Two case studies were conducted in the Shennan mining area of Shaanxi Province,China to evaluate the surrounding rock deformation and stress evolution in pre-driven longwall recovery rooms· These studies mainly m...Two case studies were conducted in the Shennan mining area of Shaanxi Province,China to evaluate the surrounding rock deformation and stress evolution in pre-driven longwall recovery rooms· These studies mainly monitored the surrounding rock deformation and coal pillar stress in the recovery rooms of the N1206 panel of 2-2 coal seam at Ningtiaota Coal Mine and the 15205 panel of 5-2 coal seam at Hongliulin Coal Mine.The monitoring results showed that the surrounding rock deformation of the main recovery room and the coal pillar stress in the N1206 and 15205 panels began to increase significantly when the face was 36 m and 42 m away from the terminal line,respectively.After the face entered the main recovery room,the maximum roof-to-floor convergence in the N1206 and 15205 panels was 348.03 mm and 771.24 mm,respectively,and the coal pillar stresses increased more than 5 MPa and 7 MPa,respectively.In addition,analysis of the periodic weighting data showed that the main roof break position of the N1206 and 15205 panels after the longwall face entered the main recovery room was-3.8 m and-8.2 m,respectively.This research shows that when the main roof breaks above the coal pillar,the surrounding rock deformation of the main recovery room and the coal pillar stress increase sharply.The last weighting is the key factor affecting the stability of the main recovery room and the coal pillar;main roof breaks at disadvantageous positions are the main cause of the support crushing accidents.展开更多
Adsorption deformation significantly affects the seepage characteristics of coal.However,effect of sorption time on coal permeability and gas pressure has not been investigated systematically.In this study,the sorptio...Adsorption deformation significantly affects the seepage characteristics of coal.However,effect of sorption time on coal permeability and gas pressure has not been investigated systematically.In this study,the sorption experiment of coal samples is conducted to elaborate the importance of sorption equilibration time.Then a coupled coal deformation and gas flow model is established considering the sorption characteristic and permeability evolution.This coupled model is implemented through finite element method to analyze the effect of sorption time on coal permeability and gas pressure.The simulation results reveal that the gas pressure of the coal will change with the adsorption time.The fracture pressure maintains a high level while the matrix pressure is relatively low during the adsorption process.The sorption time has a great influence on the distribution of gas pressure.The smaller the adsorption time is,the lower the gas pressure becomes.展开更多
In the seepage-stress-damage coupled process,the mechanical properties and seepage characteristics of coal are distinctly different between pre-peak stage and post-peak stage.This difference is mainly caused by damage...In the seepage-stress-damage coupled process,the mechanical properties and seepage characteristics of coal are distinctly different between pre-peak stage and post-peak stage.This difference is mainly caused by damage of coal.Therefore,in the process of seepage and stress analysis of coal under the influence of excavation or mining,we need to consider the weakening of mechanical properties and the development of fractures of damaged coal.Based on this understanding,this paper analyzes the influence of damage on mechanics and seepage behavior of coal.A coupled model is established to analyze the seepage-stress-damage coupled process of coal.This model implemented into COMSOL and MATLAB software to realize the numerical solving.Two examples are adopted to verify the correctness of the model and some useful conclusions are obtained.The numerical model establishes the relationship between microcosmic damage evolution and macroscopical fracture and simulates the whole process of coal from microcosmic damage to macroscopical fracture,and the dynamic simulation of fluid flow in this process.It provides a numerical tool for further research on the seepage-stress-damage analysis.展开更多
Modeling the soil evaporation under vegetation conditions is of theoretical and practical significance for water resources management in the Loess Plateau.In this study,a three-year field experiment was conducted in a...Modeling the soil evaporation under vegetation conditions is of theoretical and practical significance for water resources management in the Loess Plateau.In this study,a three-year field experiment was conducted in a bare land and three grasslands to measure soil evaporation using micro-lysimeters.The Van Bavel-Hillel model was then validated in the bare land.Based on this,the vegetation coverage resistance was proposed to reflect the comprehensive effects of vegetation,and it was applied into the Van Bavel-Hillel model to improve the model’s applicability under vegetation conditions.The results showed that the Van Bavel-Hillel model was effective in simulating evaporation from bare land,and the application of validated soil surface resistance and vegetation coverage resistance can make it perform well in the evaporation simulation in all studied grasslands.The obtained vegetation coverage resistances decreased linearly with the increase of soil moisture contents in all three grasslands,and the decreasing rates were similar in the M.sativa and P.giganteum plots,which were higher than that in the I.cylindrica plot.Soil surface resistances ranged between 533.4-746.5,767.4-1154.7,and 133.4-1334.5 s/m in the I.cylindrica,M.sativa,and P.giganteum plots,respectively,and all showed the characteristics of first increasing and then decreasing during the growing season.When compared with natural grassland,M.sativa increased the soil surface resistance in all months,while P.giganteum reduced it in the early growing season,but increased it in the middle and late growing season.This research proposes a new idea for the simulation of soil evaporation under vegetated conditions,and provides a basic reference for water resources management in the vegetation restoration of the Loess Plateau.展开更多
基金Support for this work was provided by the National Natural Science Foundation of China(No.51679199)Key Laboratory for Science and Technology Co-ordination and Innovation Projects of Shaanxi Province(No.2014SZS15-Z01)and is thankfully acknowledged by the authors.
