ENGINEERING BEHAVIOUR OF INTACT AND JOINTED MODEL ROCK IN POLYAXIAL STATE OF STRESS UNDER CYCLIC LOADING

Abstract

Polyaxial strength and deformation of the rock has been experimentally determined by using the polyaxial testing equipment. This study includes cyclic behavior of intact and jointed synthetic rock which has been tested under polyaxial condition. M20 grade concrete samples of nominal dimensions 100mm × 100mm × 100mm has been prepared under the guidelines of IS Code: 10262- 2009. Jointed samples have been prepared by cutting the samples at an angle of 0° from the horizontal plane which is making the sample into two equal halves. This work includes the testing of model rock under different combinations of intermediate and minor principal stresses. The intermediate principal stress is applied such that the ratio of intermediate to minor principal stress is kept as 1, 1.5, 2 and 2.5. The major principal stress is increased at a rate of 2 MPa/min with predetermined peak stress and constant valley stress in both jointed and intact case, cyclic loading is continued until the specimen fails. This work deals with the deformational behavior of model rock, depicted by three criterions. The variability of loading and unloading modulus, influence of normal stiffness to the material and damage model based on the energy dissipation has been discussed by comparing the intact and jointed cases.