Experimental Study On Strength Degradation Of Hot Wet Rock Under Microwave Irradiation

With the continuous improvement of China's comprehensive strength,the research significance of rock crashing technology in geotechnical engineering and mining mengineering is more and more important.At present,there are many researches on the influence of microwave parameters on rocks,but the relationship between the deterioration of rocks and the way of microvwave circulatior0,the relatiolrnship between moisture and heat and humidity in rocks is not enough.The experimental study on the strength degradation of hot and hemid rock under microwave irradiation has certain theoretical and practical value for popularizing microwave as auxiliary rock breaking technology.In this paper,microwave irrradiation and conventional static mechanical tests are carriecd out on granite specimens by means of microwave generating cdevice and universal testing machine.The strerngth deterioration law of granite under different power micarowaves,cycle times and circulation modes is discussed.At the same time,XRC,SEM and FLIR thermal imager were used to analyze the composition of the rock sample.The internal crack morphology of the sample before and after microwave irradiation and the temperature change of the sample after microwave irradiation were observed.The main research contents and conclusions are follows:(1)Combining the temperature rise characteristics of different mineral components in the rock under microwave irradiation and how the water in the rock plays a role,analyze the principle of cracking inside the rock under microwave action and the action mechanism of water on rock.It is concluded that the mineral composition of the rock,the microwave parameters and the moisture in the rock affect the strength of the granite after microwave action.(2)The granite samples were subjected to hot-wet circulation or thermal cycle treatment with 900W low-power microwave.The single microwrave irradiation time was 2min,and then the specimen was subjected to Brazilian splitting tensile mechanical properties test.The granite specimens were subjected to hot-wet circulation or thermal cycle treatment using 2kW,4kW and 6kW power microwaves.The single microwave irradiation time was 2min,and then the compressive strength of the granite samples after microwave irradiation without confining pressure was measured.It is concluded that the granite strength decreases with the increase of the number of cycles at the same power.The granite strength decreases with the increase of microwave power under the same number of cycles.The heat and humidity cycle has better effect on rock strength degradation under the same microwave power and cycle number.(3)XRD and SEM electron microscopy tests were carried out on granite specimens and control specimens irradiated by 2 kW,4 kW,6 kW power microwaves,4 times of heat and humidity cycles and heat cycles,and the high power microwave was applied by means of FIIR thermal imager.The sample was analyzed for temperature variation.It is concluded that the mineral components of granite are mainly quartz,amphibole and biotite.After microwave irradiation,a large number of intergranular fracture and trans granular fracture microscopic cracks were generated inside the granite.The maximum temperature and average temperature of the test piece after microwave irradiation are related to the microwave power,the number of cycles and the cycle mode.