Field and laboratory investigation on non-linear small strain shear stiffness of shanghai clay

Abstract

Booming infrastructure construction and rapid urban redevelopment in Shanghai demand utilization of more underground spaces, leading to a large number of geotechnical projects. There has been a growing and widespread appreciation that strains of the soil around underground structures such as foundations, excavations and tunnels are, except in some areas that undergo yielding, generally in a small strain range typically of the order of 0.01%–0.1%. In this paper, the small strain stiffness features including the elastic shear modulus G0 and stiffness degradation curve have been investigated in the field using the suspension wave velocity logging system and in the laboratory using a resonant column apparatus equipped with bender elements. At very small strains, the measured shear moduli obtained from bender element tests are fairly consistent with those from field tests. The elastic shear moduli can be well captured by an empirical power correlation considering stress levels. At small strains, the observed stiffness-strain relationships of typical Shanghai clay layers are highly nonlinear.