Open Cut

Slotting While Drilling for Reduced Blast Damage to the Coal Seam

Open Cut » Drilling & Blasting

Published: April 05Project Number: C13033

Get ReportAuthor: Mehmet Doktan, Dihon Tadic | CRCMining

This project has developed an innovative technique and tool to reduce blast damage to the coal seam. Blast damage that leads to coal loss in open cut mines is generally seen in two forms:

  • Damage to the top of the coal seam and loss of coal during mining
  • Coal edge movement or block movement and subsequent burial of coal under overburden

Research to date indicates that the confinement and excess energy at the toe is responsible for these mechanisms. The standard preventive measures include strict control of stand off distances, adherence to the plans, baby decking and seam buffering. These are complicated, difficult to achieve, expensive and in most cases ineffective while being only a partial solution to the problem.

CRCMining has proposed and developed a novel technique to overcome the problem. The technique is based on creating hollow slots at the toe of the blast hole that will effectively reduce confinement and divert excess blast energy into the rock rather than damage the coal.

The project is intended to be completed in two phases. The objectives of the first phase of the research included:

  • Develop tools and systems for blasthole slotting
  • Conduct tests to prove the concept, the system and quantify the benefits of slotting
  • Develop guidelines for retrofitting a drill rig and site trials
  • Transfer project outcomes back to the industry for next stage funding

Various options for a suitable slotting tool were evaluated and a self-extending arm concept was selected as the most suitable system. A slotter that can be mounted on a drill rig or forklift was designed, constructed, and tested on various samples.

The tests conducted showed that coal measure rocks such as sandstone, were efficiently slotted (approximately 300 mm in three minutes) while hard rock, such as granite took significantly longer (50 mm in 8 minutes).

To demonstrate the effectiveness of slots in controlling fracturing, a number of specimens were drilled, slotted and blasted at a quarry. The results showed that slotting the hole resulted in a reduction of the Peak Particle Velocity (PPV) which is a measurable indication of blast damage. The photos below illustrate the difference in the fragmentation of the toe section of the slotted and non-slotted samples after blasting.

Upon successful completion of the first stage, a set of guidelines were developed to aid in the implementation of the next stage of work. The overall recommendation for the next stage of work is to develop, test (full-scale field test), and validate a slotting system independent of the drill rig (Figure A6).

Anticipated benefits of blasthole slotting include the following:

  • Reduced blast damage to the coal seam. Slots created at the toe of the blasthole will reduce confinement and provide a route for the gases to enter and break the rock. This will effectively reduce stresses otherwise acting on the coal seam.
  • Improved presplit operation and quality. Vertical slots created around the blasthole will encourage the gas entry and promote fracturing along the plane defined by slots.
  • Improved fragmentation. Cavities (large slots) and slots created at harder segments of the overlying rocks will significantly improve the fragmentation in those sections.
  • Improved cast blast throw. Cavities created and filled with additional explosives will promote better cast and throw.
  • Reduced need for sub drill. The need for sub drill may be reduced when the fracturing is controlled at the toe of the blasthole.
  • Increased safety. Due to better fracture control and reduced blast damage to the highwall, highwalls will have smother surface and therefore will be safer.
  • Reduced blast vibration. In areas where blasting is conducted close to residential areas, reduction of blast vibration is important. This can be achieved by multiple slotting along the blast hole.

The first stage of the blasthole slotting project was completed on time and budget with all project objectives achieved.


Health and safety, productivity and environment initiatives.


Open Cut

Safety, productivity and the right to operate are priorities for open cut mine research.

Recently Completed Projects

C19024Establishing Ecologically Sustainable Mine Water Release Criteria In Seasonally Flowing Streams

Extreme rainfall conditions in the Fitzroy Catchment over an approxi...

C25030Coal Mine Open Pit Final Void Closure And Relinquishment - Addressing Uncertainty In Coal Mine Environmental Planning

This report addresses uncertainties faced by coal mine operators whe...

C27046Estimation Of True Deformation Vector From Slope Radar Monitoring

Slope deformation radar monitors are now widely used in open cut coa...

Open Cut

Coal Preparation

Maximising throughput and yield while minimising costs and emissions.

Recently Completed Projects

C27004Improving Coal Flotation With Oscillatory Air Supply

This report provides detailed information on coal flotation with os...

C25018Improving Solids Recovery And Moisture Reduction In Ultrafine Coal Dewatering

This report provides detailed information on fine coal dewatering in...

C27028Lab Froth Flotation Testing Guide With Coal Quality

Correct outcomes from laboratory froth flotation testing in coal bor...

Coal Preparation

Technical Market Support

Market acceptance and emphasising the advantages of Australian coals.

Recently Completed Projects

C26039Nanoporosity In Cokes: Their Origin, Control And Influence On CO2 Reactivity

This project using the outcomes of previous project C24060, examine...

C28063A Comprehensive Technical Review Of High-Efficiency Low-Emission (HELE) Pulverised Coal Combustion Technologies For Power Generation

Research and development has been undertaken worldwide to realise co...

C28064Carbon Structure Transformation During Coking Of Australian Coking Coals: Better Understanding The Coke Formation

Carbon structures of coke that are formed during the plastic layer a...

Technical Market Support

Mine Site Greenhouse Gas Mitigation

Mitigating greenhouse gas emissions from the production of coal.

Recently Completed Projects

C28076Selective Absorption Of Methane By Ionic Liquids (SAMIL) - Phase 2 Demonstration In A Packed Bed Reactor

An alternative approach to high temperature oxidation of ventilation...

C26004CFD Modelling Of Reverse Thermal Oxidisers For VAM Abatement - CFD Modelling Of Fixed-Bed RTO Devices

The project is part of a larger multi‐phase program of study a...

C27058Technological Assessment Of A Recycle Reactor For VAM Abatement

Underground coal mining emits high volumes of methane, diluted in ve...

Mine Site Greenhouse Gas Mitigation

Low Emission Coal Use

Step-change technologies aimed at reducing greenhouse gas emissions.

Recently Completed Projects

C17060BGasification Of Australian Coals

Four Australian coals were trialled in the Siemens 5 MWth pilot scale ga...

C17060AOxyfuel Technology For Carbon Capture And Storage Critical Clean Coal Technology - Interim Support

The status of oxy-fuel technology for first-generation plant is indicate...

C18007Review Of Underground Coal Gasification

This report consists of a broad review of underground coal gasification,...

Low Emission Coal Use

Mining And The Community

The relationship between mines and the local community.

Recently Completed Projects

C16027Assessing Housing And Labour Market Impacts Of Mining Developments In Bowen Basin Communities

The focus of this ACARP-funded project has been to identify a number...

C22029Understanding And Managing Cumulative Impacts Of Coal Mining And Other Land Uses In Regions With Diversified Economies

The coal industry operates in the context of competing land-uses that sh...

C23016Approval And Planning Assessment Of Black Coal Mines In NSW And Qld: A Review Of Economic Assessment Techniques

This reports on issues surrounding economic assessment and analysis ...

Mining And The Community


National Energy Research,Development & Demonstration Council (NERDDC) reports - pre 1992.

Recently Completed Projects

1609-C1609Self Heating of Spoil Piles from Open Cut Coal Mines

Self Heating of Spoil Piles from Open Cut Coal Mines

1301-C1301Stress Control Methods for Optimised Development...

Stress Control Methods for Optimised Development and Extraction Operations

0033-C1356Commissioned Report: Australian Thermal Coals...

Commissioned Report: Australian Thermal Coals - An Industry Handbook