京沪高速铁路阳澄湖段软土的蠕变特性和次固结特性试验研究

基于京沪高速铁路阳澄湖地区原状软土的一维固结试验,探讨该地区软土非线性蠕变变形特性。研究先期固结压力、应力水平、加荷比、加载时间以及超载预压对次固结系数Ca值的影响,得到该地区软土Ca与Cc值之间的关系。试验结果表明:该地区软土在相同的应力水平条件下,加荷比大的土样蠕变变形更小,增大加荷比可以减小次固结系数;经预压处理后,土样的次固结系数Cα与预压力p和预压时间密切相关,超载预压可以减小软土的次固结系数,进而能够有效减少工后次沉降;加载的时间间隔对次固结系数有较大影响,加载时间间隔越长,次固结系数越小,主固结和次固结的区分越不明显;次固结系数与先期固结压力无明显相关,Ca和固结压力p可用双曲线拟合;试样的次固结系数Ca与压缩指数Cc之间呈现良好的线性关系,Ca/Cc值的范围在0.018～0.035之间。

Study on Creep Behaviour and Secondary Consolidation Characteristics of Soft Soil in Yangcheng Lake District of High-speed Beijing-Shanghai Railway

One-dimensional consolidation tests of undisturbed samples of soft soil in the Yangcheng Lake.District of the High-speed Beijing-Shanghai Railway were conducted to study the nonliner creep behaviour of soft soil in that district.The influence of preconsolidation pressures,stress levels,stress ratios,loading time and overload pre-pressures on Secondary Consolidation Coefficient Ca was studied and the ratios of Ca/Cc of soft soil in that district were found.The results show as follows:Creep deformation diminishes with increasing of loading ratios at the same stress level,therefore,increasing loading ratios can reduce secondary consolidation coefficients;after preloading theatment,Ca is closely connected with Pre-pressure p and Pre-press time,surcharge preloading can decrease the value of Ca and thereby surcharge preloading is propitious for reduction of settlement after construction;loading intervals have great effect on Ca,the longer the loading interval,the smaller the Ca and the more difficult to distinguish between primary consolidation and secondary consolidation;Ca has no significant correlation with preconsolidated pressures,Ca and Consolidation Pressure p can be fitted with the hyperbolic curve;a good linear relationship is shown between Ca and Compression Index Cc,and Ca/Cc ranges from 0.018 to 0.035.