Centrifuge model tests on sand specimen under extensional load

The appearance of shear banding in granular materials has been investigated intensively during the last decades and is still of ongoing importance in terms of understanding the stress-strain behaviour of the material, the localization phenomena and the interaction between soil and structure. Only less attention has been paid to the occurrence of systems of shear bands although such systems call be identified in geotechnical structures as well as in geological formations. In this paper we present results of experiments oil sand specimens under extensional load in natural gravity as well as in increased gravity in (he Centrifuge where the influence of the stress level on the geometry of a shear band pattern, specified by the spacing of the shear bands and the angle between failure surfaces and minor stress direction. has been investigated. Xray technique has been used to visualize the failure zones inside the specimen. at) optical measurement system called Digital Image Correlation has been applied to identify and observe the appearing deformation mechanism on the sides of the specimens in natural gravity as well as during the flight in the centrifuge. It can be shown that the geometry of the shear band pattern is sparsely influenced by the change of the stress level. Copyright (C) 2004 John Wiley Sons. Ltd.