A new simplified Hypothesis B method for calculating consolidation settlements of double soil layers exhibiting creep

Abstract

This paper presents a new simplified method, based on Hypothesis B, for calculating the consolidation settlements of double soil layers exhibiting creep. In the new simplified Hypothesis B method, different stress–strain states including over-consolidation and normal consolidation states can be considered with the help of the ‘equivalent time’ concept. Zhu and Yin method and US Navy method are adopted to calculate the average degree of consolidation for a double soil layer profile. This new simplified Hypothesis B method is then used to calculate the consolidation settlements of double soil layers, which have two different total thicknesses of soil layer (4 m and 8 m) and three different OCR values (Over-Consolidation Ratio, OCR = 1, 1.5 and 2). The accuracy and verification of this new simplified method are examined by comparing the calculated results with simulation results from a fully coupled finite element (FE) program using a soft soil creep model. Four cases of double layer soil profiles are analyzed. Hypothesis A method with US Navy method for the average degree of consolidation has also been used to for calculating consolidation settlements of the same cases. For Case I(4m) and Case III(8m), it is found that curves of the new simplified Hypothesis B method using both Zhu and Yin method and US Navy method are very close to the results from FE simulations with the relative errors within 8.5%. For Case II(4m) and Case IV(8m), it is found that curves of the new simplified Hypothesis B method using Zhu and Yin method agree better with results from FE simulations with the relative errors within 11.7% than curves of the new simplified Hypothesis B method adopting US Navy method with the relative error up to 36.1%. Curves of Hypothesis A method adopting US Navy method have the relative error up to 55.0% among all four cases. In overall, the new simplified Hypothesis B method is suitable for calculation of consolidation settlements of double soil layers exhibiting creep, in which, Zhu and Yin method is recommended to obtain the average degree of consolidation.