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Unsaturated Shear Strength of a Sri Lankan Residual Soil from a Landslide-Prone Slope and its Relationship with Soil–Water Retention Curve

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Abstract

Unsaturated soil mechanics has become a topic of interest among the Sri Lankan geotechnical community owing to its importance in different applications, especially slope stability. In this study, soil samples collected from a landslide area in Sri Lanka were subjected to soil–water retention curve (SWRC) tests and suction-monitored direct shear tests. SWRC tests were conducted on both undisturbed and statically compacted samples and the results were modelled using Van Genutchen equation. The compacted samples having the same dry density as the undisturbed block samples exhibited a similar SWRC. Consolidated drained direct shear tests and suction-monitored direct shear tests were conducted on compacted samples to determine saturated and unsaturated shear strength respectively. The unsaturated shear strength followed a non-linear envelope with respect to matric suction, as shown by a good correlation for the cases of second-order polynomial correlation (R2 = 0.970) and the prediction using Vanapalli et al. model and SWRC with K = 1.2 (R2 = 0.941). These test results confirm the validity of using SWRC for predicting unsaturated shear strength of a compacted Sri Lankan silty sand.

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Acknowledgements

This research was financially supported by the National Building Research Organization, Department of Civil Engineering, University of Moratuwa, Sri Lanka and Department of Civil Engineering, Faculty of Engineering, Kasetsart University, Thailand. Their contributions are gratefully acknowledged.

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Authors and Affiliations

  1. National Building Research Organization, Colombo, Sri Lanka

    Lilanka Kankanamge

  2. Department of Civil Engineering, Kasertsart University, Bangkok, Thailand

    Apiniti Jotisankasa & Narin Hunsachainan

  3. Department of Civil Engineering, University of Moratuwa, Moratuwa, Sri Lanka

    Athula Kulathilaka

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  1. Lilanka Kankanamge
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  2. Apiniti Jotisankasa
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  3. Narin Hunsachainan
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  4. Athula Kulathilaka
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Correspondence to Apiniti Jotisankasa.

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Kankanamge, L., Jotisankasa, A., Hunsachainan, N. et al. Unsaturated Shear Strength of a Sri Lankan Residual Soil from a Landslide-Prone Slope and its Relationship with Soil–Water Retention Curve. Int. J. of Geosynth. and Ground Eng. 4, 20 (2018). https://doi.org/10.1007/s40891-018-0137-7

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