Based on the Hertz-Mindlin contact model in EDEM

the relationship between contact radius and bond strength

and the influence of contact radius on tensile and compressive strengths of rock model were investigated. A method for establishing discrete element model of rock with high compressive-tensile strength ratio was suggested. According to the strength and geometric criteria of the contact model in EDEM

the concepts of “strong bond”

“weak bond” and critical contact radius coefficient were proposed. The formulae of critical contact radius when two particles in contact move along normal or tangential directions were derived. The rock uniaxial compression and tension simulation experiments were carried out with the contact radius coefficient α as an independent variable

and the results show that: the tensile strength shows a three-stage piecewise linear relationship with the change of α. At the interval of 1.000 0≤＜1.000 8

the slope of the curve is very large. At the interval of 1.000 8≤≤1.002 5

the slope of the curve is small. When ＞1.002 5

the tensile strength is almost constant. The compressive strength shows a two-stage piecewise linear relationship with the change of α. At the interval of 1.000 0≤ ≤1.000 2

the slope of the curve is very large

and after ＞1.000 2

the compressive strength is also almost constant. In the interval of 1.000 1≤≤1.000 3

the compressive-tensile strength ratio is about 6.5 to 14.0

and it can be used to reproduce the tensile and compressive properties of real rock

so as to construct the discrete element model of rock with high compressive-tensile strength ratio.