PRELOADING FOR REDUCTION OF COMPRESSIBILITY CHARACTERISTICS OF SABKHASOIL PROFILES

Sabkha soils are coastal and inland salt flat deposits of arid climate s, which invariably contain an appreciable amount of organic materials . They are, therefore, characterized by being highly compressible with a significant part of the settlement taking place as secondary compre ssions. In this study, the applicability of a preloading technique in improving the compressibility characteristics of sabkha sediments was investigated through construction of an instrumented test embankment o n a typical sabkha formation from the southwest coast of Saudi Arabia. Settlement and pore pressure measurements were taken for an observati on period lasting 1 year. Compressibility parameters were determined i n the laboratory from extensive standard and long-term consolidation t ests on undisturbed samples taken from the site before and after the p reloading process. The laboratory test results substantiated by the re latively large settlements measured under the test embankment indicate that the precompression method is an effective technique that can eli minate the primary consolidation settlements and reduce the secondary compressions of sabkha sediments. The field behavior was predicted uti lizing the conventional theory of consolidation and the finite element method. Using laboratory-determined compressibility parameters, the o ne-dimensional theory of consolidation highly overestimated the measur ed settlements and significantly underestimated the observed settlemen t-time behavior. However, close agreement between observed and predict ed behavior was obtained when field parameters were used in the analys es. Although substantially overestimating the time required for comple tion of primary settlements, the finite element predictions of the mag nitude and the rate of settlements are considered satisfactory. (C) 19 97 Elsevier Science B.V.