基于DFOS的排灌水条件下土体变形响应模型试验研究

DFOS BASED EXPERIMENTAL STUDY OF SOIL DEFORMATION RESPONSE TO DRAINAGE AND RECHARGE

黏土层和砂土层交替变化的多层土体在强烈开采地下水作用下极易产生压密固结而引发地面沉降灾害。本文针对含水层释水引起地面沉降问题,研制了地面沉降试验装置,进行了排灌水条件下含水层系统的沉降及回弹试验。采用分布式光纤感测技术对土体内部应变分布及含水率变化进行耦合监测,并分析了各分层对水位变化的响应特征。结果表明:黏土层和砂土层均表现出了排水压缩和灌水回弹特点,黏土层变形较砂土层明显。各层变形与含水率变化具有良好的对应关系,表现为砂土层变形和含水率变化基本同步,而黏土层变形略微滞后于含水率变化。黏性土压缩曲线具有明显的分段特征,排水时当含水率低于液限后迅速减小,黏土层压缩速率明显加快;回灌时当含水率高于液限后,回弹速率明显加快。试验结果对研究地面沉降机理、评价地面沉降潜力及地下水利用具有重要意义。

Under the effect of intense exploitation of groundwater, the multi-layer soil of clayey soil and sandy soil is susceptible to be compressed, which causes the land subsidence disaster. To better understand the mechanism of land subsidence caused by groundwater withdrawal, a small-scale sand-clay interbred model box is built to carry out the consolidation and rebound tests. Distributed fiber optical sensing （ DFOS） technologies are introduced for coupling monitoring of soil strain and water content to analyze the response characteristics of each layer to water level changes. The results indicate that soil layers are compressed during drainage while rebound during recharge. In addition, the deformation of clay layer is obvious than that of sand layer. The deformation of sand layer is synchronous with water content changes, while that of clay layer is slightly lagging behind the water content changes due to its lower coefficient of permeability. The segmented compression curve of clay layer shows that water content rapidly decreases when it is lower than its liquid limit, meanwhile the clay layer compression rate obviouslyaccelerates during drainage. When water content is higher than that of its liquid limit during recharge, rebound rate significantly increases. The test results are of great significance to study the mechanism of land subsidence as well as to evaluate the compression potential of soil layers.