STRENGTH OF FIELD COMPACTED CLAYEY EMBANKMENTS

YUEH LIANG, Purdue University

Abstract

The purpose of this study was to investigate the relationships among the compaction variables (dry density, water content, and compaction energy) and the shearing behavior of a field compacted St. Croix clay. The strength tests were performed by unconsolidated- undrained (UU) and saturated consolidated-undrained (CIU)(' ) triaxials. These were run at various confining pressures to approximate the end of construction and long term conditions at several embankment depths. Samples for the triaxial tests were taken from the ten past pads, which had been compacted to three levels of effort, at five levels of water content, and by two kinds of rollers. The results of field as-compacted strength from UU tests showed that an increase in strength results from an increase in density or a decrease in water content. The strength also increased with confining pressure until a near-saturation condition was reached in the sample. A regression model for field as-compacted strength was thus developed in terms of the water content, dry density, and confining pressure. The effective stress strength parameters were evaluated for various compaction conditions through the performance of saturated consolidated undrained triaxial tests with pore water pressure measurements. The results of the testing program showed that the effective stress strength parameters, c' and (phi)', are functions of compaction water content and initial void ratio. For a constant value of initial void ratio, as the water content increases, c' increases and (phi)' decreases. The values of volumetric strain due to saturation(' ) and consolidation, and Skempton's A parameter at failure demonstrated dependency on the water content, dry density, energy level, and confinement for this field compacted soil. Comparison of the prediction models for as-compacted and saturated undrained strength of a field compacted medium plastic St. Croix clay were made with prediction models previously developed for a laboratory compacted highly plastic St. Croix clay. The coupling of the relations for field compaction with those previously established for laboratory compaction is also reported here.

Degree

Ph.D.

Subject Area

Civil engineering

COinS