Small-strain shear modulus plays a crucial role in numerical analyses of underground geotechnical Engineering issues such as excavations and tunnels. The research on small strain shear modulus of typical clay layers has rarely been reported

despite the fact that many large-scale underground construction projects have been ongoing in Shanghai. In this study

the initial shear moduli of typical clay layers at small strains in Shanghai have been investigated on spot by the field acoustic wave measurement and indoor bending element test. The experimental results show that the initial shear modulus obtained from the bending element test is consistent with that obtained from the in-situ wave velocity test if the soil disturbance is minimized and the soil stress state adopted in the indoor experiment is equivalent to the in-situ soil. It is shown that the proposed empirical formulation with considering the stress state and the void ratio of the soil can reasonably describe the variation of the initial shear modulus of the typical clay layer in Shanghai

and the empirical parameters of each soil layer are given. The experimental results can provide reference for calculating and analyzing the shear modulus of soft clay at small to medium strain.