Geological and Engineering Characteristics of Expansive Soils in Western Desert, Egypt

Expansive shale has been found extensively in all over the world especially in arid and semi-arid regions. Egypt as a country from north Africa has alot areas having expansive soil. Superficial clay soil with the potential to shrink or swell with different degree of expansion covers large areas of many cities in New Valley Government such as Garb El-Mawhoob area. These problems include cracking, break-up of pavements, heaving, and damaging building foundations. Different laboratory tests were carried out on this soil including, natural water content, grain size distribution, Aterberge limits, unconfined compressive strength, swell potential and swelling pressure. These tests were supported by mineralogical investigations such as X-ray diffraction (XRD), scanning Electron Microscopy (SEM) and Differential thermal analysis (DTA). These soils were evaluated based on physico-chemical and geotechnical measurements. Its swelling potentiality (free swelling, swelling percent and swelling pressure) has a direct relationship with clay fraction content, plasticity index (PI) and cation exchange capacity (CEC). Furthermore, the clay fraction percent has a strong direct proportional relation to free swelling, plasticity index (PI) and cation exchange capacity (CEC). Also, the results of these tests showed that the clay in this area has considerable quantities of smectite resulting in the expansive character of these soils