Studies on the monotonic and cyclic behavior of sands
Abstract
A new method for preparing reconstituted specimens of sand with a high degree of repeatability in terms of density was developed. Experimental and analytical investigations of the dynamics of pluviating grains were performed to provide a clearer understanding of the factors involved. Evaluations of fabric and uniformity were performed using image analysis of sections cut from resin impregnated sand specimens. The study identified the importance of sample size in such evaluations. The capabilities of a resonant column--torsional shear device were substantially improved by mechanical, hardware and software modifications. All operations of the device are now controlled through a single computer program written in a multi-tasking environment. The amount of torque that is transmitted through the membrane during torsional shear tests was determined theoretically and experimentally. Use of a correction is recommended particularly for testing at low strengths. The effects of various factors on the position of the steady state line determined from torsional shear test results were studied. The results indicate that the undrained steady state behavior is not only a function of composition and void ratio but is also affected by the soil structure. Strain rate did not influence the position of the steady state line for the range of loading rates used in this study. The importance of membrane compliance on the steady state line was clearly established for Ottawa 20-30 sand. This study confirmed that the maximum shear modulus varies only moderately as a result of changes in fabric, principal stress ratio and monotonic prestressing. Significant changes in the observed undrained response of cohesionless specimens were not reflected in the maximum shear modulus. The first simulation of a proposed chemical impregnation sampling technique was completed. The strength properties of specimens were actually determined following impregnation and flushing. Despite problems resulting from the poor performance of latex membranes at elevated temperatures, the test results indicate that the agar impregnation process is feasible and its development into an undisturbed sampling technique should be pursued.
Degree
Ph.D.
Advisors
Leonards, Purdue University.
Subject Area
Civil engineering
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