Geotechnical solutions prevent building distress due to expansive clay soils

Each year, billions of dollars in damage to building foundations and structures is caused by shrinking and swelling behavior caused by clay soil.

In fact, expansive clay soil is the most predominant geologic hazard across the U.S. Several geotechnical solutions can alleviate these problems. On new construction, the options are: removal and replacement, capping or burying the expansive material, and treatment with hydrated lime. Structural solutions in new construction include upgraded structural slabs (post-tension, waffle, mat) or elevated slabs supported on deep foundations.

For an existing structure, a forensic geotechnical study is needed to identify and quantify damages, assign causation, and make appropriate recommendations for remediation. Moisture control may be a suitable option for remediation and it is a design requirement for new construction.

In extreme cases, helical anchors and slab (mud) jacking or removal and reworking of soil below an existing structure is necessary. For paved surfaces, expansive clay soils can be remediated with thicker sections of asphalt, reinforced concrete pavements, and lime treatment.

New York City has two very large buildings dedicated to answering the 911 calls of its five boroughs. With more than 11 million emergency calls annually, it makes perfect sense. The second of these buildings, the Public Safety Answering Center II (PSAC II) is located on a nine-acre parcel of land in the Bronx. It’s an imposing 450,000 square-foot structure—a 240-foot-wide by 240-foot-tall cube. The gleaming aluminum cube risesthe equivalent of 24 stories from behind a grassy berm, projecting the unlikely impression that it might actually be floating. Like most visually striking structures, the building has drawn as much scorn as it has admiration.