Prediction and Performance of Deep Excavations for Courthouse Station, Boston

Abstract

AbstractConstruction of the Silverline Courthouse Station in South Boston involved 18-m-deep excavations at a site underlain by more than 24 m of normally and lightly overconsolidated Boston blue clay (BBC). The excavations were supported by 27-m-deep floating diaphragm wall panels and five levels of preloaded cross-lot bracing. This paper compares the measured performance of the excavation support system with the Class A finite-element (FE) predictions prepared during the original design phase and with the results of Class C analyses using information obtained during construction. The numerical analyses used data from a special test program of laboratory and in situ tests at a nearby site. The analyses represent coupled consolidation within the soil mass and the anisotropic stress-strain-strength properties of BBC using the MIT-E3 soil model. The Class A analyses generally overestimate the lateral wall deflections and underestimate the measured strut loads, as preloading was not included in the original ...