Strength criterion for crystalline rocks considering grain size effect and tensile-compressive strength ratio

考虑结晶岩粒径效应及拉压强度比的强度准则

The macroscopic mechanical properties of rocks are significantly influenced by their microstructure.As a material bonded by mineral grains,the grain morphology of crystalline rock is the primary factor influencing the strength.However,most strength criteria neglect the strength variations caused by different grain characteristics in rocks.Furthermore,the traditional linear criteria tend to overestimate tensile strength and exhibit apex singularity.To address these shortcomings,a piecewise strength criterion that considers the grain size effect has been proposed.A part of an ellipse was employed to construct the envelope of the tensive-shear region on the meridian plane,to accurately reproduce the low tensile-compressive strength ratio.Based on the analysis of experimental data,both linear and exponential modification functions that account for grain size effects were integrated into the proposed criterion.The corresponding finite element algorithm has been implemented.The accuracy and applicability of the proposed criterion were validated by comparing with the experimental data.

细观结构对岩石的宏观力学性能具有显著的影响。作为一种由矿物颗粒胶结而成的材料,结晶岩的颗粒形貌特征是影响其强度的主要因素。目前绝大多数强度准则没有考虑岩石颗粒特征差异引发的强度变化,并且经典的线性准则具有高估抗拉强度、存在奇异点等缺陷。针对上述不足,提出了一种考虑岩石粒径效应的分段式强度准则。采用一段椭圆曲线构建拉剪区方程,引入角隅函数修正偏平面上包线形态,基于对试验数据的归纳将线性和指数型两种考虑粒径效应的修正函数引入所提出的准则,并完成了相应的有限元算法的开发工作。通过与试验数据的对比,验证了模型的准确性和适用性。