factors in design

8/8/2019 Factors in Design

1/19

PRESENTATION ON

Factors in Designing of Blasts, Flyrock,Industrial Explosives used and safe operation

of Bulk Explosives in opencast mines

PRESENTED BY

RAVI GADI


2/19

OPEN CAST BENCH BLASTING, THEFACTORS THAT INFLUENCE THE QUALITY

OF OUTPUTCONTROLLABLE :

Hole dia, Burden (B),

Spacing (S), B/S ratio, Depth, Bench height, Subgrade, Stemming height, Stemming.material, Pattern of drilling, Size of the blast, Blast direction, Inclination of holes,


3/19

OPEN CAST BENCH BLASTING, THEFACTORS THAT INFLUENCE THE QUALITY

OF OUTPUTCONTROLLABLE :

Initiating system, Initiation sequence,

Free face, Type / energy of explosives, Charge geometry, Method of loading explosives, Presence of water

UNCONTROLLABLE : Geology of rocks, Material strengths & properties, Structural discontinuities, Weather conditions,

Water


4/19

THE OUTPUTS OF ANY BLAST ARE

FRAGMENTATION: Muck pile displacement Muck pile profile Ground vibrations Air blast

Back & side breaks Oversized fragments Fly rock/ misfires etc.

Designing of Blasts, Flyrock, Industrial Explosives and Safeoperation of Bulk Explosives

The success of any blast lies in maximizing the desiredparameters like quality of fragmentation, muck piledisplacement, profile while minimizing the unwanted outputslike ground vibrations, air blast, back & side breaks, oversized

fragments, flyrocks/misfires etc


5/19

BASICS OF ANY BLAST DESIGN:

Hole dia ( H/5 inches - H in ft ) Burden ( 20 35 D) Spacing ( 1 2 B; opt. 1.25B) Height ( 2 B ) never less than B Subgrade ( 0.2 0.5 B)

Stemming ( 0.7 1.3 B) Stemming material (Mtl 2-5% of dia, gravel) Loading density(0.0007857xD2xCf) Decking (soft zones, distribution of energy, vibrationcontrol) Min.deck : 6xD Powder factor(Cum or Tons per Kg) Specific Charge or Charge factor (Kg per Cum or Ton) Energy Factor (Kcal/Cum or Ton) Bottom Charge ( 0.3-0.5 B+Subgrade) Pre-splitting Drilling patterns/ Firing sequences


6/19

FLYROCK ISSUES IN BLASTING:

Analysis indicates that lack of blast area security,flyrock, premature blasts, and misfiresare the fourmajor causes of blasting-related injuries in surfacemining operations. Flyrock and lack of blast area

security issues continue to pose problems forblasters.

Generally, flyrock is caused by a mismatch of theexplosive energy with the geomechanical strengthof the rock mass surrounding the explosive charge.Factors responsible for this mismatch include:


7/19


* Abrupt decrease in rock resistance due to joint systems,bedding layers, fracture planes, geological faults, mud seams,voids, localized weakness of rock mass, etc.

* High explosive concentration leading to localized high energy

density,

* Inadequate delay between the holes in the same row, orbetween the rows,

* Inappropriate blast design,

* Deviation of blast holes from its intended directions,

* Improper loading and firing practice, including secondaryblasting of boulders and toe holes.


8/19


a) BURDEN

b) BLAST HOLE LAYOUT AND LOADING

c) GEOLOGY AND ROCK STRUCTURE

d) STEMMING

e) DETONATOR FIRING DELAY

f) LACK OF BLAST AREA SECURITY


9/19

BULK EXPLOSIVES

1. Definition

2. Explosive formation

3. Properties of explosives

4. Chemicals used and function

5. How the bulk explosives are manufactured

6. Delivery to site

7. Safety features in the system


10/19

Safe Practices while operating themobile unit for use of bulk explosives:

A. At the plant safe practices for loading of pre-mix:

(i) Select and wear personal protective equipment appropriate

for work activities,

(ii) Inspect work area and establish, barricade and signpost

loading area,

(iii) Identify, address and report potential risks and hazards,

(iv) Segregate incompatible goods prior to loading the vehicle

according to legislation

and Codes of Practice

(v) Inspect mobile processing unit for safe loading of

explosives materials


11/19



(vi) Ensure attachments comply with standards and licensing

requirements

(vii) Placard mobile processing unit and attachments to show

the goods carried, hazchem identity and emergency

information according to legislation and Codes of Practice

(viii) Check that safety equipment is fitted and ready for use

according to legislation and Codes of Practice

(ix) Calculate batch quantities for ingredients to manufacture

explosive to specification, and check availability of ingredients

(x) Apply parking brake throughout materials loading operation


12/19



(xi) Load materials in a safe manner to prevent spillage or

injury to personnel and observe emergency procedures

(xii) Record the details of all materials loaded according to site

procedures and legislative Requirements

B. Safe practices for Transportation to site:

(i) Carry out vehicle pre-start checks

(ii) Confirm and adhere to pre-planned route

(iii) Operate vehicle according to road conditions and in

compliance with established mine safety rules and speed limit


13/19


B. Safe practices for Transportation to site:

(iv) Follow emergency procedures for accidents that result in a

dangerous situation

(v) General precautions and rules regarding handling and

transportation of explosives shall be observed

C. Safe practices during charging of boreholes at theMine site:

(i) Select most appropriate borehole discharge point and lay

hosepipe over blast hole

(ii) Confirm the identity of blast hole and explosive loading

requirements with relevant personnel as per the blast design.

Only necessary minimum persons shall be allowed.


14/19



(iii) The area surrounding the mobile unit, not less than 10m in

all direction shall be kept free of rubbish or any combustible

material.

(iv) Before mixing and delivery from the mobile unit to any

borehole, the vehicle shall be properly earthed with chain link.

(v) Ensure that, hose with anti-static properties only should be

used.

(vi) Regulate the discharge of explosive to the blast hole to

achieve specified weight or stemming height as per the blast

design


15/19



(vii) Complete loading hole and prepare vehicle for next blast

hole by ensuring area is clear and safe to move vehicle

(viii) No smoking and no open flame should be allowed within

60m of the mobile unit

(ix) Due care shall be taken to ensure that the pre-mix is

pumped into properly drilled holes and there is no spillage.

(x) Charging of the explosives shall be done in such a manner

that to ensure continuity of the explosive column in each

borehole. For deck charging also continuity is to be ensured.


16/19



(xi) Area of loaded holes shall be conspicuously marked by

visible bright red flags during day light hours and by

fluorescent signs during night hours and unauthorized entry

shall be cordoned off effectively.

(xii) All operation of charging and firing shall be done in

daylight hours only.

(xiii) Explosives should not be allowed to sleep over in the

borehole, unless required permission obtained from the DGMS

or safety authority.

(xiv) Complete records required by site and legislation


17/19



(xv) In case of misfires, precautions as laid down in variouscoal / metal mines regulations shall be strictly followed.

(xvi) The entire operation of loading, transportation and

charging of explosives to the site shall be placed under a

competent and capable mining engineer.


18/19


D. Safe practices after completion of charging:

(i)After completion of charging operation, the mobile system

including hose should be emptied of explosives by evacuating

compressed air flushing with water. At the end of the operation

for the day, the mobile vehicle including hose shall be

completely cleaned and the vehicle shall be parked at the

support plant.(ii) All spillages of explosives shall be collected and destroyed

at a safe place and the effluents are discharged after proper

treatment


19/19THANK YOUTHANK YOU

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