温度和应力条件下北山裂隙性花岗质岩石抗剪机理实验与数值模拟研究

发布时间：2018-04-01 11:06

本文选题：抗剪强度　切入点：PFC~(2d)　出处：《中国地质大学(北京)》2017年硕士论文

【摘要】：含裂隙岩花岗岩为高放废料填埋和地热开采工程提供了较好的地质条件。将基于离散元(DEM)这种数值方法的计算机编程仿真实验与岩石物理模拟相互佐证,并将实验过程中局部应变强化带的应力分布变化和微裂隙贯通路径进行输出,解决了由于断裂效应中无法用肉眼和捕捉的变形表现,同时也揭示了从微小裂纹扩大到大尺度断裂的机理。本文中利用DEM方法,建立了3组含多项高温-冷却处理的对比实验。每组模型中预设温度为100°C、200°C、300°C和400°C,在每种温度下分别进行高温剪切实验和进行冷却处理后剪切实验,以模拟岩石断裂在不同温度条件下的扩展途径,从而为断层,特别是逆冲退覆构造中次生断层发育方式提供新观点和理论依据。实验模拟的样品是中核集团位于甘肃北山地区高仿废料填埋区的花岗岩,石英含量为30%,长石60%,云母约为10%,借助扫描电镜(SEM)对不同温度加热后的花岗岩进行观察,发现在400°C加热和冷却条件下,该花岗岩样品出现了明显的沿石英边界发育的热开裂,以及长石内部沿解理发育的穿晶开裂。将热处理之后的样品进行岩石力学实验,对其失稳断裂途径进行观察分析,发现经高温处理的岩石样品在一定程度上出现强度提升,断裂韧性加强的表现。利用数值模拟对温度处理和岩石力学实验进行细观结构分析发现,在温度提升导致热开裂密度提升的同时,某些矿物解理发育的矿物附近裂纹密度高于样品中裂纹的平均密度,导致在裂纹联合扩展过程当中受到应力分布改变的影响,同时试样的抗剪强度发生改变。
[Abstract]:The fissure rock granite provides better geological conditions for high level radioactive waste landfill and geothermal mining engineering. The computer programming simulation experiment based on discrete element method (DEM) and the rock physical simulation are proved mutually. The stress distribution of the local strain strengthening zone and the path through the microfracture are outputted during the experiment, which solves the deformation performance which can not be captured by the naked eye because of the fracture effect. At the same time, the mechanism of extending from small crack to large scale fracture is revealed. In this paper, the DEM method is used. Three groups of contrastive experiments were established, in which the preset temperatures were 100 掳C, 200 掳C, 300 掳C and 400 掳C, respectively. The high temperature shear experiments and the post-cooling shear experiments were carried out at each temperature, respectively. In order to simulate the propagation path of rock fracture under different temperature conditions, it is called fault. In particular, a new viewpoint and theoretical basis are provided for the development of secondary faults in thrusting and retreating tectonics. The sample simulated by the experiment is a granite located in the high imitation waste landfill area of Beishan area, Gansu Province. The content of quartz is 30, feldspar is 60 and mica is about 10. By means of scanning electron microscope (SEM), the granites heated at different temperatures are observed. It is found that under the heating and cooling conditions of 400 掳C, the samples of the granite show obvious thermal cracking along the boundary of quartz. And the transgranular cracking developed along cleavage in feldspar. The rock mechanics experiment of the samples after heat treatment was carried out, and the unstable fracture path was observed and analyzed. It was found that the strength of the samples treated at high temperature increased to a certain extent. Using numerical simulation to analyze the microstructure of temperature treatment and rock mechanics experiments, it is found that the increase of temperature leads to the increase of thermal cracking density at the same time. The density of cracks near some minerals developed by cleavage is higher than the average density of cracks in the sample, which results in the change of stress distribution and shear strength during the process of crack joint propagation.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU45

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