成层土中基坑降水沉降模型分析

Analysis of Dewatering and Settlement Model of Foundation Pit in Multi-Layer

针对郑州东区粉土和粉质黏土交互分布的成层土地基条件,以基坑实际降水工况为基础,建立降水井动水位面控制的基坑降水——沉降分析模型.即使在粉细砂层中给定的降水井动水位面的位置有所偏差,仅对降水深度有所影响,而对沉降计算结果的影响较小.以地铁车站基坑降水沉降模型为例,运用有限元法对成层土基坑降水所产生的位移场进行分析.结果表明,基坑降水所产生的沉降主要发生在粉细砂层中,其最大沉降量接近地表最大沉降量的一半.作为粉细砂层顶、底板的弱透水层,因降水导致的沉降也不可忽略.粉细砂层的沉降主要表现为"释水沉降",而其顶、底板土层的压密则包括"释水沉降"和"减压沉降"两部分.

The model of foundation pit dewatering and settlement by controling the hydraulic water table in tube pumping well is presented in this paper to discribe dewatering and settlement properties of the layered strata profile of silt and silty clay in Zhengzhou easten zone.The site puming conditions are considered when the model is formulated.If the values of elevation of the hydraulic water table of tube pumping wells in silt sand have a little offset,the dewatering depth will be significantly affected,but with little effect on the evaluated values of the ground surface settlement.Base on the model,the drawdown and displacement for pit of the underground railway station is simulated by finite element method.The results show that the silt sand stratum is the principal compressing one,the maximum magnitude of the vertical displacement is nearly one half of the surface settlement,and the settlement of the stratum above or beneath the silt sand stratum cannot be neglected.The settlement of the silt sand stratum can be regarded as that caused primarily by pore water flows out,but the settlement of stratum above or beneath the silt sand stratum caused by decompression of confined water and pore water flows out.