THE INFLUENCE OF END FRICTION ON ELASTIC PARAMETERS OBTAINED IN TRIAXIAL TESTS

Abstract

The effect of end restraint on elastic parameters, particularly Young's modulus and Poisson's ratio, determined from triaxial tests, is investigated. These elastic constants are not the same as those appearing in the Hooke's law. However,for a test specimen of height to diameter ratio more than or equal to 2, the expression for lateral deformation at the exterior of the middle of the lest specimen without considering end restraint, is shown to be almost exact. Hence knowing one of the two elastic parameters the other one can be determined accurately using this expression.When both the parameters are to be determined they can be obtained from a single test with the help of the graphs presented here in, provided the radial deformations at the top edge and at the exterior of the middle of the test specimen are measured. For cases where the ends can be assumed to be fully restrained, as in tests using porous stones at both ends of the sample, the true Young's modulus can be obtained directly from the results presented in this paper.