Practical Aspects of Blast Hole Drilling

In these series article, we will introduce the key knowledge on blast drilling according to our many years practical experience in Hardrock Drills.

Below is the lecture overview which will be introduced item by item, today we will start from Modern systems for surface blasting drilling.

Lecture Overview

Planning of a blast drilling

General Considerations
- What is the goal of my blasting drill work?
  - eg.: high comminution or just breaking the rock in order to transport it?
- What are the surrounding conditions?
  - Kind of rock, please read ROCK PROPERTIES and ROCK DRILLABILITY
  - Costs – drilling, explosives
  - Neighbors
First thing to do: evaluation of geology
Prior to every blast:
- Each blast has to be planned separately
- the drill rig operator and the blaster should define the blast site together
State of the art: computer based blast planning
Recommended: building up a database for the whole process “drilling and blasting”
- Save data as evidence
- Learn from prior blast
- Young engineers who are responsible for the blasting work have a basis to work on

Surveying of the face

3 systems available:
Theodolite with distance-meter
- Easy to handle system
- Produces only a very imprecise picture of the face
Laser scanner
- Very precise
- High investment costs
- Huge amount of data to deal with and save somewhere
- Time intensive
Photogrammetry
- Fast Cheap
- Precise enough for our needs
- Uses a real picture

Borehole drilling

Automation in drilling

Control System
- Hydraulic controls replaced by electric controls (30% less hydraulic components, less noise)
- Anti-jamming function
AutoRAS
- Drilling of holes to predefined depths (by spanning up a laser plane)
- ROC Manager (blast planning) and MWD (measure while drilling)
GPS and HNS
Silenced version for urban areas

Control of drill work

Measure borehole position (using theodolite and a mirror)
- Analysis for example with AutoCAD
Measure distance between holes with a measuring tape
Measure borehole deviation
3 systems available
- MDL Boretrak
- Transtronic
- Pulsar

Charging of blast holes – kind of explosive

Charging of blast holes – detonator

Charging of blast holes – Initiation

Control of blast borehole

Environmental effects – Dust/blasting fumes

Environmental effects – Noise

Stay clearly below 120 dB (threshold of pain)
- Initiation from borehole bottom
- Avoid using detonating chords (if you do: cover sufficiently)
- Use of right stemming material

Environmental effects – Vibrations

Regular measurements and documentation of results
- For own vibration prediction
- As evidence for authorities
Stay within predefined limits

Documentation

Save all gathered data on
- face surveying
- blast plan borehole position
- borehole surveying
Film and take pictures of the blast – also a cheap evidence
Save all measured data on noise and vibration

Above is the brief introduction for Modern systems for surface blasting drilling, flowing blogs will continue introduction on below two topics

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