FIELD AND LABORATORY MEASUREMENTS OF SOIL STIFFNESS. PROCEEDINGS OF THE ELEVENTH INTERNATIONAL CONFERENCE ON SOIL MECHANICS AND FOUNDATION ENGINEERING, SAN FRANCISCO, 12-16 AUGUST 1985

A simple and precise method of measuring local axial strains on triaxial samples is described and it is demonstrated that conventional methods of strain measurement can lead to very significant under estimates of soil stiffness. Results of triaxial tests on samples of London clay show that the undrained stress-strain behaviour is strongly non-linear but not greatly influenced by sampling or stress-path. The undrained stiffnesses at small strains are in good agreement with values obtained from high quality insitu tests and from back-analysis of field measurements. Good agreement is obtained between laboratory determined undrained stress-strain characteristics and insitu stress-strain behaviour deduced from three instrumented loading tests in London clay. For the covering abstract of the conference see IRRD 287689. (Author/TRRL)