Abstract:
An earth retention system (ERS), whether it is a temporary or permanent, has become a main engineering item in urban setting. The system typically is engineered to enable a below grade excavation but not for an existing basement structure’s demolition.
The demolition of One James River Plaza(OJRP), a 21 story high building was proposed and planned by an implosion method.  However, the basement of the building had to be mechanically demolished before the implosion.  The basement of the OJRP building was 260 feet by 330 feet wide and 35 feet deep at deepest and constructed about 50 years ago. It is abutting main streets of the downtown of Richmond, Virginia.
To safeguard the streets and protect adjacent properties, the mechanical demolition of the basement structure had to be planned with an installation of new support of excavation (SOE) system within the building’s property line. Because, the property is bound by streets and high rise buildings across, it is almost impossible to install the SOE system without the demolition of the basement.
To resolve this dilemma, the demolition of basement structure, wall and slab, were analyzed in a sequence with tieback installation of the new SOE system to prevent an excessive movement of retained soil and as well as sudden collapse of basement wall or slab. The structural demands on partially demolished basement wall and slabs were evaluated per demolition and tieback installation sequences to prevent a sudden collapse of the basement wall or slab before the completion of proper bracing mechanism of the new SOE system.  Depends on the evaluation outcome, the tieback elevation and deconstruction sequencing were adjusted.
Presenter will talk about the challenges of deconstruction of this deep basement wall in urban setting and discuss about engineering methodology adapted to engineer the sequences between the demolition of basement structure and the new SOE system.