Underground Ground Control Major Hazard Standard - MIRMgate

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Major Hazard StandardUnderground Ground Control** Uncontrolled copy. Use latest revision **• Are there any major structures or controllingfeatures?• What are the dips and strikes of the geologicalstructures (ore body and veins)?• What are the joint orientations, spacing andproperties?• What are the boundary conditions—prevailingstress, hydrogeological regime, geomorphologicalregime, depth?1.3 Determining the Mining Method andEquipment OptionsThe person delegated by the Mine Manager shall usethe information gathered in Section 1.3 to determinethe alternative mining methods and equipmentoptions.Whatever method is used, the following issues shallbe addressed in the Ground Control Plan:• What is the size of the deposit?• Do we need to go underground?• What are the alternative mining methods andalternative mine designs, equipment, sequencingand scheduling to minimise or eliminate theexposure of personnel to particularly hazardousexcavations? The delegate shall recommend thepreferred mining method and shall prepare thefollowing details to be included in the GroundControl Plan:– A description of the excavation layouts,orientations, sizes, shapes and type of excavationmethods in all areas of the mine for the selectedmining method– The actual or proposed serviceabilityrequirements of each excavation– Plans showing actual or proposed mine layouts• What are the methods to be used to develop steeplyinclined excavations. In selecting a rising method,the selection process should look at all the optionsin the order of preference of: non-entry methods,mechanised methods, other entry methods andladder rising. Alternative methods of establishingrises shall be considered in the mine designprocess and the need to use ladder rising designedout of the mining process where ever possible. Noladder rising shall be undertaken until anevaluation of all other alternatives has been carriedout and a risk assessment has verified that ladderrising is the only practicable method availableRefer to the supporting documentSAF-MHS01-R05 Ground Control Ladder RisingConsiderations for more detail of the issues thatshall be considered in the risk assessment.• Should dedicated, purpose-built rock-boltingapparatus be used?• What is the life of the mine?• What are the geotechnical domains (groundconditions) within the mine?• What influence will each alternative have on theregional stability?• What will be the heights and widths of drives, withconsideration given to stability, profile, and theability to inspect and scale the drives?• What extraction sequence will minimise the timeany production area remains open and active?• What are the mine design assumptions for themine?In determining the mining method and equipment tobe used, each mine shall have in place a systematicplanning and design process and a checklist orguidelines for all mine design criteria.For example, factors of safety, extraction ratios,pillar and long hole extraction sequences, maximumpowder factors, use of down-hole in preference to upholes,air, water, power and ventilation services,access and egress routes, excavation dimensions andany other factors which may be required by thatmine.1.4 Designing the Excavation and GroundControl SystemThe Ground Control Co-ordinator shall arrange for ageotechnical evaluation to be carried out for the orebody and host rock.1.4.1 Inrushes Major Uncontrolled GroundFailureTo eliminate the possibility of major uncontrolledground failure which could result in surfacesubsidence or inrushes of material such as water,mud, rock or fill material:• Each excavation or sequence of excavations (wherecaving is not part of the mining method)shall bedesigned to be stable, and the design shall be basedon sound geotechnical principles• Where the excavation sequencing is identified asbeing important for ground control, the excavationsequences:– Shall be stipulated as part of the design– Shall not be altered unless approved in writing bythe Mine Manager• The procedures and processes to create theexcavations shall not be designed to induceuncontrolled instability, either locally or regionally• During excavations, any deviations from the planor design shall be recorded, and the design reevaluatedto ensure local and regional stability ismaintained.SAF-MHS-01 Rev. 1 DOCS No. 55945 Issued: 19/06/00 Page 3 of 23
Major Hazard StandardUnderground Ground Control** Uncontrolled copy. Use latest revision **For all the excavations identified, a design andanalysis process shall be conducted to determine thedesign of the ground support, reinforcement and anyother ground-control procedures to be used duringthe actual excavation process.Refer to the standard SAF-MHS-09 Inrushes andSubsidence for more detail on inrushes.1.4.2 Determining the Most Appropriate GroundControl SystemIn determining the most appropriate ground controlsystem, the Ground Control Co-ordinator shall takeaccount of the following:• All excavations which do not meet therequirements of the current mine ground supportstandards for that excavation and rock type shallbe re-evaluated with regard to support requirementson a prioritised basis. The basis for priorities shallbe determined by a risk assessment.• The life and serviceability of each excavation type• The feasibility of installing the ground controlsystem in one passThis depends on the serviceability of theexcavation using approaches such as mesh,shotcrete or other methods to reduce the need forongoing maintenance and the need to be resupported.• If backs are higher than 3.5 m, an inspectionplatform shall be used to identify, scale and controlrockfall hazards. Manual sounding and scalingusing an appropriate steel scaling bar is the finalmethod of scaling.• To reduce the risk of rockfalls, perimeter blastingtechniques, type of explosive, blast holeorientation, blast hole size and patterns should beconsidered when designing and profilingexcavations• The adequacy of the defined minimum groundsupport standards for each excavation and rocktype shall be reviewed at least on an annual basisor more frequently if experience with groundconditions in the mine dictate.As a minimum, the following shall be considered:• What does the core log information(e.g. MRMR, Q, RQD) indicate about the rockmass?• What are the joint properties, block size and shape?• What are the geotechnical regions (e.g. stress,hydrology)?• What are the potential modes of failure?• What excavation shapes (e.g. shanty backs, archedprofile) would minimise the probability of arockfall?• What blasting techniques, such as perimeterblasting, sequence options and pattern designs, areto be used to reduce potential instability?• What is the optimal ground support andreinforcement technologies to control the modes offailure?• Application of a factor of safety to be used in thedesign of the ground support and reinforcement forvarious excavations?• What are the most appropriate (i.e. serviceable,stable and practical) ground support andreinforcement designs?1.4.3 RisingAny method of rising shall minimise the exposure ofpersonnel to a rockfall hazard.The process for designing a rise should follow thesesteps:• Determine the purpose of the rise i.e. the use forthe rise and its serviceability• Determine the size, orientation and location of therise based on the physical layout usage constraintsand ground conditions• Based on the geotechnical conditions, define:– the maximum credible rockfall that could fallfrom inside the rise (size and height of fall)– the ground control strategy required to controlany rockfall.• Determine the excavation method• Review the geotechnical conditions, size andorientation and the excavation method to determineif they are acceptable• Determine a re-entry time based on known orexpected ground conditions• Determine the services required for the excavationof the rise e.g. water pressure, air, electricity.If a risk assessment has verified that ladder rising isthe only practicable method available it shall be donein accordance with SAF-MHS01-R05 GroundControl Ladder Rising Considerations.1.4.4 Raise BoringRaise boring is considered a method of rising and assuch the requirements of rising apply.1.5 Preparing the Multi-tiered Response PlanA multi tiered response plan shall be developedwhich authorises additional ground support, over andabove the minimum support, to be installed inresponse to excavation performance. The Plan shallinclude a recording and analysis system and have theminimum standards as the base line.SAF-MHS-01 Rev. 1 DOCS No. 55945 Issued: 19/06/00 Page 4 of 23
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Underground Ground Control Major Hazard Standard - MIRMgate

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