Plate-Load Testing on Rock for Deformation and Strength Properties

Plate-load tests were conducted underground on rock to determine in situ strength and deformation properties. The plate-load test provides information on the rock mass properties as opposed to the strength of the rock substance. When a plate is placed on the surface of the material to be tested and the contact pressure increased, the plate deflects as the material deforms, and shear failure of the material ultimately occurs.

Tests were conducted on three different materials: iron ore, paint rock, and ash rock. The results were compared, in some cases, with the results of laboratory testing and, in other cases, with the results of analyzing failures of the rock mass. Moderately good agreement was obtained between these independent methods of determining the material properties. However, the principal aspect that emerges is the dispersion of strength values that must be expected in testing geological materials.

Suggested specifications are given for plate-load testing, conventional uniaxial compression testing, and classification uniaxial compression testing.