砂岩试验强度与强度准则预测结果对比分析

对山西大同煤峪口矿巷道砂岩进行了巴西劈裂、单轴和常规三轴试验，分析了其变形和强度特性，以整体平方根误差最小为依据拟合确定了5种强度准则参数，比较各准则的整体拟合效果以及抗拉强度和抗压强度预测值与试验值之间的差异。结果表明：砂岩单轴和低围压下的脆性特征显著，随着围压增大屈服段明显增加，逐渐由脆性向延性转变；对试验数据的整体拟合效果，Mohr-Coulomb准则最不理想，指数强度准则最好，Hoek-Brown准则和Bieniawski准则相接近；对抗拉强度的预测，Mohr-Coulomb准则明显高估了砂岩的抗拉强度，不适合预测抗拉强度，指数强度准则最为理想，Bieniawski准则不能反映岩石抗拉特性；单轴和不同围压下砂岩强度，直线型Mohr-Coulomb准则偏离了大多数试验数据点，特别是高围压下偏离显著结果失真，Hoek-Brown准则和Bieniawski准则预测结果几乎一致，Sheorey准则高围压下预测结果稍有偏高，指数强度准则接近大多数试验数据，预测效果最佳。

Comparative analysis of sandstone experiment strength and different strength criteria prediction results

Tested Meiyukou mine roadway sandstone Brazil splitting, uniaxial and conventional triaxial strength. Analyzed sandstone the characteristics of deformation and strength, according to the overall minimum fitting error of square root identified the parameters of 5 strength criteria, compared the difference of the overall fitting precision of various strength criteria and the difference between experiment strengths and prediction values of tensile strengths and compressive strengths of various strength criteria. Obtained the following main research conclusions:Sandstone brittle characteristics is significant under uniaxial compression and lower confining pressure, the yield stage increases obviously with the increasing of confining pressure, Sandstone failure characteristics gradually change from brittle into ductile. For the overall fitting precision of experiment data, Mohr-Coulomb criterion is not the most ideal, exponential strength criterion is the best, Hoek-Brown criterion and Bieniawski criterion have the little difference. For the tensile strength prediction value, Mohr-Coulomb criterion significantly overestimates the tensile strength, thus it is not suitable for predicting the tensile strength, exponential strength criterion is the most ideal, Bieniawski strength criterion cannot reflect the tensile strength properties of rock. For uniaxial strength and compressive strength of different confining pressure, linear Mohr-Coulomb criterion deviates from the most experimental data, the prediction results deviate significantly from the true value especially under higher confining pressure, Hoek-Brown criterion and Bieniawski criterion almost have the consistent prediction results, Sheory cri-terion prediction results are slightly higher under higher confining pressure, exponential strength criterion is close to most of the test data, the prediction precision is the best.