红砂岩中矿物颗粒的塑性应变分析

doi:10.11872/j.issn.1005-2518.2019.04.557

摘要/Abstract

摘要：

为定量研究砂岩中矿物颗粒在载荷作用下的塑性应变和应力，揭示岩石内部赤铁矿颗粒的变形行为,基于弹塑性力学理论和张量分析，采用X射线CT对砂岩三维结构进行扫描（空间分辨率为4.6 μm），分析岩石内部矿物颗粒的运移规律，并提出了岩石矿物颗粒变形梯度张量计算的方法研究其塑性应变。首先对砂岩矿物颗粒位移进行提取，并采用Non Local Means滤波算法对砂岩三维数字图像去噪；然后基于砂岩三维结构，对不同矿物组分进行分割，通过构造主轴应变的变形张量，计算砂岩矿物颗粒的变形梯度和应力、应变分量。结果表明：该滤波算法对砂岩CT图像和射束硬化现象具有显著改善效果。此外，基于X射线CT的砂岩原位测试结果显示，砂岩内部存在较复杂的变形行为和应力响应，且在断裂带和非断裂区域变形行为有着显著差异；岩石内部颗粒在Z轴方向受到压应力，而在XY平面受到拉伸应力的作用，同时矿物颗粒内部存在较大的塑性应变，且试样内部颗粒的应变和应力要远远大于试样宏观应变和应力。该方法对于揭示岩体内部结构和应力、应变状态演化过程具有重要作用。

关键词: 岩石力学, X射线CT, 矿物颗粒塑性应变, 应力分量, 应变分量, 图像滤波, 颗粒强度

Abstract:

Seldom scholars have investigated the strain and stress state of mineral particles in the rock on the microscopic scale in experiment.At the same time，due to the complex shape of the internal particles of the rock，it is necessary to find suitable research methods and high-precision research instruments.Therefore，for quantitative research on the plastic strain and stress of mineral grains in sandstone under uniaxial compression，X-ray CT was used to scan three-dimensional structure for sandstone (spatial resolution of 4.6 micrometers) to investigate the movement behavior，and put forward the method of deformation gradient tensor calculation of mineral particles to investigate the plasticity of the grains and conduct statistical analysis of the results.Firstly，the displacement of sandstone mineral particles is extracted.At the same time，non-local means filtering algorithm is used to denoise images of sandstone.Then，based on the three-dimensional structure of sandstone，different mineral components are segmented.The principle strains and stress are obtained by and the deformation gradient of sandstone mineral particles.The results show that the filtering algorithm has a significant improvement effect on the CT image of sandstone.In addition，based on the X-ray CT in-situ test results of sandstone，there are relatively complex strain behaviors and stress responses in the sandstone，and significant differences in the deformation behaviors between the fracture zone and the non-fracture zone.Rock grains in Z axis direction experience compressive stress，and in the XY plane are under the effect of tensile stress.At the same time，mineral grains exist larger plastic strain，and the internal grains test of strain and stress is greater than strain and stress the sample at macro-scale.The grain plastic strain in the fracture zone and the non-fracture zone is about 30 times and 5 times bigger than on the macroscopic strain of the sample respectively，which indicate that the deformation behavior in in the microscopic of red sandstone is significantly different from that in the macroscopic sample.This method plays an important role in revealing the internal structure of rock mass and the evolution process of stress and strain state.

Key words: rock mechanics, X-ray computed tomography, plastic strain of grains, strain components, stress components, image filter, grain strength

中图分类号:

TU45

冯春迪,黄仁东. 红砂岩中矿物颗粒的塑性应变分析[J]. 黄金科学技术, 2019, 27(4): 557-564.

Chundi FENG,Rendong HUANG. Plastic Strain Analysis of Mineral Particles in Red Sandstone[J]. Gold Science and Technology, 2019, 27(4): 557-564.

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