Centrifuge model tests on sand specimen under extensional load

Abstract

SUMMARYThe 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 can be identified in geotechnical structures as well as in geological formations. In this paper we present results of experiments on sand specimens under extensional load in natural gravity as well as in increased gravity in the 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, an 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.

Shear banding in geomaterials under extensional plane strain conditions: Physical and analytical model

“…A literature review is given in the paper of Wolf et al [19,22], Röchter et al [13], with respect to the observation of parallel normal faults in situ and also on different extensional mechanisms applied in the field of experimental models and numerical studies. In fact, only Leśniewska [7,8], Wolf [20,21], and Röchter [14] have paid particular attention to the quantitative determination of shear band spacing comparing the results of physical and numerical modeling. Leśniewska [7,8] developed an analytical approach for the calculation of the spacing of parallel shear bands behind a rotating retaining wall.…”

Measurement of higher-order stress-strain effects in granular materials undergoing non-uniform deformation

“…With granular materials, the issue of a proper continuum treatment at the macro-scale is of particular importance, because heterogeneity is inherent and pervasive and can occur at a scale that is significant when compared with a specimen's size [7,16,21,15]. Moreover, the strength of a granular material is not only affected by heterogeneity, but strength is largely a bulk expression of material behavior within localized deformation features such as shear bands, compression bands, and micro-bands [4,9,22,11,14].…”

New image analysis-based displacement-measurement system for geotechnical centrifuge modeling tests

“…Image-correlation analysis has also been used to measure the deformation of soil in centrifuge model tests (e.g. [16,6,9]). Except for being non-intrusive to the soil, image-correlation analysis also has the advantage of being highly accurate and automatic in measuring the displacements of arbitrary points within the soil during a centrifuge model test.…”