GEOE 413 Lecture Notes - Lecture 23: Screw Conveyor, Subsidence, Precast Concrete
20 Nov 2016
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Access constraints for lowering tbm: nee access shaft. Looking over all of the types of tbm"s. Open gripper tbm: bearing is the most expensive part of the machine. Double shield can move forward continuously without stopping. Epb machine can help with mixed typed (rock-solid) boundaries. Conducted to adjust soils properties (plasticity, texture, permeability, etc. ) Used more in heterogeneous soils (with sand and gravel) Use excavated soil with additives to balance the earth and water pressure. Largest tbm to date = big bertha seattle 17. 3m. Tunnelling in regions with highly permeable soil (high water pressures > 2 bars), unstable terrain, or in urban areas susceptible to surface interactions. Filter cake: air-impermeable membrane, forms when the slurry mixes and penetrates past the cutter wheel into the ground, provides surface for pressurized slurry to act on. Managed by air pressure from the air bubble. Impermeable seal to prevent groundwater form flowing into the tbm.
