静压桩的桩侧土压力分布规律数值分析

Numerical analysis of soil pressure distribution law on pile shaft of displacement pile

静压桩的贯入挤土效应导致桩侧土压力升高,探究桩贯入挤土导致的桩侧土压力变化对建立合理的桩贯入阻力计算方法具有积极的意义。因此,采用大变形数值模拟方法和南水本构模型对桩在砂土中的贯入过程进行了分析,探究了桩侧土压力系数K的变化规律。结果表明:桩贯入过程中土体受力可划分为加载、卸载和应力稳定3个阶段,在桩端到达土体所在深度时土体的应力达到峰值,远离后土体发生应力卸载,最后趋于稳定;在深度方向的最大扰动范围为5D(D为桩直径),沿径向最大扰动范围为6D。桩贯入完成后的桩侧土压力沿深度方向近似表现为线性分布,在桩端处出现极值。桩径的变化对土压力的影响不显著,不同直径的桩侧壁土压力接近。随着界面摩擦系数的增加,桩侧土压力逐渐增大。基于数值分析结果提出了考虑桩−土界面摩擦系数的桩侧土压力计算方法。

The soil compaction effect of pile penetration increases soil pressure on the pile shaft.Analyzing soil pressure changes caused by pile penetration is significance for establishing a calculation method for pile penetration resistance.The large deformation numerical simulation method and Nanshui soil model were used to analyze the pile penetration process in sandy soil.The variation of soil pressure coefficient K under different working conditions was analyzed.Numerical analysis results indicate that the change in soil horizontal stress during the pile penetration process can be divided into three stages:loading,unloading and stress stabilization.The soil horizontal stress peaks when the pile end reaches a certain depth,and then the soil enters the unloading stage as penetration continues,and finally stabilizes.The maximum disturbance range is 5D in the depth direction and 6D in the radial direction.Soil pressure on the pile shaft after penetration is approximately linear,with extreme values at the pile end.The change in pile diameter has an insignificant effect on soil pressure,and the soil pressure on the pile shaft with different diameters is similar.As the interface friction coefficient increases,the soil pressure on the pile shaft gradually rises.Based on the numerical analysis results,a method for calculating pile shaft soil pressure considering the pile-soil interface friction coefficient is proposed.