Lessons Learned from Foundation and Slab Failures on Expansive Soils

Four case histories are presented to define lessons that can be learned from the investigation of the failure of slabs, footings, and deep foundation elements caused by heaving of expansive soil. For each case history the site conditions, the nature of the distress, and the scope of the forensic investigation are presented. Several factors that contribute to the cause of the failures are identified, and commonality between the various factors is noted. The most commonly identified factors relate to inadequate soil sampling, soil testing, and analysis of the data, resulting in deficient design and poor construction practices. Another contributing factor relating to failure is inadequate drainage. The general conclusions to be drawn are that it is important to apply rigorous engineering practices on expansive soil sites. The engineers and contractors must understand the nature of expansive soil and have an appreciation for the types of problems it can cause.