土岩组合地层拱盖法隧道施工动态风险评估

发布时间：2018-06-19 21:39

本文选题：土岩组合地层 + 拱盖法隧道　；参考：《中国海洋大学》2014年博士论文

【摘要】：目前，城市交通拥挤问题愈发明显，而地铁以其绿色环保、准点迅捷、运载量大、能耗低等优点，被认为是解决城市拥挤问题的最有力手段。我国目前修建地铁的城市有20多座，青岛全市规划城市轨道交通线19条，目前在建的有3条，但由于施工经验的不足以及地层环境的复杂多变，建设工期无法保证。阻碍青岛市地铁建设工期的一个重要因素就是大跨度暗挖车站的建设。暗挖法施工风险大、工作面少且小等缺点，导致青岛地铁多处暗挖车站工期滞后。拱盖法相比较其他暗挖工法，更能合理地利用青岛地区土岩组合的地层特性，达到高效施工、节约成本、缩短工期的效果。但同时，拱盖法的施工风险因素存在于分部开挖、初支架设、临时支撑拆除等各个环节中，且一旦发生事故后果严重。为了在青岛地区推广拱盖法，有必要对其施工过程进行全面细致的风险分析及评估。本文以青岛土岩组合地层为研究背景，对土岩组合地层环境下拱盖法隧道施工动态风险评估进行研究。主要研究内容和结论如下： (1)拱盖法在土岩组合复杂地层环境中的适用性研究。研究表明：从控制围岩变形的风险角度来看，拱盖法要优于台阶法和双侧壁导坑法。通过数值模拟手段，对拱盖法施工围岩适用性进行分析，结果表明：拱脚处围岩条件相同时，拱顶沉降随埋深的增加而减小；当埋深相同时，拱脚处围岩条件对地表沉降的影响不大；拱脚座落在中风化岩层时，拱顶和地表沉降均处于安全范围内。 (2)拱盖法施工的主要风险源筛选。采用专家调查法，筛选出拱盖法施工主要风险源，即开挖工序、支撑拆除以及施工对周边环境的影响。 (3)拱盖法隧道开挖过程风险评估。采用数值计算与模型试验的方法对拱盖法施工过程中围岩压力变化及土体变形特点进行研究，研究表明：上断面开挖过程中中导洞开挖造成的位移最大，下断面开挖围岩变形几乎不发展，中洞开挖~施做拱部二衬完成阶段为变形发展最急剧阶段；在掌子面推进过程中，监测断面各部位围岩荷载的释放过程具有较大差异性，拱部围岩荷载相比于拱脚和边墙释放更快，且幅度更大。采用模糊综合评价方法对开挖过程风险评估：中洞开挖阶段风险等级为A级，拆除竖撑~施做拱部二衬阶段风险等级为B级，右导洞开挖阶段风险等级为C级，左导洞开挖阶段风险等级为D级，下断面围岩开挖阶段等级为E级。 (4)拱盖法支撑拆除风险评估。首先针对青岛土岩组合地区拱盖法施工特点，总结了适用于拱盖法隧道的拆撑过程永久初期支护安全控制方法；然后根据数值计算结果，对各拆撑方案进行风险分级，建议现场拆撑采用风险级别较小的方案3，即从两侧向中间间隔对称拆撑。 (5)拱盖法施工对周边环境的影响及风险评估。首先针对青岛土岩组合地区拱盖法隧道的施工特点，总结了适用于拱盖法隧道分部开挖的位移控制机理；其次采用模型试验的方法对大断面拱盖法施工隧道围岩渐进性塌方破坏机制进行研究，研究结果表明：在竖向超载条件下，隧道围岩破坏区域呈渐进扩大趋势，无支护段围岩最先发生破坏，然后依次扩展至初喷混凝土竖撑段和二衬施做段，最终破坏区面积顺次由大到小；隧洞破坏区均主要集中在各段拱顶部位，，是衬砌结构破坏和围岩塌落的主要来源，拱脚及边墙部位未见明显破坏。然后基于实测数据进行动态风险评估，用风险指标法作了计算，根据实测数据分析、现场巡视模型，评价拱盖法隧道施工的安全状态，把对周围环境的影响降到最低，得出了适用于青岛拱盖法隧道施工的各监测项目风险预警值和风险巡视预警标准。 (6)综合风险评估模型的工程应用。利用层次分析法，对拱盖法隧道施工主要风险因素进行权重分配，综合考虑各项风险因素，建立综合风险评估模型并在某车站中成功应用。
[Abstract]:At present, the problem of urban traffic congestion is becoming more and more obvious, and the subway is considered to be the most powerful means to solve the problem of urban congestion because of its green environmental protection, rapid transit, heavy load and low energy consumption. There are more than 20 cities in China at present, 19 in Qingdao City, and 3 in construction at present. The shortage of working experience and the complex and changeable formation environment, the construction period can not be guaranteed. One important factor hindering the construction period of the subway in Qingdao is the construction of the large span dug station. The construction risk of the dark excavation method is large and the working face is small and small, which leads to the lag of the time period of the underground excavation stations in Qingdao Metro. The arch cover method compares the other dark ways. The excavation method can make use of the stratigraphic characteristics of the soil rock combination in Qingdao more reasonably, to achieve efficient construction, save cost and shorten the effect of the construction period. At the same time, the construction risk factors of the arch cover method exist in various links such as subsection excavation, initial support erection, temporary support dismantling and so on, and once the accident consequences are serious. In order to spread in Qingdao area It is necessary to carry out comprehensive and meticulous risk analysis and evaluation on the construction process of the arch cover. This paper studies the dynamic risk assessment of the construction of the tunnel under the combined stratum of soil and rock under the environment of the combined soil and rock formation in Qingdao. The main contents and conclusions are as follows:
(1) the applicability of the arch cover method in the complex stratum environment of the soil rock combination. The study shows that the arch cover method is superior to the step method and the two side wall guide method from the angle of controlling the deformation of the surrounding rock. The application of the surrounding rock in the construction of the arch cover method is analyzed by the numerical simulation method. The result shows that the vault is the same when the surrounding rock conditions are the same. The settlement decreases with the increase of buried depth, while the surrounding rock conditions at the arch foot have little effect on the surface settlement while the arch foot is located in the medium weathered rock layer, and the vault and surface settlement are in a safe range.
