大断面隧道下穿既有高墩大跨连续刚构桥施工技术

Construction Technique of Large Section Tunnel Undercrossing Existing Continuous Rigid Frame Bridge with High Pier and Large Span

成昆铁路扩能改造工程米易至攀枝花段垭口隧道下穿既有高墩大跨连续刚构桥,极大的偏压荷载、近接净距小及连续刚构桥的变形敏感性使得工程难度极大。本文采用数值模拟方法,从桥墩变形与位移的角度分析不同工法的适用性。研究结果表明:从桥墩沉降来看,双侧壁导坑法>CRD法>三台阶法;从桥墩水平位移来看,CRD法与双侧壁导坑法对桥墩的水平位移控制效果较好,三台阶法的控制效果一般。在保证上部桥梁结构安全的前提下综合考虑造价、进度等其他因素,建议采用双侧壁导坑法。

The Yakou tunnel of the Miyi to Panzhihua railway which is part of the Chengdu-Kunming capacity expansion and reconstruction project undercrossed the continuous rigid frame bridge with high pier and large span.Great engineering diff iculty is caused by great bias load,small clear distance and deformation sensitivity of the continuous rigid frame bridge.The suitability of construction method was studied from the perspective of the deformation and displacement of bridge pier by adopting numerical simulation method.The results show that from the point of the settlement of the pier,the both side drift method is the most effective one,followed by CRD method,and the three-step method is the least effective one,the CRD method and the both side drift method can better control the horizontal displacement of the pier while the control effect of the three-step method is common from the perspective of horizontal displacement of the pier.On the premise of ensuring the safety of the upper bridge structure and by considering other factors such as cost and progress,the both side drift method is recommended.