邻近基坑开挖对千厮门大桥引桥安全性影响评估

发布时间：2019-05-19 23:31

【摘要】：随着我国城镇化建设的发展，地下空间逐渐被充分开发利用，特别地，在重庆这样的山地城市尤为明显。伴随着城市交通立体化的发展，深基坑工程紧邻城市桥梁和轨道交通车站的现象频频出现。深基坑的开挖打破了邻近桥梁和车站原有的平衡状态，势必对其安全性产生一定风险。因此，加强紧邻深基坑工程的城市桥梁风险研究显得非常重要。本文以重庆千厮门大桥为工程背景，围绕千厮门大桥引桥受邻近越洋深基坑开挖影响产生的风险展开研究，主要分析内容如下： ①风险指标体系是进行桥梁风险评估的基础和关键。基于此，从设计、施工、结构、环境、企业管理等角度总结了桥梁工程、基坑工程的风险指标体系。结合千厮门大桥引桥和越洋基坑工程特点，建立千厮门大桥引桥风险指标体系，包括边坡支护设计方案、基坑施工方式等6个一级风险指标和一阶支护、退台分阶支护、基坑开挖顺序等16个二级风险指标。 ②提出关键风险指标辨识、关键风险指标校验相结合的风险评估方法，并应用于千厮门大桥引桥的风险评估。基于熵理论，由专家打分确定单个风险指标权重，得到评判矩阵，依此建立风险辨识模型。通过计算单个风险指标熵值判断出关键风险指标。通过对千厮门大桥引桥计算表明：边坡支护设计方案为关键风险指标。基于基坑对桥梁影响机理分析，选取位移值和沉降值作为千厮门大桥引桥校验分析指标。以一阶支护和退台分阶支护两种方案作为分析模型，运用ABAQUS有限元分析技术，对千厮门大桥引桥和匝道的位移、沉降进行分析，以此校验关键风险指标，校验结果表明：关键风险指标可以接受。进一步对比分析两种支护方案下千厮门大桥引桥和匝道的位移值、沉降值，判断出退台分阶支护方案比一阶支护方案更合理。 ③风险评估是为了预防事故发生，应在风险评估基础上采取风险预控措施。基于千厮门大桥引桥风险预控体系，提出风险监控作为千厮门大桥引桥风险预控手段。根据千厮门大桥引桥风险评估结果和风险机制建立原则，从报警值、预警值、控制值建立千厮门大桥引桥三级预警机制。通过对Z01~Z18等18个沉降监测点和X01~X18等18个位移监测点进行监测，实现对千厮门大桥引桥的风险预控。基于引桥与基坑空间位置关系，选取X06~X08、X10~X12、Z06~Z08、Z10~Z12等关键监测点进行数据分析，，分析结果表明：千厮门大桥引桥和匝道的位移值、沉降值未超过报警值，风险在可控范围内。论文提出的风险评估方法在千厮门大桥引桥风险分析中适应性强，可为类似工程的风险控制提供分析思路和经验，论文构建的风险评估方法及风险监控手段具有一定应用价值。最后，对城市桥梁风险评估研究进行了展望，提出了在此领域需要进一步开展的研究工作。
[Abstract]:With the development of urbanization in China, underground space is gradually being fully developed and utilized, especially in mountainous cities such as Chongqing. With the development of three-dimensional urban traffic, the phenomenon of deep foundation pit engineering adjacent to urban bridges and rail transit stations occurs frequently. The excavation of deep foundation pit breaks the original equilibrium state of adjacent bridges and stations, and is bound to pose certain risks to its safety. Therefore, it is very important to strengthen the study of urban bridge risk adjacent to deep foundation pit engineering. In this paper, based on the engineering background of Chongqing Qianshuangmen Bridge, the risk caused by the influence of adjacent ocean-crossing deep foundation pit excavation on the approach bridge of Qianshuangmen Bridge is studied. The main analysis contents are as follows: 1 the risk index system is the basis and key of bridge risk assessment. Based on this, the risk index system of bridge engineering and foundation pit engineering is summarized from the aspects of design, construction, structure, environment, enterprise management and so on. Combined with the characteristics of the approach bridge of Qianshuangmen Bridge and the transoceanic foundation pit engineering, the risk index system of the approach bridge of Qianshuangmen Bridge is established, including six first-order risk indexes, such as slope support design scheme, foundation pit construction mode, first-order support and step-out support. There are 16 secondary risk indexes such as excavation sequence of foundation pit. (2) the risk assessment method based on the identification of key risk index and the verification of key risk index is put forward and applied to the risk assessment of the approach bridge of Qianshuimen Bridge. Based on entropy theory, the weight of a single risk index is determined by expert scoring, and the evaluation matrix is obtained, according to which the risk identification model is established. The key risk index is judged by calculating the entropy value of a single risk index. Through the calculation of the approach bridge of Qianshuangmen Bridge, it is shown that the design scheme of slope support is the key risk index. Based on the analysis of the influence mechanism of foundation pit on the bridge, the displacement value and settlement value are selected as the calibration and analysis indexes of the approach bridge of Qianshuangmen Bridge. The displacement and settlement of approach bridge and ramp of Qianjiangmen Bridge are analyzed by using ABAQUS finite element analysis technology, and the key risk indexes are verified by using the two schemes of first-order support and step-by-step support as analysis models, and the finite element analysis technique is used to analyze the displacement and settlement of the approach bridge and ramp of Qianjiangmen Bridge. The verification results show that the key risk indicators are acceptable. Furthermore, the displacement and settlement values of the approach bridge and ramp of Qianshuangmen Bridge under the two supporting schemes are compared and analyzed, and it is judged that the step-out support scheme is more reasonable than the first-order support scheme. In order to prevent accidents, risk pre-control measures should be taken on the basis of risk assessment. Based on the risk pre-control system of Qianshuangmen Bridge approach bridge, risk monitoring is put forward as a means of risk pre-control of Qianshuangmen Bridge approach bridge. According to the risk assessment results and the establishment principle of risk mechanism of Qianshuangmen Bridge approach bridge, the three-level early warning mechanism of Qianshuangmen Bridge approach bridge is established from alarm value, early warning value and control value. Through the monitoring of 18 settlement monitoring points such as Z01~Z18 and 18 displacement monitoring points such as X01~X18, the risk pre-control of the approach bridge of Qianshuangmen Bridge is realized. Based on the spatial position relationship between approach bridge and foundation pit, the key monitoring points such as X06 / X08, X10 / X12, Z06 / Z08, Z10 / Z12 are selected for data analysis. The results show that the displacement value and settlement value of approach bridge and ramp of Qianjiangmen Bridge do not exceed the alarm value, and the risk is within the controllable range. The risk assessment method proposed in this paper has strong adaptability in the risk analysis of the approach bridge of Qianshuangmen Bridge, and can provide analysis ideas and experience for the risk control of similar projects. The risk assessment method and risk monitoring method constructed in this paper have certain application value. Finally, the research on urban bridge risk assessment is prospected, and the further research work in this field is put forward.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU753;U447

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