考虑时变效应的堆载引发邻近单桩水平变形分析

Analysis of horizontal deformation of existing adjacent single pile induced by surface surcharge with time-dependent mechanism

为研究桩-土间相互作用的时变效应,提出一种预测黏弹性条件下地面堆载诱发邻近单桩水平变形的简化计算方法。采用两阶段分析法研究地面堆载对桩基产生的影响,首先,忽略既有桩体的存在,基于三维Burgers模型推导Boussinesq的黏弹性解,计算由地面堆载引发的既有桩体处的地层附加应力;其次,将桩体简化为搁置在黏弹性Pasternak地基上的Timoshenko梁,建立桩体水平变形微分控制方程,利用有限差分法和Laplace逆变换求解得到单桩水平变形的黏弹性解,并将数值模拟结果以及已有解进行对比,验证该方法的正确性,最后,分析Burgers黏弹性模型参数、堆载宽度、堆载载荷以及堆载-桩体水平距离对既有单桩水平变形的影响。研究结果表明:桩体水平变形有明显的时变效应,Maxwell弹性模量G越小,桩体水平变形越大,Kelvin弹性模量G主要反映由时变效应产生的黏弹性变形,Maxwell黏滞系数η越小,桩体水平变形速率越快,而Kelvin黏滞系数η越大,变形进入稳定阶段所需的时间越长。

In order to study the time-varying effect of pile-soil interaction, a simplified calculation method for predicting horizontal deformation of adjacent single pile induced by surface surcharge under viscoelastic condition was proposed. The influence of surface surcharge on pile was studied by two-stage analysis method. Firstly, the viscoelastic solution of Boussinesq was derived based on the 3D Burgers model, and the additional stress induced by surface surcharge was calculated. Secondly, the pile was simplified as a Timoshenko beam on the viscoelastic Pasternak foundation, the deformation differential governing equation was established, and the viscoelastic solution of pile horizontal deformation was derived by using the finite difference method and inverse Laplace transformation. The correctness of the proposed method was verified by comparison with the numerical simulation results and existing solutions. Finally, the influences of the parameters of Burgers viscoelastic model, load width,load size and load-pile horizontal distance on pile horizontal deformation were analyzed. The results show that the horizontal deformation of pile has obvious time-varying effect. The smaller the G, the greater the horizontal deformation of pile. Gmainly reflects the viscoelastic deformation caused by time-varying effect. The smaller the η, the faster the horizontal deformation rate of pile. And the larger the ηis, the longer time it takes for the deformation to reach a stable stage.