Excavation case study in Manhattan, NY with practical approach to predict ground movements

This paper presents the case study of the staged excavation for the New York University College of Nursing building in Manhattan, NY, supported by corner-braced secant pile walls. A commercial finite-element software was used to simulate the complex supported excavation and predict the retaining wall deflections using simple soil models calibrated from limited soil data. The results of the two-dimensional (2D) simulations were compared with actual wall deflections measured by inclinometers during the excavation process. The aim of this research was to determine whether the complex 3D characteristics of the problem could be captured and accurately simulated by equivalent 2D models, using soil properties estimated from limited field data, which is typically the case in engineering practice. Equivalent axial and bending stiffnesses were also estimated for simulating the square bracing system in plane-strain conditions. The numerical analyses yielded results that correlated with the measured data which indicates that – for this type of excavation problem – simplified plane-strain analyses can predict sufficiently small wall movements, given that appropriate stiffness magnitudes are assigned to the earth-retaining system.