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| Re: When the Tunnels(s) close (1361117) | |||
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Re: When the Tunnels(s) close |
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Posted by Sand Box John on Tue Jul 28 23:22:48 2015, in response to Re: When the Tunnels(s) close, posted by pragmatist on Mon Jul 27 08:17:43 2015. Tunneling not being an area of experience or expertise of mine, let me pose another question. Wouldn't the use of a conventional TBM presuppose rock tunneling, or can they also be used in silt and clay layers? We have debated diameter and single versus dual bore, and I threw out the notion of precast float into place, but I'm wondering if the geology and geography might restrict or obviate the use of a particular methodology.TBMs come in 2 flavors, pressure balanced and non-pressure balanced. Both can be configured to bore through sedimentary soils, bedrock rock or both. Pressure balanced TBMs are typically employed for boring through sedimentary soils that are below the water table. Both types were used down here in WMATA land. Pressure balanced through sedimentary soils only, Navy Yard to Southern Avenue. Non-pressure balanced through bedrock rock only, Rock Creek Park to Pooks Hill Road. John in the sand box of Maryland's eastern shore. |
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