软土基坑分步开挖卸荷时效及其对邻侧隧道影响  

Time effect of step-by-step excavation unloading in soft soils and its influence on adjacent tunnels

作　　者：李航 廖少明[1] 何君佐 杜一鸣 王元东 白乔木 LI Hang;LIAO Shaoming;HE Junzuo;DU Yiming;WANG Yuandong;BAI Qiaomu(Department of Geotechnical Engineering,Tongji University,Shanghai,200092,China;China Construction Eighth Engineering Division Co.,Ltd.,Shenzhen 518000,China;Shanghai Municipal Engineering Design Institute(Group)Co.Ltd.,Shanghai,200092,China;Shanghai Airport(Group)Co.Ltd.,Shanghai,201207,China)

机构地区：[1]同济大学地下建筑与工程系,上海200092 [2]中国建筑第八工程局有限公司,广东深圳518000 [3]上海市政工程设计研究总院(集团)有限公司,上海200092 [4]上海机场(集团)有限公司,上海201207

出　　处：《中南大学学报（自然科学版）》2023年第3期1044-1053,共10页Journal of Central South University:Science and Technology

基　　金：国家自然科学基金资助项目(52090082);上海市科技创新行动计划自然科学基金资助项目(19511100802)。

摘　　要：为研究软土地层中基坑开挖卸荷时效及其对邻侧隧道影响,设计并实施了相似比为1:20的物理模型试验,得到了基坑围护结构变形、地表沉降、坑底隆起、隧道竖向变形、隧道水平变形以及隧道断面收敛变形等数据。研究结果表明:基坑开挖引起的围护结构最大侧向变形为0.61%H(H为基坑深度),大于上海软土地区地铁车站基坑围护结构最大值的上限0.50%H;分步开挖过程中的墙体侧向变形和地表沉降具有明显的时间效应,卸荷时效对基坑变形的影响随开挖深度增加而增强;基坑开挖引起隧道变形以朝向坑内的水平变形为主,同时伴随少量朝上的竖向变形;隧道侧向变形与相同深度处围护结构侧向变形大致呈线性关系,据此可预估后续开挖引起的隧道侧向变形;基坑开挖引起邻近隧道产生径向收敛变形,隧道断面呈“横向伸长、竖向压缩”的特点,横向收敛约为竖向收敛变形的1.7倍;当隧道与基坑开挖面的竖向净距在0.2H~0.5H时,基坑开挖卸荷引起的隧道变形响应十分敏感,隧道竖向变形随坑底隆起增加而显著增加。A physical model test with a similarity ratio of 1꞉20 was conducted to study the time-effect of foundation pit excavation unloading in soft soils and its influence on nearby tunnels positioned below the pit bottom.The experiment data regarding lateral retaining wall displacement,ground surface settlement,basal heave,vertical of the tunnel and horizontal displacement of the tunnel,and convergence deformation of tunnel cross section were obtained.The results show that the maximum lateral wall displacement induced by excavation is 0.61%H(H is final excavation depth),which is greater than the upper limit of the maximum retaining wall deflection of metro station in Shanghai soft soils of 0.50%H.The development of lateral wall displacement and surface settlement during the step-by-step excavation presents a noticeable time effect,with the impact on the pit deformation becoming more pronounced as the depth of the excavation increases.Excavation-caused tunnel deformation is characterized by significant horizontal displacement towards the pit and relative smaller upward vertical displacement when the tunnel is located below the basal surface.Lateral displacement of the tunnel is approximately linear with that of retaining wall at the same depth,and hence the lateral deformation of tunnel caused by subsequent excavation can be predicted.The excavation-caused radial convergence of the tunnel is characterized by transverse elongation and vertical compression,and the transverse convergence is about 1.7 times of the vertical convergence.When the clear distance between the tunnel and excavation surface is within 0.2H−0.5H,the tunnel deformation response caused by excavation unloading is particularly sensitive and the vertical deformation of the tunnel greatly increases with the increase of basal heave.

关 键 词：相似模型试验 基坑 隧道 软土 分步卸荷时效 

分 类 号：TU43[建筑科学—岩土工程]