Code of Practice - Department of Mines, Industry ...

1 Surface Rock Support for Underground MinesCode of Practice code of PracticeMOSHABM ines Occupational Safety and Health Advisory BoardWestern AustraliaFebruary 1999 SURFACE ROCK SUPPORT FORUNDERGROUND MINESCODE OF PRACTICEMINES OCCUPATIONAL SAFETY AND HEALTH ADVISORY BOARDWESTERN AUSTRALIAFEBRUARY 1999 Surface Rock Support for Underground Mines iCode of PracticeSURFACE ROCK SUPPORT FOR UNDERGROUND MINESCODE OF PRACTICETABLE OF CONTROL Drilling and Blasting .. Support (Rock Reinforcement & Surface Rock Support).

2 Surface RISK 1:Legislative 2:Flow Diagram - Compliance with the code of 3:Geotechnical Risk 4 Rock Support for Underground Mines1 code of PracticeSURFACE ROCK SUPPORT FOR UNDERGROUND MINESCODE OF PRACTICEFOREWORDThe Surface Rock Support for Underground Mines code of Practice (hereafter referred toas the code ) applies to all underground excavations in which persons may travel or workand includes development headings and entry-method code is framed on the assumption that the necessary primary rock reinforcement is inplace to ensure the general structural stability of the code introduces the requirement to install surface rock support in high headings(ie.)

3 Those greater than or equal to a nominal in height) in all Western Australianunderground mines unless a documented geotechnical risk assessment justifiesotherwise. Where surface rock support is installed, it shall be applied to backs andside walls that are a nominal from the floor of the requirements in the code do not detract from the obligations contained inRegulation of the Mines Safety and Inspection Regulations of surface rock support, such as mesh, shotcrete or other surface treatment, inaddition to existing or primary reinforcement methods may be necessary to control the riskof injury and death that can result from small rock falls from between the installed rockreinforcement rock support is not intended to replace existing ground reinforcement methods butshould be used, where required, in conjunction with these methods, and integrated into themine s ground control system or code specifically addresses gravity induced rock falls.

4 Dynamic rock failuremechanisms are not covered by the code and must be controlled by appropriate meansaccording to the identified code should be read in conjunction with the Department of Minerals and Energy(DME) Guidelines Geotechnical Considerations for Underground Mines and UndergroundBarring Down and code has been developed through tripartite consultation and has been approvedunder Section 93(1) of the Mines Safety and Inspection Act 1994. The legislativeframework which supports the code is outlined in Appendix process for achieving compliance with this code of Practice is outlined In Appendix Rock Support of Underground MinesCode of falls are an ever-present hazard in underground mining, especially in unsupportedground.

5 They are primarily caused by discontinuities and/or high or low adverse stresses inthe rock mass. The intersection of three or more joints or fractures with the back, face orside wall of an excavation may create unstable blocks of rock. These blocks may fall or beejected into the excavation with little or no prior warning, and pose a serious risk of injury support is installed to ensure the stability of the excavation and minimise the risk ofinjury. Ground support must match the ground conditions and the excavation geometry forthe life of the excavation and must take into account both inherent and presence of ground support however does not necessarily guarantee that there will beno rock falls.

6 While an excavation can be stable in terms of its overall structure it may notnecessarily be safe. Localised surface failure can present serious combination of one or more of the following may result in unexpected rock falls: Deteriorating ground conditions; Inappropriate ground support; Inadequately installed ground support; Ground support that has deteriorated (corroded) over time; and Mining-induced or natural check-scaling is a critical step in the ground control program to maintain theintegrity of the low profile headings, that is, those nominally less than high, with adequate andcorrectly installed ground support, a person can readily visually check for localised surfacerock failure and make safe the heading or excavation with the use of a scaling.

7 In headings higher than it becomes increasingly difficult to check and scalesafely without the use of equipment to access the high backs and side walls. In addition,cap lamp illumination is inadequate for high high headings where surface rock support is installed the need for regular checking isreduced and the integrity of the excavation is greatly Rock Support for Underground Mines3 code of CONTROL METHODSSome of the methods that are available to limit or control potential rock falls include: Controlled drilling and blasting techniques; Scaling (manual and mechanised).

8 And Ground support (rock reinforcement and surface rock support), including: Meshing; Strapping; Shotcreting; and Other Surface list of controls is not necessarily exhaustive, it is likely that new techniques will bedeveloped with method is dealt with in detail Drilling and BlastingSubstantial and unwarranted damage to the rock at the perimeter of an excavationcan result from the use of inappropriate drilling and blasting practices . Controlleddrilling and blasting practices are designed to cut the rock rather than generaldemolition of the rock damage due to drilling and blasting can be minimised by: Correct placement and alignment of the holes; Selection of appropriate hole diameter, spacing and burden for blast holes, inparticular perimeter holes; Use of suitable explosives charges (eg.)

9 Low energy or decoupled) in theperimeter holes; Considering the influence that blast holes adjacent to the perimeter holes hason rock damage and, where appropriate, varying the burden, spacing andcharge density; and Where necessary, seeking the advice of the explosive manufacturer(s) on theappropriate use of various combinations of explosives and initiation system(s).Where good controlled drilling and blasting practices are consistently achieved therewill be a significant decrease in the risk of localised rock involves removing loose rock from the walls, face and backs of theexcavation.

10 Careful attention should be paid to the following: Identifying the ground conditions; Manual scaling procedures; Mechanised scaling procedures;4 Surface Rock Support of Underground MinesCode of Practice Scaling procedures for large potentially unstable blocks; Scaling procedures in ravelling ground; Progressive scaling and installation of support; Scaling in high headings; Scaling in narrow headings; and Regular check scaling of main discussion on scaling is contained in the DME Guideline UndergroundBarring Down and Support (Rock Reinforcement and Surface Rock Support)