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2014WinShotcreteEMag

Fig. 2: An initial layer of shotcrete was applied to stabilize the drill bit during the drilling operation After the pull test, geo-composite drain mats were installed between all rock bolt locations to allow drainage behind the wall. The wall was reinforced using No. 5 (No. 16M) bars horizon- tally and No. 4 (No. 13M) bars vertically. The total wall thickness was 11 in. (280 mm). In addi- tion to the reinforcing bars, 6 x 6 in.—W4.0 x W4.0 (152 x 152—MW26 x MW26) welded wire fabric was also incorporated. Guide wires were installed vertically and horizontally to maintain the tolerance require- ments. Due to the hardness of the bedrock and excavation access, large voids and indentations existed. This required additional reinforcing steel and additional shotcrete to be installed. The new three-lane bridge was constructed on the northbound side to accommodate traffic and clearance for the railroad. The old northbound bridge was then removed. Phase 2 of the MSE wall was constructed on the northbound lanes using the same construction sequence. There was significantly more shotcrete used on this phase due to the irregularity of the excavation. The shotcrete in some areas was as deep as 24 in. (610 mm) and the original wall Fig. 3: Manlifts were used to address the wall because scaffolding was thickness was specified to be 11 in. (280 mm). A not an option so close to the railroad Shotcrete • Winter 2014 23


2014WinShotcreteEMag
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