Study Notes on Blasting and Safety Measures in Mining

Technical Difficulties and Introduction

  • Technical Issues: The instructor notes some difficulties involving classroom lighting, indicating that the light will be turned off during the presentation for clarity.
  • Introduction of Speaker: The instructor introduces Ken Elslager, a mining engineer from the Office of Surface Mining Reclamation and Enforcement (OSMRE).
    • Ken Elslager has been involved in coal mining and blasting since 1985.
    • His role involves providing technical assistance, handling citizen complaints, and assessing blasting effects on people and property.
  • Speaker's Background: Elslager is involved in various instructional capacities within OSM, including blasting, mine gases, public relations, and GPS training.
    • He oversees the OSM blaster certificate program, aiding in certification and continuing education training.
    • He is a past director of the International Society of Explosives Engineers (ISEE) and chairs the ISEE standards committee.

Overview of OSM Responsibilities

  • Regulatory Agency: OSM functions as a regulatory body regarding coal mining.
    • Emblem symbolism: Scales of justice with trees representing the environment and coal representing energy.
    • OSM strives to balance national energy needs with environmental integrity and land productivity.
  • **Key Activities:
    • Regulation of active coal mining and blasting, with coordination across states.
    • Forensic investigations of blasting accidents.
    • Addressing issues related to abandoned mine lands, including occasional blasting operations.

Coal Mining Statistics and Practices

  • Geographical Impact: OSM's reach includes 34 states where coal mining occurs.
    • The states maintaining no coal deposits (16) are not direct areas of OSM operations.
  • Top Coal-Producing States (2019 Data):
    • West Virginia and Wyoming lead coal production, with Kentucky falling to fifth place, surpassed by Illinois and Pennsylvania.
    • Notably, 70% of explosives annually are used in mining, primarily in these high-production states.

Blast-Induced Effects and Control Measures

  • Overview of Effects: Elslager will discuss adverse effects related to blasting, specifically focusing on ground vibrations, air blasts, fly rock, fumes, and dust.
  • Example of Controlling Adverse Effects:
    • A railroad recut project necessitated maintaining operational train flow, all while minimizing environmental impact and ensuring safety.
    • The project utilized knowledgeable personnel and effective controls to prevent incidents during blasting.

Key Terminologies For Blasting Operations

  • Blast Hole Area: Refers to an area around the blast holes extending 50 feet, where explosives can affect the surroundings.
  • Blast Area or Permit Area:
    • Defined area where no blast debris is allowed to leave during operations to prevent injury, especially from fly rock.
    • Encompasses areas beyond the permit boundaries if necessary for safety.
  • Adverse Effects from Blasting:
    • Potential injuries caused by:
    • Concussion: Pressure waves from air blasts.
    • Fly Rock: Ejected debris from the blast site.
    • Fumes: Hazardous gases released during blasting.

Blasting Basics

  • Factors Affecting Blasting Outcomes:
    • Charge Size: Larger charges can cause more significant effects.
    • Depth of Charge: Deeper charges confine energy, potentially reducing adverse effects at the surface.
  • Illustrative Examples of Charge Influence:
    • A smaller diameter, deeper charge can produce minimal ground vibration.
    • A charge near the surface can lead to significant flying debris and air pressure spikes.

Blasting Design and Implementations

  • Blasting Technique Overview:
    • Charge sizes and configurations must be planned to minimize adverse effects and ensure effective material fragmentation.
  • Example Design Model:
    • Illustrated with a series of holes loaded with explosive charges, commonly ANFO, emulsion, or blends.
    • Priming Technique: Primers typically placed at the bottom, focusing energy on the rock mass to maximize effective breakage.
  • Powder Factor: Number of pounds of explosives required per cubic yard of material, varying with rock hardness:
    • Weaker Rocks: Such as shales require a lower powder factor.
    • Harder Rocks: Such as granite demand a higher powder factor for effective breakage.

Control Measures Against Adverse Effects

  • Calculation of Distances: Using distances to determine allowable charges per delay based on measured scale distances.
  • Importance of Charge Confinement: Charge depth and confinement significantly affect vibration generation and overall blast effectiveness.
  • Case Studies of Blasting Outcomes:
    • Different examples showcase poor designs and implementations leading to excessive vibrations or atmospheric pressures versus optimal outcomes.

Monitoring Blasting Performance

  • Seismic Monitoring: Utilization of seismographs to track the effects of blasts and catch potential oversights in field execution.
  • Seismic Signatures: They provide an independent record of blasting operations which can indicate failures or improvements needed in blasting design.

Common Challenges in Blasting Operations

  • Uncontrollable Factors Affecting Blasting:
    • Surface Terrain: Heterogeneous topographies complicate designs and execution.
    • Weather Conditions: Exacerbate air pressure challenges affecting blast outcomes.
  • Controllable Factors:
    • Critical Control Variables: Charge weight, delay intervals, and confinement are crucial factors that adjust the blast performance.
  • Operational Best Practices:
    • Maintain high standards for drilling and loading accuracy.
    • Ensure effective communication between blasters and drillers to establish safety measures.

Adverse Effects: Fly Rock

  • Definition of Fly Rock: Material ejected from a site during the blast that travels through the air or is set into motion by the blast forces.
  • Regulatory Guidelines: Fly rock must not exceed half the distance to the nearest dwelling or occupied structure and must remain within protected blast area boundaries.
  • Significant Consequences:
    • Fly rock can cause fatalities and property damages, highlighting the need for thorough preparatory measures before each blast.

Safety Protocols and Preventative Measures

  • Preventative Strategies Against Fly Rock:
    • Ensure appropriate powder factors based on rock types to avoid excessive energy release.
    • Properly place primers in the charge and use adequate stemming material to minimize venting incidents.
    • Implement precise design measures, considering the spatial relationship of surrounding structures to control fly rock trajectories.
    • Key Incident Reviews: Documented cases of accidents can serve as case studies to avoid future occurrences.

Conclusion

  • Final Reminders: Blasters must adhere to best practices in design and field implementation to ensure safety and efficiency in mining operations, underscoring the importance of thorough training and communication in preventing adverse outcomes.
  • Open Discussion: Elslager concludes and opens the floor for questions, encouraging dialogue about the impact of blasting safety and efficacy.