THE SIZE CORRECTION AND CORRELATION OF POINT LOAD INDEX WITH COMPRESSIVE STRENGTH OF SOME DIMENSION STONES OF TECTONIC ZONES, NORTH PAKISTAN

The Uniaxial compressive strength (UCS) is an important geotechnical property of rock used in tunnel design, rock mass classification and other surface and underground mining projects. It is the Key parameter of rock mass rating (RMR) and the RMR is the basic of all the slope stability analyses methods. This key parameter of slope stability analyses and tunneling can be determine easily by axial and diametral point load test (PLI/Is50). In the past irregular lumps PLI is also correlated with UCS but the data is limited particularly the rocks along Karakoram High Way (KKH), North Pakistan. In this study the diametral, axial and the irregular lumps PLI is correlated with UCS using dimension stones of tectonic regions along KKH. A methodology of size correction of irregular lumps have been set. Using regression analyses the PLI of cores and lumps have been correlated with UCS. The significance of the correlation were developed by correlations coefficients. It is found that the Is(50) of irregular lump of white marble is 1.8MPa. For pink and white granite the Is(50) value is recorded as 3.2MPa and 2.4MPa respectively. In the size correction factor (F) the power n for irregular lump is corrected as 0.8 for marble lumps and the n value for pink and white granite is 0.9 and 1.4 respectively. For diametral and axial PLI the power n is used as 0.45. The correction factor F=(De/50)0.8 is suggested for marble irregular lumps while for axial and diametral specimens of marble the correction factor is F=(De/50)0.45 is recommended. In the case of pink and white granite the correction factors are F=(De/50)0.9 and F=(De/50)1.4 respectively.