The development and achievements of modern coal mining with stowing are discussed in this paper. The necessity of developing coal mining with stowing is briefly summarized and internal damage within the strata and ext...The development and achievements of modern coal mining with stowing are discussed in this paper. The necessity of developing coal mining with stowing is briefly summarized and internal damage within the strata and external damage on surface induced by longwall working with caving are discussed. Technological features of coal mining with pneumatic stowing in Germany, and fully mechanised coal mining with solid dense stowing in China, are discussed. In German hard coal mining stowing technologies are for technical, infrastructural and economical reasons not applicable. The discussion includes the stowing material transportation system, the stowing machine, and processes at the face. Progressiveness and application universality of China's fully mechanised coal mining with solid dense stowing are illustrated through practical examples with different conditions. Obviously, the fully mechanised coal mine with solid dense stowing can be improved by automaion systems. This paper discusses further developmental potential of the technology.展开更多
Heliostats are sensitive to the wind load, thus as a key indicator, the study on the static and dynamic stability bearing capacity for heliostats is very important. In this work, a numerical wind tunnel was establishe...Heliostats are sensitive to the wind load, thus as a key indicator, the study on the static and dynamic stability bearing capacity for heliostats is very important. In this work, a numerical wind tunnel was established to calculate the wind load coefficients in various survival stow positions. In order to explore the best survival stow position for the heliostat under the strong wind, eigenvalue buckling analysis method was introduced to predict the critical wind load theoretically. Considering the impact of the nonlinearity and initial geometrical imperfection, the nonlinear post-buckling behaviors of the heliostat were investigated by load-displacement curves in the full equilibrium process. Eventually, combining B-R criterion with equivalent displacement principle the dynamic critical wind speed and load amplitude coefficient were evaluated. The results show that the determination for the best survival stow position is too hasty just by the wind load coefficients. The geometric nonlinearity has a great effect on the stability bearing capacity of the heliostat, while the effects of the material nonlinearity and initial geometrical imperfection are relatively small. And the heliostat is insensitive to the initial geometrical imperfection. In addition, the heliostat has the highest safety factor for wind-resistant performance in the stow position of 90-90 which can be taken as the best survival stow position. In this case, the extreme survival wind speeds for the static and dynamic stability are 150 m/s and 36 m/s, respectively.展开更多
Delayed settling of the ash particles and poor drainage of water from the pond ash are the major problems faced during the hydraulic stowing of pond ash. In this study the effect of polymeric flocculant on settling of...Delayed settling of the ash particles and poor drainage of water from the pond ash are the major problems faced during the hydraulic stowing of pond ash. In this study the effect of polymeric flocculant on settling of the ash particles and drainage of water during pond ash stowing are investigated. In addition, the parameters, viz. drainage and absorption of water during pond ash stowing are quantified by stowing a mine goaf model with pond ash slurries of five different concentrations added with and without flocculant. The study revealed that addition of only 5 10 6 of Sodium Carboxymethyl Cellulose (Na-CMC) flocculant with the pond ash slurries during stowing offers best result in terms of quicker settling of the ash particles and enhanced water drainage from the hydraulically stowed pond ash. Besides, it resulted in drainage of more than 85% of the total water used in the initial 45 min of stowing. The improvement in drainage is caused due to coagulation and flocculation of the pond ash particles because of charge neutralization and particle-particle bridging. This study may provide a basis for estimating the drainage and absorption of water during the real pond ash stowing operation in underground mines.展开更多
High-water material, tailings from goldmine and water are mixed into a new slurry.Testing of rheological properties of stowing slurries A and B is made to determine type and rheological parameters of the slurry. The m...High-water material, tailings from goldmine and water are mixed into a new slurry.Testing of rheological properties of stowing slurries A and B is made to determine type and rheological parameters of the slurry. The main factors influencing rheological properties of the slurry are analyzed and the rational concentration and empirical resistance calculating formula of pipe line transportation are presented.展开更多
The stowing and deploying experiment was conducted for three 700 mm long thin-walled tubes,and the structural behavior characteristics parameters were measured clearly,including strain,deformation and wrapping moment....The stowing and deploying experiment was conducted for three 700 mm long thin-walled tubes,and the structural behavior characteristics parameters were measured clearly,including strain,deformation and wrapping moment.3D finite element models(FEM)were built subsequently and explicit dynamic method was used to simulate the stowing and deploying of the lenticular carbon fiber reinforced polymer(CFRP)thin-walled tubular space boom,which was designed as four-ply(45°/-45°/45°/-45°)lay-up.The stress and energy during the wrapping process were got and compared with different wrapping angular velocity,the reasonable wrapping angular velocity and effective method were conformed,and structural behavior characteristics were obtained.The results were compared and discussed as well,and the results show that the numerical results by 0.628 rad/s velocity agree well with the measured values.In this paper,the numerical procedure and experimental results are valuable to the optimization design of CFRP thin-walled tubular space boom and future research.展开更多
文摘The development and achievements of modern coal mining with stowing are discussed in this paper. The necessity of developing coal mining with stowing is briefly summarized and internal damage within the strata and external damage on surface induced by longwall working with caving are discussed. Technological features of coal mining with pneumatic stowing in Germany, and fully mechanised coal mining with solid dense stowing in China, are discussed. In German hard coal mining stowing technologies are for technical, infrastructural and economical reasons not applicable. The discussion includes the stowing material transportation system, the stowing machine, and processes at the face. Progressiveness and application universality of China's fully mechanised coal mining with solid dense stowing are illustrated through practical examples with different conditions. Obviously, the fully mechanised coal mine with solid dense stowing can be improved by automaion systems. This paper discusses further developmental potential of the technology.
