Transactions . w-grade copper ore on an extensive scale. Three types of miningoperations have been carried on at this property—steam-shovel mining inopen pits, top-slicing in the Veteran orebody, and caving by the branchraise system in the Ruth orebody. Mining operations are still under wayin the Ruth orebody and the surface is subsiding progressively. It willbe some time before the subsiding surface will have cracked to its H. G. MOULTOX 339 ultimate limits, and the data obtained from this section of the mine atpresent is not conclusive. Mr. Lakenan states that, from his experience,he expects
Transactions . w-grade copper ore on an extensive scale. Three types of miningoperations have been carried on at this property—steam-shovel mining inopen pits, top-slicing in the Veteran orebody, and caving by the branchraise system in the Ruth orebody. Mining operations are still under wayin the Ruth orebody and the surface is subsiding progressively. It willbe some time before the subsiding surface will have cracked to its H. G. MOULTOX 339 ultimate limits, and the data obtained from this section of the mine atpresent is not conclusive. Mr. Lakenan states that, from his experience,he expects cracking to occur out to the intersection with the surface ofa line projected upward from the stopes at an angle of around 60° to70°. This corresponds very closely with the angle of a 3^^ to 1 slope,which is 63° 26. The Veteran mine, however, furnishes excellent material for was the first large-scale underground mining operation among Scale in Feet0 100 200 500 400 500 600 100 800 900 1000 1100. Fig. 10.—Typical sections op Veteran mine. the porphyry coppers. The ore stoped averaged around 23^^ to 3 per cent,copper. The copper minerals occurred principallj in porphyry, and tosome extent in limestone, the ground overlying the orebody being largelylimestone. The hmestone varied considerably in hardness and, conse-quently, the capping was not homogeneous and broke rather Veteran orebody was completely stoped out about six years agoand sufficient time has elapsed for settlement to progress until the sur-face has probably reached a condition of stable equilibrium. The minewas worked by the top-slicing system. By this method, the irregularupper portion of the body is extracted with square-set timbering, one ortwo floors high as may be necessary to level off and start with a uniform 340 EARTH AND ROCK PRESSURES top surface. The lower posts are then blasted and the ground allowed tocave, bringing with it a mat of broken timber. Another slice is thenta
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Keywords: ., bo, bookcentury1800, bookdecade1870, booksubjectmineralindustries
