Lesson 2/Learning Event 7
Learning Event 7
DESCRIBE QUARRY DEVELOPMENT CONSIDERATIONS
PROFILE
You must determine the location of the initial quarry face. To do this, a plan and several cross-sections
across the length and width of the site should be drawn. These should show the surface configuration
and structure of the in-place rock. Elevations on these drawings should be referenced to a bench mark
outside the actual quarry. After profiles of the rock surface have been plotted, the quarry floor or first
working level is superimposed at a depth equal to the planned bench height. The intersection of the
floor or access ramp with the existing grade is the point where excavation should begin. Initial and
subsequent working floors should be selected carefully to assure that continued development of the site
will proceed smoothly. Overburden removal, access construction, traffic patterns, and rock excavation
plans must be coordinated.
Steeply-Sloping Sitse. On steeply -sloping hillside sites, excavation should normally begin at the
uppermost working level. A second, lower working level may then be established as the upper working
floor approaches its intended dimensions or has been excavated enough to provide sufficient working
space for further operations. Additional working levels may be established in a similar manner.
Gently-Sloping Sites. Excavation should normally begin at the level of the final working floor when
quarries are established on gently-sloping sites. As excavation progresses, a second, higher working
floor should be established when the initial bench reaches its intended working height. Additional,
higher working levels may be established in similar, step-like stages if required.
Subsurface Sites. Like steep hillside quarries, subsurface quarries should be excavated from the top
down. When excavation of the first lift has proceeded adequately, a second, lower level may begin and
so on. Excavation plans should include provisions for access ramps and drainage sumps.
Cut Design
Open-pit quarries are normally operated with vertical faces for ease in drilling and blasting the rock.
Two types of initial cuts, toe cuts and ramp cuts, are used to establish the initial, vertical quarry face. In
addition, full face cuts parallel to the strike of the rock may be needed during the initial development of
a site.
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