深基坑开挖对邻近既有高铁桩基影响研究

Research on the Influence of Excavation of Deep Foundation Pit to Adjacent Existing High-speed Railway Bridge Pile Foundations Stability

研究目的:大中型城市的市政工程建设高速发展,其中深基坑工程越来越多,由于土地资源稀缺,其不可避免地会近接既有建筑或结构。本文针对深基坑开挖邻近既有高速铁路桥基的少见工况,结合有限元数值模拟进行研究,对基坑围护结构与桩基受深基坑开挖影响的规律进行分析,并结合现场实测数据进行对比验证,以期为今后类似的深基坑近接工程提供参考与指导意义。研究结论:(1)深基坑开挖的卸荷效应使得坑周岩土体平衡状态遭到破坏,进而发生应力重分布;(2)深基坑开挖导致基坑底部隆起,围护结构向坑内发生移动;(3)岩土体应力场改变带来位移场改变,赋存于岩土体中的结构物(如桩基)由于岩土体的运动而发生变形,基本均向坑内移动,桩基上部变形较大,下部变形较小;(4)数值模拟数据与现场实测数据对比基本吻合,基坑开挖完成后产生的变形均处于安全范围,证明了设计的围护与支撑方案对深基坑安全起到有效作用,该支护方案设计以及桩基变形规律研究可应用于今后类似工程中。

Research purposes： In large and medium- sized cities, the municipal engineering constructions have developed rapidly, which leads that the deep foundation pit engineering is more and more. Because of the lack of construction land, it＇s evitable that there will be existing building or structures around the deep excavations. In this paper, combined with the rare condition that there are high - speed railway bridge pile - foundations around the deep foundation pit, through FEM numerical simulation, the influence pattern of deep foundation pit＇ s excavation to supporting structures and pile foundations is analyzed, and then the numerical results are verified with on -site monitoring data. Finally, the conclusions can provide reference and guide for similar adjacent engineering.Research conclusions ： （ 1 ） Deep foundation pit＇ s excavation causes the unloading effect, which breaks the balance of surrounding rock and soil mass, then stress redistribution occurs. （2）The deep foundation pit excavation causes the upheaval of foundation pit, and the envelop enclosure moves forward into the pit. （3） The stress field＇ s change causes the displacement field＇ s change, and the structure such as pile foundations in the rock and soil mass moves as the result of rock and soil＇ s displacement. The direction of pile foundations is basically toward pit, whose displacement of upper part is bigger and displacement of lower part is smaller. （4）The simulation data is matched with test data, which means that the final displacements are all within the safety range, and proves that the supporting structure design in this project is effective to deep foundation pit＇ s safety. The kind of supporting structure design and pile foundations displacement patterns can be used in future similar engineering.