Extension/compression test stress-strain-volume change characterization under drained condition

The mechanical behavior of soil of principal interest from the aspect of stability and settlement of a structure are the soil's strength (peak strength associated with internal friction angle and/or cohesion) and stress-strain response (i.e. volumetric strain and normal strains) including related conditions (e.g. stress path and pore water pressure build-up). The quantitative results of laboratory tests on soil samples are necessary to analyze soil conditions/behaviors and their effect on the associated design consideration. Most commercial geotechnical laboratories employ the drained or undrained axial compression triaxial test to obtain the soil strength parameters accompanied by data of deviatoric stress versus axial strain and volumetric strain (or pore pressure) response. But the axial compression test stress path does not represent all modes of field load application for which such parameters are sought.; A modified version of Hooke's law can be employed to predict sand's drained axial/lateral extension behavior from a series of drained compression test results. This is as demonstrated through test results presented herein. The drained lateral/axial extension test behavior of two sands are successfully evaluated from a series of drained axial/lateral compression test responses coupled with the sand's associated drained isotropic rebound behavior.; Separately, this research investigates empirically assessed improvements or corrections to the axial compression test's current volume change curve formulation (after Ashour and Norris, 1999). While such empirical formulation for volume change response (in the drained axial compression test) is currently a part of various analytical tools (for laterally loaded pile and bridge abutment response and vertically loaded footing and pile tip load-deflection behavior), a more fundamentally based characterization is desired. A theoretical relationship involving the interdependence of the drained deviatoric stress-axial strain response and associated volume change behavior is proposed, one that attempts to relate the slope of the volume change curve to the mobilized friction angle. Such characterization starts with a mobilized form of Bolton's equation (associated with the critical state friction angle) but evolves to a very simple and elegant equation based, instead, on the mobilized friction angle in relation to the instantaneous constant volume friction angle. Such characterization leads to a very desirable related expression for the stress dependent tangent and secant values of Poisson's ratios.