Point-Load Strength Test

This chapter discusses that the point-load test is designed to provide a rapid, portable index test for rock strength. A sample is compressed among solid steel cones that generate tensile stress normal to the axis of loading. The point-load strength index (Is) is defined as the load measured at the point of failure of the rock sample (Fa) divided by the distance among the conical platens at the moment of failure (Ls). Empirical testing has revealed a direct correlation of the Is index to the uniaxial compressive rock strength when the test is performed using a cylindrical core the length of the core is greater than 1.4 times the diameter of the core and the diametral test is performed.