SMALL-STRAIN-SHEAR MODULUS OF SOIL BY DILATOMETER

A procedure is presented for estimating the small strain shear modulus \IG\N\dm\da\dx of soils based on flat dilatometer (DMT) test results. Previously published data from nine test sites at which both DMT and seismic tests were performed are used to develop a model. The nine sites represent various soil conditions ranging from soft clays to dense, overconsolidated sands. Earlier efforts had sought a relationship between \IG\N\dm\da\dx and either the DMT modulus or the DMT horizontal stress index. The present study shows that a semiempirical expression for \IG\N\dm\da\dx similar to Hardin’s equation produces better results for a wider range of soil types. The expression includes terms for the effective confining stresses in the directions of wave propagation and particle motion and the DMT-based total unit weight as a surrogate for void ratio. The average error between the observed \Ig\N\dm\da\dx and that determined by the model was 23%.