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复杂软土区群孔抽水下的土层沉降规律研究

Research on Stratum Settlement Analysis under Multi-well Pumping Conditions in Complex Soft Soil Areas

  • 摘要: 抽水试验获取的水文地质参数是评估深基坑岩土层水文特性及控制周边环境影响的关键指标。本文结合上海某工程深基坑工程实例,通过单井与群井抽水试验,结合场地工程地质和水文地质条件,对抽水过程中多层含水层水位变化及地表沉降进行分析,研究表明,第②3-3层、第⑤2-1层及第⑤2-2层存在显著水力联系,抽水过程中各含水层渗透系数基本一致,导水系数与释水系数存在明显层间差异;各含水层在停抽后水位恢复较快,停抽28 h内地下水位基本恢复至初始水位90%以上。抽水期间,地面沉降呈现显著空间效应,抽水中心区D0监测点最大累计沉降达37.91 mm,距离抽水井10 m、30 m处沉降量分别衰减至33.46 mm、17.76 mm;第②3-3层、第⑤2-1层、第⑤2-2层含水层在群井停抽后开始回弹,在停抽120 h后地面沉降监测点沉降回弹约36%~74%,而地下水位恢复至初始水位96.2%~98.6%,说明土体固结变形的不可逆特性。研究结果为类似水文地质条件下深基坑工程的变形预测和环境控制提供了经验参考。

     

    Abstract: The hydraulic parameters obtained from pumping tests are critical indicators for evaluating hydrogeological characteristics of deep foundation pit strata and controlling environmental impacts. This study, based on a deep foundation pit project in Shanghai, conducted single-well and multi-well pumping tests combined with site-specific engineering geological and hydrogeological conditions. The analysis of multi-aquifer water level variations and surface subsidence during pumping revealed significant hydraulic connectivity between Layers ②3-3, ⑤2-1, and ⑤2-2. The permeability coefficients remained consistent across aquifers during pumping, while notable interlayer differences existed in transmissivity and storativity coefficients. Post-pumping water level recovery showed rapid restoration, with 90% of initial water levels recovered within 28 hours across all aquifers. Surface subsidence exhibited distinct spatial effects during pumping operations. The maximum cumulative settlement at central monitoring point D0 reached 37.91 mm, with subsidence attenuating to 33.46 mm and 17.76 mm at 10 m and 30 m from the pumping wells respectively. Ground rebound initiated after multi-well pumping cessation, demonstrating 36%~74% settlement recovery at monitoring points within 120 hours, while groundwater levels recovered to 96.2%~98.6% of initial values. This contrast highlights the irreversible nature of soil consolidation deformation despite substantial water level restoration. The findings provide empirical references for deformation prediction and environmental control in similar hydrogeological conditions of deep excavation projects.

     

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