Engineering properties of loess in Libya

A 1928 study of Tripolitania, indicated clearly the presence of loess-like deposits and described their nature, pointing out that 90% of the granular material was greater than 100 μm in diameter. Some authors suggest that there is a region of Peri-Sahara loess, although earlier observations indicate quite clearly that the Sahara region is free of loess. The proposed loess in North Africa, represented by soil samples from Libya, has been investigated. Undisturbed and remoulded soil samples representing two different types of loess have been collected from various locations in Libya. Samples represent Tripoli loess from the Jefara plain in the north west and Ghat loess from the Tahala region in the south west. The specific gravity, Atterberg Limits, grain size distribution and dry density were determined according to British Standard procedures (BSI, 1975). Grain size analysis for particles passing the No. 200 sieve (63 microns) was conducted using the Sedigraph technique. Geometrical characteristics of loess particles passing the 63 microns sieve were examined using a scanning electron microscope (SEM) technique. The hydrocollapsibility properties, with particular reference to their response to wetting under different stress levels, have been measured in single- and double-oedometer tests. The results of this investigation indicated that the Libyan loess has index properties and hydrocollapse behaviour similar to those of loess from many parts of the world, and that the material can be classified as silty loess in the Tripoli region and clayey loess in the Ghat area. The large particle sizes described in the 1928 study were not found. The Scheidig classification of the North Libya loess ‘Nachgewiesen definite’ is justified.