Construction-induced effects in a cofferdam excavation using Hypoplasticity and Shotcrete models

Abstract

Construction-induced effects of concrete bracings on excavation-induced ground movements in an urban cofferdam are investigated using advanced constitutive models. Hypoplasticity model for clays and Shotcrete model for concrete were used to reproduce the performance of a bottom-up cofferdam excavation braced with seven levels of concrete ring beams. Construction effects associated with rapid cycles of soil removal and lateral bracing, low temperatures during concrete curing and installation, and concrete time-dependent effects (i.e., shrinkage, creep, and aging) are studied parametrically in terms of excavation-induced lateral wall movements. The computed results from the numerical simulations matched well field performance measurements. Concrete material time-dependent effects represented approximately 30% of the maximum lateral wall movements; aging was the predominant effect. Concrete curing and ring beam installation effects represented 25% of the computed maximum lateral wall deformations. Excavation designs ignoring the proposed effects would potentially cause damage to nearby infrastructure.