Study On The Influence Of Heating Method On Thermal Induced Damage Of Granite

With the rapid development of China's transportation industry.Tunnel construction is gradually increasing,and hard rock is often encountered during tunnel excavation,which reduces the efficiency of tunnel excavation and prolongs the construction period.Therefore,the efficient breaking of hard rock has become a new technical problem.High-temperature auxiliary rock breaking can cause thermal damage to the rock through high temperature and improve the breaking efficiency of hard rock,becoming an auxiliary rock breaking method with application prospects.There are two heating methods: traditional heating and microwave heating.Therefore,it is of great reference significance to study the effect of two heating methods on the thermal damage of hard rock for high temperature assisted rock breaking.In this paper,the experimental research on the thermal damage of granite by two heating methods,traditional heating and microwave heating,is carried out.Through the physical and mechanical tests such as uniaxial compression and CT scanning test,the physical and mechanical properties and microscopic cracks of granite by two different heating methods are studied.The impact of distribution is as follows:(1)Uniaxial compression and other physical and mechanical tests were carried out on the test block after traditional heating and microwave heating.The results showed that with the increase of temperature,the density of granite samples after traditional heating and microwave heating decreased,and both decreased.The amplitude difference is not large.After two methods of heating,the longitudinal wave velocity of granite has decreased.After microwave heating,the longitudinal wave velocity of the sample is greater than that of the traditional heating sample.The granite test after two heating methods The compressive strength and elastic modulus of the sample have decreased,and the compressive strength and elastic modulus of the sample after microwave heating are greater than that of the sample after traditional heating.At the same time,the granite samples heated by microwave are more prone to surface cracks visible to the naked eye,and tend to be ductile when damaged by compression.(2)The CT scanning test was carried out on the test blocks after microwave heating and traditional heating.The results show that the number of cracks in the two-dimensional crack diagram of the microwave heating test block at the same temperature is more than the cracks in the crack diagram of the traditional heating test block Quantity.At 500 ?,the cracks of the traditional heating test block are not obvious,but the microwave heating test block can clearly see the cracks.At 800 ?,the cracks in the microwave heating test block are more than the traditional heating test block.,The crack width is wider,and all minerals have cracks.The volume porosity of the test block after microwave heating in the three-dimensional CT image is about three times that of the traditional heating test block.The number of cracks and pores in the test block is significantly more than that of the traditional heating test block.(3)The analysis of the two-dimensional crack diagram of the test block after 800? microwave heating and traditional heating by the latitude and longitude analysis method shows that: the average dispersion of the crack distribution in the warp and weft directions of the 800 ? microwave heating test block is less than that of the traditional heating test block The average value of the dispersion of the warp and weft directions,and the anisotropy rate of the microwave test block is closer to the reference value 1 than the anisotropy rate of the traditional test block.It shows that the distribution of the cracks of the granite samples after microwave heating is better than that of the samples after the traditional heating,and it is more isotropic.