盾构施工诱发临近桥梁安全风险评价

Safety risk assessment of adjacent bridges induced by shield construction

针对地铁盾构施工诱发临近桥梁安全风险评估结果不完善、存在失真等问题,提出一种基于变权可拓云模型的盾构施工诱发临近桥梁安全风险评价方法。首先,结合以往研究基础和实际工程经验,建立盾构施工诱发临近桥梁安全事故机理模型,进而确定孕险环境、致险因子和承险体3个1级指标,其中包括有岩土层物理性能参数、隧道工程条件、盾构施工条件、盾构施工参数、施工管理风险、桥梁现状及桥梁自身条件7个2级指标和内摩擦角、弹性模量等27个3级指标为依据建立盾构施工诱发临近桥梁安全风险评价指标体系。其次,通过改进CRITIC客观赋权法获取评价指标权重,并采用变权可拓云模型构建盾构施工诱发临近桥梁安全风险评价模型,其中引入变权理论得到使评价结果更加科学合理的变化权重。最后,对某市轨道交通1号线一期工程Ⅱ标段沿线桥梁进行实例分析。研究结果表明,4座盾构施工临近桥梁安全风险等级分别为Ⅲ、Ⅱ、Ⅱ、Ⅰ级。其中,该施工场地各项土体指标、隧道覆跨比、隧道埋深、隧道直径及桥桩与隧道的相对位置等指标风险较大,即该段隧道盾构施工时对于桥梁自身情况及其施工场地环境需要重点监测,并严格做好周围土体加固等各项技术措施。研究结果可为盾构施工诱发临近桥梁安全风险防控提供科学有效的参考依据。

To address the problems such as imperfect and distorted safety risk assessment results of adjacent bridges induced by subway shield construction,a safety risk assessment method for adjacent bridges induced by shield tunneling based on variable weight extension cloud model was proposed.First of all,based on literature review and practical experience,a safety accident mechanism model of adjacent bridges induced by shield construction was established.Then,three level 1 indicators are defined including maternity environment,risk causing factor and risk bearing body were adopted.The safety risk evaluation indicator system of adjacent bridges induced by shield construction was established based on 7 second-level indicators,including geotechnical physical performance parameters,tunnel engineering conditions,shield construction conditions,shield construction parameters,construction management risks,bridge status and bridge conditions,and 27 third-level indicators,including internal friction angle and elastic modulus.Secondly,the evaluation index weight was obtained by the improved objective weighting method of CRITIC.The variable weight extension cloud model was used to construct the safety risk assessment model of adjacent bridges induced by shield construction.The variable weight theory was introduced to obtain a more scientific and reasonable change weight for the evaluation results.Finally,an example analysis was conducted on the bridges along the phase II section of the first phase of the rail transit Line 1 in a city,the results show that the safety risk levels of the bridges near the four shield construction wereⅢ,Ⅱ,Ⅱ,Ⅰ.Among them,the construction site such as soil index,tunnel overburden ratio,tunnel buried depth,tunnel diameter and the relative position of bridge pile and tunnel were main risk factors.That is,it was necessary to focus on monitoring the bridge itself and the construction site environment and strictly implement technical measures such as surrounding soil reinforcement during the shield construction of this section of tunnel.The research results can provide scientific and effective reference for prevention and control of safety risk in adjacent bridges induced by shield construction.