基坑开挖前坑内预降水对基坑变形的影响
Influence of Pre-excavation Dewatering in Pit on Foundation Pit Deformation
喻义天 1丁海滨 1刘昆 1徐长节 1童立红1
作者信息
- 1. 华东交通大学 江西省岩土工程基础设施安全与控制重点实验室, 江西 南昌 330013;江西省地下空间技术开发工程研究中心, 江西 南昌 330013
- 折叠
摘要
为研究基坑开挖前坑内预降水对基坑变形及对水位变化情况影响,依托某地铁站基坑工程,采用室内模型试验方法,研究了抽水速度和降水深度对坑外水位变化、围护结构变形、地表沉降、孔隙水压以及土压力的影响.运用MIDAS GTS NX有限元软件对实际工程进行数值模拟,将试验数据与数值计算结果进行对比.结果表明:坑外水位随着与围护结构距离的增加,水位下降越小且降水曲线斜率越小,与试验得到的"先凹后凸"形坑外降水曲线结果一致;围护结构侧移随着降水深度的增大而增大,增加幅度逐渐减小,整体呈现"悬臂"形,底部由于受到渗流力的作用产生了一个指向坑内的"踢脚变形",最大围护结构侧移出现在围护结构顶部;坑外地表沉降呈现"对勾"形分布,最大坑外地表沉降的位置并不会随降水深度改变,而是始终出现在距围护结构大约 10 m左右;围护结构侧移和地表沉降均随降水深度或抽水速度的增加而增大;基坑降水后孔隙水压无论坑内还是坑外均减小,坑内孔隙水压减小幅度明显大于坑外,且两者在变化规律上是不同的,坑内孔隙水压呈现先减后增,而坑外孔隙水压则是一直减小;坑内外侧向土压力随着降水深度的增加均显著减小;坑内土压力随着抽水速度的增大变化不明显,而坑外侧向土压力随着抽水速度增加明显减小.
Abstract
In order to study the influence of pre-excavation dewatering in a pit on foundation pit deformation and water level change before excavation,based on the foundation pit project of a subway station,the influences of pumping speed and dewatering depth on the deformation of envelope structure,surface settlement,water level change outside the pit,pore water pressure and earth pressure are studied with laboratory model test method.MIDAS GTS NX finite element software is used to simulate the actual project,and the test data is compared with the numerical calculation results.The result shows that(1)With the increase of the distance between the water level and the envelope structure,the water level drops less,and the slope of the precipitation curve is smaller,which is consistent with the results of first concave and then convex type precipitation curve obtained with the experiment.(2)The lateral displacement of the enclosure structure increases with the increase of the precipitation depth,and the increased amplitude gradually decreases.The overall pattern is cantilever type,a kick deformation pointing to the pit is generated at the bottom due to the action of seepage force,and the maximum lateral displacement of the enclosure structure appears at the top of the enclosure structure.(3)Surface subsidence outside the pit presents a cross-hook type distribution.The location of surface subsidence outside the largest pit does not change when the precipitation depth changes,and the location appears about 10 m away from the envelope structure.(4)The lateral movement of the envelope structure and the ground settlement increase with the increase of precipitation depth or pumping speed.(5)After foundation pit dewatering,the pore water pressure decreases both inside and outside the pit,the pore water pressure in the pit decreases significantly more than that outside the pit,and the change rule of the two is different.The pore water pressure in the pit decreases first and then increases,while the pore water pressure outside the pit decreases all the time.(6)The lateral earth pressure inside and outside the pit decreases significantly with the increase in precipitation depth.(7)The soil pressure in the pit does not change obviously with the increase of pumping speed,but the soil pressure outside the pit decreases obviously with the increase of pumping speed.
关键词
道路工程/开挖前预降水/模型试验/基坑/抽水速度Key words
traffic engineering/pre-excavation dewatering/model test/foundation pit/pumping rate引用本文复制引用
基金项目
国家重点研发计划项目(2023YFC3009400)
国家自然科学基金项目(52238009)
江西省自然科学基金项目(20223BBG71018)
江西省研究生创新专项资金项目(YC2023-S492)
出版年
2024
NETL
NSTL
万方数据