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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: The construction of municipal projects in large and medium-sized cities is developing rapidly. Among them, there are more and more deep foundation pit projects. Due to the scarcity of land resources, they will inevitably be close to the existing buildings or structures. In this paper, in view of the rare working condition of deep foundation pit excavation near the existing high speed railway abutment, combined with the finite element numerical simulation, the influence of the retaining structure of the foundation pit and the excavation of the deep foundation pit is analyzed and combined Field test data to verify the comparison, with a view to provide a reference and guidance for the future similar deep foundation pit project. The conclusions are as follows: (1) The unloading effect of deep foundation pit excavated the equilibrium state of soil and soil, and stress redistribution occurred. (2) Excavation of deep foundation pit caused the bottom of foundation pit to bulge, (3) The displacement field changes due to the change of stress field in rock and soil body. The structure (such as pile foundation) existing in rock and soil body will be deformed due to the movement of rock and soil body and will move to the inside of the pit , The deformation of the upper part of the pile is larger and the deformation of the lower part is smaller. (4) The numerical simulation data are in good agreement with the measured data in the field. The deformation after the excavation of the foundation pit is in the safe range, which proves that the design envelope and support plan Which plays an effective role in the safety of deep foundation pit. The design of the support scheme and the study of deformation of pile foundation can be applied to similar projects in the future.