Water injection, as a widely used technique to prevent coal burst, can restrain the fractured coal seam and released the energy storage. In this study, laboratory tests were frstly carried out on standard coal specime...Water injection, as a widely used technique to prevent coal burst, can restrain the fractured coal seam and released the energy storage. In this study, laboratory tests were frstly carried out on standard coal specimens with fve diferent water contents (i.e., 0%, 0.6%, 1.08%, 1.5%, 2.0%, and 2.3%). The failure mode, fragment size, and energy distribution characteristics of coal specimens were investigated. Experimental results show that strength, elastic strain energy, dissipated energy, brittleness index, as well as impact energy index decrease with increasing water content. Besides, the failure mode transitions gradually from splitting ejection to tensile-shear mixed failure mode as water content increases, and average fragment size shows positively related to water content. Moreover, scanning electron microscope tests results indicate that water in coal sample mainly causes the mineral softening and defects increase. Furthermore, a numerical model containing roadway excavation was established considering the water on coal burst prevention. Modelling results revealed that water injection can reduce degree of coal burst and ejection velocity of coal blocks, while it will raise up the depth of crack zone and surface displacement of roadway. Combined with laboratory tests and numerical results, the micro mechanism, energy mechanism, and engineering signifcance of water injection on coal burst prevention were fnally analyzed.展开更多
The outbreak of coronavirus disease 2019(COVID-19)has spread rapidly around the world.As of May 30,2020,a total of 84568 confirmed COVID-19 cases have been recorded in China,with a mortality rate of approximately 5.5%...The outbreak of coronavirus disease 2019(COVID-19)has spread rapidly around the world.As of May 30,2020,a total of 84568 confirmed COVID-19 cases have been recorded in China,with a mortality rate of approximately 5.5%.Taizhou is a prefecture-level city in Zhejiang Province.A total of 146 cases were diagnosed in this epidemic,with a fatality rate of 0%.This condition is due to the establishment of an“Internet+”diagnosis and treatment model based on online medical application(APP),telemedicine,WeChat service,and consultation hotline in Taizhou.Taizhou led in opening the“COVID-19 Prevention and Treatment Special Line”in China,which is conducive to pre-hospital screening,suppressing social panic,and clinical support.Hospitals also carried out related online lectures and popularization of science.We summarize Taizhou’s COVID-19 prevention and control experience with telemedicine features,with a view to providing reference for the control of the epidemic at home and abroad.展开更多
基金supported by the National Natural Science Foundation of China(Grant No:51974289)Natural Science Foundation of Anhui Province(Grant No:2108085ME155).
文摘Water injection, as a widely used technique to prevent coal burst, can restrain the fractured coal seam and released the energy storage. In this study, laboratory tests were frstly carried out on standard coal specimens with fve diferent water contents (i.e., 0%, 0.6%, 1.08%, 1.5%, 2.0%, and 2.3%). The failure mode, fragment size, and energy distribution characteristics of coal specimens were investigated. Experimental results show that strength, elastic strain energy, dissipated energy, brittleness index, as well as impact energy index decrease with increasing water content. Besides, the failure mode transitions gradually from splitting ejection to tensile-shear mixed failure mode as water content increases, and average fragment size shows positively related to water content. Moreover, scanning electron microscope tests results indicate that water in coal sample mainly causes the mineral softening and defects increase. Furthermore, a numerical model containing roadway excavation was established considering the water on coal burst prevention. Modelling results revealed that water injection can reduce degree of coal burst and ejection velocity of coal blocks, while it will raise up the depth of crack zone and surface displacement of roadway. Combined with laboratory tests and numerical results, the micro mechanism, energy mechanism, and engineering signifcance of water injection on coal burst prevention were fnally analyzed.
文摘The outbreak of coronavirus disease 2019(COVID-19)has spread rapidly around the world.As of May 30,2020,a total of 84568 confirmed COVID-19 cases have been recorded in China,with a mortality rate of approximately 5.5%.Taizhou is a prefecture-level city in Zhejiang Province.A total of 146 cases were diagnosed in this epidemic,with a fatality rate of 0%.This condition is due to the establishment of an“Internet+”diagnosis and treatment model based on online medical application(APP),telemedicine,WeChat service,and consultation hotline in Taizhou.Taizhou led in opening the“COVID-19 Prevention and Treatment Special Line”in China,which is conducive to pre-hospital screening,suppressing social panic,and clinical support.Hospitals also carried out related online lectures and popularization of science.We summarize Taizhou’s COVID-19 prevention and control experience with telemedicine features,with a view to providing reference for the control of the epidemic at home and abroad.
