Estimation of strength characteristics of different Himalayan rocks from Schmidt hammer rebound, point load index, and compressional wave velocity

Various rock types-including highly deformed to undeformed quartzites, granites, granitic gneisses, gneisses, metabasics (meta-amphibolites and meta-dolerite), and dolomites-collected from different formations of the Lesser and Higher Himalayas were tested to evaluate correlations between the uniaxial compressive strength (UCS) and the point load test (PLI), Schmidt hammer rebound (SHR) value, and compressional wave velocity (Vp). Various equations between UCS and PLI, SHR, and Vp were obtained using regression analysis. It was found that there is high scatter in the data when all lithologies are considered together, whereas this scatter is reduced when the lithologies are considered individually. This was attributed to wide variations in the mineralogical and textural characteristics of different rocks. Furthermore, it was also noted that quartzites exhibit high scatter in their data points, even though they are monomineralic. Thin section studies revealed that different microfabrics have been produced in the quartzites, due to the actions of different deformational phases during tectonic activity in the area. Therefore, it is necessary to treat deformed and undeformed rocks separately when deriving such equations.