Geologic controls on foundation damage in north

TLDR: In this paper, the authors evaluated damaged house foundations in Denton, Texas within the context of local geology and found that expansive soils pose a significant hazard to foundations and that the magnitude of this hazard is controlled by underlying rock formations.

Abstract: Damaged house foundations in Denton, Texas were evaluated within the context of local geology. Addresses of 78 damaged structures were compiled from local foundation repair companies. The Cretaceous-age Grayson and Woodbine formations outcrop in the study area. Marl and montmorillonitic clay are predominant constituents of the Grayson formation. The Woodbine formation consists of sand and sandstone interbedded with clay. Textural and compositional differences in these parent materials have lead to significantly higher plasticity indices for Grayson residual soils. The distribution of damaged founda- tions was superimposed on a geologic map to determine the number and spatial density of damages in each formation. A 324 percent higher damage density was calculated for the Grayson formation. Results of this study suggest that (1) expansive soils pose a significant hazard to foundations in Denton, and (2) the magnitude of this hazard is controlled in part by underlying rock formations.