| Summary: In this study, rock strength parameters used in tunnel applications were aimed to estimate by indirect methods. For this purpose, the engineering properties of discontinuities in different excavation faces were determined in the tunnel of a hydroelectric power plant. Laboratory tests were carried out on the core samples derived from representative rock blocks obtained from studied excavation faces. The rock masses were classified according to the RMR, Q, and RMi classification systems by using data obtained from laboratory and field studies. Schmidt rebound hammer method was proposed for indirect estimation of the UCS parameter in the problematic rock conditions. Additionally, a classification was suggested for practical estimation of Schmidt hardness classes using the ratio of UPV/UCS. The data of 490 rock samples were gathered by means of the detailed literature survey and new equations were obtained for the UCS estimation from the PLI, dividing the rocks into 12 different groups. The measured and estimated UCS values were compared in the estimation of RMR, RMi and normalize Q (Qc). In this study, prediction error (%), VAF %, RMSE and MAPE % analyses were performed for some methods (UCS, C, etc.) as well as the regression, correlation and ANOVA analyses. In the RMR system, charts used in the estimation of strength ratings were suggested using the PLI parameter for the PLI<1 MPa and PLI>1 MPa. The cohesion and internal friction angle of rock materials were determined and compared by using the various approaches. Rock mass deformation modulus (Em) was estimated more practical and cheaper compared to the equations proposed in the literature by means of the PLI and RQD. Consequently, this study brings novelty in indirect estimation of the rock strength parameters used in tunneling and provides simplicity for appliers. Furthermore, prediction models developed in this study can be used as a more convenient and practical for rock mass classification systems widely preferred in geotechnical applications. |
