Lessons Learned from Distress of Foundations on Expansive Clays in the Active Zone

Abstract

The high initial cost for a deep foundation system with a structurally suspended floor slab for light commercial and retail buildings on expansive clays would make many, if not most, projects economically prohibitive. Reality is that such structures are commonly supported on a hybrid foundation system where exterior walls and interior columns are supported on a relatively deep foundation system, and the floor slab bears on a pad of fill on expansive clays in the active zone. Most foundation systems of this design experience tolerable movements, but some experience significant distress resulting in damaging the building. This paper presents case studies on common design and construction defects (some would appear minor) that can contribute significantly to distress, and offers suggestions to address these issues.