Principles of mining : valuation, organization and administration; copper, gold, lead, silver, tin and zinc . s () winzes must be put in eveiy 50 feet or so, while in rill-stopesthey can be double this distance apart. The system is appli-cable by modification to almost any width of ore. It finds itsmost economical field where the dip of the stope floor is over 45°,when waste and ore, with the help of the rill, will flow to theirdestination. For dips from under about 45° to about 30° or 35°, METHODS OF SUPPORTING EXCAVATIOX. HI where the waste and ore will not flow easily, shoveling can b
Principles of mining : valuation, organization and administration; copper, gold, lead, silver, tin and zinc . s () winzes must be put in eveiy 50 feet or so, while in rill-stopesthey can be double this distance apart. The system is appli-cable by modification to almost any width of ore. It finds itsmost economical field where the dip of the stope floor is over 45°,when waste and ore, with the help of the rill, will flow to theirdestination. For dips from under about 45° to about 30° or 35°, METHODS OF SUPPORTING EXCAVATIOX. HI where the waste and ore will not flow easily, shoveling can behelped by the use of the rill system and often evaded alto-gether, if flow be assisted by a sheet-iron trough described inthe discussion of stope transport. Further saving in shoveling canbe gained in this method, by giving a steeper pitch to the fillingwinzes and to the ore-passes, by starting them from crosscuts inthe wall, and by cariying them at greater angles than the pitchof the ore (Fig. 36). These artifices combined have worked outmost economically on several mines within the writers experi-. FiG. 36. — Cross-section showing method of steepening winzes and ore passes. ence, with the dip as flat as 30°. For veiy flat dips, where fillingis to be employed, rill-stoping has no advantage over flat-backedcuts, and in such cases it is often advisable to assist stope trans-port by temporary^ tracks and cars w^hich obviously could not beworked on the tortuous contour of a rill-stope, so that for dipsunder 30° advantage lies with flat-backed ore-breaking. On veiy wide ore-bodies where the support of the standingore itself becomes a great problem, the filling system can beapplied by combining it with square-setting. In this case thestopes are carried in panels laid out transversally to the strikeas wide as the standing strength of the ore permits. On bothsides of each panel a fence of lagged square-sets is carried up and 112 PRINCIPLES OF MINING. the area between is fille
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