Concrete for Tunnel Liners:Mix Design Recommendations for Prototype Extruded Liner System.

摘要

Fiber reinforced,quick-setting cement concrete mix designs are suggested for use in the development of a prototype extruded liner system. These mix designs can meet the structural and durability requirements of the tunnel liner and can be placed in a slipform by pumping. The mix designs are governed mainly by the fact that the mix must be pumpable. Aggregate shape and gradation are critical. A mix with a high likelihood of pumpability can be formulated by adherence to a procedure based on prevention of segregation failure,the most common pumping failure mode of fiber reinforced concrete. Fiber reinforced concrete mixes proportioned for pumping are of high strength,by normal standards,because of the paste content necessary for workability. Conventional pumping equipment is believed adequate for placing properly designed fiber reinforced concrete mixes if components are selected to minimize line head losses and minimize remolding of the concrete. Mixes for a specific field application should be tested for set times, pumpability and strength,using field procedures for batching,mixing,and placing,prior to actual field use.