框架桥下穿既有铁路施工风险监控研究

框架桥顶进施工会引起铁路周围路基土体的位移,如何有效控制位移,对施工及确保铁路行车安全非常重要。分析框架桥施工的风险等级,对其不利位置进行重点监控,通过整理现场监控点的位移变化,来分析施工过程的风险情况,监测数据一旦超出规定的容许范围,及时采取合理的风险控制措施来纠正施工。通过建立三维数值模型,计算出路基最终沉降模拟结果,并与现场监控值进行对比分析,以验证模型的合理性;通过数值模拟进一步研究单因素开挖步尺对路基沉降的影响,提出最佳开挖步尺,为框架桥工程提供借鉴性参考。结论:(1)路基最大沉降位置在偏移轴线一定距离处;(2)水平位移在框架桥轴线位置最大;(3)最佳开挖步尺为2 m/d。

Research on the Risk Monitoring of Frame Bridge Construction under Existing Railway

Because of the displacement of surrounding subgrade soil caused by frame bridge jacking construction,the method to effectively control the displacement is very important for construction safety.In this paper,risk level of the frame bridge construction is analyzed,and the unfavorable positions are monitored intensively. By sorting out displacement changes of site monitoring points,the risks in the construction process are analyzed. Once themonitoring data exceeds the allowable range,reasonable risk control measures are timely taken to correct the construction. Through the establishment of three-dimensional numerical model to calculate the results of the final subgrade settlement simulation,the rationality of the model is verified after comparison with the on-site monitoring data. Numerical simulation is conducted to further study the influence of single-factor excavation step size on subgrade settlement. Then the best excavation step size is put forward to provide reference for the frame bridge project. The results of the analysis are as follows:(1) the maximum settlement position of the subgrade is at a certain distance from the offset axis;(2)the horizontal displacement is the maximum in the axis position of the frame bridge;(3)the optimal excavation step size is 2 m/d.