脆性岩石与有机玻璃受力红外辐射特征的比较

COMPARISON OF INFRARED RADIATIONS OF BRITTLE ROCK AND POLYMETHYL MECHACRYLATE INDUCED BY STRESS

近年来的遥感岩石力学研究表明,岩石受力及灾变过程存在规律性的红外辐射效应,岩石破裂前存在红外异常前兆。为更好了解岩石受力的红外辐射特征、并进一步探索其物理机制,基于实验结果对脆性岩石和有机玻璃受力的红外辐射特征进行分析比较,发现:(1)有机玻璃在加载过程中表面的红外辐射强度呈整体上升趋势,而多数岩石在临破裂前热像出现条带状的分异现象,条带与岩石破裂位置吻合;(2)两种材料虽然在不同的应力阶段都存在不同的AIRT变化特征,但规律不同。有机玻璃随压力的上升呈现分阶段的直线上升,而岩石呈现多种变化形式,且在破裂前存在AIRT的异常变化前兆。对两种材料受力红外辐射的机制讨论认为,岩石加载过程的热效应包括热弹效应、气体逸出吸热效应以及微破裂的摩擦热效应,而有机玻璃存在热弹效应、热塑效应和热黏效应。两种材料热力耦合机制不同是导致受力红外辐射特征差异的根本原因。

The studies on remote sensing rock mechanics(RSRM) in recent years show that rock has regular features of infrared radiation(IR) when the rock is loaded,and the anomalous IR phenomena appear before rock fracture. In order to understand the IR feature of loaded rock and its physical mechanism,the IR features of rock under uniaxial compression are compared with those of polymethyl mechacrylate(PMMA) under similar conditions. The results show that:(1) during the whole loading process,the radiation intensity of PMMA increases symmetrically and no local anomaly appears in the thermal image,but the anomalous radiation appears frequently in the thermal image of rock before fracture,and it appears in strips and the location of strips corresponds to those of rock fractures;and (2) different stress stages show different IR features,but the IR patterns of two materials are different. The average IR radiation temperature(AIRT) of PMMA rises in the form of sectional line with the variation of stress state. However,AIRT variation curve of rock with time presents diverse forms,and the anomalous AIRT precursors appear before rock fracture. The mechanism of thermomechanical coupling is discussed and the result shows that the thermomechanical coupling effects of rock include thermoelastic effect,endothermic effect caused by gas escaping,and friction heat effect due to generation of a mass of cracks. Comparatively,PMMA has thermoelastic effect,thermoplastic and thermoviscous effects. The difference of thermomechanical coupling effect is the cause to result in IR feature difference between rock and PMMA.