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为探讨双层非均质地基中单桩的受扭承载特性,基于单层土体剪切模量呈幂函数分布的假定,考虑桩–土接触面上极限摩阻力随深度非线性变化,建立出桩顶扭矩作用下的桩身扭转控制方程,进而导得桩顶及桩身的扭矩(T)与扭转角(Φ)等解答,并将其退化为单层非均质及双层均质地基后与已有成果进行了对比验证。同时,桩顶T–Φ曲线参数分析结果表明:增加桩体剪切模量G_p有利于控制桩顶扭转角;桩径r0增加一倍,相同扭转角下桩顶能承受的扭矩值增大4~6倍;随地面处土体剪切模量μ_1和模量分布函数中非线性系数α_1,α_2的增加,桩身受扭性能得到显著改善。此外,桩顶扭转影响因子I_Φ的对比分析表明:桩身在ζL<0.2和ζL>5.0时分别表现为刚性桩和柔性桩,且后者传至桩底的扭矩极小而可忽略;当ζL>5且上下土层顶部剪切模量比μ_1/μ_2>1时,0.2倍桩长(L)范围内的上部土层对桩身受扭性能影响较大;当ζL>10且μ_1/μ_2<1时,桩身受扭能力主要源自0.4L的表层土。
In order to investigate the torsional load-bearing characteristics of single pile in double-layered heterogeneous foundation, based on the assumption that the shear modulus of single-layer soil is power function distribution, considering the non-linear variation of ultimate friction at the pile-soil interface The equation of torsion of pile torsion under the action of pile top torque is deduced, which leads to the solutions of torsion angle (Φ) and torsion angle (Φ) of pile top and pile body, which are degenerated into single-layer heterogeneous and double-layer homogeneous After the base with the existing results were compared and verified. At the same time, the parameter analysis of pile top T-Φ curve shows that increasing the pile shear modulus G_p is beneficial to control the pile top torsion angle; the pile diameter r0 doubled and the pile torsion angle can withstand the same torsional angle increased by 4 ~ 6 times. With the increase of the nonlinear coefficient α_1 and α_2 of the soil shear modulus μ_1 and the modulus distribution function, the torsional behavior of the pile body is significantly improved. In addition, the comparative analysis of the influence factor I_Φ of pile top torsion shows that the pile body behaves as a rigid pile and a flexible pile respectively when ζL <0.2 and ζL> 5.0, and the torque transmitted to the bottom of the pile is negligible; when ζL > 5 and the upper soil layer shear modulus ratio μ_1 / μ_2> 1, the upper soil layer within 0.2 times of the pile length (L) greatly affected the torsional behavior of the pile. When ζL> 10 and μ_1 / μ_2 < At 1 o’clock, the torsional capacity of the pile mainly comes from the 0.4L topsoil.