基于单轴受压的岩石三轴应变指标确定方法研究

 在单轴受压的基础上可以采用Mohr准则或Hoek-Brown准则确定三轴受压下岩石的强度指标，但应变指标的确定一直没有较好的求解办法。根据岩石在弹性极限点(损伤门槛值)处微裂纹密度变化梯度为一常量的特点，运用岩石损伤演化的宏细观损伤复合模型，通过岩石应力–应变曲线上临界损伤值及门槛损伤值的相关性，由单轴受压下在弹性极限强度点处的损伤门槛微裂纹密度值和微裂纹密度变化梯度，得到不同围压下在弹性极限强度点处的临界损伤值，应用Mohr-Coulomb准则或Hoek准则得到不同围压下的岩石峰值强度，进而得到相应的应变指标；推导由岩石单轴受压指标确定三轴受压指标的计算公式，通过计算实例和试验验证公式的合理性。

STUDY ON DETERMINATION METHOD OF ROCK'S TRIAXIAL STRAIN INDEX BASED ON UNIAXIAL COMPRESSION

Based on the uniaxial compression,the strength index of rock under triaxial compression can be determined with Mohr criterion or Heok-Brown criterion,however,there has been not a proper method to determine the index of strain. According to the characteristics that the vary grads of microcrack density is a constant at rock's elastic limit point(the damage threshold value),the macro- and meso-damage composite models have been set up,according to the correlation between the critical value of damages on rock's stress-strain curve and the damage threshold value,the critical value of damage at the elastic limit point under different confining pressures has been derived from the microcrack density on the damage threshold and the vary grads of microcrack density at the elastic limit point under uniaxial compression,and the rock peak strength may be given by the Mohr-Coulomb criterion or Heok criterion under different confining pressures,and then the index of corresponding strain has been gained. The calculative formula of determining the index of triaxial compression by the index of uniaxial compression has been derived. The rationality of the formula has been proved by calculation case and experiments.