Search

In the practice of the deep engineering, it is expected to improve engineering ef- ficiency by introducing the microwave energy. Therefore, based on 1050 m deep sandstone, the heating characteristics of sandstone and its constituent minerals in the microwave field are comprehensively explored through experiments and numerical simulations. In the paper, the asynchronism of the temperature rise in different areas of the sandstone depends on the local characteristics of dielectric loss and maximum heat storage capacity. With increase of the temperature, the evaporation of the water leads to the decrease of the dielectric properties, the increase in the constant-pressure heat capacity and the increase in the heat dissipation coeffi- cient, which suppresses the temperature growth trend. The temperature rise of the amplitude of the material is lower than that expected from the microwave power. The maximum temperature of dolomite, feldspar and quartz under the power of 2000 W is 1.86, 1.71, and 1.63 times that of the power of 1000 W, respectively. It is necessary to select the reasonable microwave power to maximize the engineering efficiency. The results are expected to provide the theoretical and technical supports for the electromagnetic heat generation in deep engineering. [ABSTRACT FROM AUTHOR]

The In-situ coring has a significant effect on the exploration of deep earth. However, in deep hard rock coring, the cutting heat in the process of coring generates high temperature and causes fidelity distortion of the in-situ core. Exploration of the mechanism of heat effect in the coring process is necessary to achieve the continuous control of temperature and obtain in-situ core. Due to the lack of systematic study on the surface and internal temperature rise of core samples during coring process, this paper uses the finite element simulation study the heat effect on the surface of the core under the influence of various cutting parameters. The numerical simulation results show that the surface of the core will not be burned under the cutting speed of 100 mm/s. At the condition of cutting speed 100 mm/s, feed rate 0.03 mm/r, thermal conductivity coefficient 1 W/m°C, the whole temperature rise will not exceed 1 °C. The interest results showed that cutting fluid has little effect on the temperature rise in the cutting process. If the requirement of core quality should avoid the pollution by drilling fluid, this study has supported the no drilling fluid for in-situ coring. [ABSTRACT FROM AUTHOR]