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Richard Wan

University of Calgary
« An effective stress tensor for unsaturated pendular-state granular media»
Jeudi 24 avril 2014 à 14h00

Richard Wan University of Calgary animera Jeudi 24 avril à 14:00, petit amphi du batiment K, LEGI un conférence ayant pour titre :

« An effective stress tensor for unsaturated pendular-state granular media»

abstract :

The expression of a proper effective stress tensor in unsaturated granular media has been a longstanding issue essentially because of the difficulty to account for interfacial effects. While the analysis of unsaturated conditions goes beyond Terzaghi’s effective stress, the commonly used Bishop’s effective stress is fraught with its own issues. In this connection, we derive a single effective stress tensor that encapsulates evolving liquid bridges, interfaces, particle packing, and water saturation through a micromechanical analysis of force transport in an unsaturated pendular-state granular material. The total stress tensor then emerges as the sum of three tensorial terms, namely, (1) the skeleton stress, (2) the stress induced by suction between particles due to air-water pressure difference, and (3) the stress due to surface tension along the air-water interface forming the so-called contractile skin. The latter two stress contributions are a function of the distribution of liquid bridges, degree of saturation as well as particle packing, and thus provide an adequate effective stress definition to describe both the constitutive behaviour and strength of unsaturated media. Finally, Discrete Element Method (DEM) numerical simulations of triaxial compression tests of pendular-state granular samples at different degrees of saturation are conducted to verify the proposed effective stress equation.