FOR MINING STUDENTS WHICH WORKING ON A SEMINAR REPORT

1. GUIDED BY :- Er. DEEPAK PANDAY
SUBMITTED BY :- PANKAJ KUMAR PATIDAR
SEMINAR REPORT ON
ROLE OF STEMMING IN OPENCAST MINE

2. INTRODUCTION
• STEMMING ENHANCES FRAGMENTATION AND ROCK DISPLACEMENT BY
REDUCING PREMATURE VENTING OF HIGH PRESSURE EXPLOSION GASES TO
ATMOSPHERE. GOOD STEMMING MAINTAINS HIGH GAS PRESSURE WITHIN BLAST
HOLE FOR LONGER PERIOD OF TIME.
• THIS METHOD HELPS IN CONFINE THE GASES WITHIN A BOREHOLE AND HELPS
TO PREVENT HIGH COST OF BLASTING , AIR BLAST , EXCESSIVE GROUND
VIBRATION , FLY ROCK AND BOULDERS.
• THIS REDUCES ENERGY WASTE , MINIMIZES AIR BLAST AND IMPROPER
FRAGMENTATION.
• A SUITABLE INERT INCOMBUSTIBLE MATERIAL USED TO CONFINE OR SEPARATE
EXPLOSIVE IN A DRILL HOLE OR TO COVER EXPLOSIVE IN MUD CAPPING IS
CALLED STEMMING MATERIAL.

4. DIFFERENT TYPES OF STEMMING MATERIALS
COMMONALLY USED FOR STEMMING

5. DIFFERENT STEMMING MATERIALS USED IN
DIFFERENT CASES :-
• (1) SAND - CLAY MIXTURE
• (2) SAND AND CRUSHED ROCK
• (3) FLY ASH – CLAY MIXTURE
• (4) MOIST CLAY
• (5) PVC AMPOULES
• (6) WATER AND GEL FILLED AMPOULES
• (7) STEM PLUGS
• (8) ROCK LOCK
• (9) FOAM STEMMING PLUGS
• (10) AIR DECKING

6. SEND - CLAY MIXTURE :-
• IT IS EASY TO HANDLE AS CLAY AND OFFERS ALMOST NO
RESISTANCE AS SAND.
• GENERALLY ACCEPTED AS MOST CONVENIENT AND
EFFECTIVE FOR GENERAL USE.
• THE MIXTURE SHOULD CONSIST OF COARSE SEND ,
BRICK DUST AND TOGETHER WITH 5% CALSIUM
CHLORIDE TO KEEP IT MOIST.
• WATER SHOULD BE ADED TO MAKE A STIFF PASTE (UPTO
10% WATER).

7. SAND AND CRUSHED ROCK :-
• SAND CAN NOT BE INSERTED IN THE NORMAL WAY IN HORIZONTAL AND
UPWARDLY INCLINED HOLES.
• THIS OFFERS A VERY HIGH RESISTANCE IN DISLODGING.
• FOR BLAST HOLES DIAMETER IN THE 50 TO 130mm RANGE , ANGULAR CRUSHED
ROCKS HAVING SIZE 6 TO 13 mm IN THE MOST SUITABLE STEMMING MATERIAL.
• IN WET BLAST HOLES COURSE ANGULAR STEMMING SINKS MORE READILY THAN
DRILL CUTTINGS.

8. FLY ASH – CLAY MIXTURE :-
• A MIXTURE OF FLY ASH – RED CLAY CAN BE USED EFFECTIVELY IN COAL MINES
FOR STEVMMING, BECAUSE FLY ASH IS READILY AVAILABLE IN COAL MINES SO
THIS MIXTURE REPRESENTS A COST EFFICTIVE OR ECONOMICALLY CHEAP
STEMMING MATERIAL.

9. MOIST CLAY :-
• ADVANTAGE =
# IT IS CHEAP AND PLENTIFUL
# IT NEEDS NO PREPARATION BEFORE TAKING IT TO THE BLASTING SITE .
# IT IS INCOMBUSTIBLE.
# WHEN MOISTENED , IT REMAINS MOIST FOR A CONSIDERABLE TIME.
• DISADVANTAGE =
# IT IS FOUND AT CLAY STEMMING IS LIABLE TO EJECT IN MASS BY THE EXPLOSIVE
CHARGE AND IT THAN FAILS TO FULFILL ITS INTENDED PURPOSE.
# HOLES STEMMED WITH TWO OR MORE CLAY TYPE STEMMING CARTRIDGES
SHOWED NO VENTING AND DELIVERED THE BEST BLASTING RESULTS.

10. PVC AMPOULES :-
• GENERATION OF DUST AND FUMES BEING MINIMUM.
• LOWER DOWN DEGREE OF FRAGMENTATION.
• THIS REDUCING THE RISK OF METHANE IGNITION OR COAL DUST EXPLOSION.

