中主应力对岩石材料影响的机理及理论模型研究

发布时间：2018-03-08 14:00

本文选题：中主应力效应　切入点：颗粒离散元　出处：《中国科学:技术科学》2017年03期 　论文类型：期刊论文

【摘要】：利用颗粒离散元法分析了中主应力对岩石在真三轴条件下峰值应力、微裂纹数目变化、颗粒摩擦耗散能、破坏方式、微裂纹分布的影响.数值模拟再现了随中主应力增大,岩石材料强度先增大后减小的变化规律.细观层面,中主应力增大使得微裂纹在加载平面上投影由均匀变得不均匀.中主应力比b大于0.5,岩样在屈服阶段产生微裂纹显著增多,颗粒摩擦耗能增大非常明显.中主应力一方面抑制了法向沿中主应力方向(或存在该方向分量)的微裂纹的扩展,这将导致岩样强度的增加.另一方面,法向沿小主应力(或存在该方向分量)的微裂纹的扩展得到了促进,这导致岩样强度的减小.这种对不同方向微裂纹扩展的抑制或者促进作用导致岩样宏观强度呈现先增大后减小的变化规律.基于Weibull统计理论,建立了能反映岩石强度中主应力效应的概率统计强度模型.采用剪应力来表示计算强度,推导出一个新的能反映中主应力和材料不均匀性综合影响的强度准则.该准则可以视为Mohr-Coulomb准则的修正,当材料绝对均匀时该准则可以退化为Mohr-Coulomb准则.通过和真三轴压缩试验结果、数值模拟结果以及常用强度准则对比发现本文强度准则能很好地反映中主应力对岩石强度的影响规律.
[Abstract]:The effects of the medium principal stress on the peak stress, the number of microcracks, the energy dissipation of particles, the mode of failure and the distribution of microcracks in rock under true triaxial conditions are analyzed by means of particle discrete element method. The variation of the strength of rock materials increases first and then decreases. In meso-plane, the increase of meso-principal stress makes the projection of microcracks on the loading plane from uniform to non-uniform. The ratio of medium principal stress b is greater than 0.5, and the microcracks of rock samples increase significantly in the yield stage. The increase of friction energy consumption of particles is very obvious. On the one hand, the medium principal stress inhibits the propagation of microcracks along the direction of the central principal stress (or the existence of this component), which will lead to the increase of the strength of the rock samples, on the other hand, The propagation of microcracks along a small principal stress (or in which there is a component in this direction) is promoted. This leads to the decrease of the strength of rock samples. The inhibition or promotion of microcrack propagation in different directions leads to the change of macroscopic strength of rock samples which increases first and then decreases. Based on the Weibull statistical theory, A probabilistic statistical strength model which can reflect the effect of principal stress in rock strength is established. The shear stress is used to express the calculated strength. A new strength criterion, which can reflect the combined effect of principal stress and material inhomogeneity, is derived. The criterion can be regarded as a modification of Mohr-Coulomb criterion. When the material is absolutely uniform, the criterion can degenerate into Mohr-Coulomb criterion. The numerical simulation results and the comparison of the commonly used strength criteria show that the strength criterion in this paper can well reflect the law of the influence of the medium principal stress on the rock strength.
【作者单位】：同济大学土木工程学院;南京理工大学机械工程学院;
【分类号】：TU45

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