Compression Test of Rock(IS 9143 · IS 13047)
Laboratory compression testing of rock cores — uniaxial (unconfined) strength per IS 9143 and triaxial strength under confining pressure per IS 13047 — the primary inputs for foundation, tunnel and slope design in rock.
What is the Compression Test of Rock?
Compressive strength is the defining engineering property of rock. It is measured two ways: uniaxial (unconfined) compression per IS 9143:1979, where a prepared core is loaded axially to failure, and triaxial compression per IS 13047:1991, where the core is loaded inside a Hoek cell under lateral confining pressure that simulates in-situ stress at depth — yielding the Mohr strength envelope, cohesion and angle of internal friction of the rock material.
Global Lab prepares cores to the specified length-to-diameter ratio with ground, parallel ends, and tests them on calibrated compression frames. Uniaxial results feed bearing-capacity and rock-classification systems (RMR, Q); triaxial envelopes feed tunnel liner, deep-foundation and slope-stability design. This page covers the umbrella service — see the dedicated Uniaxial Compressive Strength (UCS) page for the IS 9143 test in detail.
How the Compression Test of Rock is Conducted
- 1
Core Logging & Selection
Received cores are logged, photographed and representative intact specimens selected free of induced fractures. - 2
Specimen Preparation
Cores are cut to the specified L/D ratio and ends ground flat, parallel and perpendicular to the axis within standard tolerances. - 3
Uniaxial Loading (IS 9143)
The specimen is loaded axially at the specified stress rate to failure; peak load and failure mode are recorded and UCS computed. - 4
Triaxial Loading (IS 13047)
Specimens are tested in a Hoek cell at a series of confining pressures; peak axial stresses define the Mohr strength envelope. - 5
Envelope Analysis
Cohesion and angle of internal friction are derived from the Mohr circles for design use. - 6
Reporting
Strength values, failure modes, moisture state and envelope parameters are issued via Autovity QLMS.
Applicable Test Standards
| Standard | Title | Scope | Type |
|---|---|---|---|
| IS 9143:1979 | Method for the Determination of Unconfined Compressive Strength of Rock Materials (Reaffirmed) | Uniaxial Compression | Indian Standard |
| IS 13047:1991 | Method for Determination of Strength of Rock Materials in Triaxial Compression (Reaffirmed) | Triaxial Compression | Indian Standard |
| ISRM SM | ISRM Suggested Methods for Rock Characterization, Testing and Monitoring | Supplementary Practice | International |