Effects of stress path rotation angle on small strain responses

The results of experimental studies on the stress-strain behavior of Chicago glacial clays are presented and discussed. This paper describes small strain responses as a function of stress path rotation angle. Undrained compression and extension tests with three different preshear stress paths were conducted on high quality, hand-cut block samples obtained at two different depths from the excavation for the Block 37 project in Chicago. One preshear stress path was applied to investigate the stress-strain response representative of the in situ conditions via a recompression technique. The other two preshear stress paths were selected to isolate the effects of recent stress history such that the only difference between the two sets of paths was the direction of loading to a common effective stress condition. A period of drained creep at constant effective stress was imposed on all specimens prior to shearing to negate the possible effects of creep on the small strain responses. The results are discussed in terms of secant shear modulus, shear strain, and stress path rotation angle. The results of experiments show that recent stress history affects the small strain behavior of compressible Chicago clays.