坑内留土对双排桩支护结构的影响分析

摘要

为研究坑内留土对双排桩支护结构的影响,采用有限元数值分析方法,对坑内留土尺寸、加固效果、弹性模量大小等进行参数化分析,深入研究双排桩的位移、弯矩及被动区土压力的变化规律.结果表明:①增加留土宽度和高度均能减小双排桩的位移和内力,且后者对位移和内力的控制效果更显著;②加固留土后可显著减小双排桩的位移;③当留土弹性模量E增大到80 MPa及以上时,双排桩位移减小不明显;④当留土宽度达到一定数值时,继续增加留土宽度对被动区土压力的提升效果甚微.详细介绍了双排桩结合坑内留土的支护形式,施工中对留土平台硬化处理是防止雨水浸泡导致留土平台失稳的有效措施;同时,留土平台上适量堆载可有效提高被动区土压力,对控制双排桩位移是有利的.将结论应用于凯德广场古田项目深基坑工程,取得了较大的经济效益和社会影响力.%To investigate the evolution of horizontal shift,bending moment and passive earth pressure of the retaining structure with double-row piles,finite element analysis was conducted to analyze parameters including earth berm size,reinforcement effect and elastic modulus.Results suggest that:1) increasing the width and height of earth berm could both reduce the horizontal shift and bending moment,and increasing the height of earth berm has better effects;2) reinforcing the earth berm could remarkably reduce the horizontal shift of the double-row pile;3)elastic modulus of earth berm over 80 MPa has little effect on the decrease of horizontal shift;4) further increment of the width of earth berm after reaching a threshold has slight impact on improving the earth pressure in passive zone.The conclusion is applied in the Capital Land Shopping Mall at Gutian,and had great economic returns and social benefits.In addition,hardening of the earth berm is an effective measure to avoid platform instability in the construction caused by rainwater soaking.Proper surcharge on the earth berm is an effective way to improve the earth pressure in passive zone,beneficial for controlling the horizontal shift of double row piles.