Nonlinearity of one-dimensional creep characteristics of soft clays

This study focuses on the quantitative description of the evolution of creep coefficient (C (alpha e)) with both soil density and soil structure under 1D compression. Firstly, conventional consolidation test results on various reconstituted clays are selected in order to investigate the evolution of C (alpha e) with void ratio of soils, which can be described by a simple nonlinear creep formulation. Secondly, the contributions of the inter-particle bonding and debonding for soft structured clays to C (alpha e) are analyzed based on test results on intact and reconstituted samples of the same clay. A material constant rho, function of the bonding ratio chi, is introduced in order to quantify the contribution of the soil structure to C (alpha e), and a nonlinear creep formulation accounting for both soil density and soil structure is finally proposed. Furthermore, the parameters used in the formulation are correlated with Atterberg limits, allowing us to suggest a relationship between C (alpha e), Atterberg limits and inter-particle bonding for a given soil. Finally, the validity of the proposed formulation is examined by comparing experimental and predicted C (alpha e) values for both reconstituted and intact samples of natural soft clays. The proposed formulation is also validated by comparing the computed and measured void ratio with time on two intact clays.