. Canadian engineer. Fig. 9.—Showing Method of Excavating and Nature ofMaterial, Section 2. had been completed the trestlework and tracks were re-moved, all the surplus concrete was trimmed off and thebrick invert laid. The concrete in the arch was mixedrather wet until the centre of the arch was nearly reached,when it was stiffened up and rammed back on the formswith hoes. In the invert the concrete was made as wetas possible to assure that no voids would be left, as it wasbeing poured in a rather awkward place and tamping wasalmost Fig. 10.—Tunnel Part of Section 4, Showing Met
. Canadian engineer. Fig. 9.—Showing Method of Excavating and Nature ofMaterial, Section 2. had been completed the trestlework and tracks were re-moved, all the surplus concrete was trimmed off and thebrick invert laid. The concrete in the arch was mixedrather wet until the centre of the arch was nearly reached,when it was stiffened up and rammed back on the formswith hoes. In the invert the concrete was made as wetas possible to assure that no voids would be left, as it wasbeing poured in a rather awkward place and tamping wasalmost Fig. 10.—Tunnel Part of Section 4, Showing Method ofE-vcavating and Underpinning. As in the open cut, electric motors were used to drivethe mixers, which were situated in a hole excavated along-side the shaft, large enough for mixer and motor. Theconcrete was deposited through a chute in the shaft tocars below, which conveyed it to the forms. \7S THE CANADIAN ENGINEER Volume 30. Labor. Excavation . Cost perCu. yds. CM. 11,332 $ Barkfillina . Surplus Nil Forms This met hot! dI conslniclion proved vcr) satisliiLiory,lor, had tiic whole bore of sewer, which was 12 ft. 6 size, been removed at once, sheeting in all probabilitywould have been required to protect the arch excavation,«iwing to the wet sand in the invert; whereas, the excava-tion in the entire length of tunnel, with the exception of50 ft. where a dry sand pocket in the arch was encoun-lered, was carried on without the aid of timbering, whichis a very heavy item of expense in tunnel construction,&l
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