施工荷载下理想砂井地基弹黏塑性固结分析

为深入研究饱和黏土流变特性及施工荷载对理想砂井地基固结性状的影响,在Barron理想砂井固结理论基本假定的基础上,引入考虑时间效应的统一硬化(UH)本构模型描述饱和黏土的弹黏塑性变形,同时将施工荷载简化为线性加载,重新推导了理想砂井固结方程,并给出了固结方程的隐式差分格式。通过与文献中变荷载下砂井地基非线性固结方程解析解的对比,验证了研究方法的有效性。探讨了施工荷载和UH模型参数等对砂井地基固结进程的影响。结果表明:施工阶段砂井地基内出现的孔压升高现象不仅是施工荷载随时间增加造成的,黏土的黏滞性也是原因之一; 延长工期和增大UH模型参数均会使砂井地基孔隙水压力的整体消散时间延长,从而减小其固结速率; 当工期较长时,按瞬时加载情况计算砂井地基的固结进程将会产生较大误差,而忽略土体的黏滞性将会高估砂井地基的固结速率。

Elastic Visco-plastic Consolidation Analysis of Foundation with Ideal Sand Drains Under Construction Load

In order to further study the rheological properties of saturated clay and the influence of construction load on the consolidation properties of ideal sand drain foundation, based on the basic assumption of Barron's ideal sand drain consolidation theory, a unified hardening(UH)constitutive model considering time effect was introduced to describe the elastic visco-plastic deformation of saturated clay. At the same time, the construction load was simplified as linear load, the consolidation equation of ideal sand drain was derived again, and the implicit difference scheme of the consolidation equation was given. Compared with the analytical solution of the nonlinear consolidation equation of sand drain foundation under variable load in the literature, the validity of the research method was verified. The influence of construction load and UH model parameters on consolidation process of sand drain foundation was discussed. The results show that the increase of pore pressure in sand drain foundation during construction is not only caused by the increase of construction load with time, but also by the viscosity of clay. Prolonging the construction period and increasing the parameters of UH model will prolong the dissipation time of pore water pressure and reduce the consolidation rate. When the construction period is long, the calculation of the consolidation process of the sand drain foundation under the condition of instantaneous loading will produce large errors, and neglecting the viscosity of soil will overestimate the consolidation rate of sand drain foundation.