ENGIN3503 : Surface Mining Operations and Equipment

Question 1

Advice to the Mines on the Practicality and Utility of Using Conveyors:

I. Strip Mine Operation:

1. The practicality of Using a Conveyor

• Using a conveyor system can considerably improve efficiency and decrease operating costs for a strip mine operation. The primary considerations are the mining depth (37m) and the coal transportation rate (1.2 million tons per month).
• A conveyor system is compatible with this operation as it could continuously transport coal from the strip to the surface, removing the requirement for trucks and shovels for this task. It can reduce labor costs, consumption of fuel, and maintenance expenses (Darling, 2011).
• Conveyors are reliable and need less human intervention, which could enhance safety.
• The depth of 37m is comparatively shallow for a conveyor system. Conveyor belts can handle this depth efficiently.
• Given the high monthly coal transportation rate, the investment in a conveyor system could be justified by long-standing cost savings.

Utility of Using a Conveyor

• The conveyor system will improve the predictability and consistency of coal transportation, lessening the risk of production disruptions.
• Conveyors operate continuously, which implies that coal could be transported around the clock, raising production.
• It enhances environmental sustainability by lessening emissions from trucks and getting better the utilization of mined coal.
• It is beneficial and convenient for the strip mine operation to implement a conveyor system to add on the current fleet of trucks and shovels

II. Open-Pit Operatio

The practicality of Using a Conveyor

• The open-pit operation is considerably deeper (300m) as compared to the strip mine, and it includes transporting both waste and coal. The monthly transportation rate is also considerable (1.22 million tons/month) with a stripping ratio of 3:1. This operation indicates more challenges for conveyor use.
• Though a conveyor could transport coal proficiently, it may be less practical for hauling waste to a dump as it can need a long and complex conveyor route. Trucks may still be required for such cases.
• The depth of 300m poses engineering challenges regarding conveyor design and support structures. The cost of installing such a deep conveyor system could be considerable.

Utility of Using a Conveyor

• A conveyor system is highly efficient in transporting coal from the open pit to a processing plant on the surface, lessening the requirement for trucks and improving consistency.
• The stripping ratio of 3 to 1 implies that waste material is a substantial component, and conveyor systems may need to be more profitable for waste transportation because of the volume involved.
• Consider using a conveyor system to transport coal to the processing plant, where it is most effective or the open-pit operation, and continue using trucks for waste transportation for the open-pit operation. This strategy could balance efficiency and cost-effectiveness (Kazanin, 2017).

Additional Equipment for Combining Existing and New Conveyor Systems

If they decide to combine current and new conveyor systems, they could require the following additional equipment for both mines

Firstly, robust Conveyor Support Structures are vital. It is necessary to design these structures to withstand the weight and stress related to conveying materials over changing distances. Their design needs to be tailored to the particular needs and challenges of each mine, in view of factors such as load capacity, terrain, and environmental conditions.

Conveyor Transfer Points play a major role in the smooth transfer of material. Adequate design and planning of these points are essential to avoid bottlenecks and maintain a steady flow of materials. Effective transfer points optimize the efficiency of the conveyor systems.

Conveyor Control Systems are the brains behind the operation. Advanced control systems are necessary to manage conveyor speed, distribution of load, and material flow. These systems usually incorporate sensors, monitoring tools, and automation tools to maintain a constant and safe operation.

Conveyor Maintenance Equipment is crucial to mitigate downtime. It includes tools for conveyor belt splicing and a ready supply of spare parts. Regular maintenance is necessary to keep the conveyor systems in optimum working condition.

Safety Measures could not be overlooked. Safety equipment and training are vital to protect personnel working near or with conveyor systems. It is essential to place appropriate safety protocols and procedures to prevent accidents and for the well-being of workers.

Material Loading and Unloading Facilities should be set up to impeccably integrate the conveyor systems with other equipment. Efficient loading and unloading infrastructure makes certain a smooth flow of materials to and from the conveyors.

Environmental Mitigation Measures are necessary to address environmental concerns. The application of dust control and spillage containment systems could aid the environmental impact of material transportation.

Emergency Response and Contingency Plans are vital to prepare for unexpected events, such as conveyor breakdowns or emergencies. Having suitable response plans in place makes sure that operations can be quickly restored and reduces disruptions.

Question 2

Hole Diameter= 200mm

Bench Height=12m

Burden= typically, the burden needs to be approximately 1.2 times the bench height, so in this case, it's about 14.4m.

Hole spacing is according to burden and the desired fragmentation size. A common practice is to use a burden-to-hole diameter (B/D) ratio of 10 to 12. 

