| 3.1. |
The use of bagged stone dust barriers |
The use of bagged stone dust barriers is an alternative to employing shelve (polish) stone dust barriers or water barriers.
| 3.2. |
Minimum requirements of bagged barriers |
| 3.2.1. |
Each plastic bag must contain either 5kg for low seams or 6kg for high seams of dry stone dust complying with the specifications specified previously. |
| 3.2.2. |
The quality, hook and ring as well as the rupture characteristics of the plastic bags used in bagged stone dust barriers must comply with the specifications of the products tested at the GP Badenhorst research facility. Documentary evidence as to the source and quality at each batch of bags purchased must be kept at the mine. |
| 3.2.3. |
COPs must detail how the bags are to be closed so as to exude water when bags are installed in barriers underground. |
| 3.2.4. |
COPs must clearly specify how the bags are to be suspended below the roadway roof. |
The system must ensure that the vertical distance between suspended bags and the roof, and the horizontal distance between bags and between the outer bags and sidewalls, are to be maintained at all times.
| 3.3. |
Construction of bagged stone dust barriers |
The following requirements on the construction of a bagged stone dust barrier apply:
| 3.3.1. |
The horizontal distance between the hooks of the bags on a plane must be not less than 0,4m and not greater than 1m when measured across the roadway width. The actual distances are determined by the total mass of stone dust that needs to be incorporated into a barrier which is itself determined by the roadway dimensions. To cover a range of workings heights, the following requirements apply: |
| 3.3.1.1. |
For roads in the height range of less than 3,0m, each row must have a single level of bags suspended below the roof; |
| 3.3.1.2. |
For roads in the height range 3m to 3,5m, each row must have a single level of bags suspended not more than 0,5m below the roof; |
| 3.3.1.3. |
For roads in the height range 3,5m to 4,5m, each row must have two levels of bags suspended at approximately 3m and 4m above floor level; |
| 3.3.1.4. |
For roads in the height range of more than 4,5m but less than 6m, each row must have three levels of bags suspended at approximately 3m, 4m and 5m above floor level; |
| 3.3.1.5. |
The distance between the bags and the side of the pillar must not be nearer than 0,5m and not further than 1m. |
| 3.3.1.6. |
The distance measured along the road between rows of bags within the barrier must be not less than 1,5m and not greater than 3m; |
| 3.3.1.7. |
If MA is the mass of stone dust based on cross-sectional area and MV is the mass based on volume, then MA must be at least 100kg per square meter of cross-section area and MA must be at least 1kg of stone dust per cubic meter of roadway volume; and |
| 3.3.1.8. |
The total mass of stone dust to be used in a barrier must be based on the greater of MA and MV. |
| 3.4. |
Layout of the stone dust barrier |
A full-bagged stone dust barrier must consist of four sub-barriers installed over a minimum distance of 100m of continuous roadway.
Three complete sub-barriers must be in position at all times, while the fourth sub-barrier may be in the process of being moved ahead as the section advances. The following distances must be maintained:
| 3.4.1. |
The first sub-barrier, closest to the last road, must not be installed closer than 60m and not further than 120m from the last through road; |
| 3.4.2. |
The fourth sub-barrier, furthest from the last through road, must be installed not more than 120m from the first sub-barrier; |
| 3.4.3. |
The two intermediate sub-barriers must be equidistant between the first and fourth sub-barriers; |
| 3.4.4. |
The presence of splits must be ignored in determining distances; and |
| 3.4.5. |
The maximum distance between sub-barriers must not exceed 30m. |
| 3.5. |
Siting of bagged stone dust barriers |
| 3.5.1. |
Conveyor belt roads |
An inertisation barrier must be provided in every production section in the road carrying a conveyor belt. The construction of the barrier will be based on the dimensions of the belt roads.
Every single entry must be protected with a barrier the same as per conveyor belt roads.
Must be protected either by high level of incombustible matter (80%) for the first 1000 m out bye of the face area or by a barrier to be installed and moved forward in line with the conveyor belt road barrier. Thereafter a 65% of incombustible matter must be maintained.
Gas Regulator Levies Act, 2002
