Damage to Foundations Produced by Swelling Soil in Smara, Morocco - Mineralogical and Geotechnical Characterization

This paper deals with a characterization study of swelling mudstone, which is the major constituent of the stabilized layer used for the foundations of the city of Smara, in the south of Morocco. Granulometric analysis and determination of the Atterberg limits revealed that the clayey fraction of the mudstone is insufficient to explain its swelling characteristics. X-ray diffractometry, together with the examination of several samples under a scanning electron microscope, show that this property has its origins mainly in the presence of sulfate minerals (gypsum and anhydrite) contained in the mudstone matrix. In situ rigid plate tests, using loading pressures of 3, 5 and 7 bars for each studied site, allowed the swelling pressure of the Smara mudrock to be determined. The measured values vary between 2.5 and 6 bars, and should be taken into account to improve the size of the foundations in this city.