Characterization of transverse anisotropy in Poisson's ratio using three-point radial deformation measurements

• Main Authors: Toker Nabi Kartal, Büyükyılmaz Kemal Sercan
• Format: Article
• Language: English
• Published: EDP Sciences 2019-01-01
• Series: E3S Web of Conferences
• Online Access: https://www.e3s-conferences.org/articles/e3sconf/pdf/2019/18/e3sconf_isg2019_02006.pdf

Poisson's ratio (v) of rock specimens can be experimentally determined from radial deformation measurements in an unconfined compression test. This is commonly achieved by mounting a compressometer with diametric or perimetric measurement capability, both of which assume the specimen cross-section remains a circle. If there is anisotropy among the horizontal directions, this assumption fails and measurements err. In this study, a compressometer with three radial deformation measurements is developed. The accuracy of new compressometer in determining the mean of the two v values along the two axes of anisotropy is theoretically investigated, assuming the deformed specimen is an ellipse in cross-section. Then, to capture separate v values along the axes of anisotropy, data from actual tests employing the new device were analysed in two different approaches: Assuming the centroid of the cross-section remains stationary (1) does not produce physically reasonable results. Assuming the specimen moves laterally and v values are constant (2) is possible through a grid search-type optimization algorithm. This results in calculation of the orientation of axes of anisotropy with respect to the compressometer, as well as the corresponding v value.