【作者】 赵冬安；

【导师】 郑俊杰；

【作者基本信息】 华中科技大学 ， 桥梁与隧道工程， 2011， 博士

【摘要】 随着我国经济的飞速发展,多数大中城市正在或即将修建地铁。由于城市地铁隧道建设的时间跨度大,动态变化大,管理难度大,因此地铁隧道施工风险具有多样性和多层次性,加之缺乏科学的风险评估工具和科学的风险管理体系,在现有城市地铁隧道建设过程中,安全事故时有发生。本文应用模糊理论故障树法和贝叶斯网络故障树法,对地铁盾构隧道施工成本风险、盾构隧道管片失效风险、车站深基坑工程失事风险展开了系统的分析和研究。首先,系统地介绍了故障树分析法的基本原理和分析步骤,以及构建故障树的基本方法、原则和具体步骤,阐述了故障树中逻辑门和系统结构函数的表达形式。介绍了故障树定性分析中利用上行法和下行法求解故障树最小割集的方法,以及定量分析中底事件重要度的基本原理和计算方法。鉴于传统故障树法的局限性,引入模糊数学理论对其进行改进,介绍了模糊理论中模糊集合与隶属度、模糊集运算、扩张原理、凸模糊集与兄截集、L-R型模糊数等相关知识,并给出了故障树分析的模糊算子,利用模糊数描述故障树底事件的发生概率,解决了实际中无法获取底事件精确概率的不足,而利用模糊门算子代替故障树的逻辑门算子,便得到了顶事件发生的概率模糊数,更能反映实际情况。最后重点介绍了两种常用的模糊重要度及计算方法。其次,应用三角模糊数故障树分析法,对地铁盾构隧道施工成本的风险进行了深入分析,计算得出了相应的成本重要度,并比较三角模糊数故障树法、传统故障树法和经济损失比相乘法三种方法的计算结果,结果表明：①三角模糊数考虑了各个风险因素对整个工程项目的影响以及底事件概率的模糊特性,计算结果具有较高的准确度。②在广佛地铁菊村站至西朗站城市地铁盾构隧道施工成本的实例计算中,“盾构进出洞时漏水漏浆情况”和“盾构掘进中遭遇障碍物”两项风险因素最为严重,应予以高度重视,建议在盾构施工前应高度重视和首先规避。然后,应用模糊故障树分析法,对地铁盾构隧道管片上浮、错台与开裂的失效进行了风险分析,计算表明：①基于模糊数表现定理,推导了模糊数乘法运算的精确求解法,为模糊数学在故障树理论中的应用打下了坚实基础。②从结构重要度的角度看,应首先规避“盾构机开挖推进姿态”和“注浆浆液参数”两项风险；对于“硬岩含水地层等不良地质”、“管片外弧面开裂”、“管片间的不均匀顶力”概率影响虽小,但结构重要度较大,应酌情采取提高施工水平及防护措施规避。③在三角模糊数相乘的运算中采用基于表现定理的精确求解法,可使计算结果更加精确；同时采用信心指数和三角模糊数修正专家评分数据,精确性很高,且操作简单,推荐使用。最后应用贝叶斯网络的故障树分析法,对地铁车站深基坑工程的风险进行了分析,结果表明：通过深基坑工程体系的贝叶斯网络模型计算分析,既得到了较精确的结果,又在表达形式的复杂程度上和运算速度上都明显优于传统故障树模型,且容易发现系统的薄弱环节。武汉地铁2号线循礼门车站深基坑的实例分析表明,基于贝叶斯网络的故障树分析法比传统故障树分析法更便捷更实用,同时解决了传统故障树模型中的规模问题和建模后的调整问题。本文的研究成果对于地铁盾构隧道的施工风险分析与控制具有重要的参考价值。更多还原

