Behavior of composite ground reinforced by sand compaction piles

Abstract

Stress transfer characteristics as well as the settlement reduction factor are the most important elements in design and analysis of the SCP (sand selection pile) method. This study suggests new theoretical equations in order to estimate stress transfer parameters in the laboratory and the field without any instrumentation which can cause some errors in the ground. Laboratory measurement data verify the applicability of these equations. From a series of laboratory tests for single sand pile and multi sand piles, variations of stress transfer parameters according to different influential factors and the test methods are studied. Composite ground shows somewhat different behavior between a single-pile test and a multi-pile test. These differences seem to be caused by the fact that the stiffness of the sand pile in a single-pile test was overestimated, because the ratio of the pile length to the diameter decreased as the replacement increased. Also, this study takes up the point that design based on the stress concentration ratio can cause some mistakes, because the stress reduction factor of clay and the stress increment factor of a sand pile estimated from the replacement ratio and stress concentration ratio cannot have unique trends even if the stress concentration ratio is the same.