富水地层管廊基坑开挖变形及损伤演化分析

Deformation and damage evolution analysis of pipe gallery foundation pit in water-rich stratum

富水地层土体较为软弱,管廊基坑施工过程中易产生安全问题,研究富水地层管廊基坑开挖对指导类似工程具有重要意义。文章基于济南市开源路综合管廊工程,构建数值计算模型,考虑桩嵌固深度、钢支撑数量、支护桩类型等因素,研究不同工况对管廊基坑开挖变形的影响,并引入了损伤变量的概念,分析了基坑施工过程的损伤演化情况。结果表明:基坑开挖对于周边地表土体沉降的影响范围要大于对水平变形的,而对水平位移的影响范围约为3倍的开挖宽度;增加钢支撑数量对坑底隆起的改善要比对地表沉降的改善效果好;增加桩嵌固深度,可以明显地改善土体变形,但对于地表土体沉降量的限制作用随土体与基坑距离的增加有所削弱;基坑开挖过程中土体的损伤呈现“快速增长-缓慢增长”两个阶段,施作支护桩对土体的影响最大,土体损伤破坏急剧增加,约大于总体损伤的90.0%,施作支护桩之后土体损伤情况得到缓解。

Construction of pipe gallery foundation pit in water-rich strata presents significant safety challenges due to the inherent weakness of the soil.The study on the excavation of pipe gallery foundation pit of rich water stratum is of great significance to guide similar projects.Based on the comprehensive pipe gallery project of Jinan Kaiyuan Road,this study constructs a numerical calculation model taking into account variables such as pile embedding depth,steel support quantity,supporting pile type and so on.The study examines the impact of various working conditions on the excavation deformation of pipe gallery foundation pit and introduces the concept of damage variable to analyze the damage evolution throughout the construction process.The results show that the impact range of foundation pit excavation on the surrounding surface soil settlement exceeds its impact on the horizontal deformation.And the influence range of horizontal displacement is about 3 times of the excavation width.The improvement effect of increasing the number of steel supports on the uplift of pit bottom is better than that on the surface settlement.Additionally,while deeper pile embedding markedly improves soil deformation,its effectiveness at limiting surface soil settlement diminishes with greater distances between soil and foundation pit.In the process of foundation pit excavation,the damage of soil presents two stages of"rapid growth and slow growth",and the application of supporting piles has the greatest impact on the soil,and the damage of soil increases sharply,reaching about 90.0%of the total damage.After the application of supporting piles,the damage of soil is alleviated.