Design and construction of North America's largest unbraced cofferdam

In Boston, Massachusetts (U.S.A.), a new immersed tube tunnel has recently been built. Adjacent to this tunnel, a subsurface ventilation building is planned. To allow construction of this ventilation building, a temporary cofferdam has been designed and built. The paper describes this cofferdam, the many load cases, the effects of the different soil layers, and its construction method.