Hole spacing = 12 x Hole Diameter = 12 x 200mm = 2.4m

The blast pattern is the layout of blast holes on the bench. The staggered pattern is the common pattern. The blast holes are placed with particular spacing between holes in each row. The next row will be staggered in between the previous row's holes. Compute the number of rows needed to encompass the whole bench face. The spacing between rows could be modified according to the requirements of the site.

ANFO density = 0.80 g/cm³

Primer density, refer to the specific product's technical data for the density.

Powder Factor (PF)=Total Explosive Mass /Volume of Rock

The desired PF is at least 0.60 kg/m³, and you have a hole diameter of 200mm (0.2 meters). The volume of rock that should be displaced by a single blast hole can be is calculated by the following formula for the volume of a cylindrical hole

Volume of Rock per Hole=3.14×(hole diameter/2)2×bench height

Total Explosive Mass per Hole=PF×Volume of Rock per Hole

Hole Diameter=0.2 meters

Bench Height=12 meters

Volume of Rock per Hole=3.14× (0.2/2)2×12=0.0942 m3

Total Explosive Mass per Hole=0.60 kg/m³× 0.0942=0.05652 kg

Table 1: Drilling and Blasting Schedule and Production

2. Blasthole Drilling Pattern

The blast hole drilling pattern is the layout of drill holes on the bench face. There are numerous common patterns in surface mining, and the selection of patterns depends on factors such as the bench geometry, rock type, and production requirements. The pattern is staggered as shown below

3. Details of Blasthole Parameters

Table 2: Blasthole parameters details

4. Blast Control Techniques Employed

The blast control techniques are

• Sequencing

This pattern starts at the perimeter and progresses in the direction of the center to allow for a controlled release of energy.

• Delay Timing

Delays in the introduction of blast holes could be employed to control the sequence of detonation. Long delays between rows or sections of blast holes help to lessen the maximum instantaneous release of energy.

• Buffer Holes

 Buffer holes separate sections of the blast pattern. They control shock wave propagation.

• Decking

Decking is the division of blasts into smaller blasts within the same pattern to lessen an energy release at any one time.

• Electronic Blasting Systems

Modern blasting systems use electronic initiation technology for precise control of the timing of detonations, providing better control over the blast, reducing flyrock, and lessening environmental impact.

• Vibration Monitoring

Vibration monitoring equipment measures ground vibrations during a blast. These measurements help comply with regulatory limits and prevent damage to nearby structures (Rylnikova et al., 2017).

• Air Overpressure Monitoring

Monitoring air overpressure aids in controlling noise and blast-induced air overpressure so that it remains within acceptable limits.

• Flyrock Control Measure

 Flyrock is a safety hazard. Proper blast design, stemming, and other measures minimize the risk of fly rock reaching unsafe distances.

5. Blast Circuit/Initiation Pattern

Question 3

Ho (Height of overburden) = 16 m

Hc (Height of coal) = 4.5 m

Pit width = 40 m

φo (Angle of repose for overburden) = φc

 (Angle of repose for coal) = 70°

θ (Swing angle) = 40°

Overburden Thickness (T) = Ho - Hc 

T = 16 m - 4.5 m = 11.5 m

The swell factor is given as 1.25 to 1.30. Assume a swell factor of 1.3, which implies that the volume of the excavated material will enhance by 30% when it is dumped.

Td = T / (1 + Swell Factor) Td = 11.5 m / (1 + 0.3) Td ≈ 8.85 m

Re (effective radius)= Pit Width / (2 * (1 - cos(θ))) Re = 40 m / (2 * (1 - cos(40°))) Re = 58.84 m

The amount of overburden and coal removed remains the same over time. This means that for every unit of coal mined in a constant stripping ratio scenario, the same amount of overburden is removed. The simple cross-section is

     2. Increasing Stripping Ratio

When the pit deepens, more overburden should be removed to access the deeper coal seams in an increasing stripping ratio scenario. This results in a high stripping with the passage of time. The sketch is

     3.Decreasing Stripping Ratio

When the pit deepens, the coal seams get thicker, and the amount of coal relative to overburden increases in a decreasing stripping ratio scenario. It will lead to a lower stripping ratio with the passage of time. The simple sketch is

References

Darling, P. (Ed.). (2011). SME mining engineering handbook (Vol. 1). SME.

Kazanin, O. I., & Drebenstedt, C. (2017). Mining education in the 21st century: global challenges and prospects. Записки Горного института, 225, 369-375.

Rylnikova, M., Radchenko, D., & Klebanov, D. (2017). Intelligent mining engineering systems in the structure of Industry 4.0. In E3S Web of Conferences (Vol. 21, p. 01032). EDP Sciences.

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