基于模型试验及耦合数值分析的XCC桩挤土效应研究

Study on Squeezing Effect of XCC Pile Based on Model Experiment and Coupled Numerical Analysis

针对当前数值模拟方法、理论解答等对异形桩沉桩挤土效应研究的不适应性,通过室内模型试验结合FLAC-PFC耦合数值模拟方法对XCC桩与圆形桩的挤土效应进行比较分析,获取了XCC桩沉桩后桩周土体位移变化模式及XCC桩与圆形桩沉桩挤土效应的异同性。此外,基于修正的圆孔扩张理论,提出了XCC异形桩的沉桩挤土径向位移公式,并结合室内模型试验,证明了修正扩孔理论的准确性和可行性。研究结果表明:(1)XCC桩的沉桩挤土径向位移场可以分为r<1.25 D范围内的十字形扩张过渡区、1.25D≤r<2.5D范围内的方形扩张区和r≥2.5D范围内的圆形均匀扩张区;(2)XCC桩的挤土效应大于等截面圆形桩挤土效应,其径向挤土位移约为圆形桩的1.0~1.4倍;(3)XCC异形桩的沉桩挤土径向位移公式为:u_(Xr)=r_(X)(θ)[r_(X)(θ)/(kr)]^(n(θ)),r≤1.6D;u_(Xr)=u_(Xr)=1.6D(1.6D/r)^(n),r>1.6D。

In view of the inadaptability of the current numerical simulation methods and theoretical solutions to the research on the soil-squeezing effect of special-shaped piles,the soil-squeezing effects of XCC piles and circular piles were compared and analyzed through indoor model tests and FLAC-PFC coupled numerical simulation methods.The change mode of soil displacement around the pile after XCC pile driving and the similarities and differences of the soil compaction effect between XCC pile and circular pile are obtained.In addition,based on the modified circular hole expansion theory,the radial displacement formula of the XCC special-shaped pile is proposed,and the accuracy and feasibility of the modified hole expansion theory are proved by combining with the indoor model test.The research results show that:(1)The radial displacement field of the XCC pile can be divided into a“cross”-shaped expansion transition zone within the range of r<1.25D,a“square”shape within the range of 1.25D≤r<2.5D and a“circle”shaped uniform expansion area within the range of r≥2.5D;(2)The soil-squeezing effect of XCC piles is greater than that of circular piles of equal cross-section,and the radial soil-squeezing displacement is about 1.0~1.4 times that of circular piles;(3)The radial displacement formula of XCC special-shaped piles is:Abstract:In view of the inadaptability of the current numerical simulation methods and theoretical solutions to the research on the soil-squeezing effect of special-shaped piles,the soil-squeezing effects of XCC piles and circular piles were compared and analyzed through indoor model tests and FLAC-PFC coupled numerical simulation methods.The change mode of soil displacement around the pile after XCC pile driving and the similarities and differences of the soil compaction effect between XCC pile and circular pile are obtained.In addition,based on the modified circular hole expansion theory,the radial displacement formula of the XCC special-shaped pile is proposed,and the accuracy and feasibility of the modified hole expansion theory are proved by combining with the indoor model test.The research results show that:(1)The radial displacement field of the XCC pile can be divided into a“cross”-shaped expansion transition zone within the range of r<1.25D,a“square”shape within the range of 1.25D≤r<2.5D and a“circle”shaped uniform expansion area within the range of r≥2.5D;(2)The soil-squeezing effect of XCC piles is greater than that of circular piles of equal cross-section,and the radial soil-squeezing displacement is about 1.0~1.4 times that of circular piles;(3)The radial displacement formula of XCC special-shaped piles is:u_(Xr)=r_(X)(θ)[r_(X)(θ)/(kr)]^(n(θ)),r≤1.6D;u_(Xr)=u_(Xr)=1.6D(1.6D/r)^(n),r>1.6D.