Intact rock and rock mass
- Intact rock is the material between discontinuities; a rock mass also includes joints, faults, fractures, weathering, and infill.
- Rock-mass strength depends on discontinuity orientation, persistence, roughness, infill, and condition, as well as the rock matrix.
Specimen preparation
- Select a representative sample, record source and orientation, and inspect weathering or fractures before cutting.
- Core, trim, and grind faces to the method’s geometric tolerances; poor preparation affects failure mode.
- Rock properties vary. Document defects and do not treat rock as if it were homogeneous concrete.
Characterizing discontinuities
- A joint profilometer allows roughness comparison with reference profiles and estimation of a JRC index.
- Rebound on a joint wall can support hardness assessment; a tilt test provides an empirical observation of friction angle.
- Direct shear across a joint evaluates sliding resistance under a defined normal stress.
Durability and application
- Water-durability or abrasion tests study degradation relevant to fill, rockfill, excavation, and building stone.
- Interpret results with geology, project scale, and rock-mass structure; one specimen value does not represent an entire rock mass.
Index properties and phase relationships
- Water content: w = Mw/Ms, or 100·Mw/Ms as a percentage; Mw is water mass and Ms is dry-solids mass.
- Phase relationships: e = Vv/Vs; n = e/(1+e); Sr = w·Gs/e, with w as a decimal fraction. Check that 0 ≤ Sr ≤ 1 apart from rounding or incompatible data.
- Plasticity: PI = LL − PL; liquidity index IL = (w − PL)/PI locates natural water content relative to the plastic range.
- Grading: Cu = D60/D10 and Cc = D30²/(D10·D60). D10, D30, and D60 are diameters at 10, 30, and 60 percent passing; report how sieve and sedimentation results were combined.
- RQD: RQD = 100·ΣLpiece/Lcore run, summing sound core pieces longer than the defined threshold. Record core diameter, run length, and the distinction between natural fractures and drilling breaks.
Educational reference guide. Check the current standard, calculation assumptions, and project specification before applying a procedure or acceptance criterion.