The pressure of clay backfill against retaining structures

Abstract

This paper investigates the pressures exerted by clay backfills against retaining structures. The lateral pressures are developed during three main phases: placement, compaction, and burial; horizontal total stress reduction at constant moisture content; and swelling or consolidation under approximately constant vertical stress. Experimental data from laboratory and pilot-scale studies, using clays of intermediate and high plasticity, are presented and used to assess the magnitude of the pressure changes in each phase. The process of compaction is examined and it is concluded that previously developed theories for assessing the pressures on retaining walls developed by compaction of granular soils are inapplicable for cohesive soils. The factors controlling the swelling of cohesive backfill are reviewed and results from a preliminary numerical study are used to provide an indication of the likely effects of plasticity and placement moisture content. Key words: earth pressure, retaining walls, clay, compaction, swelling.