Foundations on collapsible soils: a review

This paper describes studies done by various researchers on one form of problematic soils that are not suitable to be used as foundation subsoil. Methods to identify these soils are provided, and various methods suggested for the design of proper foundations to combat their detrimental effects. These types of soils are commonly termed ‘collapsible’. Collapsible soils are moisture sensitive in that an increase in moisture content is the primary triggering mechanism for their volume reduction (compression). These weak soils usually have low dry densities and can be identified with various types of laboratory and field tests. Because of their very low bearing capacity (when wetted) they are not considered for any types of foundations or pavements in their original or natural conditions. Their load-bearing capacity can be improved by various measures, such as the use of sufficiently strong footings that will remain undamaged in spite of possible differential settlements, or by transmitting the structural loads to a deeper and stronger soil layer by means of various types of piles. Also, whenever feasible, the weak soil should be treated with cementing agents such as Portland cement, or preloading techniques should be used to strengthen the collapsing soils and carry the actual loads further.