La determinazione della resistenza a compressione uniassiale nelle rocce: un confronto tra i principali metodi applicati alla serie dolomitica

Most of the rock mass classifications consider Uniaxial Compressive Strength (UCS) as a fundamental input parameter. The estimation of UCS is often carried out through field tests (i.e. Schmidt hammer test); therefore, it is very important to analyze the accuracy and precision of the results from in situ testing. To this end, we carried out a geomechanical characterization of some of the most important formations of the dolomitic stratigraphic sequence and, for each one, calculated the uniaxial compressive strength through the Schmidt hammer test, PLT and uniaxial compressive strength. Then, we compared UCS values obtained through graphic and statistical methods calculating variance accounted for (VAF) and root mean square error (RMSE), to evaluate the performance of Schmidt hammer and PLT in estimating UCS. The study has demonstrated the reliability of Schmidt hammer in evaluating UCS of the rocks, especially if they are used the equations proposed by Deer and Miller (1966) e Beverly et al. (1979: in Xu et al., 1990). Finally, we calculated, for each rock mass analyzed, the value of Hoek-Brown failure criterion parameters, friction angle and cohesive strength of Mohr-Coulomb criterion, and rock mass strength, using the UCS values obtained from the different methods. This test has been done to evaluate the magnitude of the error we commit in determining UCS on the parameters normally used in the design