加热-冷却过程中花岗岩细观热破裂机制  

Thermal cracking mechanism of granite during heating and cooling processes

作　　者：王飞[1] 邹岩琳 庞瑞 何本国 范立峰[2] 孟德昊 刘甜甜 石垚 WANG Fei;ZOU Yanlin;PANG Rui;HE Benguo;FAN Lifeng;MENG Dehao;LIU Tiantian;SHI Yao(Northeastern University,Key Laboratory of Ministry of Education on Safe Mining of Deep Metal Mines,Shenyang 110819,China;Beijing University of Technology,Faculty of Architecture,Civil and Transportation Engineering,Beijing 100124,China;CCTEG Coal Mining Research Institute,Beijing 100013,China)

机构地区：[1]东北大学教育部深部金属矿山安全开采重点实验室,辽宁沈阳110819 [2]北京工业大学城市建设学部建筑工程学院,北京100124 [3]中煤科工开采研究院有限公司巷道研究分院,北京100013

出　　处：《岩土工程学报》2024年第10期2138-2147,共10页Chinese Journal of Geotechnical Engineering

基　　金：国家自然科学基金项目(52104120,52222810)。

摘　　要：由于高温试验设备的限制,在实验室中研究岩石真实热破裂规律通常需要依据冷却后试样的细微观结构观测结果来进行分析推断,无法获得热破裂的实时动态演化过程。为此,基于考虑温度和裂纹滑移效应的节理本构关系,构建花岗岩热力耦合UDEC晶粒模型,以深入探究加热和冷却过程中花岗岩的实时热破裂行为。研究发现,在加热状态下,花岗岩热诱导微裂纹在75℃左右开始萌生,随着温度的升高,微裂纹数量在α→β石英相变温度附近快速达到峰值,但微裂纹密度在600℃降温到25℃的冷却过程中并没有明显变化。虽然冷却效应引起的裂纹数量变化可以忽略不计,但会导致裂纹开度的增加或减少。在加热过程中,微裂纹的萌生主要是由于相邻晶粒的热膨胀不同导致局部应力累积造成的。而石英高温相变引起的细微观结构变化可以增强不同晶粒之间的相互作用,导致晶粒尺度上的压缩和剪切运动加剧,使得热应力裂纹继续变形拓展。在冷却过程中,由于加热过程中热破裂导致的细微观应力释放和冷却效应导致的不同矿物晶体收缩,使得微裂纹的数量虽然不变,但其形态却能发生较为明显的变化,从而使得冷却后花岗岩的宏观应力-应变行为受到很大影响。基于离散元数值模拟对花岗岩热力耦合试验结果作出了细微观阐释,揭示了加热和冷却过程中花岗岩的实时热破裂机制,进一步加深了对高温岩石热力耦合规律的理解。Due to the limitations in high-temperature test equipment,the studies on the real thermal cracking of rocks in laboratory typically involve inverse analysis based on microstructure observations of cooled specimens.The real-time cracking evolution at high temperatures cannot be obtained through this method.Therefore,in this study,a thermo-mechanical coupled UDEC grain-based model for granite is established based on the modified joint constitutive law considering temperature and crack slip effects so as to investigate the real-time thermal cracking behavior of granite during heating and cooling processes.It is found that the thermally induced microcracking in granite begins to occur at around 75°C under heating conditions.The number of microcracks rapidly increase near theα→βquartz phase transition temperature,but the microcrack density does not change significantly during the cooling process.Although the change in the crack number caused by the cooling effects is negligible,it can lead to an increase or decrease in the crack opening.During the heating process,the initiation of microcracks is mainly formed by the local stress accumulation due to different thermal expansions of the adjacent grains.The microstructure changes caused by quartz transition can enhance the interaction between different grains,leading to the increasing compression and shear motion on the grain level.This results in thermal-induced cracks continuing to deform and develop.During the cooling process,the local microscopic stress release due to the thermal cracking during heating and the shrinkage of different mineral crystals due to the cooling effects make the number of microcracks hardly change,but their morphological characteristics can change more significantly.This greatly affects the macroscopic stress-strain behaviors of granite after cooling.The findings of thermo-mechanical coupling tests on granite based on the discrete element numerical simulations are interpreted in a micro-meso-scale manner,revealing the real-time thermal cra

关 键 词：花岗岩 晶粒模型 实时高温 热破裂 

分 类 号：TU45[建筑科学—岩土工程]