【Abstract】 With the rapid development of China’s economy, subways are being or will be constructed in most large and medium cities. Due to the long construction period, dynamic design scheme and difficult management, the risk of subway tunnel construction has the characteristics of diversity and multilevel, In addition, the scientific evaluation tool and management system of risk have not been formed, the contingencies usually occur in subway tunnel construction. In this dissertation, Fuzzy Fault Tree mathod and Bayesian Network Fault Tree method are employed to systematically study the risk of construction cost of shield tunnel, failure risk of segment of shield tunnel and failure risk of deep foundation pit of subway station.First of all, the fundamental principles and analysis procedure of fault tree method, as well as the general principles and specific steps of establishing a fault tree are systematically introduced. The logic gates and system structure function expression of the fault tree are also explained. The qualitative analysis method of fault tree describes uplink and downlink methods for solving the minimum cut set of the fault tree, the quantitative analysis method of fault tree explain the basic principles and calculation methods of importantance degree of events. Fuzzy theory is introduced to eliminate the limitations of the traditional fault tree. The theory of fuzzy sets and fuzzy membership, fuzzy set operations, expansion theory, convex fuzzy set andλcut set, L-R type fuzzy number and other relevant knowledge are also introduced, and fuzzy operator of fault tree analysis are given as well. Fuzzy numbers are used to describe the probability of the basic events in the fault tree, the problem that the precise probabilities of the basic events cannot be obtained is solved. The fuzzy gate operator used instead of the logic gate operator results in the fuzzy numbers of probability of occurrence of the top event, which can reflect the actual situation better. Finally, two kinds of commonly used fuzzy importance degree and their calculation methods are introduced.Secondly, the fault tree method based on triangular fuzzy numbers is applied to analyze the risk of construction costs of shield tunnel of subway, and the corresponding cost importance degrees are calculated and obtained. The calculated results obtained from the fault tree method based on triangular fuzzy number, the traditional fault tree method and economic loss multiplication method are compared, and the results show that:①the impact of various risk factors on the whole project, the fuzzy characters of bottom event probability are both considered in triangular fuzzy numbers method, and the results are relatively accurate.①during the construction period of a shield tunnel, the two most severe risks to total cost are "leakage of water and grout when the shield enters and leaves" and "encountering obstacles during advancing", which should be paid attention to and evaded by carrying out effective measures.Thirdly, the fuzzy fault tree method is employed to investigate the risks of the shield tunnel segment floating, the dislocation and cracking failure in subway shield tunnel, and the calculation results show that:①based on fuzzy number representation theorem, the exact solving method for multiplication of fuzzy numbers is derived, it is a solid foundation for the application of fuzzy theory in fault tree method.①according to the requirement of the important degree of the structures, the "shield machine advancing posture" and "grouting slurry parameters" risks should be avoided at first. The other three risks "poor geologic condition of water-bearing strata in hard rock", "cracking of segment extrados" and the "uneven jacking force between segments", although their probability impacts are small, the importance degrees of structures are great. Thus commensurate construction standards and appropriate protective measures should be adopted.③when the exact solving method based on the representation theorem is employed to calculate the multiplication of the triangular fuzzy number, it can make the results more accurate. Meanwhile, the confidence index and the triangular fuzzy number are used to modify the experts rating, and the obtained results have high accuracy and the method is simple to use. So this method is highly recommended.Finally, fault tree analysis method based on Bayesian network is employed to analyze the construction risk of deep excavation of the subway station, the results show that by using Bayesian network model on the deep excavation system, more accurate results are obtained and the complexity of the expression and the calculation speed are significantly superior to the traditional fault tree model, and it is easy to find the weaknesses in the system. Case study on deep fondation pit of Xunlimen station of Wuhan metro line 2 shows that the fault tree analysis method based on Bayesian network is more convenient and practical than the ordinary fault tree analysis method. Meanwhile, the problems in calculation scale and post adjustment of the ordinary fault tree model are also solved.The achievements In this dissertation can be valuable references for risk analysis and control of shiel tunnel in subway construction.更多还原