Direct Shear Testing (shear box)
NGI has an advanced shear box for direct shear testing of fractured or intact rock specimen at high stresses and large displacements.
- Shear box can accommodate large (150 x 150 x 300 mm) intact or fractured rock specimens
- Testing can be done with axial load up to 500 kN and horizontal load up to 250 kN
- Hydraulic shear actuator enabling static and dynamic testing
- Measuring fracture flow by application of fluid pressure
- Single- or multistage testing at several levels of normal stress and rate of shear displacement
- Fracture friction and deformation properties; friction angle and cohesion, dilation during shear and dilatancy angle, normal deformation during normal loading, normal and shear stiffness
- Fracture conductivity; Stress dependent fluid flow behavior of fracture undergoing normal stress and shearing. Back calculation of fracture conductivity and conducting aperture
- Seismic potential; Velocity stepping test for testing at different rates to evaluate velocity weakening vs. strengthening for evaluation of seismic vs. aseismic response. This is of relevance for micro seismic monitoring, and can be used as a supplement to Acoustic Emission (AE) testing.
Figure 1: NGI's high stress direct shear rig and a schematic for interior of shear box illustrating fluid flow.