Roof disaster has always been an important factor restricting coal mine safety production.Acidic effect can reform the rock mass structure to weaken the macroscopic strength characteristics,which is an effective way t...Roof disaster has always been an important factor restricting coal mine safety production.Acidic effect can reform the rock mass structure to weaken the macroscopic strength characteristics,which is an effective way to control the hard limestone roof.In this study,the effects of various factors on the reaction characteristics and mechanical properties of limestone were analyzed.The results show that the acid with stronger hydrogen production capacity after ionization(pK_(a)<0)has more prominent damage to the mineral grains of limestone.When pKa increases from−8.00 to 15.70,uniaxial compressive strength and elastic modulus of limestone increase by 117.22%and 75.98%.The influence of acid concentration is manifested in the dissolution behavior of mineral crystals,the crystal defects caused by large-scale acid action will lead to the deterioration of limestone strength,and the strength after 15%concentration reformation can be reduced by 59.42%.The effect of acidification time on limestone has stages and is the most obvious in the initial metathesis reaction stage(within 60 min).The key to the strength damage of acidified limestone is the participation of hydrogen ions in the reaction system.Based on the analytic hierarchy process method,the influence weights of acid type,acid concentration and acidification time on strength are 24.30%,59.54% and 16.16%,respectively.The research results provide theoretical support for the acidification control of hard limestone roofs in coal mines.展开更多
Historical case studies of climate change impacts and the resulting social responses can provide analogies for better under- standing the impacts of current and future climate changes. Around the turn of the 19th cent...Historical case studies of climate change impacts and the resulting social responses can provide analogies for better under- standing the impacts of current and future climate changes. Around the turn of the 19th century, the climate of the North China Plain experienced a shift from a relatively warm stage in the 18th century to a colder stage in the 19th century, which was characterised by a much colder climate and more frequent and severe floods and droughts. Historical information about refu- gees, social disorder, grain transportation, and disaster relief on the North China Plain in 1780-1819 is collected from the Ver- itable Records of the Qing Dynasty （a collection of official records）. The mechanism of climate change affecting the food se- curity of the society, as indicated by the development of a refugee problem around the turn of the 19th century, is analyzed by examining the social vulnerability. There are four basic findings： （1） In the 40 years from 1780-1819, the society on the North China Plain was unstable and characterised by a significant deterioration of the refugee situation. The number of refugees in- creased markedly, and their behaviour became increasingly violent. In the 1780s, most of the disaster victims chose to stay at their residences waiting for relief. From 1790 to 1800, hundreds of thousands of refugees migrated to northeast China. In the 1810s, the frequency of farmer rebellions increased sharply. （2） The increase in instability corresponded to the climatic cooling over the same time period. The increased instability was a result of the negative impacts of climate change accumulating and transmitting to the social level. （3） For food security, a precondition for the negative impacts of climate change on human soci- ety was the vulnerability of the regional socioeconomic system, which had a high sensitivity and low capacity to respond. This vulnerability could be described by the following three observations： O The regional balance of supply and demand for food was in a critical state, which led to a high sensitivity and dramatic reduction in yield that was caused by climate change; （~ the capacity for disaster relief efforts by the government was too low to meet the needs of crisis management; （~ the capacity for refugees＇ resettlement in eastern Inner Mongolia and northeast China, which both border the North China Plain, was se- verely restricted by climatic conditions or the quarantine policy. （4） It is estimated that climate change caused the social vul- nerability to reach a critical level approximately 20 years earlier on the North China Plain.展开更多
基金Project(2021YFC2902102)supported by the National Key Research and Development Program of ChinaProject(52374142)supported by the National Natural Science Foundation of ChinaProject(JSTU-2022-066)supported by the Young Talent Support Project of Jiangsu Association for Science and Technology,China。
文摘Roof disaster has always been an important factor restricting coal mine safety production.Acidic effect can reform the rock mass structure to weaken the macroscopic strength characteristics,which is an effective way to control the hard limestone roof.In this study,the effects of various factors on the reaction characteristics and mechanical properties of limestone were analyzed.The results show that the acid with stronger hydrogen production capacity after ionization(pK_(a)<0)has more prominent damage to the mineral grains of limestone.When pKa increases from−8.00 to 15.70,uniaxial compressive strength and elastic modulus of limestone increase by 117.22%and 75.98%.The influence of acid concentration is manifested in the dissolution behavior of mineral crystals,the crystal defects caused by large-scale acid action will lead to the deterioration of limestone strength,and the strength after 15%concentration reformation can be reduced by 59.42%.The effect of acidification time on limestone has stages and is the most obvious in the initial metathesis reaction stage(within 60 min).The key to the strength damage of acidified limestone is the participation of hydrogen ions in the reaction system.Based on the analytic hierarchy process method,the influence weights of acid type,acid concentration and acidification time on strength are 24.30%,59.54% and 16.16%,respectively.The research results provide theoretical support for the acidification control of hard limestone roofs in coal mines.
基金supported by National Basic Researh Program of China(Grant No. 2010CB950103)National Natural Science Foundation of China (Grant No. 41071127)
文摘Historical case studies of climate change impacts and the resulting social responses can provide analogies for better under- standing the impacts of current and future climate changes. Around the turn of the 19th century, the climate of the North China Plain experienced a shift from a relatively warm stage in the 18th century to a colder stage in the 19th century, which was characterised by a much colder climate and more frequent and severe floods and droughts. Historical information about refu- gees, social disorder, grain transportation, and disaster relief on the North China Plain in 1780-1819 is collected from the Ver- itable Records of the Qing Dynasty （a collection of official records）. The mechanism of climate change affecting the food se- curity of the society, as indicated by the development of a refugee problem around the turn of the 19th century, is analyzed by examining the social vulnerability. There are four basic findings： （1） In the 40 years from 1780-1819, the society on the North China Plain was unstable and characterised by a significant deterioration of the refugee situation. The number of refugees in- creased markedly, and their behaviour became increasingly violent. In the 1780s, most of the disaster victims chose to stay at their residences waiting for relief. From 1790 to 1800, hundreds of thousands of refugees migrated to northeast China. In the 1810s, the frequency of farmer rebellions increased sharply. （2） The increase in instability corresponded to the climatic cooling over the same time period. The increased instability was a result of the negative impacts of climate change accumulating and transmitting to the social level. （3） For food security, a precondition for the negative impacts of climate change on human soci- ety was the vulnerability of the regional socioeconomic system, which had a high sensitivity and low capacity to respond. This vulnerability could be described by the following three observations： O The regional balance of supply and demand for food was in a critical state, which led to a high sensitivity and dramatic reduction in yield that was caused by climate change; （~ the capacity for disaster relief efforts by the government was too low to meet the needs of crisis management; （~ the capacity for refugees＇ resettlement in eastern Inner Mongolia and northeast China, which both border the North China Plain, was se- verely restricted by climatic conditions or the quarantine policy. （4） It is estimated that climate change caused the social vul- nerability to reach a critical level approximately 20 years earlier on the North China Plain.
