EVALUATION OF MODULUS AND POISSON'S RATIO FROM TRIAXIAL TESTS.

A method is suggested to determine piecewise linear, stress-dependent relationships for the modulus and Poisson's ratio of soils. The method is based on linear elasticity and conditions associated with conventional triaxial tests at different states of stress. The tangent modulus at a given stress level is shown to be the slope of the axial stress-axial strain curve at the stress level, and the value of Poisson's ratio is evaluated by use of theoretical considerations and a simple graphical construction. This method of interpretation is applied to experimental data from two natural soils used in an actual full-scale field installation of buried concrete pipe, and the results are shown to be in reasonable agreement with those determined by more sophisticated analyses and more extensive experimental measurements. It is also demonstrated that other analytical methods for interpreting these test data may yield significantly different values for the mechanical properties of soils, and this must be taken into account when such results are incorporated into mathematical models for the response of soil-structure systems.