BRAZILIAN SPLITTING STRENGTHS OF DISCS AND RINGS OF ROCKS IN DRY AND SATURATED CONDITIONS

To study the effect of saturation on the tensile strength of rock,dry and saturated rings of 30 mm in thickness,50 mm in external diameter,and 0-20 mm in internal diameter were conducted by Brazilian splitting test for four rocks.The broken discs after Brazilian splitting were point loaded.Dry and saturated cylindrical specimens were uniaxial compressed.Based on the statistical analysis of Brazilian splitting results of discs,the average strength of repeated test in 5 times may eliminate the dispersion from specimens except marble.The softening coefficient of Brazilian tensile strength is higher than and linear relative to that of uniaxial compressive strength.The influence of saturation on the Brazilian tensile strength mainly results from the high compressive stress in the neighbourhood of the load point and the cohesion decrease.Correspondingly,the splitting strengths are nearly the same for dry and saturated rings with 20 mm in internal diameter,which means that the compressive stress does not influence the ring splitting greatly.An exponential equation is proposed for rings to describe the relation between Brazilian splitting force and its inner diameter;and the Hobbs'equation based on the elastic mechanics has great difference from the experimental results.