矿物组构对花岗岩抗拉强度影响分析

Influence of Mineral Fabric on Tensile Strength of Granite

大量岩石力学试验表明,岩石矿物组构对其力学性质有重要影响。鉴于此,以花岗岩为研究对象进行巴西劈裂试验,分析矿物组构对其抗拉强度的影响。首先对含有标记线的花岗岩试件进行不同组构系列巴西劈裂试验;然后借助核磁共振、显微成像、数字图像处理技术对试件1-1进行了含组构信息的数值模拟试验;最后,对数值模拟试件承载区域内低强度云母组构进行了统计分析以及对不同载荷下破裂点进行了分形分析。研究结果表明:(1)不论是室内试验还是数值试验,不同加载方向的花岗岩试件峰值抗拉强度均存在差异性;(2)数值试验结果说明了花岗岩峰值抗拉强度的差异性是其加载方向上不同的矿物组构造成的,其中主要承载区低强度组构处于优势时(即低强度组构与加载方向所成夹角越小,平均长度越长,总体含量越高),试件强度较低;(3)破裂点分形结果表明,矿物组构的不同导致巴西盘破裂点扩展方式不同,当低强度组构处于优势时,在加载过程中破裂点的扩展方式为沿着低强度组构趋向于集中扩展,应力集中明显,反之,则趋向于发散扩展,对于同一类型花岗岩来说,初始阶段破裂呈现分散扩展将致使其峰值荷载相对要大。

A large number of rock mechanical tests show that the rock mineral fabric has an important influence on its mechanical properties.In view of this,the Brazilian splitting test was carried out to analyze the influence of mineral fabric on the tensile strength of granite.Brazilian splitting tests with different fabric series were carried out on granite specimens with marker lines.Then,the numerical simulation tests containing fabric information of specimens 1-1 were carried out by means of nuclear magnetic resonance,micro imaging and digital image processing technology.Finally,the low-strength mica fabric in the bearing area of the numerical simulation specimen was statistically analyzed and fractal analysis of fracture points under different loads were carried out.The results are concluded as follows.Firstly,the peak tensile strength of granite specimens with different loading directions is different,whether in laboratory or numerical tests.Secondly,the numerical test results show that the difference of peak tensile strength of granite is caused by different mineral fabrics along the loading direction.And the strength of the specimen is low when the low-strength fabric in the main bearing area is in the dominant position(namely,the smaller the angle between the low-strength fabric and the loading direction,the longer the average length and the higher the overall content).Thirdly,the fractal results of fracture points show that the difference of mineral fabrics leads to different fracture point propagation modes.When the low-strength fabric is in the dominant position,the propagation mode of the fracture points tends to concentrate along the low-strength fabric,and the stress concentration is obvious.On the contrary,the propagation tends to be dispersion.For the same type of granite,the peak load will be relatively large due to the dispersion of fracture in the initial stage.