APPLICATION OF THE C-ALPHA C-C CONCEPT TO SECONDARY COMPRESSION OF SABKHA SOILS/

Sabkha soils are coastal and inland saline deposits of arid climates c onsisting mainly of loosely cemented sandy silt to silty clay particle s. Invariably the soils contain an appreciable amount of organic mater ial and are characterized as being highly compressible. Despite increa sed interest in various aspects of sabkha soil behavior, little is yet known about the nature and magnitude of secondary compression of thes e distinct sediments. In this paper, the secondary compression behavio r of a typical sabkha formation from the southwestern coast of Saudi A rabia was investigated. Series of conventional and long-term, one-dime nsional consolidation tests were conducted on natural and preloaded un disturbed samples taken from the compressible sabkha layer. The result s of the laboratory investigation, substantiated by existing field dat a, indicated that a significant portion of sabkha settlements takes pl ace as a secondary compression. The coefficient of secondary compressi on, C-alpha, was found to be constant, and the ratio of C alpha to the compression index, C-c, is within the range reported in the published literature for various geotechnical materials. The applicability of t he C-alpha/C-c, concept to sabkha soils was further ascertained by com paring the secondary settlements estimated based on this concept with those measured directly in the field under an instrumented test embank ment. Reasonable agreement was found between predictions and field obs ervations.