ABSTRACT
ABSTRACT: The paper presents some investigations carried out on a heavily compacted swelling FoCa7 clay (pd, = 1.9 Mg/m3). Tests were run on a high pressure oedometer with double lever arm, developed in the laboratory. The device is able to multiply the load placed on it by a ratio of 50. The maximum possible applied stress is equal to 30 MPa on a 70 mm diameter ring. The suction is controlled by circulating air at a controlled relative humidity at the basis on the sample. The relative humidity is controlled using saturated salt solutions. Tests in which the sample is submitted to suction cycles under constant loads were carried out. The results obtained showed a reversible response in volume, confirming previous results obtained under a zero stress. This particular behaviour is related to the high density of the samples tested, and to the major influence of physico-chemical clay-water interactions occurring at a microscopical level. In these dense samples, due to the very high compaction stress (60 MPa), no inter-aggregate pores are believed to exist, and therefore no irreversible collapse can take place, explaining the reversible response obtained.
