Rock Mechanics Testing
Direct Shear Test
Intact rock strength for a homogeneous sample, or shear strength of a discontinuity where planes of weakness are present. The discontinuity may be open, or partially or completely filled.
Typical test output
- Shear strength as a function of normal stress
- Shear stress as a function of shear displacement
- Friction angle
- A representative artificial fracture for subsequent testing
Recommended sample dimensions: 1″ diameter × 2″ length.
- The test is conducted on a 1″ × 2″ plug, undrained, with an applied constant normal load.
- Shear stress is applied by custom-designed endcaps that keep the shear load acting on a plane parallel to the plug axis, so the measured strength reflects the rock rather than the fixture.
- Run on an intact plug, the shear fracture that develops resembles a natural fracture far more closely than a saw-cut surface does.
- That makes the same sample useful afterwards for fracture conductivity and proppant embedment work, rather than needing a separate preparation.
