Abstract

For a deep excavation in sandy cobble stratum, the loss of fine sand particles caused by dewatering generally leads to ground settlement. This paper first analyzed the rules of land subsidence caused by dewatering in the water-rich sandy cobble stratum by dewatering experiments. It is found that even after the groundwater level was restored, the land subsidence basically did not rebound, which shows that the land subsidence is consolidation settlement caused by the loss of fine particles. Then the coupled CFD-DEM numerical model was used to analyze the relationship between the fine particle loss, surface settlement and the grain size of filter media, dewatering rate. On this basis, the rules of land subsidence under the coupling effect of foundation pit dewatering and excavation were further explored by numerical calculation and field measurement. Foundation pit dewatering and excavation in the sandy cobble stratum is the key stage for land subsidence control, As the grain size of the filter media increases, the impact of dewatering on land subsidence gets stronger, therefore, the filter media grain size should be less 8 mm. This study is of great significance to the design of deep foundation pit dewatering in water-rich sandy cobble strata.

摘要

对于砂质鹅卵石地层的深基坑开挖，由于脱水造成细砂粒的流失，一般会导致地面沉降。本文首先通过脱水试验分析了富水砂质鹅卵石地层脱水引起的地面沉降规律。研究发现，即使在地下水位恢复后，地面沉降也基本没有反弹，说明地面沉降是细颗粒物流失引起的固结沉降。然后利用耦合CFD-DEM数值模型分析细颗粒损失、表面沉降与滤料粒度、脱水率之间的关系。在此基础上，通过数值计算和现场实测，进一步探索了基坑排水与开挖耦合作用下的地面沉降规律。砂质鹅卵石地层基坑脱水开挖是地面沉降控制的关键阶段，随着滤料粒度的增加，脱水对地面沉降的影响越来越大，因此滤料粒度应小于8毫米。本研究对富水砂质鹅卵石地层深基坑脱水设计具有重要意义。