Transactions . sible to keep the atmosphere clear of powdersmoke by turning on a little compressed air after blasting. Before the chute raises are started, the engineers mark off the place,giving the exact height and the angle of raise. This raise is started only4 by4ft. ( by m.), and carried this dimension for about three drift is then widened out opposite to where the chute is to be built G. T. JACKSON 473 and the back is taken up to a height of 14 ft. ( ni.), after which it isready for the timberman to commence. The timberman first hnes up theposition of the chute, cent
Transactions . sible to keep the atmosphere clear of powdersmoke by turning on a little compressed air after blasting. Before the chute raises are started, the engineers mark off the place,giving the exact height and the angle of raise. This raise is started only4 by4ft. ( by m.), and carried this dimension for about three drift is then widened out opposite to where the chute is to be built G. T. JACKSON 473 and the back is taken up to a height of 14 ft. ( ni.), after which it isready for the timberman to commence. The timberman first hnes up theposition of the chute, centering the raise and cutting hitches in the backof the drift to fasten the side posts the proper distance from the then completes building the chute, installs the gates, loading platform,etc. When the rock is trimmed off in the mouth of the chute just flushwith the sides, it gives a chute opening of 3 ft. 6 in. ( m.) high by 5ft. 4 in. ( m.) wide. The chute raise is then continued until the ore-. FiG. 7. body is encountered. The bulldozing raises are then driven, and cross-cuts driven from the bulldozing raise to the chute raises. No grizzly barsare used at present, as most of the rocks can be caught before they getinto the chute from the bulldozing chambers. Fig. 12 shows a detailed drawing of a chute, underswung arc gate andcheck gate. The underswung arc gate was designed by the writer in1912. It is used in all the chutes, both large and small, is very easy toconstruct, and can be operated without difficulty by one man whenproperly installed. 474 MINING METHODS IN ALASKA The costs of building these chutes, including the raise and wideningout the drift, amounts to about $615, of which 1400 is for rock and $215for material and labor of building the chute. After the chute raises reach the orebody, they are connected by shortraises driven up from each chute at an angle of 40°. A small raise is thendriven from the end of each stope to connect with the nearest manw
Size: 1456px × 1717px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bo, bookcentury1800, bookdecade1870, booksubjectmineralindustries
