Before any Regional / Local / Geological or Protection Pillar can be extracted a comprehensive Issue Based Risk Assessment must be conducted for each pillar that will be extracted, the following procedures must form part of the detailed Risk Assessment and be signed off by all concerned. The risk assessment must also detail the mining method and sequence that must be followed.
Survey
- Surveys plans are to be acquired and referred to before pillar extraction.
- Pillars envisaged to be extracted are to be scanned and updated on Survey plans before mining commences, this must include all the latest geological information and all the required information from the ventilation and rescue plan.
Reece Procedure
- Reece Procedure to be followed as outlined in the applicable SOP 121- Reece Procedure I Abandoned
- Areas which should be signed off before undertaking a recce, this must also be led by a competent person.
- Access and second escape way to be determined and inspected from plans and during underground assessments.
- Ventilation and temperature to be taken regularly in the proposed working area.
- Entry examination and safe declaration to be completed as required in the appropriate SOP before any mining may commence
- A Reece register should be implemented whereby survey and mining keep records of areas investigated. Comments on mine plans to ensure that areas previously deemed non-minable, for various reasons, to avoid duplication of work. Documentation for this purpose should be kept by the MRM department.
Pillar Categorization
- Note the type, size and shape of the pillar.
- Specify the purpose and the reasons for the extraction of the pillar. Note the type of support that the pillar provides, if a support pillar.
- Note all geological structures and ground conditions surrounding the proposed pillar to be extracted. Choose which pillars to be extracted (grade & ground condition play a role in choosing which pillars to be extracted).
- Note current scaling from the pillars in the area.
- What is the depth below surface of the identified pillar.
Support
- Decide if the normal SOP-1 standard or if Special Area instructions are required to extract the identified pillar, this will be based on the outcome of the detailed risk assessment.
- Support to be installed on the extraction side of the pillar under Special Area
- Current installed support in the area surrounding the identified pillar. Condition of the installed support.
- Large unsupported span in the area.
- Are there any large falls of ground in the area.
Pillar mining
- Note pillar extraction percentage/undercutting and which pillars to be extracted. Pillar extraction sequence e.g. Top to down and /or retreat sequence.
- Cleaning of material above and surrounding the pillar and the repercussions thereof.
- In general Pillars not to be split. However, if the circumstances require this, the Risk Assessment should stipulate the mining and support requirements under the Special Area Instruction.
- Barricades to be installed in all areas that the pillar extraction affects.
Blasting
- Advance rate to be determined by the Risk assessment and recommendations.
- Blasting only of one pillar at a time per area (no multi-pillar blasts) unless otherwise specified by the Risk Assessment and commensurate Special Area instruction.
- Extraction volume to be determined by the Risk assessment and recommendations. This will entail whether multiple pillars will be mined simultaneously.
Post Pillar Extraction Procedure
- Area to be re-surveyed after pillar extraction.
- All falls of grounds to be noted and demarcated on the survey plans.
Special Area
- All pillar extraction area s must be declared as Special Areas and have detailed support requirement, mining method and sequence which must be signed off by all concerned in the extraction process. These stipulations will form part of the Special Area Instruction.
- Pillar extraction areas should follow the Pillar Extraction Procedure.
