Experimental Research On Mechanism Of Rock Damage Caused By Microwave Irradiation

Rock blasting and mechanical crushing are the main methods of rock breaking in tunnel construction, while both of them have shortconings in the practice of engineering. The former method has a large disturbance to the original rock which causes difficulties on supporting, the latter needs high investment costs but low efficiency in case of hard rock. Studies shows that microwave irradiation can greatly reduce the rock strength and improve the efficiency of mechanical crushing. "Microwave combined with Mechanical" is expected to become a new and efficient method of rock breaking.This article will study the mechanism of rock damage caused by microwave irradiation by changing a variety of factors such as rock types, moisture content, microwave power and irradiation time, etc. The author analyzes the mechanism of rock damage through CT scans and shear tests of rock. Specific research and the results achieved are as follows:(1)This article elaborate the mechanism of rock damage caused by microwave irradiation and discuss the internal factors of the damage evolution based on the theoretical analysis. Some of the zones which contain a variety of absorbing microwave minerals in rock causes the rock damage caused by microwave irradiation. Conclusions show that the mineral composition, moisture content and other factors have some influence on the evolution of rock damage caused by microwave irradiation. In the rage of different moisture content which set by the researcher, the higher moisture content of the rock,the lager degree of injury and stronger damage discretion.(2) Set up the rock test based on the different parameters of microwave irradiation. Results show that the thermal expansion of the rock grains weakened the original binding force between grains,which causes the decrease of rock shear strength,High power and short time microwave irradiation can reduce the strength of the rock effectively.(3)Determine the variable of damage rock under the different conditions of microwave irradiation by the CT scans. The results show that the damage evolution of rock under the microwave irradiation performs localized features. The damage of granite caused by the absorbing microwave minerals in it such as biotite, hornblende, magnetite, while for the basalt these minerals maybe olivine and pyroxene.(4)The research shows that high power and short time microwave irradiation can reduce the rock strength effectively. On the basis of this, two microwave-assisted devices for rock breaking are designed. The hydraulic support is used to connet the edge hob and the cutter while the microwave antennas installed on both sides of the edge hob. The edge hob cut the rock in the condition of microwave irridation. All of these can reduce the wear of the cutter and improve the effeneicy of rock breaking. The antennas in the microwave-assisted drilling transmit the microwave. The strength of rock is reduced caused by microwave irridation.This device will improve the effeneicy of hard rock breaking in the deep formations such as granite and basalt.