Jim Dowling - Mining Engineer

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SUBLEVEL OPEN STOPING (SLOS)

 

Sublevel start positions are created by a trackless ramp at around 1 in 7 usually in the footwall. Stopes are mined by sublevel development advancing along the vein to the stope limit, followed on the retreat by slot raising and progressive blasting of the intermediate pillars with longholes. The stope remains open during its working life but may be subsequently filled as a convenience or to aid pillar recovery. Broken ore falls to the bottom of the stope where drawpoints are used for loading.

 

 

Longitudinal and cross section of SLOS showing sublevel development from the ramp to the stop position – in this case a rib pillar

Longitudinal and cross section of SLOS showing sublevel development from the ramp to the stop position – in this case a rib pillar

 

 

Longitudinal section of SLOS showing slot raising and drawpoint development

Longitudinal section of SLOS showing slot raising and drawpoint development

 

 

Longitudinal section of SLOS showing longholes and mining direction

Longitudinal section of SLOS showing longholes and mining direction

 

 

Longitudinal section options for SLOS stope faces

Longitudinal section options for SLOS stope faces

 

 

Cross sections showing different sublevel orientations for differing vein conditions

Cross sections showing different sublevel orientations for differing vein conditions

 

The planning options shown in the sketch above are applicable as follows:

1. Narrow vein, say around 2–5 m. Hanging and footwall exposed in the sublevels, parallel long hole drilling. Good recovery and dilution.

2. Medium vein, say 5–12 m. Strong orebody, allowing wide sublevels. Hanging and footwall exposed in the sublevels, parallel long hole drilling. Good recovery and dilution.

3. Medium to wide vein, say >10 m. Weak orebody does not permit wide sublevels. Hanging and footwall exposed in the sublevels, fan drilling. Good recovery and dilution. More expensive layout – two sublevels per drilling horizon.

4. Wide or variable vein, say >20 m. Predictable contacts. Lower value ore does not allow method 3 (fewer sublevels). Ring drilling so potentially poor recovery and dilution.

5. Irregular vein, narrow so contacts exposed in sublevels. Parallel drilling – good recovery and dilution as long as the vein is straight between sublevels – unlikely scenario.

 

 

Isometric view of longitudinal SLOS in a medium to narrow vein

Isometric view of longitudinal SLOS in a medium to narrow vein

 

 

Isometric view of transverse SLOS in a wide vein

Isometric view of transverse SLOS in a wide vein

 

 

Longitudinal section of SLOS showing the formation of rib pillars

Longitudinal section of SLOS showing the formation of rib pillars

 

 

Longitudinal section of SLOS showing the formation of waste pillars

Longitudinal section of SLOS showing the formation of waste pillars

 

 

When a straight ramp is used, awkward pillars are left where mining stops when stoping retreats back to the ramp crosscuts

When a straight ramp is used, awkward pillars are left where mining stops when stoping retreats back to the ramp crosscuts

 

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