基于离心试验下软黏土地区窄基坑稳定性分析

Stability Analysis of Narrow Foundation Pit in Saturated Soft Clay Area Based on Centrifugal Test

针对软土地区基坑坑底土层为饱和软黏土的情况,以福建省某城区电缆隧道的窄基坑工程为依托,开展了不同插入比条件下窄基坑稳定性研究。通过设计3种不同插入比工况进行离心模型试验,模拟窄基坑开挖,观察土体位移和基坑稳定破坏模式。结果表明,当插入比为1∶1和1∶0.8时,围护挡墙变形较小,挡墙的变形表现为“两端小中间大”的鼓形变形模式,且插入比为1∶0.8较插入比为1∶1时挡墙变形会出现轻微的增加,但能满足变形要求,插入比定为1∶0.8时更加经济合理;当插入比为1∶0.67时,基坑由于挡墙插入深度不足而失去窄基坑的宽度效应,挡墙呈现倒“八”字型的变形模式,坑底土体大量隆起,基坑破坏。最后采用数值模拟方法进行对比验证。本文研究成果可大幅度地优化窄基坑插入深度问题,从而减少工程造价,提高资源的利用效率。

Aiming at the state of affairs that the backside soil of the basis pit in the tender soil location is saturated smooth clay,the stability of narrow foundation pit under different insertion ratios is studied based on the slender foundation pit of a cable tunnel in a city of Fujian Province.Centrifugal model tests with three different insertion ratios were designed to simulate narrow foundation pit excavation,and the soil displacement and stable failure mode of foundation pit were observed.The results show that:When the insertion ratio is 1∶1 and 1∶0.8,the deformation of the retaining wall is small,and the deformation of the retaining wall indicates a drum-shaped deformation mode of"small at each end and giant in the middle.Whe insertion ratio is 1∶0.8,compared with the situation of insertion ratio is 1∶1,the deformation of the retaining wall enlarges slightly,which can meet the deformation requirements.It is more economical rationl when the insertion ratio is set to 1∶0.8.When the insertion ratio is 1∶0.67,the width effect of narrow foundation pit is lost due to the insufficient penetration depth of retaining wall.The retaining wall reveals an inverted"八"structure deformation pattern,a massive quantity of soil at the backside of the pit uplifts,and the basis pit is destroyed.Finally,the numerical simulation method is used for assessment and verification.The lookup consequences of this paper can notably optimize the insertion depth of slender basis pits,thereby decreasing engineering costs,saving development resources,and enhancing aid utilization efficiency.