Stiffened Slab-On-Grade on Shrink-Swell Soil: New Design Method


Stiffened slabs-on-grade are one of the most economical solutions for 1- to 3-story buildings on shrink-swell soils. They consist, for example, of 1-m-deep, 0.3-m-wide beams resting on the soil, spaced 4 m apart in both directions covered by a 0.1-m-thick slab-on-grade. The challenge is to optimize the beam depth, width, and spacing for the slab to be stiff enough that the movement of the soil at the edges of the slab will not cause undue bending of the foundation and the structure above it. Indeed, shrink-swell soils are affected by the weather and/or by the irrigation at the edges of the foundation and will swell and shrink as a result. This article presents a new method to design stiffened slabs on grade such that the differential movement divided by the length over which this movement takes place is within tolerable limits. The method gives the beam depth necessary to achieve such stiffness as well as the bending moment and shear force to be resisted. The method is automated in a spreadsheet called TAMU-SLAB.


Civil, Architectural and Environmental Engineering

Keywords and Phrases

Geotechnical engineering; Beam depth; Design method; Shear force; Slab-on-grade; Swell and shrink; Thick slab; Wide beam; Soils; Bending; Design; Shrinkage; Soil mechanics; Stiffness; Swelling

International Standard Serial Number (ISSN)

1090-0241; 1943-5606

Document Type

Article - Journal

Document Version


File Type





© 2016 American Society of Civil Engineers (ASCE), All rights reserved.

Publication Date

01 Jul 2016