Investigation of the factors that effect the point load strength test by using synthetic samples

Point load index test is an index test which is used to estimate the uniaxial compressive strength of rock materials. In this study a total of 280 synthetic cyelidrical samples whose uniaxial compressive strength values range between 2 and 52 were prepared using alpha plaster and concrete. These samples were prepared using 1, 2, 3 and 4 length to diameter ratio. On these samples point load index tests were performed and it was determined that length to diameter ratio has no meaningful effect on point load strength between for 1 to 4 length to diameter ratio. Uniaxial compressive strength tests were performed on samples having a length to diameter ratio of 2. Variation of k coefficient which is the ratio of uniaxial compressive strength value to point load strength was studied and it was determined that k coefficient is controlled by ?c/?t ratio. Tensile strength of samples were determined using Brazillian test and a relationship between tensile strength and point load strength was developed. This relationship is statistically more powerfull than the relationship between uniaxial compressive strength and point load strength. Cohesion and internal friction angle of samples were calculated using uniaxial compressive strength and tensile strength values. Various regression analyses were performed between all parameters. Finally an equation between point load strength and cohesion having a high coefficient of determination was developed.