Interpreting measurements of small strain elastic shear modulus under unsaturated conditions

University of Glasgow, School of Engineering, Rankine Building, G12 8LT, Glasgow, UK

^a Corresponding author: Simon.Wheeler@glasgow.ac.uk

Abstract

Bender element testing of unsaturated isotropically compacted speswhite kaolin samples was used to investigate the variation of small strain elastic shear modulus G under unsaturated conditions. Testing was performed in a suction-controlled triaxial cell and involved combinations of isotropic loading and unloading stages and wetting and drying stages. Analysis of the experimental results indicated that the variation of G could be represented by a simple expression involving only mean Bishop’s stress p* and specific volume v, with the only significant mismatches between measured and predicted values of G occuring at the end of final unloading. No significant improvement of fit was achieved by incorporating additional dependency on degree of saturation S_r or a bonding parameter ζ. The proposed expression for G reverts to a well-established form for saturated soils as S_r tends to 1.