How is UCS estimated from Schmidt hammer rebound?

Multiple correlations exist. Miller (1965): UCS = 0.000140 × γ^1.7 × e^(0.0725R) MPa where γ is dry density (kg/m³). Aydin & Basu (2005): log(UCS) = 0.47 × log(γ) + 0.027R - 1.47. Testing per ISRM (1978/2007): take 20 readings on a smooth, dry surface, discard those differing by more than 5 units from the mean, and average the 10 highest values.

What are the limitations of the Schmidt hammer test?

The test is sensitive to surface roughness, orientation, moisture, and rock discontinuities. It is only valid for intact rock (not rock mass) and does not account for anisotropy. The tool should be calibrated against the manufacturer's test anvil (R = 80 ± 2). Results are only reliable for R > 30; below this, the rock is too soft. All limitations per ISRM Suggested Methods.

Schmidt Hammer Rebound Correlation

Estimate uniaxial compressive strength and deformation modulus of rock from Schmidt hammer rebound (R) values using ISRM and Aydin & Basu (2005) correlations.

2D stress state at a point. All stresses in MPa.

σx — Normal Stress X (MPa)

σy — Normal Stress Y (MPa)

τxy — Shear Stress (MPa)

⚙ Mechanical Note: Results are based on standard textbook formulas and ISO/AASHTO references. Always verify critical designs with applicable codes (ISO 898, AASHTO 1993, AISC, Eurocode 3) and a qualified engineer.

How to Use

Enter the values for the patient or scenario you are assessing. Estimate uniaxial compressive strength and deformation modulus of rock from Schmidt hammer rebound (R) values using ISRM and Aydin & Basu (2005) correlations. Use the schmidt hammer rebound result to inform your clinical assessment.

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Frequently Asked Questions

How is UCS estimated from Schmidt hammer rebound?

What are the limitations of the Schmidt hammer test?