Suction-Monitored Direct Shear Testing of Residual Soils from Landslide-Prone Areas
This article has been corrected.
VIEW CORRECTIONPublication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 136, Issue 3
Abstract
The apparent cohesion due to soil suction plays an important role in maintaining the stability of steep unsaturated soil slopes with deep ground water table. In this paper, a modified direct shear box is used to determine the relationships between the value of this additional cohesion and the associated soil suction. The apparatus incorporates a miniature tensiometer which allows for the simple and direct measurement of suction during shearing. The soil-water characteristic curves and shearing behavior of intact residual soils, being low-to-medium plasticity silts, as well as silty sand, taken from four landslide-prone areas in Thailand, have been investigated. The relatively low air-entry suctions (0–7 kPa) and bimodality of the soil-water characteristic curves gives an indication of the structured pore size distribution of the materials tested. Samples with higher suction tend to display stronger bonding at particle contacts and thus are more brittle. The shear strength is found to increase nonlinearly with suction, though linearization can be reasonably assumed for suction below around 30 kPa. Prediction of shear strength based on soil-water characteristic curves agrees better with ultimate than peak values. A simple equation is proposed for the minimum ultimate strength that can be expected in an unsaturated residual soil with a suction lower than about 30 kPa.
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Acknowledgments
The writers gratefully acknowledge the research Grant No. UNSPECIFIEDMRG4980086 of the Thailand Research Fund and Commissions of Higher Education, Thailand, and thank Mr. Narin Hansachainun, Mr. Nattapong Paiboonsombat, and Mr. Lerdchao Kenganantanon for their assistance in performing some direct shear tests in this research project. The writers also thank Dr. Auckpath Sawangsuriya, Dr. Rafael Monroy, and other anonymous reviewers for their invaluable comments.UNSPECIFIED
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© 2010 ASCE.
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Received: Aug 19, 2008
Accepted: Aug 13, 2009
Published online: Aug 26, 2009
Published in print: Mar 2010
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