Performance and Analysis of Braced Secant Pile Wall for a Multi-Story Building in Manhattan, NY-Paper

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The paper examines the construction and performance of a secant pile wall supporting a 43-foot-deep excavation for two basement levels of an 11-story building at New York University’s College of Nursing in Manhattan. The site’s main challenge was a 25-story residential building immediately adjacent to the west wall. Its proximity constrained drilling, and its foundations and basement needed to be considered when assessing wall movement.<br /><br />The 192-pile wall was socketed into rock to provide excavation support and groundwater cutoff. Three levels of internal corner bracing supported the wall during excavation. To avoid damaging the neighboring building, contractors adjusted the west wall layout in the field, using a foam guide-wall template to create a local taper and maintain clearance from the building.<br /><br />Two inclinometers installed in the west wall recorded horizontal movement as excavation progressed. The authors compared these measurements with a retrospective two-dimensional PLAXIS finite-element analysis. The model used a Mohr–Coulomb soil model and soil properties estimated from SPT data, correlations, and engineering judgment. It also represented the adjacent building’s basement and pile foundations, whose support reduced lateral loading on the wall.<br /><br />Predicted wall deflections agreed reasonably well with measured movements in both shape and magnitude. The study concludes that a simplified two-dimensional analysis can provide useful, accurate estimates of retaining-wall performance even when detailed geotechnical data are limited. It also highlights the value of secant pile walls in dense urban settings, where excavation support, groundwater control, and protection of neighboring structures are all essential.

Keywords

secant pile wall

retaining wall performance

deep excavation

basement excavation

New York University

Manhattan construction

adjacent building impact

PLAXIS finite element analysis

wall deflection monitoring

urban geotechnical engineering