硬岩弹塑性变形破坏过程中强度参数及剪胀角演化模型研究

Study on strength parameters and dilation angle evolution models in hard rock elasto-plastic deformation and failure process

根据大量试验资料,研究硬岩弹塑性变形破坏过程中强度参数及剪胀角演化规律,并建立相应演化模型。分析26例硬岩临界塑性应变与围压之间的关系,提出一种具有广泛适用性的3参数幂函数型围压函数,并将其引入塑性内变量中。基于Mohr-Coulomb屈服准则,分析塑性强化-软化变形过程中强度参数及剪胀角随塑性内变量的演化规律,并建立高斯型强度参数演化模型和考虑围压及塑性内变量的剪胀角演化模型。考虑到工程应用中往往将硬岩峰前视为线弹性变形,进一步研究提出峰后强度参数及剪胀角演化模型。对比多组硬岩试验结果与模拟结果,发现应用所建塑性强化-软化变形过程中强度参数及剪胀角演化模型,可正确模拟不同围压下硬岩塑性强化-软化变形过程中轴向变形及环向变形规律;应用所建峰后强度参数及剪胀角演化模型,也可合理模拟不同围压下硬岩峰后塑性软化变形过程中轴向变形及环向变形规律。上述力学模型对不同种类硬岩均适用,具有良好的应用前景。

Based on a large number of experimental data, the evolution law of strength parameters and dilation angle in hard rock elasto-plastic deformation and failure process is studied to establish their evolving models. Firstly, by analyzing the relationship between critical plastic strain and confining pressure of twenty-six types of hard rocks, a widely suitable three-parameter power-type confining pressure function is proposed and introduced into the definition of the plastic internal variable. The evolution law of strength parameters and dilation angle with the plastic internal variable in the plastic strain hardening-softening process is studied with respect to the Mohr-Coulomb criterion. The Gaussian model for describing the nonlinear evolution of strength parameters is then proposed, and the evolving model of dilation angle considering the influence of both confining stress and plastic internal variable is established. And then, considering that the pre-peak stress-strain relationship of hard rocks is usually simplified as linear in practical engineering, the strength parameters and dilation angle evolving models specifically in the post-peak process are studied. Finally, by comparing the simulated and experimental results of multiple sets of hard rocks, it is found that the models of strength parameters and dilation angle in the plastic strain hardening-softening process can correctly reproduce the axial and circumferential deformation under different confining pressures. The proposed evolving models can also reasonably describe the post-peak deformation in the plastic strain-softening process under different confining pressures. The proposed models are applicable and showing good prospect for different types of hard rocks.