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基于SEM所获取的岩石非均质数字图像,提出了一种既能考虑预制和原生缺陷,又能近似反映材料非均匀性的三维细观结构有限元模型的方法,即单元质心对应法.应用该方法进行了热力耦合下岩石的热开裂及变形破坏数值模拟.结果表明,北山花岗岩热开裂临界温度大约为82℃,与实验值68～88℃基本吻合.低温时北山花岗岩热开裂以沿颗粒热开裂为主;而高温后既有沿颗粒热开裂,又有穿颗粒热开裂.温度的升高导致花岗岩由脆性向延性转变,破坏将由低温下以载荷裂纹为主的裂纹模式转为高温下以热裂纹为主的裂纹模式.对比实验结果发现,数值模拟得到的拉伸强度在低温下高于实验测试值,而中高温度下基本与实验结果吻合.
Based on the heterogeneous digital images of rock obtained by SEM, a three-dimensional finite element model of mesostructures, which can consider both prefabricated and primary defects and approximate the non-uniformity of materials, is proposed, which is the unit centroid correspondence method. The results show that the thermal cracking critical temperature of Beishan granite is about 82 ℃, which is basically consistent with the experimental value of 68 ~ 88 ℃ .Besulting from the thermal cracking of Beishan granite at low temperature, Thermal cracking is the main, while both the thermal cracking along the grain and the thermal cracking of the grain wear after the high temperature, the granite changes from brittleness to ductility due to the increase of temperature, and the failure will change from the mode of crack under load at low temperature to the high temperature The crack patterns dominated by hot cracks.Compared with the experimental results, it is found that the tensile strength obtained by numerical simulation is higher than the experimental value at low temperature, while the experimental results are basically consistent with those at high temperature.