Prediction of Unconfined Compressive Strength for Jointed Rocks Using Point Load Index Based on Joint Asperity Angle

Abstract

This research paper is aimed to briefly highlight the correlation between unconfined compressive strength and point load index for jointed rocks based on joint asperity & orientation. In this observe, specimens were tested to obtain their unconfined compression strength and point load index for a different joint condition. The different joint conditions considered for this study were clean joint and joint filled condition. For both clean joint and joint filled specimens were prepared by various asperity angles of 30°, 45°, 60° and 90° with different orientation angles such as 0°, 30°, 45°, 60°, 90°. Plaster of Paris was used as model material to simulate weak rock mass in the field. By testing intact model specimens for unconfined compressive strength leads to revealing of optimum moisture content for further testing. The curing period for the model specimens is 3 days at room temperature. To simulate jointed rocks, various moulds of different orientation of joint with respect to major principal stress are prepared separately. The inner diameter of the mould is 50 mm and height is 100 mm. After casting, a rough joint was created by cutting the prepared sample using the cutter. The specimens are tested for both clean joint and joint filled condition to determine the favorable joint orientation and asperity angle. After curing, the specimens are tested for unconfined compressive strength and Point load index. The new multi-linear correlation for determining unconfined compressive strength with the help of point load index is developed and cross checked with equations formed for actual rock. On comparing both results it is found that the new equation can suitable for assessing the unconfined compressive strength of limestone and serpentinite rocks through point load index value.