坑内降水基坑底不同位置土体变形性状的室内试验研究  

Experimental studies on influence of pit dewatering on soil deformation at different locations below excavation base

作　　者：郑刚[1] 魏少伟[1] 

机构地区：[1]天津大学土木工程系,天津300072

出　　处：《岩土工程学报》2011年第2期247-252,共6页Chinese Journal of Geotechnical Engineering

基　　金：国家重点基础研究发展计划(973计划)项目(2010CB732106);国家自然科学基金项目(51078263)

摘　　要：在分析坑内降水的基坑开挖中坑底土体的应力变化的基础上,对基坑降水与开挖交替作用下坑内不同位置土体的变形性状进行研究,并与仅考虑基坑开挖作用下土体的变形性状进行比较。试验结果表明,分步降水、开挖交替作用下坑底不同位置土体的变形性状相对于仅考虑开挖时均显著改善,其初始卸荷变形模量均明显提高。对于坑底不同位置的土体,降水均能显著减小基坑回弹总量。但由于降水使每开挖步土单元释放的应力加大,分层每开挖步基坑的回弹变形比没有考虑降水时的回弹变形大。模拟靠近地连墙附近土单元应力路径的试验结果表明,降水开挖交替作用下地连墙附近土单元其开挖步的回弹变形明显大于基坑中心的土单元,并且可能导致考虑降水条件下基坑边部土体单元总的回弹变形大于没有降水时的总回弹变形。最后,坑内降水对基坑内土体变形性状、坑底回弹的影响与降水时间、降水深度、土层渗透系数等密切相关。对地下水位以下的超深开挖,应考虑大深度降水对坑内土体力学性状及回弹变形的影响。Based on the analyses of soil stress changes in passive region under the alternate effect of excavation and dewatering,the deformation properties of the soil with different horizontal locations are studied using triaxial tests.Compared with those just considering the effect of excavation,the following conclusions can be drawn.First,the deformation properties of the soil in the excavation base with different horizontal locations under the alternate effect of dewatering and excavation are all significantly improved and the initial unloading modulus is remarkably increased compared with that just considering the effect of excavation.The total heave of the soil in all the horizontal locations is also decreased.However,the dewatering will increase the soil heave in each excavation step compared with that just considering the effect of excavation,as the soil stress relief in each excavation step is significantly increased due to the effect of dewatering.The test results also show that the heave of soil elements close to diaphragm wall under the alternate effect of excavation and dewatering is remarkably larger than that in the center of excavation.The total heave of the soil elements close to diaphragm walls under the alternate effect of excavation and dewatering is even larger than that just considering the effect of excavation.The influences of dewatering inside the pit on the deformation properties and soil heave are closely related to the dewatering time,dewatering depth,the coefficient of permeability of pore water and so on and should be considered in deep pit excavation under the groundwater level.

关 键 词：基坑工程 坑内降水 回弹变形 三轴试验 卸荷模量 

分 类 号：TU411[建筑科学—岩土工程]