文摘Two case studies were conducted in the Shennan mining area of Shaanxi Province,China to evaluate the surrounding rock deformation and stress evolution in pre-driven longwall recovery rooms· These studies mainly monitored the surrounding rock deformation and coal pillar stress in the recovery rooms of the N1206 panel of 2-2 coal seam at Ningtiaota Coal Mine and the 15205 panel of 5-2 coal seam at Hongliulin Coal Mine.The monitoring results showed that the surrounding rock deformation of the main recovery room and the coal pillar stress in the N1206 and 15205 panels began to increase significantly when the face was 36 m and 42 m away from the terminal line,respectively.After the face entered the main recovery room,the maximum roof-to-floor convergence in the N1206 and 15205 panels was 348.03 mm and 771.24 mm,respectively,and the coal pillar stresses increased more than 5 MPa and 7 MPa,respectively.In addition,analysis of the periodic weighting data showed that the main roof break position of the N1206 and 15205 panels after the longwall face entered the main recovery room was-3.8 m and-8.2 m,respectively.This research shows that when the main roof breaks above the coal pillar,the surrounding rock deformation of the main recovery room and the coal pillar stress increase sharply.The last weighting is the key factor affecting the stability of the main recovery room and the coal pillar;main roof breaks at disadvantageous positions are the main cause of the support crushing accidents.
基金This study is sponsored by the National Natural Science Foundation of China(No.51679199)the Special Funds for Public Industry Research Projects of the Ministry of Water Resources(No.201501034-04 and 201201053-03)the Key Laboratory for Science and Technology Coordination&Innovation Projects of Shaanxi Province(No.2014SZS15-Z01).
文摘Adsorption deformation significantly affects the seepage characteristics of coal.However,effect of sorption time on coal permeability and gas pressure has not been investigated systematically.In this study,the sorption experiment of coal samples is conducted to elaborate the importance of sorption equilibration time.Then a coupled coal deformation and gas flow model is established considering the sorption characteristic and permeability evolution.This coupled model is implemented through finite element method to analyze the effect of sorption time on coal permeability and gas pressure.The simulation results reveal that the gas pressure of the coal will change with the adsorption time.The fracture pressure maintains a high level while the matrix pressure is relatively low during the adsorption process.The sorption time has a great influence on the distribution of gas pressure.The smaller the adsorption time is,the lower the gas pressure becomes.
基金This study is sponsored by the National Natural Science Foundation of China(no.51679199)the Special Funds for Public Industry Research Projects of the Ministry of Water Resources(no.201501034-04 and 201201053-03)the Key Laboratory for Science and Technology Coordination&Innovation Projects of Shaanxi Province(no.2014SZS15-Z01).
文摘In the seepage-stress-damage coupled process,the mechanical properties and seepage characteristics of coal are distinctly different between pre-peak stage and post-peak stage.This difference is mainly caused by damage of coal.Therefore,in the process of seepage and stress analysis of coal under the influence of excavation or mining,we need to consider the weakening of mechanical properties and the development of fractures of damaged coal.Based on this understanding,this paper analyzes the influence of damage on mechanics and seepage behavior of coal.A coupled model is established to analyze the seepage-stress-damage coupled process of coal.This model implemented into COMSOL and MATLAB software to realize the numerical solving.Two examples are adopted to verify the correctness of the model and some useful conclusions are obtained.The numerical model establishes the relationship between microcosmic damage evolution and macroscopical fracture and simulates the whole process of coal from microcosmic damage to macroscopical fracture,and the dynamic simulation of fluid flow in this process.It provides a numerical tool for further research on the seepage-stress-damage analysis.
基金financially supported by the Natural Science Basic Research Plan in Shaanxi Province of China(Grant No.2023-JC-ZD-30 and 2019JZ-45)the National Natural Science Foundation of China(Grant No.42301047,41771259 and 41171034)+1 种基金the Shaanxi Provincial Water Conservancy Science and Technology Project(Grant No.2016slkj-11)the Shaanxi Provincial Key Laboratory Project of Department of Education(Grant No.14JS059).
文摘Modeling the soil evaporation under vegetation conditions is of theoretical and practical significance for water resources management in the Loess Plateau.In this study,a three-year field experiment was conducted in a bare land and three grasslands to measure soil evaporation using micro-lysimeters.The Van Bavel-Hillel model was then validated in the bare land.Based on this,the vegetation coverage resistance was proposed to reflect the comprehensive effects of vegetation,and it was applied into the Van Bavel-Hillel model to improve the model’s applicability under vegetation conditions.The results showed that the Van Bavel-Hillel model was effective in simulating evaporation from bare land,and the application of validated soil surface resistance and vegetation coverage resistance can make it perform well in the evaporation simulation in all studied grasslands.The obtained vegetation coverage resistances decreased linearly with the increase of soil moisture contents in all three grasslands,and the decreasing rates were similar in the M.sativa and P.giganteum plots,which were higher than that in the I.cylindrica plot.Soil surface resistances ranged between 533.4-746.5,767.4-1154.7,and 133.4-1334.5 s/m in the I.cylindrica,M.sativa,and P.giganteum plots,respectively,and all showed the characteristics of first increasing and then decreasing during the growing season.When compared with natural grassland,M.sativa increased the soil surface resistance in all months,while P.giganteum reduced it in the early growing season,but increased it in the middle and late growing season.This research proposes a new idea for the simulation of soil evaporation under vegetated conditions,and provides a basic reference for water resources management in the vegetation restoration of the Loess Plateau.
