富水软弱地层基坑开挖中的土体变形与渗流特性

Soil Deformation and Seepage Characteristics of Foundation Pit Excavation Engineering in Water-rich Soft Stratum

针对深基坑降水开挖引起坑周水土演变的研究不足,以无锡地铁旺庄路车站深基坑工程为案例,通过现场监测基坑地下水位、孔隙水压力以及降水井流量,分析了基坑降水随时间和空间的变化规律;通过分析土体沉降和围护结构水平变形的实测结果,研究了基坑降水开挖引起的变形与渗流特性规律。研究结果表明:基坑降水过程中,深地层孔隙水压力降低幅度大于埋深较浅的地层;承压井单井出水量初期明显大于疏干井,随后承压井出水量基本稳定,疏干井出水量随着时间的推移逐步下降;基坑降水开挖时,一开始距离基坑较近的地方沉降较大,随着降水开挖的进行,距离基坑较远处的沉降逐步增加;降水开挖过程中,基坑水平位移沿深度呈先增大后减小的趋势,最大水平位移出现在地下连续墙中间部位。

Water and soil changes caused by deep foundation pit excavation engineering and dewatering lack research.Taking the deep foundation pit project of Wangzhuang Road Station of Wuxi Metro as an example,the variation law of dewatering over time and space is analyzed by detecting foundation pit underground water level,pore water pressure and flow volume of dewatering well on site.By detecting soil settlement and horizontal displacement of enclosure structure,the deformation and seepage characteristics caused by foundation pit dewatering are studied.Research results show that during the process of foundation pit dewatering,the reduction of deep stratum pore water pressure is larger than that of shallow stratum pore water pressure.The water flow volume of single well of confined well is obviously larger than that of drainage well at the beginning,then the water flow volume of confined well is gradually stable.The drainage well water flow volume gradually decreases as time passes.In the process of foundation pit dewatering,the soil settlement close to the pit is larger at the beginning,and the soil settlement far away from the pit increases gradually over time.In the process of foundation pit dewatering excavation,the horizontal displacement of foundation pit shows trend of increasing first then decreasing along the buried depth of soil.The maximum displacement occurs in the middle of diaphragm wall.