Relating Undrained Triaxial and Pressuremeter Stress-Strain Characteristics by Using Multi-Yield Surface Model Parameters

Multi-yield surface model parameters, which define the stiffness (H_i), size (k⁽ⁱ⁾), and location (α₁⁽ⁱ⁾) of a nest of yield surfaces were fitted to triaxial compression and extension data for nine fine grained soils [1,2]. Each set of model parameters were used in a computer program to calculate the total stresses (σ_rr,σ_zz,σ_ϑϑ) and strains (ε_ϑϑ, ε_rr) for an idealized load/unload pressuremeter stress path. The pressuremeter stress and strain data for all nine soils were utilized as the bassis for developing an empirical procedure which could be used to extract multi-yield surface model parameters from shear stress-strain data, (σ_rr − σ_ϑϑ) versus ε_γγ. The empirical procedure was used to extract values of H_i, k⁽ⁱ⁾, and α_i⁽ⁱ⁾ for each soil from the corresponding pressuremeter stress-strain data. The nine sets of model parameters fitted to (σ_rr − σ_ϑϑ) versus ε_rr data where specified as input for a computer program which were then used to calculate the corresponding load/unload triaxial compression and extension stress-strain data, (σ_yy-σ_xx) versus ε_yy.