不同挤压扰动下黏土的次固结特性研究

Research on secondary consolidation of clay under different squeezing disturbance

地基处理和盾构施工都会对土体产生挤压,破坏土体的原生结构和状态,引起土体的扰动,从而改变土体的次固结特性。通过不同预压荷载对土体产生不同程度的挤压扰动,进行分级加载压缩试验。试验结果表明:结构屈服应力随着预压荷载的增大逐渐增大;压缩指数在预压荷载小于结构屈服应力时相差不大,当预压荷载大于结构屈服应力时,压缩指数突然减小,且趋于稳定值;次固结系数随着荷载的增大呈现先增大后减小,再趋于稳定的变化趋势;随着扰动度的增加,次固结系数有所减小。同时,提出了次固结系数的计算模型,对多组试验数据的拟合表明,模型计算结果较好,具有较好的预测能力,对工后沉降的研究有一定的指导意义。

Foundation treatment and shield construction disturbance are the causes of squeezing soil which damages the initial structure and state, leads to the disturbance of soil, and changes the property of secondary consolidation. According to the squeezing disturbance of different levels caused by different preloads, a series of step-loading consolidation tests are conducted. The results indicate that, with the increase ofpreloads, the structure yield stress increases, compression index is almost the same when preload is less than structure yield stress, and decreases suddenly when preload is larger than structure yield stress; then it comes to a steady value. The secondary consolidation coefficient increases firstly, then decreases, finally gets to steady with the increase of pressure; and the secondary consolidation coefficient would decrease when disturbance increases; and a computational model for secondary consolidation coefficient is put forward; and the model coincides well according to the several testing data, and does well in predicting, which is useful for the prediction of post-load settlement.