Principles of mining : valuation, organization and administration; copper, gold, lead, silver, tin and zinc . Fig. 28. — Longitudinal section of stull-supported stope. position. The stull system can, in inclined deposits, befurther strengthened by building waste pillars against them, inwhich case the arrangement merges into the system of artificialpillars. Square-sets (Figs. 29 and 30), that is, trusses built in the open-ing as the ore is removed, are applicable to almost any dip or width ^^^^M^. (4^ O 9 U U ^ i3 ij ti Fig. 29. — Longitudinal section showing square-set timbering. of ore, but g
Principles of mining : valuation, organization and administration; copper, gold, lead, silver, tin and zinc . Fig. 28. — Longitudinal section of stull-supported stope. position. The stull system can, in inclined deposits, befurther strengthened by building waste pillars against them, inwhich case the arrangement merges into the system of artificialpillars. Square-sets (Figs. 29 and 30), that is, trusses built in the open-ing as the ore is removed, are applicable to almost any dip or width ^^^^M^. (4^ O 9 U U ^ i3 ij ti Fig. 29. — Longitudinal section showing square-set timbering. of ore, but generally are applied only in deposits too wide, or to, rock too heavy, for stulls. Such trusses are usually constructed on METHODS OF SUPPORTING EXCAVATION. 105 vertical and horizontal lines, and while during actual ore-breakingthe strams are partially vertical, ultimately, however, when theweight of the walls begins to be felt, these strains, except invertical deposits, come at an angle to lines of strength in thetrusses, and therefore timber constmctions of this type present
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Keywords: ., bookcentury1900, bookdecade1900, bookpublishernewyorkmcgrawhillb
