对隧道长期变位的影响不大，而地铁线型虽然对隧道的长期垂向沉降影响也不大但会显著影响隧道的长期横向侧移。项目的研究成果对工程实践中盾构隧道车致长期变位问题的分析及处治将起到一定的推动和指导作用。