Mixed transitional ground impact on a TBM. The OCIT Experience in Akron, Ohio, USA

For the first time in North America a dual mode Rock/EPB TBM, 9.26m diameter bore was used to excavate the Ohio Canal Interceptor Tunnel (OCIT) in the downtown Akron area, USA. Tunneling was carried-out at a uniform slope of 0.15 percent through ground conditions that consisted of soft ground, mixed face soft ground over bedrock, and bedrock. The Mixed Transitional Ground (MTG) resulted in the biggest challenge for the TBM. This paper specifically addresses the influence of the MTG on the TBM Utilization Factor and present the counter-measures implanted in these special geological conditions.