地震断裂带高铁大跨拱桥深基坑钢板桩围堰支护试验与监测

Experiment and monitoring on support of steel sheet pile cofferdam for deep foundation pit of large-span arch bridge for high-speed railway through seismic fracture zone

针对大跨度高速铁路拱桥建设对深基坑开挖施工的安全性要求,为了研究钢板桩围堰支护在大跨度高速铁路拱桥深基坑施工中的可行性,以新建徐盐高铁徐洪河特大桥工程项目为依托,通过数值模拟及现场试验监测,对深基坑钢板桩围堰支护在施工过程中的形变及受力情况进行分析。结果表明:通过有限元模拟分析,钢板桩围堰最危险受力点处于钢板桩中部、中上部及四角连接处,围堰第4道内支撑内力较其他3道内支撑大。整个施工过程中工况5为施工最不利工况。由监测结果可知,在施工过程中钢板桩单日最大位移值为2.8 mm,最大累计位移值为24.0 mm,均未达到预警值,施工过程中钢板桩形变稳定。钢支撑轴力受基坑周边荷载的影响明显,围堰钢支撑最大压力值为147.31 kN,最大拉力值为24.95 kN,未达到预警值,结构安全。研究结果可供同类型工程施工参考。

Aiming at the safety requirements for the excavation of deep foundation pit for the construction of large-span arch bridge for high-speed railway, the deformation and stress statuses of the support for the steel sheet pile cofferdam for deep foundation pit are analyzed through the numerical simulation and the relevant in situ experiment and monitoring in accordance with the newly constructed project of Xuhonghe River Super-Large Bridge for Xuzhou-Yancheng High-speed Railway, so as to study the feasibility of the application of steel sheet pile cofferdam to the construction of deep foundation pit for large-span arch bridge for high-speed railway. The study result shows that through the relevant finite element simulative analysis, the most dangerous stress points of the steel sheet pile cofferdam are located at the mid part, the mid-upper part and the four corner joints of the steel sheet pile, while the internal force of the fourth support of the cofferdam is larger than that of the other three supports. During the whole construction condition, the working condition V is the most unfavorable one. It is known from the relevant monitoring that the maximum displacement/day of the steel sheet pile during the construction process is 2.8 mm and the maximum cumulated displacement is 24.0 mm, and then both of them do not reach their early warning values, thus the deformation of the steel sheet pile is stable during the construction process. The impact from the surrounding load of the foundation pit on the steel support is obvious, while the maximum pressure of the steel support of the cofferdam is 147.31 kN and the maximum tensile force is 24.95 kN, and then both of them do not reach their early warning values, thus the structure is safe. The study result can provide reference for the similar project.