Built by a geologist

Geotechnical Logging

Geotechnical logging captures rock mass quality information essential for mine planning, ground support design, and understanding structural controls on mineralization. Rock Quality Designation RQD RQD measures the degree of jointing/fracturing in rock: Formula : RQD = Sum of core pieces ≥10cm / Total core run length × 100% RQD Classification | RQD % | Rock Quality | |-------|--------------| | 90-100 | Excellent | | 75-90 | Good | | 50-75 | Fair | | 25-50 | Poor | | 0-25 | Very Poor | RQD Measurement Rules - Only count pieces ≥10cm along the core axis - Ignore mechanical breaks fresh, fit together - Count natural fractures and joints - Measure per core run typically 1.5m or 3m Core Recovery Formula : Recovery = Length of core recovered / Length drilled × 100% Low Recovery Causes - Fault zones and gouge - Soft or friite material - Voids and cavities - Drilling problems Important : Low recovery zones often coincide with mineralization veins, faults - always note and sample what remains! Structural Logging Measuring Orientations Angles are measured relative to the Core Axis CA : - Alpha α : Angle between structure and core axis - Convert to True Dip using known hole orientation Structural Features to Log - Joints and fractures natural vs. mechanical - Veins and veinlets - Bedding/foliation - Faults note gouge, slickensides - Contacts lithological, intrusive Fracture Description For each significant fracture, record: - Depth - Type joint, fault, vein, etc. - Alpha angle - Roughness smooth, rough, stepped - Infill none, clay, quartz, calcite, etc. - Weathering state Rock Mass Rating RMR A more comprehensive system combining: 1. Intact rock strength 2. RQD 3. Spacing of discontinuities 4. Condition of discontinuities 5. Groundwater conditions 6. Orientation adjustment RMR is used for tunnel design, slope stability, and mine planning.