粉细砂地层高承压水基坑突涌破坏受力变形特征分析

Stress and Deformation Characteristics Analysis of Surge Damage of High-Confined Water Foundation Pit in Silty Sand Stratum

摘要: 针对无锡地铁粉细砂地层高承压水基坑，建立了基坑突涌塑性破坏的有限元计算模型，研究了基坑突涌塑性破坏受力变形特征，分析了承压水位降深和坑底土粘聚力对基坑突涌的影响。结果表明：基坑开挖导致坑底土应力场产生了重新分布，应力重分布情况在端头井中部靠近标准段附近表现尤为突出，使得靠近标准段隆起位移最大，并且坑底土较周边产生应力突增的现象。端头井在靠近标准段两侧的坑底土底部的屈服应力比最大，所以在承压含水层顶板处最先发生破坏，然后破坏范围自底向上扩展，直至基坑底部发生破坏。坑底土最大竖向位移随着承压水水位降深增加而逐渐减小，大致呈线性变化；坑底土最大应力比随着承压水水位降深增加而逐渐减小，刚开始变化幅度较大，随后趋于平缓；坑底土最大竖向位移和坑底土最大应力比随着坑底土粘聚力增加而逐渐减小，粘聚力的增加对于基坑突涌稳定性的影响十分显著。

Abstract: Aiming at the foundation pit with high confined water in silty sand stratum, based on the plastic deformation and failure characteristics of inrush, the finite element model of inrush seepage failure of foundation pit is established, and the influence of the depth of confined water level and the cohesion of soil at the bottom of the pit on the inrush of foundation pit is studied. The results show that the stress field of the pit bottom soil is redistributed due to the excavation of the foundation pit, which is especially prominent near the standard section in the middle of the end well, and makes the stress of the pit bottom soil increase sharply compared with the surrounding soil. The yield stress ratio of the end well is the largest at the bottom of the pit soil near the standard section, so the failure occurs first at the top of the confined aquifer, and then the failure range expands from bottom to top until the bottom of the pit is damaged. The maximum vertical displacement of pit bottom soil decreases gradually with the increase of confined water level, which shows a linear change. The maximum stress ratio of pit bottom soil decreases gradually with the increase of confined water level, and changes greatly at first, then tends to be flat. The maximum vertical displacement of pit bottom soil and the maximum stress ratio of pit bottom soil decrease gradually with the increase of cohesion of pit bottom soil, and the cohesion increases. It has an obvious effect on the stability of the foundation pit gushing.