Research On Infrared Radiation Characteristics During The Fracture Process Of Fractured Sandstone

In recent years,with the rapid development of our country's economy,the large water conservancy projects have been planed,constructed and put into operation,the problems of rock mechanics involved have become more and more complex.Because of the different geological structural planes in the rock play a key role on control deformation and failure of rock,the stability problems of rock become more complex.We could find that the failure of rock mass engineering mainly caused by geological structural planes initiation,expansion and coalescence under external loads from existing engineering cases.Hence,it has great engineering significance to study the failure characteristics of rock mass containing flaws under external loads.Effectively supervising the process of it is extremely important to safe construction and production.According to quantum mechanics,any object with temperature above absolute zero,spontaneously emits outwardly infrared radiation energy,which varies according to the object's temperature.In the process of deformation and failure of rock under compression,the infrared radiation intensity varies according to the changes of stress,and the anomalies of infrared radiation will occur near the failure.Combined infrared technology and rock mechanics formed a new subject,named REMOTE SENSING ROCK MECHANICS.Through non-contact and non-destructive monitoring of crack initiation,expansion and coalescence,assess the rock mass stability at real-time.Infrared radiation temperature is a geophysical method monitoring rock dynamic disaster.The infrared temperature and infrared thermal image have the effect of reflecting the spatial evolution and compression time of rock.To solve the problem that previous researches on rock mass infrared radiation study are lacking quantitative description which is wide suitability and further study the infrared thermal effect and its precursory rule of fractured sandstone.This paper makes the red sandstone as the research object,pre-flaw prepared by high speed water cutting technology,effect of flaw inclination were considered,uniaxial compression test and infrared technology were combined,maximum infrared radiation temperature,minimum infrared radiation temperature and average infrared radiation temperature were introduced,the whole failure process,the characteristics of infrared radiation temperature and failure precursor information were monitoring and analyzing.This study is helpful to reveal the failure mechanism of the sandstone containing a pre-flaw from a new way.In sum,contents in this paper can be summarized in the following:(1)According to the stress-strain curve and the characteristics of crack expansion,the deformation and failure process of sandstone containing a pre-flaw could be divided into four stages,micro-crack closure stage,elastic deformation stage,micro-crack initiation and propagation stage and post-peak stage,respectively.The failure mode in the specimen can be classified into two groups,named wing crack and shear failure(failure mode ?)and anti-wing crack failure(failure mode ?).The specimens,flaw inclination from 15° to 60°,fail in mode ?.Other specimens fail in mode ?.(2)The compression stress of sandstone specimen is differently blunted by pre-flaw.With the increase of flaw inclination,the compression stress of specimen decreases first and then increases.When the flaw inclination is 45°,the compression stress of specimen reached minimum,the weakening effect reached maximum.When the flaw inclination is 75°,the compression stress of specimen reached maximum,the weakening effect reached minimum.(3)According to two failure modes,infrared thermal characteristics modes of specimen could be classified into two groups,named mode ? and mode ?,respectively.Because of the interactions of the pore gas desorbing-escaping effect,the thermoelastic effect,the fracture effect,and the friction-thermal effect,when through micro-crack closure stage,elastic deformation stage,micro-crack initiation and propagation stage and post-peak stage,the sandstone containing a pre-flaw will show the different infrared radiation characteristics,and the temperature rises rapidly at the failure.(4)The infrared radiation temperature will show the rise-to-drop before the failure by analysis and comparing the stress-strain curve and infrared radiation temperature-strain curve.The corresponding rise-to-drop change point could be as failure precursor points.