复合地层中考虑线路坡度的盾构隧道开挖面稳定性研究

发布时间：2018-05-10 09:49

本文选题：盾构隧道 + 开挖面稳定　；参考：《湖南大学》2015年硕士论文

【摘要】：随着我国经济实力的快速增长,全国各地的城市建设脚步不断向前,许多地区的现有交通建设已不能满足现代化城市的需求。如何有效地建设地下交通,以解决日益严峻的城市交通拥挤问题,已成为工程界与学术界共同关注的热点问题。盾构技术以施工速度快,劳动强度低等优点在地铁施工中得到了广泛应用。而在工程实践中,许多复杂的工程难题尚待解决,如何寻求更经济安全的施工方法,需要工程师与学者们来共同探讨。当盾构机在迎坡条件下经过软硬不均的复合地层时,由于线路坡度的影响和复合地层中上下土层的软硬不均和强度差异较大,从而导致盾构隧道开挖面支护力的控制与在平坡条件下的均质地层相比,相对来说要难把控得多。该支护力若没有施加得当,可能会导致盾构隧道开挖面的坍塌和地表塌陷等一系列工程事故。基于此原因,本文对盾构隧道在迎坡和复合地层条件下的的开挖面稳定性进行了针对性分析,以期为工程实践提供指导。首先,选用有限元数值软件ABAQUS进行盾构隧道开挖模拟。将计算结果与文献参考值对比,以验证其在分析此问题上的可行性。接下来利用该数值软件建立迎坡条件下复合地层中的盾构隧道开挖模型,以分析开挖面的稳定性。模拟得到了不同支护应力比下的盾构隧道开挖面前方土层的水平位移和竖向沉降等值云图,结合前人研究,给出了盾构隧道开挖面的极限支护力的值。然后分析开挖时的地表沉降规律。盾构隧道开挖面前方地层的水平位移和竖向沉降的值随支护力的逐渐降低而变大,而且影响的范围的越来越大,其竖向沉降的影响范围在隧道失稳破坏的时候已经扩展到了地表,水平位移相对来说,其影响范围则要小一些,水平位移的变化扩展范围仅集中在盾构隧道开挖面的前方区域。并对隧道进行了敏感性参数分析,讨论了线路坡度、土体内粘聚力和内摩擦角对开挖面极限支护力的影响。其次,对已有楔形体模型进行归纳总结,基于极限平衡法及筒仓理论提出了适用于迎坡条件下的复合地层中的楔形体模型,通过对平衡方程的求解得到极限支护力的表达式。进一步分析了埋深、开挖面土层厚度以及线路坡度和土体强度指标对极限支护力的影响。得到了如下结论:当线路破度相差较大时,开挖面极限支护力亦相差很大,迎坡条件与平坡条件应加以区分,不可等同对待。地层情况较均匀,土体强度参数差异不大时,考虑分层与否所得结果较为吻合;但在上下地层硬软不均时,其结果差异较大。最后,将前章所述的理论计算方法与有限元数值模拟方法应用于工程实例,并进行对比验证,证明利用本文方法研究盾构隧道开挖面稳定性问题的合理性与可行性。
[Abstract]:With the rapid growth of China's economic strength, the pace of urban construction in various parts of the country is constantly moving forward, and the existing traffic construction in many areas can no longer meet the needs of modern cities. How to effectively construct underground traffic to solve the increasingly serious urban traffic congestion has become a hot issue that the engineering and academic circles pay attention to. Shield technology has been widely used in subway construction with the advantages of fast construction speed and low labor intensity. In engineering practice, many complicated engineering problems remain to be solved. How to find more economical and safe construction methods needs engineers and scholars to discuss together. When the shield machine passes through the soft and hard composite strata under the condition of facing the slope, due to the influence of the gradient of the line and the difference of the soft and hard and the strength of the upper and lower soil layers in the composite stratum, Therefore, it is more difficult to control the support force of shield tunnel compared with the homogeneous stratum under the condition of flat slope. If the support force is not properly applied, it may lead to a series of engineering accidents such as excavation surface collapse and surface collapse of shield tunnel. For this reason, this paper analyzes the stability of excavation surface of shield tunnel under the conditions of facing slope and composite stratum, in order to provide guidance for engineering practice. Firstly, the finite element numerical software ABAQUS is used to simulate the excavation of shield tunnel. The results are compared with the reference values to verify the feasibility of the analysis. Then the excavation model of shield tunnel in composite stratum is established by using the numerical software to analyze the stability of excavating surface. The equivalent cloud map of horizontal displacement and vertical settlement in front of excavation surface of shield tunnel is obtained by simulation under different support stress ratio. Combined with previous studies, the value of limit support force of excavation surface of shield tunnel is given. Then the law of surface subsidence during excavation is analyzed. The horizontal displacement and vertical settlement of the stratum in front of the excavation surface of shield tunnel become larger with the decreasing of the supporting force, and the range of influence becomes larger and larger. The influence range of vertical settlement has been extended to the surface at the time of tunnel instability, but the horizontal displacement is relatively small, and the range of horizontal displacement is only concentrated in the front area of shield tunnel excavation surface. The sensitivity parameters of the tunnel are analyzed, and the effects of the slope of the tunnel, the cohesion of the soil and the angle of internal friction on the ultimate support force of the excavated surface are discussed. Secondly, based on the limit equilibrium method and silo theory, the wedge body model in composite strata is proposed, and the ultimate support force is obtained by solving the equilibrium equation. Furthermore, the influence of buried depth, excavation surface thickness, line slope and soil strength index on the ultimate support force is analyzed. The conclusions are as follows: when the breaking degree of the line is quite different, the ultimate support force of the excavated face is also very different, and the conditions of facing slope and the condition of flat slope should be distinguished and can not be treated equally. When the soil strength parameters are not different from each other, the results of stratification are consistent, but when the upper and lower strata are hard and soft, the results are quite different. Finally, the theoretical calculation method and the finite element numerical simulation method mentioned in the previous chapter are applied to engineering examples, and the feasibility and rationality of using this method to study the stability of excavation surface of shield tunnel are proved.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U455.43

【参考文献】