Top-Down Methods Utilizing Secant Walls at 110 N. Carpenter: Design and Construction-Paper

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The 110 N. Carpenter project in Chicago used top-down construction to accelerate delivery of a nine-story office building with two underground parking levels. This approach allowed above- and below-grade construction to proceed simultaneously, shortening the schedule by several months.<br /><br />A perimeter secant pile wall was selected over slurry walls for its lower cost, flexible design, and more efficient use of equipment. The system also supported earth pressures, building and curtain-wall loads, tower cranes, and in-plane lateral forces. It was integrated with interior drilled shafts and columns, a shear-wall core built within a temporary sheet-pile cofferdam, and structural slabs.<br /><br />Construction proceeded in stages: the core, perimeter piles, and interior shafts were built from grade; a first-floor slab tied these elements together; then excavation and lower-level construction continued through openings in the slab while the superstructure rose above. The initial substructure work—including 458 secant piles, 100 drilled shafts, and the cofferdam—was completed within the required 90 days. By completion of the two basement levels, five of the building’s nine above-grade floors were already built.<br /><br />Design accounted for Chicago’s soft “Blue Clay,” groundwater, staged excavation conditions, and varied loads. Analyses were checked using soil–structure interaction models. Inclinometers recorded maximum wall movement of 1.27 cm, substantially below the estimated 2.87 cm.<br /><br />The project’s success depended on coordinated design-build planning, adaptable foundation design, and careful site logistics, demonstrating how secant walls can support efficient top-down construction on a demanding urban project.

Keywords

top-down construction

Chicago office building

secant pile wall

underground parking

staged excavation

soil-structure interaction

foundation design

shear-wall core

perimeter piles

urban construction