Abstract
To explore the fracture mechanism of surrounding rock for thermal-mechanical coupling in deep mining, the theoretical solution of the internal temperature and stress evolution of the underground chamber cold boundary subjected to cold impact was obtained by thermoelastic theory. The conduction law of temperature and the evolution characteristics of stress were studied by theoretical formulas, and the influence of the convective heat transfer coefficient on the rate of tensile stress reduction was analyzed. The results show that the theoretical solution is in good agreement with the field measured value, which proves that the theoretical calculation method adopted in this paper is reliable and accurate. When the surface of the underground chamber is impacted by the change of temperature, the cold boundary temperature drops sharply at first, then gradually slows down, and finally reaches the same temperature as the air; the tensile stress decreases sharply from the initial high-stress value, then gradually decreases, and finally tends to be stable. The effects of different convective heat transfer coefficients on the change of temperature resistance of rocks were considered by numerical simulation. The numerical simulation results show that increasing the convective heat transfer coefficient not only increases the tensile stress of the heat transfer boundary but also increases the possibility of cracks, which makes the rock easier to crack. Based on the research results, we introduced the thermal-mechanical coupling disturbance range coefficient β = L/2D (β = 6–8) and proposed that the convective heat transfer coefficient is the reference index of the deep mining support structure, which can provide a theoretical basis and technical support for the selection of support materials.
Highlights
In situ stress is the natural stress existing in the stratum and not disturbed by engineering
Based on the theory of thermal stress, the temperature and stress field of the surrounding rock induced by temperature change are studied by numerical simulation and field data
E following can be seen from the results: (1) Based on the engineering background of coastal mines, combined with the in situ stress data collected in the field and the theoretical calculation of thermal stress, the influence range of thermal-mechanical coupling on the surrounding rock in the process of deep mining is studied
Summary
In situ stress is the natural stress existing in the stratum and not disturbed by engineering. The surrounding rock bears the in situ stress and the thermal stress caused by temperature change under the condition of mine ventilation and cooling. Many scholars have performed experimental studies on the physical and mechanical properties of rock under high-temperature conditions. E experimental results showed that the mechanical parameters of granite change with temperature, and the rock changes from brittleness to plasticity with increasing temperature. Chen et al [6] utilized Beishan granite as the study object and carried out compression fracture and acoustic emission tests of thermally damaged rock samples with different sizes and confining pressures. To solve a series of problems of the surrounding rock in deep mining, we utilized the coastal mine, that is, Sanshandao gold mine, as the study object and preliminarily discussed the law of thermal stress coupling the environmental stress evolution of surrounding rock
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