粉砂与粉土固结蠕变特性对比的试验研究

Experimental study on comparison of consolidation creep characteristics between silty sand and silty soil

为了解释基坑预降水引发的基坑周边地面沉降的滞后性,依托某地铁车站基坑预降水工程,开展场地中典型粉砂和粉土的一维固结蠕变试验。通过试验结果分析,得到土的压缩指数、回弹指数和次固结系数,给出了回弹指数与压缩指数和次固结系数与压缩指数的经验关系。蠕变试验结果表明,粉砂和粉土的次固结系数与固结荷载之间呈现良好的线性关系,提出了次固结系数与固结压力的经验公式。从固结压力下砂土天然结构破坏的角度,解释了次固结系数随着固结压力的增加而增大的原因,为解释预降水引起的基坑周边地面沉降滞后效应和地面沉降合理估算提供了实验依据。

In order to explain the lagging settlement in the surrounding ground induced by pre-dewatering of excavations,one-dimensional consolidation creep tests are conducted on typical silty sand and silty soil at a metro station site of Jiangsu Province.Based on the experimental results,the compression index,rebound index and secondary consolidation coefficient of the soil are obtained,and the empirical relationships between the rebound index and the compression index,as well as the secondary consolidation coefficient and the compression index,are given.The results of the creep tests demonstrate a well-defined linear relationship between the secondary consolidation coefficient and the consolidation load for both the silty sand and the silty soil,leading to the development of an empirical formula correlating the secondary consolidation coefficient with consolidation pressure.Furthermore,the increase in the secondary consolidation coefficient with rising consolidation pressure is explained from the perspective of the natural structural breakdown of the sandy soil under consolidation pressure.These findings provide valuable experimental evidence for understanding the lagging effects of ground settlement around the excavations induced by pre-dewatering and for the rational estimation of ground settlement.