11. WATER OR GEL FILLED AMPOULES :-
• WATER OR GEL FILLED AMPOULES (96% WATER MIXED WITH CHEMICAL GELLING
AND BACTERICIDE AGENTS) HAVE BEEN USED
# TO SEAL THE HOLE
# QUENCH OR COOL THE FLAME OF EXPLOSION
# SUPPRESSION OF DUST AND ALSO TO ABSORB FUMES.
• IT IS VERY EFFICIENT SYSTEM ,AND REDUCE THE EXPLOSIVE CHARGE PER
TONNE COAL PRODUCTION AND HENCE VERY COST EFFECTIVE.
• DURING CHARGING A SHOT HOLE FIRST CONVENTIONAL STEMMING MATERIAL
MADE OF CLAY AND SAND IS INSERTED INTO THE HOLE ,THEN EXPLOSIVE
CARTRIDGE AND FOLLOWED BY ONE OR TWO WATER OR GEL FILLED AMPOULES
OR WATER FILLED PVC BAGES ARE INSERTED.
• WITH THE USE OF WATER OR GEL FILLED STEMMING RISK OF COAL DUST ,FIRE
DAMP EXPLOSION AND DUST DURING THE BLASTING IS REDUCES.

12. STEM PLUGS :-
• THESE STEM PLUGS COMES FROM THE FACT THAT AN INCENSEMENT OF THE
CONFINEMENT OF THE EXPLOSIVE ENERGY WITHIN THE BOREHOLE ,DRASTIC
IMPROVEMENTS IN FRAGMENTATION CAN BE ACHIEVED.
• THIS IS CAUSED BY THE EXTRA TIME THAT THE EXPLOSIVE FORCE CAN WORK ON
THE SURROUNDING MATERIAL.
• OVER 2 MILLION PLUGS HAVE BEEN USED WORLDWIDE TO INCREASE THE
EFFECIENCY OF THE BLASTING PROCESS.
• IN THIS METHOD ,SAVES ON SECONDARY BLASTING ,CRUSHER MAINTENANCE
,REDUCTION IN FLY ROCK AND AIR BLAST ,HIGHER LOADING IN CAP ROCK OR AIR
DECKING.

14. ROCK - LOCK ;-
• CREATING CONFINEMENT AND ELIMINATING THE VENTING OF EXPLOSIVE
GASSES IS THE CONCEPT BEHIND ROCK LOCK STEMMING PLUGS.
• THE ROCK LOCK PLUGS IMPROVE THE OVERALL ROCK FRAGMENTATION OF THE
BLAST AND INCREASE BLASTING SAFETY.
• THIS REDUCES ENERGY WASTAGE ,MINIMIZES AIR BLAST.

15. FOAM STEMMING PLUGS :-
• CAN BE USED TO STEM BLAST HOLES , PLUG BACK OUT HOLES OVER OLD
WORKS OR IN SILL PILLAR, PLUG CORE HOLES TO REDUSE SHOT GUNNING ,
PACK OVERHAND HOLES TO PREVENT EMULSION SLIPPAGE , AND SEAL
PREDRILLED HOLES PRIOR TO LOADING .
• FOAM PLUG HAS ALSO BEEN USED TO PLUG SURFACE DRILL HOLES TO PREVENT
TO SURFACE WATER INFILTRATION.

16. AIR DECKING :-
• IT IS A TECHNIQUE USED TO PRE SPLIT ROOFS , RIBS , PILLARS , AND HIGH
HOLES .
• WHEN AN AIR GAP IS INTRODUCES IN THE MIDDLE OF TWO COLUMN OF
EXPLOSIVE IN A BLAST HOLE , EXPLOSION PRODUCT FROM TWO EXPLOSIVE
COLUMN PORTIONS GENERATE AIR SHOCK WAVES IN THE DECK COLUMN. THE
GENERATED SHOCK WAVES FROM EITHER ENDS OF THE EXPLOSIVE COLUMN
MOVES AND COLLIDES AT THE AIR GAP PROVIDED IN DECKING.

17. CONCLUSION :-
• SAND IS THE BEST STEMMING MATERIAL AMONG ALL OTHER COMPOSITIONS OF
STEMMING. BUT INSERTING INTO HORIZONTAL INCLINED UPWARD HOLES IS
DIFFICULT IN MANUAL STEMMING.
• IN THE DIFFERENT PERCENTAGE OF FLY ASH : CLAY COMPOSITION 35 : 65 IS THE
OPTIMUM COMPOSITION FOR EFFECTIVE STEMMING.
• IN WATERY PLACES THE PERFOMANCE OF STEMMING WITH FLY ASH : RED CLAY
IS REDUSED. BUT SAND IS EFFECTIVE IN THIS SITUATION.

18. THANK YOU