Experimental investigation on the point load strength of red-bed siltstone with different shapes

The point load test is an indirect method to estimate the uniaxial compressive strength (UCS) of rock. In order to investigate the influence of the shape effect on the point load test strength of the siltstone in the Red Stratum, a series of point load tests were carried out on siltstone specimens with different shapes (cylinders, blocks, irregular specimens). The results show that the point load strength index of red-bed siltstone specimens with different shapes exhibits significant dispersion. As long as being corrected, the specimen shape has no significant effect on the point load strength index I s(50) . The average value of I s(50) from formula correction is consistent with the value obtained by the graphical method with all different shape specimens in consideration. An empirical relation is proposed for the estimation of UCS by the point load strength I S(50) . The red-bed siltstone specimens under the point load test are broken into two pieces or three pieces, but the former failure is dominant.