Gravity bypass of ore down weakened pit wall in upland quarries

Abstract

There are many currently known studies and methods concerned with gravity rock flow down the slopes of upland quarries to the receiving sites or into ore chutes. At the same time, the gravity flow of rocks down the highwall of a quarry, which is weakened and is subjected to cumulative load applied by tectonic faults and natural slope above the upper edge of the pit wall, needs extra investigation. The operating experience of upland quarries shows that higwalls often contain eroded areas and tectonic faults. The latter, given certain conditions, can cause large shears, deformations and rock falls in highwalls. Particular hazards can arise when highwall intersects and shears off faults composed of clayey rock layers and dipping toward the mined-out void of the pit. This article offers a brief analysis of the common methods available for gravity rock flows down ore passes in upland quarries in the world. The authors propose a new safe and efficient approach including construction of a support pillar shaped as a truncated pyramid in the weakened pit wall. This engineering solution enables overburden haulage by motor roads made at the top of the support pillar shaped as a truncated pyramid, which allows smooth movement of dump trucks along such roads. Depending on the complexity of geotechnical conditions and cumulative load applied by tectonic faulting and natural slope above the upper edge of the quarry, it is possible to make a number of the support pillars in the weakened pit wall.