离散单元法软件EDEM中接触半径对岩石力学特性的影响及其应用

Influence of contact radius on rock mechanical property and its application in discrete element method software EDEM

以EDEM软件的Hertz-Mindlin接触模型为对象,对接触半径与黏结键强度的关系及其对岩石抗拉和抗压强度的影响进行研究,提出了一种建立高压拉强度比岩石离散元模型的方法。根据接触模型的强度准则和几何准则,提出了黏结键受拉状态下的“强键”、“弱键”以及临界接触半径系数的概念,推导出了接触颗粒间法向运动和切向运动时的临界接触半径表达式。以接触半径系数α为自变量进行了岩石单轴压缩和单轴拉伸仿真试验,结果表明:抗拉强度随α变化呈三阶段分段线性关系,1.0000≤α<1.0008区间内,曲线斜率很大;1.0008≤α≤1.0025区间内,曲线斜率较小;α>1.0025后,抗拉强度几乎不变化。抗压强度随α变化呈两阶段分段线性关系,在1.0000≤α≤1.0002区间内,曲线斜率很大;当α>1.0002后,抗压强度几乎不变化。在1.0001≤α≤1.0003区间内,抗压强度和抗拉强度之比约为6.5~14.0,可以较好地拟合真实岩石的抗拉和抗压特性,从而构建出具有高压拉强度比的岩石离散元模型。

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 coefficientαas an independent variable,and the results show that:the tensile strength shows a three-stage piecewise linear relationship with the change ofα.At the interval of 1.0000≤α<1.0008,the slope of the curve is very large.At the interval of 1.0008≤α≤1.0025,the slope of the curve is small.Whenα>1.0025,the tensile strength is almost constant.The compressive strength shows a two-stage piecewise linear relationship with the change ofα.At the interval of 1.0000≤α≤1.0002,the slope of the curve is very large,and afterα>1.0002,the compressive strength is also almost constant.In the interval of 1.0001≤α≤1.0003,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.