Square 673 Residential Building
The project consists of a 500,000 SF, 18-story, 470-unit reinforced concrete residential building, with three below-grade parking levels. The proposed amenities included a rooftop pool, resident theater, fitness center, library, meeting rooms, and outdoor movie area.
Hillis-Carnes was contracted to provide Geotechnical Engineering and Construction Materials Testing and Inspection services. Prior to Hillis-Carnes’ involvement in the project, geotechnical engineering studies had been completed by two other firms.
Hillis-Carnes performed classic investigations using Standard Penetration Test (SPT) borings and laboratory unconfined compressive strength results from undisturbed tube samples to recommend bearing capacities for foundation design. To more accurately measure the soil bearing capacity, Hillis-Carnes performed a series of flat plate Dilatometer Tests (DMT) and four additional SPT borings. The DMT is a flat plate pushed with a ballasted or anchored drill rig. The plate diaphragm is expanded at regular depths, and the pressure required to expand the plate is related to the elastic parameters of the soil. These moduli are used to calculate anticipated settlement of shallow foundations. The available bearing capacity was determined by the shear strength results from the DMT testing. The results were used to determine the ultimate and allowable (Safety Factor of 3.0) bearing capacity of exterior and interior column footings. The results showed allowable bearing capacities of 17,000 to 29,000 ksf. These results were analyzed to determine the predicted settlement at various bearing pressures. Based on the results and other data evaluated, Hillis-Carnes recommended that the footings be proportionate for a net allowable bearing capacity of 10,000 psf. Although higher bearing pressures are available for ultimate bearing capacity, Hillis-Carnes recommended limiting the soil pressure to keep settlement within typical tolerances. The bearing capacity recommended by Hillis-Carnes was significantly greater than those recommended in the prior studies reviewed.
Subsequently, Hillis-Carnes also provided materials testing and inspection services during construction. The major elements of inspection included sheeting & shoring, mat foundation, footings, foundation walls, shear walls, slab-on-grade, suspended slabs, concrete toppings, and building frame members.