| 上海市地下水位大幅抬升条件下土层变形特征分析 |
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| 引用本文： | 罗跃,叶淑君,吴吉春,焦珣,王寒梅.上海市地下水位大幅抬升条件下土层变形特征分析[J].高校地质学报,2015,21(2):243. |
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| 作者姓名： | 罗跃 叶淑君 吴吉春 焦珣 王寒梅 |
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| 摘 要： | 过去对地下水位持续下降条件的地面沉降研究较多，但对水位大幅持续抬升过程中的地面沉降研究较少。本文根据
上海大量地面沉降、水位观测和钻孔资料，系统分析上海市90年代末以来地下水位大幅抬升条件下各土层的变形特征。自
1998年以来，上海市通过大幅压缩开采量、回灌地下水等措施使第二、三、四和五承压含水层水位分别平均抬升2.1 m，
3.6 m, 12.4 m, 12.7 m。水位的抬升使上海市地面沉降平均速率由1998年的12.2 mm/a减小到2011年的1.83 mm/a,减少85%。
通过对27组分层标数据分析发现：现阶段主要压缩层位在第一、二软土层，年沉降速率为2~4 mm/a；而第二含水层以下土
层已经有少量回弹。在水位持续大幅抬升过程中，本文总结了两种变形特征：1） 变形和水位变化基本同步，残余变形量非
常小，变形可概化为线弹性变形，这种变形主要发生在第一、二、三和五承压含水层、第五和六弱透水层；2） 压缩速率逐
渐减小，无明显持续回弹趋势，有较大残余压缩量且存在变形滞后现象，变形可概化为弹塑性变形，这种变形主要发生在
地第二、三和四弱透水层。第四承压含水层变形较复杂，两种变形特征都有。其中较大残余变形量主要由塑性贮水率比弹
性贮水率大2个数量级引起；变形滞后主要由弱透水层中超孔隙水压力消散较慢引起。本文研究成果对于掌握水位抬升过
程中土层变形方式、发生发展机理、预测未来地面沉降及地下水科学管理和资源评价具有重要意义。
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| 关 键 词： | 变形特征 弹性变形 滞后变形 地面沉降 |
Characterization of Land Subsidence During Recovery of Groundwater Levels in Shanghai |
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| LUO Yue,YE Shujun,WU Jichun,JIAO Xun,WANG Hanmei.Characterization of Land Subsidence During Recovery of Groundwater Levels in Shanghai[J].Geological Journal of China Universities,2015,21(2):243. |
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| Authors: | LUO Yue YE Shujun WU Jichun JIAO Xun WANG Hanmei |
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| Abstract: | Previous research was focused mainly on land subsidence during decline of groundwater levels. However, there have been
few studies for land subsidence during the recovery of groundwater levels. This paper analyzes the deformation of each individual
aquifer or aquitard after 1998, when groundwater levels in aquifers continued to rise due to reduced pumpage and increased artificial
recharge. From 1998 to 2012, the average groundwater level in the second, third, fourth and fifth confined aquifers rose on average by
2.1 m, 3.6 m, 12.4 m and 12.7 m, respectively. Because of the recovery of groundwater levels in Shanghai, the land subsidence rate
gradually decreased from 12.2 mm/a in 1998 to 1.83 mm/a in 2011. And the strata below the second confined aquifer even became
uplifted after 2009. Land subsidence was primarily contributed by compaction of the first soft layer with a compaction rate of 2-4 mm/a
in recent years. During the recovery of groundwater level, two kinds of deformation characteristics were recognized. One is thatdeformation basically instantaneously responds to groundwater level change in the confined aquifer, and residual deformation is small.
This type of deformation occurs in the first, second, third and fifth confined aquifer and the fifth and sixth aquitard. The second type is
that deformation is delayed and residual deformation is obvious, but the deformation rate decreases gradually. This type of deformation
occurs in the second, third and fourth aquitard. Deformation of the fourth confined aquifer is complex and includes both kinds of
deformation characteristics. The large residual deformation resulted from the fact that non-recoverable skeletal specific storage is
greater than the less-recoverable skeletal specific storage. The delayed deformation resulted from the delayed response of water level
within aquitard to the change in the adjacent aquifers. |
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| Keywords: | deformation characteristics residual deformation delayed deformation land subsidence |
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