为确定岩石节理的剪切强度,在MTS815型程控伺服岩石刚性试验机上对含不规则、无充填岩石节理试件进行三轴试验.利用伺服控制系统连续获得同一试件在不同围压条件下对应的最大轴压,并根据弹性力学理论求得不同围压下节理面的正应力和剪应力.对每一试件的试验结果按线性Mohr-Coulomb准则拟合获得摩擦角和内聚力,利用MATLAB软件的曲线拟合工具对所有试件的正应力和剪应力分别进行线性Mohr-Coulomb准则拟合、幂函数拟合和非线性Barton公式拟合,对比其拟合效果可知:1)线性Mohr-Coulomb准则拟合明显比幂函数拟合和Barton公式拟合要差,尤其是在低正应力条件下线性Mohr-Coulomb准则拟合高估了岩石节理的剪切强度;2)幂函数和Barton公式拟合的曲线几乎重合,且总体反映了岩石节理剪切强度的非线性特征;3)在较高正应力下,线性Mohr-Coulomb准则、幂函数和非线性Barton公式对应的剪切强度均偏高.同时,为估计拟合公式基本参数的合理性,根据试验成果对Barton公式基本参数进行了比较可靠的区间估计.%In order to determine the shear strength of rock joint,the triaxial tests for specimens with irregular and unfilled rock joints were conduc-ted using the rock mechanics test system (MTS815).A series of maximum axial failure stresses under different confining pressures applied to the same specimen was continuously acquired on MTS and the normal and shear stresses of joint surface under different confining pressures were ob-tained through the theory of elastic mechanics combined with the maximum axial failure stresses.In addition to deriving the cohesive force and friction angle with the test results of each specimen by linear Mohr-Coulomb criterion fitting,the curve-fitting tool in MATLAB was employed to treat the linear Mohr-Coulomb criterion fitting,the power fitting,and the nonlinear Barton criterion fitting.The comparison of the three fitting methods showed that when it comes to determine the shear strength of rock joints,the fitting of linear Mohr-Coulomb criterion is obviously worse than the power function fitting and Barton formula fitting,especially under the low normal stress conditions.Linear Mohr-Coulomb criterion fit-ting will overestimate the shear strength of rock joints.The curves of Power function fitting and Barton formula fitting are nearly overlap,as well as both of them can reflect the nonlinear characteristics of shear strength of rock joints.Under the high normal stress,the fitting results of the shear strength of rock joints will higher when using Mohr-Coulomb criterion,power function and nonlinear Barton formula to fit.In addition,the reliable interval is estimated for the basic parameters of Barton formula fitting getting from the triaxial testing results.
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