Foundation Failures Associated with Salt Rock and Surrounding Coastal Plain

A detailed investigation has been conducted to study the causes of severe and widespread damages in a town situated on a salt dome. The study includes a thorough assessment of ground conditions in the coastal plain surrounding the salt dome for possible utilization of the plain as redevelopment areas. Major geological features in the study area comprised of collapsible windblown sands which are underlain by salt rock in the old town and soft/loose sabkha deposits in the proposed redevelopment zones. It has been found that the extensive damages in the buildings and roads are primarily due to subsidence phenomenon associated with the dissolution of salt rock. The properties of the sabkha sediments and anticipated geotechnical problems have been described

Foundations on Stone Columns Resting on Coralline Limestone

The subsoil conditions along the Red Sea coast in Saudi Arabia are complex due to existence of very thick beds of coralline limestone of recent geological origin. These coral beds are soft, porous and nonhomogeneous. They are often interspaced with large cavities and soft sandwiched layers of finer particles. Analysis of the subsoil conditions to a fifty meter depth based on data from deep boreholes, Standard Penetration Tests (SPT), Quasi Static Cone Tests (DCT) and large size Plate Load Tests is presented. The strength and compressibility characteristics of the strata and the correlation factors for the SPT and DCT in coralline limestone are evaluated. The results from the plate load tests conducted on natural soil and on soil compacted with stone columns are included. An evaluation of the performance of the foundation for the heavy turbines resting on soil compacted with vibro-compaction replacement method with stone columns was made

Preloading for reduction of compressibility characteristics of sabkha soil profiles

Sabkha soils are coastal and inland salt flat deposits of arid climates, 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 compressions. 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 on a typical sabkha formation from the southwest coast of Saudi Arabia. Settlement and pore pressure measurements were taken for an observation period lasting 1 year. Compressibility parameters were determined in the laboratory from extensive standard and long-term consolidation tests on undisturbed samples taken from the site before and after the preloading process. The laboratory test results substantiated by the relatively large settlements measured under the test embankment indicate that the precompression method is an effective technique that can eliminate the primary consolidation settlements and reduce the secondary compressions of sabkha sediments. The field behavior was predicted utilizing the conventional theory of consolidation and the finite element method. Using laboratory-determined compressibility parameters, the one-dimensional theory of consolidation highly overestimated the measured settlements and significantly underestimated the observed settlement-time behavior. However, close agreement between observed and predicted behavior was obtained when field parameters were used in the analyses. Although substantially overestimating the time required for completion of primary settlements, the finite element predictions of the magnitude and the rate of settlements are considered satisfactory.Corresponding Author: Prof. Mosleh A. Al-Shamrani, Professor Geotechnical Engineering, College of Engineering, Department of Civil Engineering, King Saud University, Riyadh, Saudi Arabia. Email: [email protected]

Swell Behavior of Expansive Soil with Free Lateral Movements

Expansive soils are characterized by volume increase upon saturation. Extensive damages to structures may occur as a result of soil heave. Prediction of field expansion is essential prior to foundation construction. Experimental tests using oedometer equipment are used to predict field swell. However, in these tests, full lateral expansion is restrained which does not represent the actual field behavior where part of volume increase is consumed in the lateral direction. To improve the quality of field swell estimation, different testing techniques must be adopted. In this paper, experimental testing program is carried out on expansive soil with no lateral restraint. It is found that the lateral swell constitutes about one third of the total swell. More attention should be directed to such unconventional testing procedure to replace the oedometer tests for more accurate heave prediction. Keywords: Expansive soil, Swell pressure, Swell index, Lateral restrain