In-situ estimation of uniaxial compressive strength of igneous rock based on point load strength

The size effect law of rock strength can provide a theoretical basis for the development of portable point load equipment. It can effectively reduce errors in traditional computing, and improve the estimation accuracy of point load strength by calculating the equivalent diameter from the contact area of pressure point. Extensive experimental results of homogeneous cement materials show that the portable point load equipment has better stability and the correlation coefficient of the improved calculation formula is as high as 0.994. The resilience hammer(SHR), point load(PLI) and uniaxial compressive strength(UCS) of igneous rock samples obtained from different engineering sites were measured and statistically analyzed. The effective estimation method of uniaxial compressive strength based on the rebound value and point load index and its applicability were studied. Experimental results show that the fitting strength conversion formula of medium hard rock fits well with that of very hard rock with SHR > 40, which is reasonable in reality. The strength conversion formulas for different igneous rocks are greatly affected by the hardness of rock and uniform conversion formula cannot accurately estimate the uniaxial compressive strength. The point load test results of irregular specimens from the engineering site show that the uniaxial compressive strength of in situ igneous rock can be estimated using portable point load equipment and related strength conversion formulas proposed in the paper when the rock rebound value is given. © 2020, Science Press. All right reserved.