Concrete Construction Methods and Costs by Halbert Powers Gillette & Charles Shattuck Hill

Author:Halbert Powers Gillette & Charles Shattuck Hill [Gillette, Halbert Powers]
Language: eng
Format: epub
Tags: Concrete construction
Publisher: Project Gutenberg
Published: 2008-03-16T04:00:00+00:00

METHOD OF LINING CASCADE TUNNEL, GREAT NORTHERN RY.—The Cascade Tunnel, 13,813 ft. long, built in 1897-1900, was lined throughout with concrete from 24 ins. to 3½ ft. thick, mixed and placed in the following manner: It was necessary to place the lining without interfering with the transportation of materials and excavated material to and from the work ahead. The arrangement adopted to secure this end is shown by Fig. 132. A platform 500 ft. long was constructed at the elevation of the wall plates; the rear end of this platform was reached by an incline, up which the cars loaded with concrete were hauled by an air hoist and cable and delivered to any point on this platform. While each 500 ft. of tunnel was being concreted, the next 500 ft. of platform in advance was being built, with its approach incline, so that there was no delay in the work.

Complete concrete plants were installed at each portal, advantage being taken of the side hills of the approach into the[Pg 337] mountain to handle as much material as possible by gravity. Each plant was equipped with a No. 6 Gates crusher, 40-in.×8-ft. rock screens, and 16-in.×16-ft. screw concrete mixers. Large storage bins for the cement, sand and stone were built adjacent to the mixer plant. A 1-3-5 concrete was used. The stone was crushed from the best rock obtained in the tunnel excavation. This rock was loaded into the regular muck cars, taken to the portal by electric motors, and then dumped into other cars below the level of the muck cars. These cars were hauled by hoisting engine and cable to the crusher floor and then dumped and sorted to avoid danger from pieces of unexploded dynamite. It was then run through the crushers, washers and screens to the stone bin and thence to the mixers. The mixed concrete was discharged into cars on the level of the muck car tracks and these cars were taken by motor into the tunnel to the incline, up which they were hauled by cable and dumped on the platform. From the platform the concrete was shoveled into the wall forms or onto the centers as desired.

Fig. 132.—Traveling Platform Used in Lining Cascade Tunnel. Fig. 132.—Traveling Platform Used in Lining Cascade Tunnel.

The walls were concreted in alternate 12-ft. sections, the weight on the timber arch thus being gradually transferred from the plumb posts to the walls. The roof arch was also built in 12-ft. sections, the centers being[Pg 338] in sections of corresponding length which were moved forward on dollies and jacked up as the work advanced. Ten sections of centering were used at each end. An average of 7 bbls. of cement were used per lineal foot of lining. The average monthly progress of lining was about 600 ft. at each end. The concrete lining cost $44 per lin. ft. of tunnel, done by company forces.

METHOD OF RELINING HODGES PASS TUNNEL, OREGON SHORT LINE RY.—The centers and side wall forms and the methods of work adopted in relining the Hodges Pass tunnel on the Oregon Short Line Ry.

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