determination of a formula for the interpolation of experimental results for determining appropriate starting values for the estimation of the model parameters of the cam-clay behavioral model

the cam-clay model is formulated within the infinitesimal-strain hypothesis in three dimensional spaces. approach to the reasonable form of cam-clay yield curves does have some needs. one of the most important needs is applying the three dimensional stresses with three different principal values (σ1 ≥ σ2 ≥ σ3) conducting true triaxial compression tests that in most of the countries is not yet available. in addition, in some projects, during the construction of a dam, the principal mechanical parameters of cam-clay model are not evaluated and also the stress–strain curves are not available or even during the construction, this tests have not been done. fortunately values of cohesion c and friction φ of the soil achieved from the stress–strain curves of common axisymmetric triaxial compression tests are realistic and often available. angle of internal friction, ф is a dominant parameter that employed as a representative characteristic in identification and classification of a soil. in this research, results of triaxial compression tests on different soils are investigated. according to the angle of internal friction, ф of the specimens an interpolation has been done. the resulted interpolations give an initial feeling about the value of the principal mechanical parameters of cam-clay model, like λ and ĸ in three dimensional space of p', q' and υ.