Pengenalan singkat mengenai tambang bawah tanah dan faktor kritis permodelan geologi dan estimasi sumber daya dan mitigasi kesalahan penaksiran
Mining divided into 2 types:
- Surface mining
This method is used for near surface / shallow deposit and has lateral or horizontal distribution. This method considers surface soil/overburden/waste that must be dug and how big ore body can be mined. This ratio is known as stripping ratio. If stripping ratio is still economic, surface mining becomes priority, yet this method has weakness such as higher potential of environmental damages and needs outsized area to banish the waste.
- Underground mining
If surface mining is deeper, so its stripping ratio and production cost will increase. When surface mining is not economic any longer, surface mining need to be replaced by underground mining. Underground mining needs higher operational cost. This method considers lot of critical factors according to condition of subsurface, such as : air ventilation, groundwater draining, geotechnical, and mine plan.
The principle is to ensure the availability of ore was worthy according to plan during the LOM (Life Of Mine) through suitable mine plan scheduling (schedule mining plan).
In underground mines, mining plan schedule should be arranged so that the pressure (stress) can be evenly distributed and not collected at one location within a specified period. Mine schedule issued by mine engineering and undertaken by the operation group by arranging draw document-order form (short term plan). Draw-order in principle establish how many tonnase / bucket to draw from each draw points. Monitoring the draw-order performed using manual recording of operator and sensors in each draw-draw-point to ensure the order is followed properly. Draw-order information is based on block model of geology (resources / exploration model or ore control / mining model).
Block Model Geology is a result of the computational geological modeling activities and resource estimation that is displayed in the form of blocks. Each block reflects the geological information such as rock type, alteration, geological structures and resource information such as copper-gold grade, RQD character and so forth. There are two common types of block models:
- Regular block models where each block has the same size.
- Irregular block models where the block size is different.
Block model is a combination of geological modeling and resource estimation for both since they relate to each other.
Geological modeling is a process of interpretation using the data surface mapping (2D), the data sub-surface (3D-Drilling data) additional data and other (Geophysics, Magnetic susceptibility) which aims to describe the extent and limits of units of certain geological (can be any type of rock, the type of alteration-mineralization and characteristic of geological structure) and deformation of geological conditions (regional and local).
Resource estimation is the process of calculating the total tonnage and grade material valuable ore from a sediment geological performed using various mathematical approach and geological limits (limit ore-waste, contact rock types, the deployment of alteration and mineralization and type deposit geology) so as to provide best information for the mining process. Resource estimates done due to the limited number of samples or data points, and also because of a design limitation ideal exploration. There are two common types of resource estimation exploration model (resource model) and mining model (ore control model / reserve model).
Reconciliation is an indicator of the success of mining. Reconciliation can provide information for improvement include:
- The estimation of better method
- Mine design more efficient
- Good mine schedule and plan
- Mining techniques to minimize ore loss and dilution
Delimitation – extraction error relates to the process of selecting and taking the wrong / unrepresentative sample. Analytical error is caused by protocol violations in sample preparation and assaying of samples. Geological Error is fault in determining geological periphery. Geostatistical error is mistake in determining wrong estimation.