A new simplified method and its verification for calculation of consolidation settlement of a clayey soil with creep

Abstract

The calculation of the consolidation settlement of clayey soils with creep behaviour has been a challenging issue with a long history. After a brief review the assumptions made in the two methods based on Hypothesis A and Hypothesis B, the authors present a new simplified hypothesis B method for calculation of consolidation settlement of a clayey soil with creep. Equations of this method are derived based on the “equivalent time” concept for different stress–strain states. This simplified Hypothesis B method is then used to calculate the consolidation settlement of a number of typical consolidation problems. The approximation and verification of this simplified method are examined by comparing the calculated settlements with settlements computed using two fully coupled finite element (FE) consolidation analysis programs using elastic viscoplastic (EVP) constitutive models (Hypothesis B) and the Hypothesis A method. It is found that the curves calculated using the new Hypothesis B simplified method with a factor α = 0.8 are close to curves from two FE model simulations with relative errors in the range 0.37%∼8.42% only for three layers of Hong Kong marine clay (HKMC). In overall, the settlements calculated using Hypothesis A method are smaller than those from the two FE simulations with relative error in the range 6.52%∼46.17% for the three layers of HKMC. In addition, this new simplified Hypothesis B method is used to calculate the average strain of consolidation tests done by Berre and Iversen in 1972. The calculated results are compared with the test data, and values from a fully coupled finite difference (FD) consolidation analysis using Yin and Graham’s EVP constitutive model (Hypothesis B), and Hypothesis A method. It is found that, again, the results from the new simplified Hypothesis B method are very close to the measured data. In conclusion, the new simplified Hypothesis B method is a suitable simple method, by spread-sheet calculation of the consolidation settlement of a single layer of a clayey soil with creep.