珠三角深厚软土层公路隧道深基坑围护结构变形分析

Supporting Parameter Sensitivity Analysis on Deep Foundation Pit of Highway Tunnel in the Pearl River Delta

摘要: 在以“围护桩 + 内支撑”支护方案下的软土深基坑中，围护结构参数的取值直接关系到支护的安全稳定性和经济合理性。本文以珠三角公路隧道深基坑工程为背景，采用非线性有限元分析软件MIDAS/GTS对该深基坑围护结构施工过程进行数值模拟，并将计算结果与监测结果进行对比分析。采用建立的计算模型，按单因素分析方法对深基坑围护结构变形的影响因素进行分析。结果表明：当桩径和支撑刚度增大时，围护结构的水平位移显著减小，从经济性考虑，二者存在一个最优值，当桩径达到1.1 m、支撑刚度达到2倍原设计值时，继续增大2类参数效果不再明显；围护桩嵌固深度主要影响墙体底部位移，围护桩的入土深度以嵌入基岩为上限，以保证不发生“踢脚”破坏为下限。

Abstract: The value of retaining structure parameter is directly related to the supporting security and eco-nomic rationality of deep foundation pit supported by “retaining pile + support within” in soft soil. This paper used analysis software MIDAS/GTS to simulate numerically retaining structure of deep foundation construction process by taking a foundation pit excavation in the section of highway tunnel as object. Meanwhile, analysis was made from its results compared with monitoring data. The influence factor of retaining structure of deep foundation excavation deformation was analyzed by single factor analysis using established calculation model. The results show that, the wall displacement was obvious affected by two parameters of the pile diameter and bracing stiffness, which existed an optimal value from economic considerations. When the pile diameter reached 1.2 m and support stiffness reached 2 times of the original design value, displacement constraints effect will be no longer obvious to continually increase these two types of parameters value. Depth of retaining pile mainly affects the displacement of bottom wall, and the upper limit depth is to make the wall embedded in bedrock, and the lower limit depth is to avoid the “skirting” damage.