The point load test, Geotechnical database created from investigations for infrastructure projects in the Republic of Macedonia-Anisotropy analysis

Abstract

The point load test is one of the most exploited techniques to obtain preliminary information of the strength of the rocks. The paper deals with statistical analysis of large amount of results from the test, obtained for the needs of geotechnical investigations on various structures which are part of the European transport corridors VIII and X in Republic of Macedonia. Additional number of results have been taken from investigations for other structures. Most rocks had clearly expressed anisotropy. All results are systemized in a GIS database and classified according rock type and belonging in specific geotectonic unit. After that, various analytical regressions with different level of confidence had been established. Effort was made to correlate the values of the point load index parallel and perpendicular to the anisotropy, as well as the values of the point load with the unit weight & unit weight with depth of samples. Most important finding is that some of these correlations, mainly related to the anisotropy of the values of the point load show high level of correlation and can be suggested for use in preliminary levels of investigations or during control investigations. The use of such correlations is limited in regard of the rock type and the geotectonic unit. Confident correlation for the point load vs. unit weight & unit weight vs. depth of samples was not obtained. Similar analysis is proposed to be done for massive rocks and rocks in frames of specific mineral deposits, where the authors believe it is possible to obtain stronger correlation coefficients also for the two latter correlations.