A New Apparatus for Studying Laterally Restrained Swell of Compacted Clay with Lateral Pressure Measurement

Abstract

Abstract Wetting of compacted clays, and their subsequent swelling, often results in damage to structures and infrastructures. In some cases, for example, if the clay is adjacent to a structure such as a retaining wall, pile, or pipeline, lateral swell is restrained, resulting in heave in the vertical direction and development of swelling pressure laterally. Standard procedures for testing the swell of clays on wetting are limited to the definition of a vertical pressure-swell relationship. This paper presents an investigation of the laterally restrained swell of a highly plastic compacted clay in a new rectangular test cell designed to provide additional and more reliable test information. Lateral soil pressure is measured using null pressure gauges flush with the cell walls. Cell sidewall friction is evaluated by measuring the load applied to the specimen top and the load reaching its base, and it is minimized by incorporating friction reduction measures. It was found that pressure-swell curves, based on vertical pressure, horizontal pressure, and mean pressure, all plot as straight lines on a semi-log basis. Although inundation of the test specimen is standard practice for swelling tests, this procedure represents an extreme wetting condition in the field. The study demonstrates that swell is affected by the characteristics of the hydraulic head responsible for wetting the soil; wetting by suction alone, or by combination of suction and gravity head, result in different degrees of swell.