Experimental investigation for constitutive modeling of fine sand under cyclic loading using hollow cylinder specimens
Dakoulas, Panos C.
Doctor of Philosophy
An experimental program for the understanding of the behavior of fine cohesionless soil under monotonic and cyclic loading and for the development and refinement of constitutive models has been undertaken. An experimental program for both loose and dense saturated fine Ottawa Silica sands under monotonic loading using both solid and hollow cylinder specimens has been conducted. The failure surfaces have been established from twenty drained monotonic load tests. Results were found in good agreement with the failure surfaces incorporated in Lade's constitutive model. The soil behavior and deformation characteristics under undrained conditions have been investigated under a cyclic experimental program for loose sand. Results indicated that the circular rotation of principal stress axes with a constant amplitude deviator stress, as well as the stress direction reversals have significant effects on the rate of pore water pressure buildup, the triggering of a liquefaction flow failure in contractive sand and the rate of accumulation of deformation. The rate of excess pore water pressure buildup is faster during a cyclic test with circular rotation of principal stress axes than during a cyclic triaxial shear test or a cyclic torsional shear test having same amplitude of shear stress. The rate is faster during a cyclic triaxial extension test than in a cyclic triaxial compression test or a cyclic torsional simple shear test with the same amplitude of shear stress. The deformation and significant pore water pressures are developed during the first cycle and more remarkably during the last cycle. The pore water pressures (and mean effective stress reduction) and developed fast when the stress path reaches the failure surface which was established in monotonic load tests. The pore water pressure and deformation increase fast in the case of shear stress reversal. The pore water pressure buildup and mean effective stress reduction are more pronounced during extension loading than in compression loading. Moreover, the amplitude of shear stress has significant effects for the pore water pressure development and deformation. Significant pore water pressure and deformation can occur, during the rotation of the principal stress axes, even when the deviator stress is maintained unchanged. (Abstract shortened with permission of author.)
Civil engineering; Applied mechanics; Computer science