Design Considerations for Quarrying Operations in Aggregate Production Systems

Aggregates constitute the fundamental components of concrete, with approximately 1.5 cubic metres of aggregate required per cubic metre of concrete. Artificial aggregates exhibit favourable gradation and quality, finding extensive application in infrastructure development. The artificial aggregate processing system primarily comprises the following stages: raw material extraction and transportation, primary crushing, secondary and tertiary crushing, sand manufacturing, screening, and washing. This article focuses on the first stage: raw material extraction and transportation.

(1) Extraction Plan

Typically, quarries employ stepwise mining operations. The extraction plan must determine key parameters such as step height, slope gradient, haulway width, and support/protection methods based on the quarry's topographical and geological conditions, alongside the type and model of excavation equipment to be utilised.

Transportation schemes for quarries commonly consider road haulage or vertical (inclined) shaft haulage.

Road transport necessitates suitable terrain and site conditions for road layout. While typically involving longer haulage distances and requiring more loading/unloading equipment during production operations, it offers simpler production management, lower geological risks, and greater stability in production.

Vertical (inclined) shaft transport necessitates geological conditions suitable for shaft construction, reducing haul distances and requiring fewer loading/unloading facilities. However, comprehensive consideration must be given to protective measures for the shaft and connecting adits, along with contingency plans for collapses or debris blockages. The impact of blasting operations on stability must be assessed, potentially requiring reduced blast scales. Production management is complex, and geological risks are elevated.

(2) Blasting Operations

Blasting operations at the quarry primarily include: ① Large-scale blasting of raw rock, typically employing drill-and-blast methods. For extensive production, chamber blasting is occasionally utilised. To reduce single-blast charge quantities and thereby mitigate seismic waves and air shock waves, micro-delayed staggered blasting between rows (or holes) is commonly employed; ② Slope treatment blasting, typically employing pre-splitting blasting (large-area, large-diameter holes) or smooth blasting (localised, small-diameter holes) to minimise impact on permanent (or temporary) slopes and enhance slope stability; ③ Working face (road surface) levelling, commonly achieved through hand-held drill hole blasting and finishing.

(3) Slope Stabilisation

Prior to slope surface construction, top drainage ditches are frequently installed beyond the excavation perimeter. Pre-splitting blasting and small-scale smooth blasting have become standard measures for maintaining rock surface flatness and minimising bedrock disturbance during quarry slope excavation, thereby enhancing slope stability. Advanced techniques like shaped charge blasting are increasingly adopted for pre-splitting due to their superior efficacy and cost-effectiveness. High slopes shall incorporate access walkways (including safety and maintenance walkways). Locally loose material on the slope face shall be removed mechanically or manually. Protective measures shall be determined based on geological conditions, including: - Grass planting and hydroseeding for earth slopes; - Cable anchors, anchor piles, rock bolts, (mesh-supported) shotcrete, mortar-jointed stone, or concrete backfill for rock slopes.