Relationship between point load strength and uniaxial compressive strength of hydrothermally altered soft rocks

摘要

We clarified relationships between point load strength (PLS) and uniaxial compressive strength (UCS) in hydrothermally altered soft rocks found in northeastern Hokkaido, Japan, using axial and irregular lump PLS test specimens. The numbers of specimens tested were 1,755 and 2,123 rock specimens for the axial and irregular lump PLS tests, respectively, and 329 rock specimens for the UCS test. The rock specimens underwent PLS and UCS tests using a laboratory testing machine with specimens in forced-dry and forced-wet states. The correlations between the PLS and the UCS were linear. The UCS was 11.1 times larger than the axial PLS, and 4.7 times larger than the irregular lump PLS, respectively, in soft rocks with a UCS below 25MPa.We could calculate the UCS from PLS tests on soft rocks only when their UCSs were below 25MPa.