Tunneling Challenges on the East 140th Consolidation and Relief Sewer (E140CRS)

摘要

The East 140th Street Consolidation and Relief Sewer is a Consent Decree project for the Northeast Ohio Regional Sewer District (NEORSD). The project involves over 11,000 feet of 60 to 84-inch diameter two-pass tunnel and 285 feet of 84-inch hand mined tunnel. The tunnel depths vary from 20 to 50 feet. Modifications to 29 near surface regulators are also part of the design.The first design challenge involved two-pass tunnel mining from soft predominantly sandy/clayey silt material into shale which required permeation grouting at the soil/rock interface. The grouting stabilizes the soil material, increases stand up time and greatly reduces groundwater inflow. Grouting was proposed to be performed from the ground surface prior to TBM excavation so the voids in the soil material and the joints in the rock are completely filled with grout material. The grouting zone extended outside the tunnel excavation a minimum of 5 feet in all directions or a maximum distance of 5 feet below the top of bedrock. The Contractor had the option to grout from within the tunnel so long as the means, methods, and equipment can perform the grouting work ahead of the tunnel heading.The second design challenge: An 84-inch hand mining operation is necessary to avoid disruptions to a local stakeholder for approximately 285 feet from Access Shaft NM-1 to Nine Mile Creek Outlet. This tunnel section will be excavated below the groundwater table within the very stiff silty clay soil materials that has relatively low permeability. Liner plates will be utilized for ground support.