An Examination of Changes within the Active Zone Moisture Content and Soil Swell Potential of Expansive Clay Soils at a Site in Denton County, Texas

Expansive clay soils are prevalent in North Texas and have historically caused damage to thousands of residential foundations annually in the Dallas-Fort Worth area. Efforts to minimize the effects of expansive clay on foundations and reduce financial losses have included the use of geotechnical investigations. These studies are used to examine the subsurface soil conditions prior to the start of construction. The recommendations developed during these investigations are utilized by designers and builders to construct foundations which can perform satisfactorily in harsh soil conditions. This study examines an agricultural site in Denton County, Texas, upon which a residential subdivision is to be constructed. Two geotechnical investigations were performed at the site within nine months of each other. This study evaluated the changes in soil moisture that occurred in the upper 10 feet (305 cm), the resulting changes in soil swell potential for vertical movement (PVM) that occurred during the delay, and the subsequent impact on the geotechnical recommendations that were provided to reduce the PVM to design levels for residential foundation design. Although precipitation levels were near normal during the delay, significant drying occurred in areas of the site. The result of this drying and the subsequent impact on the soil swell PVM is that substantially more cost and effort will be required to construct residential building pads.Alliance Geotechnical Group, Inc., Dallas, TexasNo embarg