Use of Rigid Foundation System on Expansive Soils

Expansive soils pose a major maintenance nightmare for geotechnical practicing engineers in the semi-arid and arid zones of the world. The introduction of rigid substructure is a costly approach but can be made practical and financially tolerable for soils where expansion is characterized within medium to low problematic classes. This paper outlines justifications and design concepts for a rigid substructure foundation of a two story concrete frame structure. The project was constructed in a district in Saudi Arabia where many buildings experienced serious damage due to expansive soil problems. Upheaval forces likely to act against the proposed structure were determined and used in the finite element analysis and design of an appropriate rigid substructure design. Plots of moments and forces were determined and critical sections were pointed out. Methods and stages of construction were monitored and a baseline vertical movement was established for future verifications. The advantages and limitations of this system are also discussed.