基金Project(CYB14010)supported by Chongqing Graduate Student Research Innovation Project,ChinaProject(51405209)supported by the National Natural Science Foundation of China
文摘Heliostats are sensitive to the wind load, thus as a key indicator, the study on the static and dynamic stability bearing capacity for heliostats is very important. In this work, a numerical wind tunnel was established to calculate the wind load coefficients in various survival stow positions. In order to explore the best survival stow position for the heliostat under the strong wind, eigenvalue buckling analysis method was introduced to predict the critical wind load theoretically. Considering the impact of the nonlinearity and initial geometrical imperfection, the nonlinear post-buckling behaviors of the heliostat were investigated by load-displacement curves in the full equilibrium process. Eventually, combining B-R criterion with equivalent displacement principle the dynamic critical wind speed and load amplitude coefficient were evaluated. The results show that the determination for the best survival stow position is too hasty just by the wind load coefficients. The geometric nonlinearity has a great effect on the stability bearing capacity of the heliostat, while the effects of the material nonlinearity and initial geometrical imperfection are relatively small. And the heliostat is insensitive to the initial geometrical imperfection. In addition, the heliostat has the highest safety factor for wind-resistant performance in the stow position of 90-90 which can be taken as the best survival stow position. In this case, the extreme survival wind speeds for the static and dynamic stability are 150 m/s and 36 m/s, respectively.
文摘Delayed settling of the ash particles and poor drainage of water from the pond ash are the major problems faced during the hydraulic stowing of pond ash. In this study the effect of polymeric flocculant on settling of the ash particles and drainage of water during pond ash stowing are investigated. In addition, the parameters, viz. drainage and absorption of water during pond ash stowing are quantified by stowing a mine goaf model with pond ash slurries of five different concentrations added with and without flocculant. The study revealed that addition of only 5 10 6 of Sodium Carboxymethyl Cellulose (Na-CMC) flocculant with the pond ash slurries during stowing offers best result in terms of quicker settling of the ash particles and enhanced water drainage from the hydraulically stowed pond ash. Besides, it resulted in drainage of more than 85% of the total water used in the initial 45 min of stowing. The improvement in drainage is caused due to coagulation and flocculation of the pond ash particles because of charge neutralization and particle-particle bridging. This study may provide a basis for estimating the drainage and absorption of water during the real pond ash stowing operation in underground mines.
文摘High-water material, tailings from goldmine and water are mixed into a new slurry.Testing of rheological properties of stowing slurries A and B is made to determine type and rheological parameters of the slurry. The main factors influencing rheological properties of the slurry are analyzed and the rational concentration and empirical resistance calculating formula of pipe line transportation are presented.
基金the National Natural Science Foundation of China(No.50878128)the Shanghai Aerospace Foundation(No.HTJ10-15)
文摘The stowing and deploying experiment was conducted for three 700 mm long thin-walled tubes,and the structural behavior characteristics parameters were measured clearly,including strain,deformation and wrapping moment.3D finite element models(FEM)were built subsequently and explicit dynamic method was used to simulate the stowing and deploying of the lenticular carbon fiber reinforced polymer(CFRP)thin-walled tubular space boom,which was designed as four-ply(45°/-45°/45°/-45°)lay-up.The stress and energy during the wrapping process were got and compared with different wrapping angular velocity,the reasonable wrapping angular velocity and effective method were conformed,and structural behavior characteristics were obtained.The results were compared and discussed as well,and the results show that the numerical results by 0.628 rad/s velocity agree well with the measured values.In this paper,the numerical procedure and experimental results are valuable to the optimization design of CFRP thin-walled tubular space boom and future research.
