考虑固结流变的软土地基单桩下拉荷载计算

Calculation of dragload of single pile in soft soil considering consolidation and rheology

为研究大面积堆载作用下软土地基中单桩下拉荷载计算方法,基于非达西流动定律引入软土流变模型,建立了拉格朗日坐标系中考虑固结和流变共同作用下软土地基大变形长期沉降非线性计算模型.模型中考虑了固结流变过程中孔隙比与渗透系数随孔隙水的排出而发生变化.进而以荷载传递法为基础,重点研究了固结流变土体中桩土相互作用时界面抗剪强度的时间效应,提出了软土地基在大面积堆载作用下考虑非达西流动固结与流变耦合效应时单桩下拉荷载理论计算方法,通过假定桩顶变形进行迭代求解,获得了桩身下拉荷载分布与中性点长期变化规律.最后与传统固结计算方法进行比较,并分析了平均固结度、非达西流固结参数、流变参数以及堆载大小对下拉荷载变化的影响.研究结果表明,基于传统土体固结理论的计算结果偏于保守,考虑固结流变共同作用对单桩受力的不利影响极为必要.

To study the calculation method of dragload of the single pile in soft soil under large-area loading,the rheological model of soft soil is introduced based on the non-Darcy flow law.A nonlinear calculation model for the long-term settlement of large deformation of the soft soil foundation is established by considering the combination of the consolidation and rheology in Lagrangian coordinates.The model considers that the void ratio and the permeability coefficient change with the discharge of pore water during the consolidation rheology.Based on the load transfer method,the time effect of the interface shear strength is studied during the interaction between the pile and the soil in the consolidated rheological soil.The theoretical calculation method of dragload of the single pile is proposed by considering the coupling effect of the non-Darcy flow consolidation and rheology of soft soil under large-area surcharge.The long-term variation law of the dragload distribution and neutral point's position of the pile is obtained by assuming the deformation of the pile top to carry out an iterative solution.Finally,the proposed method is compared with the traditional consolidation calculation method,and the effects of average consolidation degree,non-Darcy consolidation parameters,rheological parameters and surcharge on the dragload are analyzed.The results show that the calculation results based on the traditional soil consolidation theory are conservative,and it is necessary to consider the adverse effect of the consolidation rheology on the bearing capacity of single pile.