Engineering and Contracting . f which were di-rectly under the building foundations. Forabout one-third of the piers, where theground was soft, rectangular steel shieldsabout 3 ft. deep were used. These werejacked down as the excavation proceeded,the concrete slabs being bolted in place be-hind them in a manner similar to thatemployed in ordinary sliield shields were left in place at the bot-tom of the pier. If tliey should turn intorust they will still be more solid thanthe earth which they replace. After the en-lire combined Imderpinning and tunnel wallwas in place the westerl
Engineering and Contracting . f which were di-rectly under the building foundations. Forabout one-third of the piers, where theground was soft, rectangular steel shieldsabout 3 ft. deep were used. These werejacked down as the excavation proceeded,the concrete slabs being bolted in place be-hind them in a manner similar to thatemployed in ordinary sliield shields were left in place at the bot-tom of the pier. If tliey should turn intorust they will still be more solid thanthe earth which they replace. After the en-lire combined Imderpinning and tunnel wallwas in place the westerly barrel of the tun-nel was built in sections 7 to 8 ft of the concrete slabs were removedfrom the face of the underpinning wallwhere it was joined by the tunnel archand invert, thus allowing the steel rein-forcing rods from the arch and invert tobe carried through the openings into theliollow piers. These piers were filled withconcrete when placing the concrete for theinvert and arch, thus making tlie pii^r filling. monolithic with the rest of the tunnel sec-tion, as shown by Fig. i. This method, with some modifications tosuit the different conditions, was later usedto underpin the Washington-St. front ofthe Devonshire Building on the oppositeside of the street. Owing to the unusual problcniL; involvedand the consequent desirability of beingable to alter the plans or vary methodsat any stage of .the work, the section wasbuilt almost entirely by day labor underthe direct control of the engineering de-partment. Several contractors, includingColeman Brothers and John E. Palmer,furnished men and tools for the work. Atotal of 9,215 cu. yds. of excavation and3,350 eu. yds. of concrete was the former, about 800 cu. yds. was doneunder contract by Patrick McGovern. The work of underpinning the AmesBuilding and the construction of the wes-terly barrel of the tunnel was carried onwith three 8-hour shifts per day. Theremainder of the section was then com-plete
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Keywords: ., bookcentury1900, bookdecade1900, bookpublisherchicago, bookyear19
