Deep Soil Densification for Shallow Foundations

Abstract

Most residential development in Florida is done without any testing for foundation design, as the builders rely on traditional foundation design methods with assumed bearing capacity and no settlement control. As a result, few step cracks appear within months of completion of the residential structure. Lack of understanding the soil behavior and the lack of adequate quality control tests result in the structure suffering differential settlements. Design of shallow foundations in sandy soils using elastic theory is adequate unless loose soils were present within the zone of influence. Some form of soil stabilization would be required to improve the relative density of loose soils and to control settlements. Surficial compaction methods do not achieve the required densification beyond a depth of about 1 m below the surface. Traditionally, stone columns have been used for commercial buildings but this is not an affordable option in residential construction. A method of soil stabilization called CSV soil stabilization introduced recently has proven effective, fast and easy to install, and is reasonably economical. This paper discusses the use of the CSV method for one to three-story residential structures on shallow spread footings. Case histories are presented to show that the CSV stabilization is a viable and economical alternative to vibro-compaction and stone columns, which are currently the most frequently used techniques. The CSV automatically records certain parameters that provide a reasonable quantitative measurement of the effectiveness of the soil densification.