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Mixed mode fracture tests and inversion of FPZ at crack tip of overlying strata in underground coal gasification combustion cavity under real-time high temperature condition
Engineering Fracture Mechanics ( IF 5.4 ) Pub Date : 2020-11-01 , DOI: 10.1016/j.engfracmech.2020.107298
Tao Meng , Xue Guangwu , Ma Jiwei , Yue Yang , Wen Liu , Jing Zhang , Jiao Bosen , Shihui Fang , Guoliang Ren

Abstract Measuring the fracture parameters of rock materials under real-time high temperature is of great significance for accurately evaluating the stability and safety of high-temperature underground tunnels. At present, the related research is focused on the fracture properties of rocks after treatment with high temperature. To this end, we independently developed a set of testing apparatus with effect of THMC coupling of high temperature and high pressure. Using this equipment, a serious of mixed mode I ± II fracture experiments of overlying strata (red sandstone) in combustion cavity under real-time high temperature conditions (20–700 °C) are carried out. And, the variations of fracture toughness, fractal dimension of fracture trajectory and fracture initiation angle with respect to temperature and notch angle are clarified. In addition, in order to predict the fracture process and fracture behavior of red sandstone at real-time high temperature, the experimental fracture envelopes are compared with that predicted by traditional fracture criterion. It is concluded that the fracture process zone (FPZ) size at the crack tip plays a crucial role in the effectiveness of the fracture criterion, and it is temperature-dependent. Finally, based on the generalized tangential stress criterion (GMTS), the effective FPZ sizes of red sandstone under different high temperature conditions are determined by using particle swarm optimization (PSO) algorithm combined with least square method. The research results of this paper are of great significance for evaluating the stability and safety of overlying strata (red sandstone) in combustion cavity.

中文翻译:

实时高温条件下煤炭地下气化燃烧腔上覆地层裂尖混合模式断裂试验及FPZ反演

摘要 实时测量高温下岩石材料的断裂参数对于准确评价高温地下隧道的稳定性和安全性具有重要意义。目前相关研究主要集中在高温处理后岩石的断裂特性。为此,我们自主研发了一套具有高温高压THMC耦合效应的试验装置。使用该设备,在实时高温条件下(20-700℃)进行了燃烧腔内上覆地层(红砂岩)的一系列I±II混合模式断裂实验。并且阐明了断裂韧性、断裂轨迹分形维数和断裂起始角相对于温度和缺口角的变化。此外,为了实时预测红砂岩的断裂过程和断裂行为,将实验断裂包络与传统断裂准则预测的断裂包络进行比较。结论是裂纹尖端的断裂过程区(FPZ)尺寸对断裂准则的有效性起着至关重要的作用,并且它与温度有关。最后,基于广义切向应力准则(GMTS),采用粒子群优化(PSO)算法结合最小二乘法确定不同高温条件下红砂岩的有效FPZ尺寸。本文的研究成果对评价燃烧腔内上覆地层(红砂岩)的稳定性和安全性具有重要意义。
更新日期:2020-11-01
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