盾构隧道穿越上软下硬地层扰动机理及应对措施研究

发布时间：2018-05-28 03:27

本文选题：盾构隧道 + 上软下硬地层　；参考：《西南交通大学》2017年硕士论文

【摘要】：上软下硬地层是盾构隧道施工中经常遇到的一种特殊地质条件,由于开挖面地层特性的不均一性,在"软硬不均地层"中盾构掘进过程中,常常出现盾构姿态不佳、管片局部应力集中甚至发生破损、地表沉降难以控制等诸多难题,使得施工质量及工期等难以得到保障。探明盾构在上软下硬地层掘进过程中对周围地层的扰动机理及管片衬砌结构的受力特性,对于提升盾构隧道在上软下硬地层安全快速掘进具有重要意义。论文以深圳地铁7号线西西区间盾构隧道穿越上软下硬地层为工程背景,综合采用理论分析、离散元数值模拟等研究方法,从宏观和细观层面上对上软下硬地层中盾构掘进引起的地层扰动机理进行了系统分析,对上软下硬地层盾构施工中的地层改良进行了探讨,并通过将不同掘进参数对地层扰动的影响与现场对掘进参数的统计数据相结合,开展了盾构穿越上软下硬地层掘进参数的优化研究,得出以下主要成果:1、对上软下硬地层中盾构掘进对地层的扰动机理进行理论分析,采用三维颗粒流离散元数值模型模拟了上软下硬地层中盾构掘进所引起的扰动影响,在盾构掘进引起地层扰动分区的基础上,提出了上软下硬地层中盾构掘进引起的地层扰动分区。2、对岩性地层进行细观参数标定,采用颗粒流离散元分析软件PFC建立土压平衡盾构机(包括刀盘、刮刀、滚刀、土仓及盾壳等结构)—上软(软岩)下硬(硬岩)地层的三维离散元精细化模型,考虑滚刀破岩机理,提出了滚刀模型先随刀盘平动和转动微小时段再自转相同步数的滚刀破岩离散化模拟方法。3、针对硬岩部分占掌子面25%、50%、75%等三种不同比例条件,在细观层面上从地层中土体颗粒间接触状态、颗粒位移及地层应力的变化对上软下硬地层中盾构掘进引起的地层扰动进行了对比分析,探明了上软下硬地层硬岩占比不同条件下盾构掘进对周围地层的扰动规律。4、采用三维数值模拟对不同地层条件及掘进参数下盾构掘进引起地层扰动进行了对比分析,探明了加固软弱地层对有效降低盾构掘进对地层变形及管片内力的影响,并结合掘进参数的现场统计数据,给出了盾构穿越上软下硬地层时盾构顶推力、掘进速度与刀盘转速的参数优化结果。
[Abstract]:Upper soft and lower hard stratum is a special geological condition often encountered in shield tunneling construction. Due to the heterogeneity of stratum characteristics of excavating surface, shield tunneling posture is often not good in the course of shield tunneling in "soft and hard uneven strata". The local stress concentration and even the damage of the segment, the surface subsidence is difficult to control and so on, which makes the construction quality and construction period difficult to be guaranteed. It is of great significance to prove the disturbance mechanism of shield tunneling to surrounding strata and the mechanical characteristics of segment lining structure in the driving process of upper soft and hard stratum, which is of great significance for the safe and rapid excavation of shield tunnel in upper soft and hard stratum. Based on the engineering background of the shield tunneling in the west section of Shenzhen Metro Line 7 through the upper soft and the lower hard strata, this paper synthetically adopts theoretical analysis, numerical simulation of discrete element and other research methods. In this paper, the mechanism of stratum disturbance caused by shield tunneling in upper soft and hard stratum is systematically analyzed from macro and micro level, and the formation improvement in shield construction of upper soft and hard stratum is discussed. By combining the influence of different tunneling parameters on formation disturbance and the statistical data of field tunneling parameters, the optimization of tunneling parameters of shield tunneling through upper soft and hard strata is studied. The following main achievements are obtained: 1. The disturbance mechanism of shield tunneling in upper soft and hard strata is theoretically analyzed, and the disturbance effect caused by shield tunneling in upper soft and hard stratum is simulated by using three dimensional particle flow discrete element numerical model. On the basis of the division of stratum disturbance caused by shield tunneling, the zone of stratum disturbance caused by shield tunneling in upper soft and hard stratum is put forward, and the meso-parameters of lithologic strata are calibrated. A three dimensional discrete element fine model of earth pressure balance shield machine (including cutter head, scraper, hob, earth bin and shield shell) under hard (hard rock) strata is established by using particle flow discrete element analysis software PFC. Considering the rock breaking mechanism of hob, a numerical simulation method of hob breaking rock discretization is put forward, in which the hob model firstly moves and rotates the same number of steps with the small time interval of the cutter head, and aiming at three different proportion conditions, such as the hard rock part occupies 2550% and 75% of the face of the palm. At the meso level, the disturbance caused by shield tunneling in upper soft and hard strata is compared and analyzed from the contact state of soil particles in stratum, the change of particle displacement and formation stress. The disturbance law of shield tunneling to surrounding strata under different conditions of hard rock ratio in upper soft and hard strata is proved. The three dimensional numerical simulation is used to compare and analyze the stratum disturbance caused by shield tunneling under different formation conditions and tunneling parameters. The effect of strengthening soft stratum on effectively reducing the deformation of stratum and the internal force of segment in shield tunneling is proved. Combined with the field statistical data of tunneling parameters, the top thrust of shield is given when the shield passes through the upper soft and lower hard stratum. Optimization results of the parameters of tunneling speed and cutter speed.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U455.43

【参考文献】