In-situ experiment on the identification of shallow hidden mining-induced ground fissure using UAV infrared technology

High mining intensity of coal mines can induce disasters easily, such as surface subsidence and ground fissures, and damage surface ecology. Moreover, the spontaneous combustion of residual coal also appears, which can threaten the safety of coal mine production. In addition, the degree of desertification is relatively serious in the western mining area.The surface of some coal mines is covered with aeolian sand, which easily leadsto the ground mining-induced fissures covered by aeolian sand. The shallowhidden mining-induced ground fissures are difficult to be identified by the conventional monitoring methods. To explore the feasibility of identifying shallow hidden mining-induced ground fissures, a method based on an unmanned aerial vehicle (UAV) infrared technology was proposed. Taking working face No.52605 of the Daliuta coal mine in the Shendong Mine area as the engineering background, the hidden mining-induced fissures with different buried depths were designed and prepared. At night, the infrared images at different times were obtained by continuous monitoring. The temperature of the hidden mining-induced fissures, aeolian sand, and vegetation in infrared images at different times were statistically analyzed. The results show that a UAV equipped with an infrared camera can effectively identify the shallow hidden mining-induced ground fissures, and the buried depth of the identified hidden mining-induced fissure is different at different times. The greater the temperature difference between hidden mining-induced fissures and surrounding ground objects, the easier it is to be identified. The temperature of the hidden mining-induced fissure is different from that of surrounding ground objects under the combined action of heat conduction of mining-induced fissure and ambient temperature and has an obvious correlation with burial depth. Under the research conditions of this paper, the temperature of the hidden mining-induced fissure, ground mining-induced fissure, aeolian sand, and vegetation decreases continuously from 9:00 pm to 5:00 am. The absolute temperature difference between hidden mining-induced fissures with different burial depths and aeolian sand and vegetation is large between 1:00 am and 5:00 am. The absolute temperature difference between hidden mining-induced fissureswith different buried depths and aeolian sand is ≥1.2 ℃, and the absolute temperature difference between hidden mining-induced fissures and vegetation is ≥2.1 ℃. Therefore, the hidden mining-induced ground fissuresare easy to be identified during this period. However, at 9:00 pm, the absolute temperature difference between hidden mining-induced fissures buried 15, 20, and 30 cm and aeolian sand is 0.8, 0.6, and 0.8 ℃, respectively.At 11:00 pm, the absolute temperature difference between hidden mining-induced fissures buried 20 cm and aeolian sand is 0.7 ℃.The absolute value of temperature difference is relatively small, and the hidden mining-induced fissures with the aforementioned buried depths are difficult to be identified from 9:00 pm to 11:00 pm. © 2022, Editorial Office of Journal of China Coal Society. All right reserved.