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Wetting-induced softening behavior of an unsaturated expansive clay

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Abstract

Studying the wetting-induced softening behavior of unsaturated soils is important for understanding rain-induced slope failures in unsaturated soils. However, experimental studies on expansive soils are limited. This study investigates the wetting-induced softening characteristics of an unsaturated expansive clay via suction-controlled triaxial tests on recompacted and natural specimens. It was found that the wetting-induced swelling of the soil included a significant component of plastic strain and its magnitude decreased with the net confining stress. When a soil specimen was subjected to wetting at a constant deviator stress, a threshold value of soil suction was identified after which the axial strain increased greatly. This value tended to increase with the applied net stress ratio. After the threshold suction, the wetting process for recompacted specimens could be divided into a yielding process associated with volumetric strain hardening/softening and a failure process in which the volumetric behavior depended on the applied net stress ratio. The natural specimens exhibited a brittle failure like a heavily overconsolidated soil during wetting at a constant deviator stress and continuous volumetric dilation occurred after the threshold suction. The wetting-induced softening soil behavior revealed from the present study could interpret the rain-induced progressive slope failure in unsaturated expansive soils.

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Acknowledgments

The authors acknowledge financial support from research grants no. 2012CB719800 provided by National Basic Research Program of China, no. 2011KYJD006 supported by the Fundamental Research Funds for the Central Universities, and no. 50909030 provided by National Natural Science Foundation of China.

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Authors and Affiliations

  1. MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering, Zhejiang University, Hangzhou, China

    T. L. T. Zhan

  2. Shenzhen Key Laboratory of Urban and Civil Engineering for Disaster Prevention and Mitigation, Shenzhen Graduate School, Harbin Institute of Technology, Shenzhen University Town, Xili, Shenzhen, China

    R. Chen

  3. Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR, China

    C. W. W. Ng

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  1. T. L. T. Zhan
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  2. R. Chen
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  3. C. W. W. Ng
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Correspondence to R. Chen.

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Zhan, T.L.T., Chen, R. & Ng, C.W.W. Wetting-induced softening behavior of an unsaturated expansive clay. Landslides 11, 1051–1061 (2014). https://doi.org/10.1007/s10346-013-0449-6

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  • DOI: https://doi.org/10.1007/s10346-013-0449-6

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