Formulation of Gmax from Reconstituted Clayey Soils and its Application to Gmax Measured in the Field

The elastic shear modulus of natural sedimentary clay ground, G_max, is estimated based on laboratory tests for fifteen different reconstituted clays. Two types of tests were performed, i.e., Bender Element and Cyclic Triaxial tests. The proposed formulation is not based on void ratio, e, but consists of only three parameters: w_L (liquid limit), p′ (the current mean effective stress) and p′_max (the maximum mean consolidation pressure). To apply it to the field, this equation is modified for using σ′_v0 (the in situ effective overburden pressure) and OCR, instead of p′ and p′_max. Since existing formulae for G_max are mostly based on e, they are not able to apply to both reconstituted soil and field, without considering the correction factor for structure. This is because e in the field is much larger than that for reconstituted soil even though their consolidation pressures and OCR are the same for these clays. The applicability of the proposed formula was examined by using investigated results from the in-situ seismic surveys performed at eleven worldwide sites. It is well demonstrated that the proposed equation in this paper is capable of predicting G_max of natural sedimentary clay deposits with higher accuracy than the existing empirical formulae using a function of e.