Characterization of land subsidence induced by groundwater withdrawals in Su-Xi-Chang area, China
Characterization of land subsidence induced by groundwater withdrawals in Su-Xi-Chang area, China
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DOI：
10.1007/s00254-006-0446-3
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发表时间：
2007-02
期刊：
影响因子：
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通讯作者：
Xiaoqing Shi;Yuqun Xue;S. Ye;Jichun Wu;Yun Zhang;Jun Yu
中科院分区：
文献类型：
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作者：
Xiaoqing Shi;Yuqun Xue;S. Ye;Jichun Wu;Yun Zhang;Jun Yu
苏锡常地区是我国地面沉降严重的典型地区之一。综合多种地面沉降监测手段，研究了该地区地面沉降的特征和机理。该地区地面沉降的发生、发展与地下水开采在时间和空间上都有很强的相关性。软土层是主要的固结层，但桑迪层的压缩性不容忽视。第二和第三承压含水层贡献了总沉降量的30%以上。同时，在桑迪中也观察到不可恢复的变形。不同的桑迪在不同的应力条件下产生不同的变形。有些具有弹性。但位于地下水位降落锥中心的土层（包括桑迪层和粘土层）表现出明显的粘性力学行为，导致了常见的滞后现象。砂体成分（夹小粘土颗粒或夹层）和砂体流变性是造成桑迪滞后现象的两个主要原因。通过一系列室内试验模拟地下水开采引起的有效应力变化，研究了滞后现象的机理。根据试验结果，得到了饱和砂土的应力-应变-时间关系，其可用幂函数表示。桑迪层的压缩变形具有时间依赖性，且变形显著。在建立地面沉降模型时，由于地下水位波动的不同，相似土层的变形可以是弹性变形、粘弹性变形，甚至是粘弹塑性变形。
Su-Xi-Chang area is one of the typical regions in China which suffers from severe land subsidence. Various tools of field monitoring were integrated to study the characteristics and mechanisms of land subsidence in this region. The occurrence and the development of the land subsidence in this region are strongly related to the groundwater pumping both in time and space. The main consolidation layers are the soft mud layers; however, the compressibility of the confined sandy layers should not be ignored. The second and third confined aquifers contributed more than 30% of total subsidence. Meanwhile, irrecoverable deformations were also observed in the sandy layers. Different sandy layers deform diversely under different stress conditions. Some have the elastic feature. But the soil strata, including both sandy layers and clayey layers, located in the center of the groundwater level depression cone exhibited obvious viscous mechanical behavior which caused the common lag phenomenon. The sand composition (mingled with small clay particles or interbeds) and sand rheology are the two main reasons for the lag phenomena in sandy layers. A series of laboratory tests for modeling the effective stress changes due to groundwater withdrawals, were conducted to investigate the mechanism of the lag phenomenon. Based on the test results, the relationship of stress–strain–time for saturated sands is obtained; and it could be expressed as power functions. The results also showed that the compression of the sandy layers was time dependent, and its deformation could be remarkable. When establishing land subsidence model, the deformation for the similar soil formation could be elastic, visco-elastic and even visco-elastic–plastic, because of the different groundwater level fluctuation experienced.