高水压砂土地层中泥水盾构隧道开挖面失稳机理与风险评估研究

发布时间：2019-04-12 07:22

【摘要】：随着我国地下空间的大规模开发利用,盾构隧道工程的环境条件越来越复杂,施工中出现了诸多问题,其中较为突出的是支护压力不足造成的开挖面失稳及地层变形过大。特别是近年来我国水下盾构隧道工程快速发展,由于覆土厚度一般较浅、水压较大,开挖面稳定难以控制,稍有不慎就有可能发生开挖面坍塌和水体倒灌等事故。因此,研究高水压条件下盾构隧道开挖面失稳风险具有现实意义。本文结合南京地铁10号线江心洲站～中间风井区间过江隧道工程,通过理论分析、数值模拟以及现场调查和实测等方法,对高水压条件下砂土地层中泥水盾构隧道施工过程中的开挖面稳定性相关问题进行了研究,主要工作和研究成果包括以下几个方面： (1)利用Handy拱效应理论和Mohr-Coulomb准则得出了失稳土体形状的计算方法,失稳土体形状类似贝壳形。基于极限平衡分析理论建立了盾构隧道开挖面稳定性分析模型,并将模型的计算结果与其他理论分析方法、离心试验以及数值模拟分析的结果进行了对比。提出了可用于指导施工的开挖面支护压力极限值工程参考图。 (2)利用FLAC3D有限差分程序计算了高水压条件下砂土地层中大直径泥水盾构隧道开挖面支护压力极限值,分析了砂土内摩擦角、黏聚力、弹性模量、隧道埋深、直径、水位等因素对开挖面支护压力的影响,研究了失稳破坏模式以及失稳过程中土压力的变化规律。结果表明,高水压条件下开挖面支护压力极限值比无水压时增大约一个量级。 (3)借鉴W. Kent Muhlbauer提出的在管道风险管理领域应用广泛的肯特法的基本思想,对泥水盾构隧道开挖面失稳风险进行了分析,将风险因素分为地质指数、隧道指数、设计指数、施工指数等项,建立了风险评估模型。修改肯特法中相关指数的评分准则,采用风险指数先相加、再与后果系数相乘的算法计算相对风险评估值,得分越高,风险越大。 (4)结合南京地铁10号线江心洲站～中间风井区间过江隧道工程,利用本文建立的泥水盾构隧道开挖面失稳风险评估模型,选取了开挖面失稳风险相对较大和较小的2个典型断面进行了开挖面失稳风险评估,并根据评估结果分析了导致事故发生的主要风险因素,给出了在施工过程中对盾构施工参数进行有针对性的动态调整的建议。
[Abstract]:With the large-scale development and utilization of underground space in China, the environmental conditions of shield tunnel project are becoming more and more complex, and there are many problems in construction, especially the instability of excavation surface and excessive deformation of strata caused by insufficient support pressure. Especially in recent years, with the rapid development of underwater shield tunnel engineering in China, due to the shallow thickness of soil and high water pressure, it is difficult to control the stability of excavation surface. Some accidents such as the collapse of excavation surface and the backfilling of water body may occur when the excavation surface collapses. Therefore, it is of practical significance to study the risk of shield tunnel excavation surface instability under high water pressure. In this paper, through theoretical analysis, numerical simulation and on-the-spot investigation and measurement, this paper combines the Jiangxinzhou station-middle wind shaft tunnel project of Nanjing Metro Line 10 with the methods of theoretical analysis, numerical simulation, field investigation and measurement, etc. The problems related to the stability of excavated face during the construction of mud-water shield tunnel in sand-soil formation under high water pressure are studied in this paper. The main work and research results are as follows: (1) based on Handy's arch effect theory and Mohr-Coulomb 's criterion, the calculation method of unstable soil shape is obtained. The shape of unstable soil is similar to shell shape. Based on the theory of limit equilibrium analysis, the stability analysis model of shield tunnel excavation surface is established, and the calculation results of the model are compared with the results of other theoretical analysis methods, centrifugal tests and numerical simulation analysis. This paper puts forward the engineering reference drawing of the limit pressure value of the excavation face support which can be used to guide the construction. (2) FLAC3D finite difference program is used to calculate the limit value of support pressure in large diameter mud-water shield tunnel under the condition of high water pressure, and the internal friction angle, cohesion, elastic modulus, tunnel depth and diameter of sand are analyzed. The influence of water level and other factors on the supporting pressure of excavation surface is studied. The failure mode of instability and the variation rule of soil pressure in the process of instability are studied. The results show that the limit value of support pressure under high water pressure is about one order of magnitude higher than that without water pressure. (3) referring to the basic idea of Kent method, which is widely used in the field of pipeline risk management proposed by W. Kent Muhlbauer, this paper analyzes the risk of instability in the excavation surface of mud-water shield tunnel, and divides the risk factors into geological index, tunnel index and design index, and the risk factors are divided into geological index, tunnel index and design index. Construction index and other terms, established a risk assessment model. The relative risk evaluation value is calculated by adding risk index and multiplying the result coefficient. The higher the score is, the greater the risk is, the higher the score is, the more the risk is calculated by using the algorithm of adding risk index first and multiplying the result coefficient. (4) combined with the Jiangxinzhou station-middle wind shaft cross-river tunnel project of Nanjing Metro Line 10, the risk assessment model of mud-water shield tunnel excavation surface instability is established in this paper. In this paper, two typical sections with relatively large and small risk of excavation surface instability are selected to evaluate the risk of excavation surface instability, and the main risk factors leading to the accident are analyzed according to the evaluation results. Some suggestions for dynamic adjustment of shield construction parameters during construction are given.
【学位授予单位】：北京交通大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：U455.43

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