RETC (Rapid Excavation Tunneling Conference) - June 25, 2013
Typically permanent concrete linings for underground structures have been installed using cast-in-place methods. Although a proven technique it does have its downsides especially where non-uniform shapes are required. Building and installing complex forms is time consuming and can lead to logistical restraints in the tunnels. The use of free or non-formed concrete has recently been adopted on several underground projects in New York for non-uniform and junction concrete operations. This paper describes the use of this technique, the challenges to using it and the paradigm shift in thinking that is needed to ensure successful implementation.