Design Guide for Rigid Foundation Systems on Expansive Soils

Abstract

Expansive soils pose a major nightmare for practicing geotechnical engineers in the semiarid 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 because of expansive soil problems. Upheaval forces likely to act against the proposed structure were determined and used in a finite-element analysis to design an appropriate rigid substructure. Plots of moments and shear forces were determined, and critical sections were pointed out. The main reason for choosing the rigid alternative is to reduce the differential settlement, which is likely to be exaggerated in flexible designs. The settlement measured on site indicated that the rigid system design gives a reduced total settlement and differential settlement.