Accession Number : ADA297858

Title :   Micromechanics and Constitutive Modeling of Granular Materials in Stress Reversal and Cyclic Loading.

Descriptive Note : Final technical rept. 1 Oct 91-30 Nov 94,

Corporate Author : CALIFORNIA UNIV SAN DIEGO LA JOLLA

Personal Author(s) : Nemat-Nasser, S.

PDF Url : ADA297858

Report Date : 12 JUN 1995

Pagination or Media Count : 186

Abstract : The work performed under this grant, focused on fundamental research on cyclic response and response in unloading and stress reversal regimes of granular materials. The research program included a careful examination of grain-to-grain interaction during load reversal, which results in a dramatic change in the overall response of granular materials, from loading to unloading. This was then followed by a fundamental examination of the cyclic response of granular materials under confinement, with repeated stress reversals. Parallel with the theoretical work, the research program included a series of coordinated experiments using UCSD's special large hollow cylindrical load cell and the biaxial and simple shearing load frames with photoelastic granules. These experiments served several specific purposes: (1) appropriately incorporating lead shot in the large hollow cylindrical sample, a series of X-ray photographs were taken to identify the micromechanical response during load reversal; (2) densification and/or dilatancy measurements in load reversal and cyclic loading provided guidance for the theoretical work; (3) by direct observations, using the biaxial and simple shearing facilities, micromechanical changes in unloading, load reversal, and cyclic loading were examined with the ald of photoelastic granules; and (4) controlled independent experiments were used to validate the resulting models, and to evaluate the key parameters. (MM)

Descriptors :   *SAND, *MICROMECHANICS, *GRANULAR MATERIALS, *COHESIONLESS SOILS, DENSITY, PARTICLE SIZE, LOADS(FORCES), TEST EQUIPMENT, STRAIN(MECHANICS), VOIDS, SHEAR STRESSES, FRICTION, PORE PRESSURE, LIQUEFACTION, TORSION, AXIAL LOADS, PHOTOELASTICITY, CYCLIC LOADS, X RAY PHOTOGRAPHY.

Subject Categories : Soil Mechanics
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE