ismr blaster retraining workshop jasper, indiana december 07, 2009 jasper inn & convention...
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ISMRISMRBLASTER RETRAININGBLASTER RETRAINING
WorkshopWorkshop
• Jasper, Indiana
• December 07, 2009
• Jasper Inn & Convention Center
FLYROCKFLYROCK
&&
“ “ PREVENTION”PREVENTION”
Dennis Clark, PEDennis Clark, PE
Mining EngineerMining Engineer
OSMRE – KFOOSMRE – KFO
Number One Rule of BlastingNumber One Rule of BlastingALL BLASTING SHALL be ALL BLASTING SHALL be
CONDUCTED to PREVENT:CONDUCTED to PREVENT:
• Injury to Persons
• Damage to Public or Private Property
• Throw off the Permit/Blasting Site
Adverse Effects of Fly-rockAdverse Effects of Fly-rock
• Increases the Area of Disturbance On & Off the Permit
• Endangers Employees and Equipment
• Physical Damage to Private Property
• Endangers Humans and Livestock
• Can Result in Death – Flyrock Kills!
Tools to Assist in Fly-rock Tools to Assist in Fly-rock Investigations Investigations
• Blast Hole Drill Logs for each Hole • Blast Report or Log:
1) with Diagrams of how Holes are Loaded 2) the Site Specific Drill & Blast Pattern
• On Site Investigation• Eye-Witness Accounts• Instrumentation & Monitoring Data
Before “Blasting” You Drill the HolesBefore “Blasting” You Drill the HolesWhat is Going on Here?What is Going on Here?
Drill Log – ExampleDrill Log – ExampleA Requirement Prior to LoadingA Requirement Prior to Loading
AAlso log any rock type changeslso log any rock type changes
HOLE
Number
HOLE
Depth
LOOSE
Material
in feet
Depth to SOLID
Contact
SEAMS
&
CRACKS
CAVITIES
Location
in feet
Location of Soft Formation
In feet
Depth to
WATER
1 42' 0-2 3' -- -- -- 38'
2 44' 0 0 -- 22-24 -- -- 3 43' 0-4 5' -- -- 20-25 36'
4 41' 0-2 3' 33' -- -- -- 5 42' 0-1 2' -- -- -- 40'
BLAST REPORT or LOGBLAST REPORT or LOG• Location of Blast• Date & Time• Drill & Blast Pattern • Explosives & Delays used• Max. Pounds/8ms Delay• Location of Closest “House”• Distance & Direction to “”• Compliance Method Data• Assure Accuracy Of Blast
Log Information• Any Blast Log Discrepancies
will require additional in-depth investigations
• Every Blank Space of the REPORT should be Filled
Flyrock per 816.67(c)Flyrock per 816.67(c)Rock cast from blasting site via the air or Rock cast from blasting site via the air or
along the groundalong the ground
• Rock traveled > ½ distance to nearest dwelling
• Beyond the area of control
• Beyond the permit boundary
PROJECTED ROCK-CAST RANGESPROJECTED ROCK-CAST RANGES
• Blaster projects expected rock-cast range & determines security zone (area of control)
• Flyrock is any throw outside the security zone, within the permit and always outside the permitted site.
Throw Distances for Varying Size Throw Distances for Varying Size Rock (Spherical in Meters)Rock (Spherical in Meters)
for a Given Hole Diameterfor a Given Hole Diameter
Swedish Rule-of ThumbSwedish Rule-of ThumbBlasting of Dense RockBlasting of Dense Rock
• Maximum Fly-rock Range 100 meter distance for every
centimeter of Bore-Hole-Diameter
• Example in English System5 inch Blast-Hole-DiameterMaximum Throw = 4,128 feet
• Note: Less Dense Rocks will not Travel as Far!!!
Common Optimum Fly-rock DistancesCommon Optimum Fly-rock DistancesFor a 8 Inch Diameter Blast Hole For a 8 Inch Diameter Blast Hole
Sandstone: 6,000 ft.
Sandstone/Shale 5,000 ft.
Limestone: 6,200 ft.
Shale: 4,100 ft.
Decomposed Rock: 6,700 ft.
Bedded Clay: 2,100 ft.
Examples of Flyrock Travel DistancesExamples of Flyrock Travel DistancesState of Virginia/State of Virginia/Pit & Quarry 1991Pit & Quarry 1991
• Rock Distance PFLS 3,063 ft. 0.45LS 1,159 ft. 0.90LS 4.057 ft. ~1.70LS 5,050 ft. 0.70LS 4,057 ft. -------LS 6,292 ft. -------Trap Rock 828 ft. 0.68Taconite 11,360 ft. 1.20Porphyry 2,119 ft. -------Sandstone 1,987 ft. 0.53
Material Displacement via Material Displacement via AirAir GroundGround
• Primary Cause due to “Blast Confinement”
• Conventional throw from within the permit
• Material propelled by “Explosive Energy”
• Primary Cause due to “Blast Site Location”
• Common along permit boundaries
• Material propelled by “Gravity”
Points to Consider when Blasting Points to Consider when Blasting Adjacent to Permit BoundariesAdjacent to Permit Boundaries
• Displaced material has tendency to “roll” downhill &/or bounce off the permit
• Any & all “throw” has the opportunity to land or roll off the permit
• Occurrence can result even if all “Rules-of-Thumb” are observed
• Prevention requires pre-planning & thoughtfulness prior to drilling & Loading
Primary Reasons for Material Off the Primary Reasons for Material Off the PermitPermit
• Material displaced by design – the movement toward the ‘vertical free face’ by the intended use of explosive energy
• Material displaced by the adverse reaction of explosive energy - back break & swell, vibration plus unintended movement toward a natural slope or vertical outcrop
Corrective Actions When Blasting Corrective Actions When Blasting Adjacent to Permit BoundariesAdjacent to Permit Boundaries
By Blast Design @ Drilling & Loading By Blast Design @ Drilling & Loading
• Orient ‘Blast Pattern’ to ensure multi-free-face movement
• Reduce ‘Loading Densities’ in front rows of holes
• Decrease # of rows so throw from rear is lessened
• Modify ‘Drill Hole Pattern’ to facilitate a proper ‘Blast Pattern’
• Ensure proper Timing• Decrease # of rows of
holes to be loaded• Reduce ‘Loading
Densities’ in rear rows
Conventional FlyrockConventional Flyrock
• Results from available ‘Explosive Energy’ far exceeding the competency and inherit strength of overburden material being blasted
• Flyrock is not from the Hole-Collar or Stemming ejection
• Flyrock is from material adjacent to the explosive• Therefore You Require Confinement in terms of
Burden & Confinement via the Stemming
Examples of the Effects of ConfinementExamples of the Effects of ConfinementBased on Military Cratering UsageBased on Military Cratering Usage
CONFINEMENT = PERFORMANCECONFINEMENT = PERFORMANCE
All Results in Blasting Performance are All Results in Blasting Performance are Due to the Degree of Confinement, Due to the Degree of Confinement,
Based on the Columns of the Blasting Based on the Columns of the Blasting Product being Utilized for a Given Product being Utilized for a Given
Overburden MaterialOverburden Material
Bell Curve Showing Bell Curve Showing EfficiencyEfficiency of of Explosive YieldExplosive Yield & &
Blast ConfinementBlast Confinement
BURDENBURDEN is the DETERMINING FACTOR for is the DETERMINING FACTOR for
all OTHER BLAST DIMENSIONSall OTHER BLAST DIMENSIONS
BURDEN & STEMMINGBURDEN & STEMMINGDEFINEDEFINE
CONFINEMENTCONFINEMENT
Seismographs Provide Data onSeismographs Provide Data onGround Motion Over Pressure Ground Motion Over Pressure
• Real Blast Detonation Time a
check on Total Delay Time• PPV depends on Max. Lbs
per Delay & Distance, a check on # Holes/Delay Interval
• Over-Confinement yields Higher than Normal PPV
• Under-Confinement results in Lower than Normal PPV
• Assist in Determining Distance to Seismograph
• Higher than expected dBs? Confinement Concerns
• Over-Confinement results in Rifling, Cratering & Throw from Back Rows
• Under-Confinement results in Flyrock well beyond the Area of Control
TWO PRINCIPLES MUST BE KEPT IN TWO PRINCIPLES MUST BE KEPT IN MIND DURING THE DESIGN PROCESSMIND DURING THE DESIGN PROCESS
• Explosives Function Best When There is a Free Face Approximately Parallel to the Explosives Column at the Times of Detonations
• There Must be Adequate Space into Which the Broken Rock can Move and Expand
THE USBM (IC-8550 & 8925) Presented Principles by THE USBM (IC-8550 & 8925) Presented Principles by Dr. Richard Ash of “Mo. School of Mines” Dr. Richard Ash of “Mo. School of Mines”
““Rules of ThumbRules of Thumb Based on Based on TwoTwo Major Points” Major Points”
1: 1: Rock Density Rock Density is the Basis for the is the Basis for the Amount of Amount of ExplosivesExplosives Required to Break a Given Required to Break a Given Volume of Volume of
RockRock
2: Blast Designs for 2: Blast Designs for Harder Rock Require Closer Harder Rock Require Closer Control & Tighter Tolerance Control & Tighter Tolerance Than Those for Than Those for
Softer RockSofter Rock
General Causes of Flyrock General Causes of Flyrock
• Blasthole Overloading• Inadequate Burden @ Face• Excessive Burden @ Face• Loose Material in Front of Free Face • Excessive Burden Between Rows • ‘Multiple’ Row Blasts (> 5 Rows)• Inadequate Timing Between Rows• Excessive Powder Factor• Adverse Geology
For a Solution to the Flyrock For a Solution to the Flyrock Problem!Problem!
The Following is a MUST The Following is a MUST • Anticipated Blast Designs & Blasting Plans
Certified Blaster in Charge Prior to Loading - Review Drill Logs Explosives & Stemming Placed in Competent Rock
Prior to Loading check & Double check Best Management Practices for all Blasting Scenarios must be Used
What is What is COMPETENT ROCKCOMPETENT ROCK
• Competent Rock is rock that is of sufficient hardness and integrity that it Requires Explosive Energy to break into fragments to muck
• Therefore: One places not only the Explosive in Competent Rock, but also the Stemming that retains the energy
• If not, Cratering & Throw is Guaranteed !
Use When Non-Competent Rock is at the Collar of Use When Non-Competent Rock is at the Collar of the Blast Holethe Blast Hole
Adjust for Rock Type & ExplosivesAdjust for Rock Type & Explosives
Summary: Rule-of-Thumb for BurdenSummary: Rule-of-Thumb for BurdenFor First ApproximationsFor First Approximations
Typical OverburdenTypical Overburden
• Low Density Blasting Agents & Typical Rock: – Burden in ft. = 2.5 x Hole Diameter– 20 ft. of Burden for a 8 inch Hole
• Emulsions & Typical Rock:– Burden in ft. = 3 x Hole Diameter– 24 ft. of Burden for a 8 inch Hole
Rule-of-Thumb for BurdenRule-of-Thumb for BurdenContinuedContinued
• Low Density Blasting Agents in
– Weak Shale: Burden = ≥ 2.5 Hole Diameters– 22 ft. to 24 ft. of Burden for a 8 inch Hole
– Cap Rock: Burden = ≤ 2.5 Hole Diameters– 16 ft. to 18 ft. of Burden for a 8 inch Hole
Rule-of Thumb for BurdenRule-of Thumb for BurdenContinuedContinued
• Emulsions in
– Weak Shale: Burden = ≥ 3 Hole Diameters– 26 ft. to 28 ft. of Burden for a 8 inch Hole
– Cap Rock: Burden = ≤ 3 Hole Diameters– 20 ft. to 22 ft. of Burden for a 8 inch Hole
Summary: Rules-of-Thumb for StemmingSummary: Rules-of-Thumb for StemmingIn Competent Rock Where Flyrock Must be PreventedIn Competent Rock Where Flyrock Must be Prevented
• To prevent Violence stemming should vary from 14 to 28 times the B.H.D.
Example: for a 10″ dia. hole the range by the ‘blast design rules-of-thumb’ is between 0.5 to 1.0 the B. Typically 0.7 x 25 ft. = 18 feet
Using the ratios above: stemming = 14' to 28′
Additional stemming is required in competent rock when the rock sonic velocity exceeds detonation velocities or where rock is fractured or a less dense material like a shale overburden
SHORT CASE HISTORYSHORT CASE HISTORYWhen Things Go Wrong – Every Thing Goes WrongWhen Things Go Wrong – Every Thing Goes Wrong
• One Innocent Victim– Wrong Place @ the Wrong Time
• One Blaster Not Following Good Practice– Not Present– Not Communicative– Not Observant
– Not Performing per Regulations
Post-Blast High-wall Geology Post-Blast High-wall Geology
Site Conditions Prior to BlastSite Conditions Prior to Blast
Varying Geology Row by RowVarying Geology Row by RowHole by HoleHole by Hole
RESULTS: Craters & Fly-rockRESULTS: Craters & Fly-rock
SUMMARY of ERRORSSUMMARY of ERRORS
• Did not Observe Changes in Geology Visible in High-wall Faces
• Did not have Drill-Logs Available• Did not Know that Each & Every Hole Encountered a
Varying Thickness of or Type of Overburden• Did not Vary Loading Parameters Based on Varying
Material• Did not Change Stemming Lengths to Compensate for
Overburden Strengths• Did not Change Timing Between Rows to Ensure
Movement to a Free-Face (‘Rock’ Reaction Time)