Effects of water content on the shear behavior and critical state of glacial till in Tianmo Gully of Tibet, China

• Published in: Journal of mountain science 2019-08, Vol.16 (8), p.1743-1759
• Main Authors: Zhou, Gordon G. D., Chen, Lei-lei, Mu, Qing-yi, Cui, Kahlil Fredrick E., Song, Dong-ri
• Format: Article
• Language: English
• Subjects: Dilatancy; Dilation; Earth and Environmental Science; Earth Sciences; Ecology; Environment; Failure mechanisms; Geography; Glacial till; Gullies; Landslides; Moisture content; Plastic deformation; Rain; Rainfall; Shear; Shear tests; Stresses; Water content
• ISSN: 1672-6316; 1993-0321; 1008-2786
• DOI: 10.1007/s11629-019-5440-9

Glacial tills are widely distributed in Tibet, China, and are highly susceptible to landslides under intense rainfalls. Failures of the slope during rainfall are closely related to the shear behavior of glacial tills at different moisture conditions. This study investigates the shear behavior and critical state of saturated and unsaturated glacial tills through a series of drained direct shear tests. The tests were conducted on two types of compacted glacial tills with different water contents and total normal stresses. A strain softening mode of failure is observed for all water content conditions accompanied by noticeable dilation. Dilatancy is found to decrease with increasing water content. Unsaturated samples showed increased rates of dilation as water content is decreased for all applied normal stresses a behavior which cannot be predicted well by classical stress-dilatancy models. Furthermore, it was found that the Critical State Line (CSL), plotted on the ( e -lnσ n ) plane, can be used to define the shear behavior of unsaturated glacial tills at different water contents. The CSL of saturated glacial tills run parallel to this line. The experimental results in this study are aimed to provide a basic understanding to the underlying failure mechanisms of glacial tills.