(2) screening the main risk sources of the arch cover method construction. By using the expert investigation method, the main risk sources of the arch cover method are screened out, that is, the excavation process, the support demolition and the influence of the construction on the surrounding environment.
(3) the risk assessment of tunnel excavation process of arch cover method. Numerical calculation and model test are used to study the changes of surrounding rock pressure and soil deformation during the construction process of the arch cover method. The study shows that the displacement of the middle tunnel in the process of upper section excavation is the largest, the deformation of the surrounding rock is almost not developed, and the middle cave excavation is applied to the tunnel. At the completion stage of the two lining of the arch, it is the most dramatic stage of deformation development, and the release process of the surrounding rock load of each part of the monitoring section is quite different during the process of pushing the face of the palm, and the load of the surrounding rock of the arch is faster and larger than the arch foot and the side wall. The risk assessment of the excavation process by the fuzzy comprehensive evaluation method: the opening of the middle hole. The risk grade of the excavation stage is grade A, and the risk grade of the two lining phase of the two stage is C, the risk grade of the right diversion stage is D, the risk grade of the left guide tunnel is grade D, and the grade of the lower section of the surrounding rock is E grade.
(4) the arch cover method to support the risk assessment of demolition. Firstly, according to the construction characteristics of the arch cover method in Qingdao soil rock combination area, this paper summarizes the permanent initial support safety control method suitable for the arch cover method tunnel opening process, and then according to the numerical calculation results, the risk classification is carried out for the dismantling schemes. Case 3, that is, the symmetrically dismantling from both sides to the middle interval.
(5) the influence of the arch cover method on the surrounding environment and the risk assessment. Firstly, according to the construction characteristics of the arch cover tunnel in Qingdao soil rock combination area, the displacement control mechanism suitable for the subsection excavation of the arch cover tunnel is summarized. Secondly, the model test method is used to carry out the progressive collapse mechanism of the surrounding rock of the tunnel under the large section arch cover method. The research results show that under the vertical overloading condition, the surrounding rock failure area of the tunnel is gradually expanding, and the surrounding rock of the non supporting section first breaks down, and then extends to the initial spraying concrete vertical bracing section and the two lining section, and the area of the final destruction area is from large to small, and the tunnel failure area is mainly concentrated in the different sections of the vault. The main source of lining structure destruction and surrounding rock collapse is not obvious damage. Then the dynamic risk assessment is carried out based on the measured data, and the risk index method is used to calculate. According to the measured data analysis, the site inspection model is used to evaluate the safety state of the tunnel construction in the arch cover method, and to minimize the influence on the surrounding environment. The risk early-warning value and risk inspection and early warning standard of each monitoring project applicable to Qingdao arch tunnel construction are presented.
(6) the engineering application of the comprehensive risk assessment model. By using the analytic hierarchy process (AHP), the main risk factors of the tunnel construction are weighted, and the risk factors are taken into consideration, and the comprehensive risk assessment model is established and applied successfully in a station.
【学位授予单位】：中国海洋大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：U455

【参考文献】