Site investigation · Laboratory: rock & aggregates
Rock uniaxial compressive strength & modulus calculator
UCS of a rock core with the L/D correction, tangent modulus at 50% and the ISRM strength term.
Standard: AS 4133.4.2.1 · ASTM D7012 · ISRM
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Inputs in the worked example
The live calculator starts with these values; change any of them and every result, check and diagram updates instantly.
| Input | Value | Unit |
|---|---|---|
| Failure load | 182 | kN |
| Core diameter | 54 | mm |
| Core length | 112 | mm |
| Stress increment around 50% load | 20 | MPa |
| Axial strain over that increment | 1250 | µε |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| Measured strength P/A | 79.47 | MPa |
| L/D correction (0.88 + 0.24 D/L) | 0.996 | |
| Corrected UCS | 79.81 | MPa |
| Tangent modulus E50 | 16.00 | GPa |
| ISRM strength | strong |
- ✓ L/D between 2.0 and 2.5
Method, formulas and assumptions
- Measured strength P/A = 182*1000/(PI()*54^2/4) = 79.468 MPa
- L/D correction (0.88 + 0.24 D/L) = 0.88+0.24*54/112 = 0.99571
- Corrected UCS = 79.468/0.99571 = 79.81 MPa
- Tangent modulus E50 = 20/(1250/1E6)/1000 = 16 GPa
- ISRM strength = IF(79.81<5,"very weak",IF(79.81<25,"weak",IF(79.81<50,"medium strong",IF(79.81<100,"strong",IF(79.81<250,"very strong","extremely strong"))))) = strong
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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.