Introduction
In open pit mining rotary core drilling is the most widely used method of subsurface investigation. For pit slope design, it helps determine within acceptable levels of confidence the geotechnical relationships and engineering properties of the rocks that will form the walls of the pit.
Planning and scoping (Guidelines for Open Pit Slope Design – 1st Edition – John Read – Peter, n.d.)
Planning and scoping the objectives of the drill hole are the most important steps of the drilling investigation. There must be clear primary and secondary objectives to extract the maximum amount of potential information.
For example, geotechnical data collection may be the primary objective of the hole, but at the same time it may be possible to gain important geometallurgical and/or geohydrological information and/or use the completed hole for groundwater or other monitoring purposes.
Ideally, before objectives are finalised, they should be reviewed by a multidisciplinary team to ensure that all such possibilities have been taken into account. There are other critical points.
- Before the location and orientation of the drill hole are finalised, the objectives of the hole must be checked to ensure they are consistent with the current geological, structural and hydrogeological models.
- When they have been finalised, the objectives of the drill hole must be recorded in a written memorandum that includes alternative actions in case drilling difficulties are encountered and/or it is not possible to complete the hole. The memorandum must be signed-off by all members of the team responsible for preparing the document.
- Before drilling commences, the rig site should be reviewed to ensure its location is compatible with all current and planned mining activities in the area.
- When drilling commences, it is essential that the core be photographed and logged by a properly qualified and experienced person at the rig site before it is disturbed and moved from the site to the core shed.
- Each step in the drilling process must be owned by the appropriate person. For example, the driller must accept responsibility for the core recovery process, the engineering geologist for the core logging and any downhole testing, and the environmental team for decommissioning the site.
- A plan and geological section showing the drill hole trace and the expected geological/structural pierce points should be available to the drillers and loggers at the rig site.
- The drilling and logging and any downhole testing must be regularly reviewed using an appropriate QA/ QC procedure.
- The potential of the drill hole for future monitoring and/or downhole testing should be continuously reviewed.
The importance of planning and scoping in core drilling
Planning and scoping is an important phase in any core drilling operation to ensure efficiency and cost optimisation. This crucial aspect helps to minimise risks by maximising the chances of obtaining good quality data, whether in mineral exploration drilling, geotechnical investigations or even groundwater studies. As a result, it offers a number of advantages.
Optimising drilling costs
Drilling is one of the most expensive phases of exploration or site investigation. A well-planned campaign ensures efficient resource allocation and avoids unnecessary drill holes, reducing overall costs. Selecting the right drilling method (diamond core drilling, sonic drilling, etc.) ensures the best balance between cost and quality.
Defining clear objectives
Proper scoping ensures that drilling is conducted with a clear purpose, whether for ore body delineation, rock property assessment, or hydrogeological studies. It Helps in determining target depths, hole orientation, and sampling intervals to obtain the most relevant data.
Ensuring Data Quality and Accuracy
Good planning helps select the correct core diameter (HQ, NQ, PQ) to balance sample recovery and geological detail. It ensures proper drilling fluid selection and techniques to minimize core loss and contamination.
Geological and Structural Understanding
Pre-planning with geophysical surveys, geological mapping, and historical drill data improves the placement of drill holes. It ensures that drill holes are positioned to intersect the target structures at the best angles for meaningful results.
Conclusion
Planning and scoping is a key aspect as far as core drilling program is concerned. A well-planned and properly scoped drilling program reduces costs, enhances safety, ensures data quality, and optimizes exploration success. It serves as the foundation for accurate geological interpretations and informed decision-making in mining and geotechnical projects.
Reference
Guidelines for Open Pit Slope Design—1st Edition—John Read—Peter. (n.d.). Retrieved January 29, 2025, from https://www.routledge.com/Guidelines-for-Open-Pit-Slope-Design/Read-Stacey/p/book/9780415874410?srsltid=AfmBOoooj-LceHcry67vBKTfXqyMCLqgPBvXg1VywTGF-elgzTRLJBEd
