Abstract
A semi-arid shale formation in the northern and central part of Saudi Arabia showed frequent near surface cracks and distress at several sites. This phenomenon was found to be of a serious risk to structures founded on or near cracks or failure zones. This study was carried out for an area where several centimeters wide ground cracks extending over more than one kilometer distance across a populated area in Saudi Arabia. The dominant subsurface formation in the area is reddish brown stiff to hard silty to clayey shale underlain by sandstone formation. The subsurface material was explored and clayey shale samples were extracted. The study included borehole drilling and test pit excavations. Soil classification and consistency tests were performed. A series of physical and chemical testing confirmed the expansive nature of the shale. The possible causes of cracks and the mechanisms of failure in semi-arid shale were covered and discussed in sufficient details. Engineering guides for buildings and construction in typical zones were presented. Keywords: Shale; Expansive; Clay; Cracking; Semi-arid.