A laboratory study of tiebacks in cohesive soil

Abstract

The short-term and long-term behaviour of tiebacks anchored in cohesive soils are not well understood, particularly regarding basic component responses of the overall tieback system. There are shortcomings in the predictive capacity for short-term and long-term performances both in individual tiebacks and complete systems. Nevertheless, the methods currently being used to calculate the ultimate resistance to pull-out of individual or groups of tiebacks appear to be conservative.A physical-model laboratory test facility has been designed to investigate the short-term and long-term behaviour of small-scale straight-shafted tiebacks anchored in cohesive soils to provide the following: pore-water pressure measurements, tieback lock-off, measurement of total and residual tieback movement, measurement of load distribution along the tieback, and unearthing of the tieback. The laboratory tieback behaviour has been studied using both consolidated and compacted clay, to indicate the effects of stress history, loading test technique, and overburden pressure on tieback performance. Key words: clay, creep, laboratory tieback test, tieback, soil anchor, consolidation, soil–structure interaction.