Transactions Volume 40 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1910 Excerpt: ...cut considerably less than 1 per cent, of the material; the tunneling-machiue proposes to cut up practically all the material into chips, or to do more than a hundred times as much mechanical cutting of the rock with the time multiplied only by three or four, and no allowances for machine-or drill-arrangements or other time-losses. Were nitro-glycerine and dynamite undiscovered, the tunneling-machine would be of great importance. It would seem fundamental that, in counting the cost, it is more economical to dislodge rock from its strong place in a tunnel-heading by discharging a high explosive at the bottom of a hole than by doing all of this work through the pulverization of the entire mass, especially so as the material removed may be of large or small size, the main point being to get it out of the way. An argument used by the advocates of tunneling-machines is that the chief problem in driving is to get rid of the material. There is a good deal of truth in this when applied to tunnels of large diameter and to headings where the material is discharged en masse at the face and in large and irregular pieces. The Alpine system reduces the importance of the problem of getting rid of the material, for the reasons that have been stated. A tunneling-machine which attempts to bore a hole 2, 3, or 4 ft. in diameter is a reasonable proposition, but the difficulties are usually increased out of all proportion as the diameter of the tunnel is enlarged. It is not uncommon to put in holes with a large rock-drill, using bits 6, 8, and even 12 in. in diameter. This might be extended to several feet by increasing the diameter of the drill in proportion as the size of thebit is enlarged. The most reasonable of the numerous tunneling-machines that have been suggested is th...