In Situ Shear Test

Sial.tec performs shear tests on rock joints and concrete-rock or concrete-concrete interface.

Purpose of these tests are:

• determination of the peak and residual shear strength characteristics of a rock joint;
• determination of the characteristics of peak and residual creep resistance of the interface surface between concrete and rock or between concrete and concrete (typical situations: contact of the base of a dam with the underlying rock, contact between design concrete and concrete in place, in the case of modernization or safety projects of existing dams).

At the customer’s request, both surface tests (excavations, trenches) and underground tests (tunnels, side niches, wells) are performed.

The equipment and experimental / interpretative procedures used have characteristics that adapt to various situations:

• possibility of using a beam and tie rods placed on the sides of the block for the normal contrast (open-air situation), or the vault of the tunnel or niche in case of underground tests;
• possibility of using another series of tie rods for tangential contrast, or by contrasting hydraulic jacks against a rock wall or a reinforced concrete structure;
• in case of cutting on a rock joint, dimensions of the isolated rock block (avoiding block disturbance): approx. 70 cm x 70 cm x 40 cm (length x width x height), with walls regularized with a thin layer of cement mortar;
• in case of concrete-rock or concrete-concrete sliding: dimensions of the specially cast block: 70 cm x 70 cm x 40 cm (length x width x height).

Normal and tangential stresses are applied by means of cylindrical hydraulic jacks, connected to pressure gauges and precision pressure transducers (stroke of the hydraulic jacks greater than 70 mm, test pressures up to 12 MPa.

The displacements in the 3 directions (x, y, z) are automatically measured and acquired by 3 displacement transducers (LVDT) for each of the 4 edges of the block, connected to the PC.

The surfaces subjected to tests are detected (pre and post-cutting) by laser relief and with a Barton comb to determine the roughness of the surfaces.