Abstract
The upper 75 m of the alluvium beneath Shanghai can be divided into three clay layers. Consolidation of the upper soft clay contributes to the average 3 mm/year land subsidence which occurs in the Shanghai region, despite mitigation measures including reduction in groundwater exploitation from the underlying aquifer and groundwater recharge. Data indicate that the soft clay is semi-dispersed, marginally stable, and susceptible to compaction. The study reports an analysis of the granulometric characteristics and aggregate components, pore-size distribution, microstructure, pore solution composition and cation exchangeability of the soft clay. The results indicate the deformation/consolidation of the soft clay is related to its microscopic physical and chemical characteristics rather than the fluctuation of the groundwater level in the underlying aquifer.
Résumé
Les 75 m supérieurs d’alluvions sous la ville de Shanghai peuvent être divisés en trois couches argileuses. La consolidation de la couche supérieure d’argile molle contribue pour une moyenne de 3 mm/an à la subsidence qui s’observe dans la région de Shanghai, malgré des mesures de limitation du phénomène comportant la diminution des pompages d’eau souterraine dans l’aquifère sous-jacent et des techniques de réalimentation de cet aquifère. Les données indiquent que l’argile molle est en partie sous forme colloïdale, très peu stable et sensible à la compaction. L’étude présente une analyse de la composition granulométrique et des aggrégats du sol, de la courbe porosimétrique, de la microstructure, de la composition de l’eau des pores et de la capacité d’échange de cations de l’argile molle. Les résultats indiquent que la déformation de l’argile molle par consolidation est en rapport avec ses caractéristiques physiques et chimiques microscopiques plutôt qu’avec les fluctuations de la surface piézométrique dans l’aquifère sous-jacent.
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Acknowledgments
The work presented in this paper was supported by Cooperative project of Shanghai Municipal Government and the Ministry of Land and Resources, and Programme of Excellent Young Scientists of the Ministry of Land and Resources, P. R. China.
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Yang, TL., Gong, SL. Microscopic analysis of the engineering geological behavior of soft clay in Shanghai, China. Bull Eng Geol Environ 69, 607–615 (2010). https://doi.org/10.1007/s10064-010-0305-z
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DOI: https://doi.org/10.1007/s10064-010-0305-z