Safe Design Pattern and Procedure for Safe blasting in Hard Rocks.
The Design pattern of Drill is very important for safe blasting, here we will talk about how we can design Drilling pattern for safe blasting.
Following step can be followed for safe design
1. Calculate Burden and spacing.
2. Decide powder factor : Powder factor generally the amount of explosive required for blasting 1 cum of rock Mass.
3. Free Face: Maximum free face control Fly rocks and Vibration which may impact surrounding areas.
4. Stemming: 20 – 30 D of drill holes diameter is the best depth for Stemming, proper stemming restrict energy to dissipates vertically which results good blast and fragmentation.
5. Delay Sequencing: Ensuring delays in in hole detonator and surface detonator always gives good fragmentation after blast and always keep in mind in hole detonator should not blast before surface detonator.
6. Always use in hole detonators type as per your sequence which gives better result and fragmentation as shown below.
7. Check last hole blast sequence and type of in hole detonator should be used accordingly.
Figure Showing Blast Design pattern
8. Always use different type of sequence for Centre line delays and delays in other rows of surface detonators.