African Mining February 2021 | Page 20

• OPERATIONS

HEED REGULATIONS WHEN BLASTING CLOSE TO BUILDINGS

Strict regulations and principles apply when mine blasting is to be conducted within half a kilometre ( 500m ) of buildings or areas with any significant human activity to avoid injury and damage to property , writes Nico Pienaar , director of surface mining industry organisation Aspasa .

The requirements of the relevant Mine Health and Safety Act

Explosives Regulations , 2018 - Regulation 4.16 ( 2 ) are clear and should provide a minimum baseline for procedures to ensure safe blasting . The regulation covers all aspects of the requirement and in addition to providing safe blasting , compliance with the regulation mitigates legal action in the event of a mishap .
To understand the regulation , it is best to break it down and note that it needs to be applied wherever blasting operations are to be carried out within a horizontal distance of 500m from structures and places which may be necessary to protect to prevent any significant risk ; and to provide some guidelines regarding the application to be submitted to the Principal Inspector of Mines ( PI ) for written approval .
Assessing risks The employer must also take reasonable measures to ensure that no blasting operations are carried out within a horizontal distance of 500m of any public building , public throughfare , railway line , power line , any place where people congregate or any other structure , which it may be necessary to protect to prevent any significant risk .
This is unless a risk assessment has identified a lesser safe distance and any restrictions and conditions to be complied with or a written application is submitted to the PI accompanied by the following documents for approval : i . A sketch plan indicating the distance from the blasting area to the affected structures . ii . The risk assessment . iii . A proof of consultation with the owners of the affected structures and iv . Restrictions and conditions . ( c ) a written approval has been granted by the Principal Inspector of Mines ; and ( d ) any restrictions and conditions determined by the Principal Inspector of Mines are complied with .
The Regulation provides clear requirements for the application to be submitted to the PI for decision - Reg . 4.16 ( 2 ) ( a ) and ( b )
18 • African
Mining • February 2021 the application must provide the following safety , technical and legal aspects :
• Risk assessment in consultation with the explosive ’ s supplier and other subject matter experts identify structures and places to be protected .
• Determine the minimum distance blasting to be carried out .
• Specify and articulate measures to limit blast induced hazards including recommended restrictions and conditions ( air blast , ground vibrations and fly rock and dust ).
The application must prove consultation with the owners of the affected structures and how any concerns will be addressed .
Measuring blasts Limiting and measuring of blasting-related hazards is an interesting and complex field , which can fill an entire book . However , if we limit the discussion to a high-level overview relevant to air blast and ground vibration it is clear to see the complexity . Although numerous regulations place the onus on the mine owner to ensure that the blasting operations do not cause damage to private property , there are no statutory limits for air blast and / or ground vibration , laid down in South African law .
The mine owner , in turn , relies on advice from experts such as engineers employed by the major suppliers of explosives or independent consultants . The South African Bureau of Standards ( SABS ) adopted the International Organisation for Standardisation ( ISO ) standard ISO4866 ( 2nd edition in 2010 ) which provides guidelines for the measurement of vibrations and evaluation of their effects on fixed structures , not safe limits of vibration for structures .
Explosive manufacturers and suppliers in South Africa generally play a key role and make recommendations based on the USBM RI 8507 limits tables :
• Maximum PPVs at frequencies below 50Hz are recommended for a variety of building types .
• Maximum charge sizes ( per delay ) for a range of distances to ‘ typical ’ and ‘ sensitive ’ structures . Compilation of vibration limits
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