真空预压下考虑渗透系数变化的吹填土地基固结分析

摘要

Hydraulically reclaimed soil's water content is more than 80% with high void ratio. When the hydraulically reclaimed soil is strengthened by vacuum preloading,its void ratio varies greatly,which makes its permeability change greatly. Reclaimed soil's consolidation properties and mechanical parameters under vacuum loading are obtained by laboratory vacuum model test. Using the modified Cambridge model,and taking into account the relation between permeability coefficient and void ratio,Biot's consolidation theory is used to analysis the pore pressure and void ratio of reclaimed soil in the model tank under vacuum loading. Compared with measured results,the calculation results show that this model can well be used to analyze the reclaimed soil's consolidation under vacuum loading. The calculation results also show that the soil close to the prefabricated drains is compacted in a very short time, resulting in the slow consolidation of the reclaimed soil. If the degree of consolidation is calculated by using a model that doesn't consider the change of permeability, the calculated valves will be higher than the calculated results by using a model that considers the change of permeability. Therefore,the consideration of the change of permeability during the consolidation of reclaimed soil foundation is necessary.%　　吹填土的含水率高达80%以上，孔隙比大。使用真空预压法加固吹填土，土体孔隙比变化很大，土体的渗透系数也随之发生很大的变化。通过室内真空模型试验获取土样在真空荷载下的固结规律和力学参数。采用修正的剑桥模型，并考虑渗透系数随孔隙比变化的非线性关系，运用比奥固结理论分析模型槽试验中土体在真空荷载下的孔压、孔隙比变化规律。其计算结果与实测值对比表明，该模型能很好地分析吹填土在真空荷载下的固结规律。计算结果显示：贴近排水板的土体在很短时间内被压密，造成吹填土地基固结缓慢。因此，若采用不考虑渗透系数变化的计算模型计算吹填土的固结度，该模型的计算值比考虑渗透系数变化模型的计算值大，与实际情况不符。故在进行吹填土地基固结计算时，考虑渗透系数变化是非常必要的。