非贯通细观裂纹节理介质CT试验的数值模拟及影响参数讨论

NUMERICAL ANALYSIS OF MESO-CRACK AND MESO-DAMAGE LAWS AND ITS INFLUENTIAL PARAMETERS FOR NON-INTERPENETRATED JOINTED MEDIA BASED ON CT EXPERIMENT

对非贯通细观裂纹节理介质CT试验进行了数值模拟,得到6个材料参数对细观损伤的影响。采用灰度作为主要计算参数,考虑预埋裂隙处发生损伤和破裂的准则,采用Fortran语言编制主程序,并利用三维十六节点等参元计算预埋裂隙及其附近单元,以及三维八节点等参元计算远离裂纹处的单元。计算获得了随外荷载增加情况下模型中截面的灰度分布、破裂分布、平均灰度分布和损伤等值线分布等结果。同时,通过与试验结果进行对比,得到一些与试验吻合的各层次破裂与灰度的演化规律,补充了部分试验无法观测到的结果。最后,根据蒙特卡罗概率设计方法分析了6个材料参数对细观损伤的影响,为进一步定量描述节理介质细观破裂和损伤演化规律提供参考依据。

Based on real-time computerized temography（CT） experiment on concrete samples with three sets of cracks under uniaxial loading, some new phenomena and laws on meso-crack and meso-damage by numerical computation for non-interpenetrated jointed media are presented; and the effect of six material parameters on the meso-damage of sample is predicted by Monte Carlo probabilistic design method. Over double decades, the experimental technology of computerized tomography has provided an efficient approach to obtain visible picture for micro or meso damage and fracture of rock and soil media, which leads to the micro or meso problems not to be guessed. However, some complicated phenomena and evolutional laws have to be explored and discussed through the numerical analysis due to the limit of equipment, method and sample of experimental situation, etc. Hence, the latest development of CT experiment results is reviewed firstly. Considering the elementary concept of the problem, the data from test and special criteria about meso-crack and meso-damage, the parameters of grey-scale are regarded as the main variable for computing simulation. In fact, the meso-crack and meso-damage could occur in the case of tension and shear based on the damage criteria for 3D elements. According to computing demand of higher precision, the main program is compiled by Fortran language using 3D isoparametric elements with 16 nodes to simulate the crack and the surrounding elements, and that with 8 nodes to simulate the elements far from the crack. Meanwhile, except for shear transfer coefficient for crack open and that for crack closure obtained by probabilistic design approach, all the other parameters are determined by the experiment. As a consequence of computation, the grey-scale distribution, meso-crack distribution, meso-damage distribution, average grey-scale curve and meso-damage isoline distribution on the middle section of the sample are presented in detail. Furthermore, meso-crack and meso-damage inherent evolution laws are come out as well. Finally, the influential parameters of meso-damage model on the middle section such as initial elastic modulus, Poisson ratio, shear transfer coefficient of crack open, shear transfer coefficient of crack closure, limit uniaxial stress of tension and initial density are predicted. The study shows that the characterization of meso-crack and meso-damage for rock or soil is of a stage-like behavior, which varies with material properties, initial situation of sample and loading style, etc. The results may be useful for the research on the evolution law of non-interpenetrated jointed media.