Non-pillar mining technology with automatically formed roadway is a new mining method without coal pillar reservation and roadway excavation.The stability control of automatically formed roadway is the key to the succ...Non-pillar mining technology with automatically formed roadway is a new mining method without coal pillar reservation and roadway excavation.The stability control of automatically formed roadway is the key to the successful application of the new method.In order to realize the stability control of the roadway surrounding rock,the mechanical model of the roof and rib support structure is established,and the influence mechanism of the automatically formed roadway parameters on the compound force is revealed.On this basis,the roof and rib support structure technology of confined lightweight concrete is proposed,and its mechanical tests under different eccentricity are carried out.The results show that the bearing capacity of confined lightweight concrete specimens is basically the same as that of ordinary confined concrete specimens.The bearing capacity of confined lightweight concrete specimens under different eccentricities is 1.95 times higher than those of U-shaped steel specimens.By comparing the test results with the theoretical calculated results of the confined concrete,the calculation method of the bearing capacity for the confined lightweight concrete structure is selected.The design method of confined lightweight concrete support structure is established,and is successfully applied in the extra-large mine,Ningtiaota Coal Mine,China.展开更多
To better design and analyze concrete structures, the mechanical properties of concrete subjected to impact loadings are investigated. Concrete is considered to be a two-phase composite made up of micro-cracks and sol...To better design and analyze concrete structures, the mechanical properties of concrete subjected to impact loadings are investigated. Concrete is considered to be a two-phase composite made up of micro-cracks and solid parts which consist of coarse aggregate particles and a cement mortar matrix. The cement mortar matrix is assumed to be elastic, homogeneous and isotropic. Based on the Moil-Tanaka concept of average stress and the Eshelby equivalent inclusion theory, a dynamic constitutive model is developed to simulate the impact responses of concrete. The impact compression experiments of concrete and cement mortar are also carried out. Experimental results show that concrete and cement mortar are rate-dependent. Under the same impact velocity, the load-carrying capacity of concrete is higher than that of cement mortar. Whereas, the maximum strain of concrete is lower than that of cement mortar. Regardless of whether it is concrete or cement mortar, with the increase in the impact velocity, the fragment size of specimens after experiment decreases.展开更多
Phosphogypsum(PG)is a potential resource for rare earth elements(REEs).Several studies have been carried out on REE leaching from PG.However,few in-depth studies have investigated the kinetics of this leaching process...Phosphogypsum(PG)is a potential resource for rare earth elements(REEs).Several studies have been carried out on REE leaching from PG.However,few in-depth studies have investigated the kinetics of this leaching process.In this study,the leaching kinetics of REEs from PG in nitric acid at different temperatures were explored in depth.The experiments show that the maximum leaching recovery for ΣREE was 58.5%,75.9%and 83.4%at 30,60 and 80℃,respectively.Additionally,among La,Ce,Y and Nd,Y had the highest leaching rate.A new shrinking core model(SCM)based on the dissolution reaction of a cylindrical solid particle with interfacial transfer and diffusion across the product layer as the rate-controlling step was deduced and could well fit the leaching process of REEs from PG.The activation energies for the leaching of La,Ce,Y and Nd were determined on the basis of the new cylindrical SCM.In summary,the cylindrical SCM was a more suitable fitting model than the spherical SCM,and the interfacial transfer and diffusion across the product layer were the rate-controlling step for REE leaching from the PG sample.展开更多
A set of equations is suggested to describe the kinetics of degradation of organic compounds applied tosoils and the kinetics of growth of the involved microorganisme:where x is the concentration of organic compound a...A set of equations is suggested to describe the kinetics of degradation of organic compounds applied tosoils and the kinetics of growth of the involved microorganisme:where x is the concentration of organic compound at time t, m is the number of forcroorganisms capableof degrading the organic compound at time t, while j, k, f and g are positive constaats. This model cansatisfactorily be used to explain the degradation curve of organic compounds and the growth curve of theinvolved microorganisms.展开更多
The factors influencing on soil expansion are reviewed in the paper. A mechanics model to determine swelling potential of expansive soils is presented. The mechanics model is based on the softening of expansive soil f...The factors influencing on soil expansion are reviewed in the paper. A mechanics model to determine swelling potential of expansive soils is presented. The mechanics model is based on the softening of expansive soil following absorption of water. The constitutive relationships of the mechanics model include the relationship among swelling under free load, swelling under load, and vertical pressure, and the relationship of swelling under free loading and swelling pressure. A concept of additional compression modulus is introduced and the method determining the modulus is proposed. Finally, the predicted results of swelling potential using the mechanics model compare well with the measured data.展开更多
Heavy metals are well recognized as potential health hazards as they can neither be degraded nor biologically detoxified. This experimental study aims to investigate the possible use of Libyan local soil, Ashkida soil...Heavy metals are well recognized as potential health hazards as they can neither be degraded nor biologically detoxified. This experimental study aims to investigate the possible use of Libyan local soil, Ashkida soil, mined in the Southern Province of Libya as a low cost adsorbent to remove copper ions from aqueous solutions. In this work, the effects of various parameters such as adsorbent dosage, initial concentration of copper, agitation rate, contact time and solution pH level on the adsorption efficiency are investigated through batch experiments at room temperature. The results indicate that the optimum conditions for copper removal from aqueous solutions are 60 minutes contact time, 10 g/L adsorbent dose and 500 rpm agitation rate at natural pH value. The results are fitted to Freundlich, Langmuir, Temkin and Dubinin-Radushkevich isotherms. A satisfactory agreement between the experimental data and the model-predicted values is expressed by the correlation coefficient, r^2, and the total mean error, E%. Freundlich model offers the best representation of adsorption process revealing a monolayer adsorption capacity, qmax, of 27.03 mg/g. A comparison of kinetic models applied to the adsorption of copper ions on the adsorbent is evaluated by simple first order, pseudo first order and pseudo second order kinetic models. Kinetic parameters, rate constant, equilibrium sorption capacities and related correlation coefficients for each kinetic model are determined revealing that the pseudo second order kinetic model is in a better correlation with the experimental data in comparison with the other isotherms.展开更多
This paper deduces a kinetic model for microbial degradation of pesticides in soils:where x is the concentration of pesticide at time t, so the initial concentration of the pesticide, me the initial number of pesticid...This paper deduces a kinetic model for microbial degradation of pesticides in soils:where x is the concentration of pesticide at time t, so the initial concentration of the pesticide, me the initial number of pesticide-degrading microorganisms, M the carrying capacity for the microorganisms, μ the specific growth rate of the microorganisms, and k the rate constant for the pesticide degradation.In periodic applications of pesticides, this model can be used to continuously describe every degradation curve. Whether a lag phase occurs or not, we can obtain the minimum residue of the pesticide (xe):xe=xdexp(-kMr)/[1-exp(-ker) ]where r is the regular time internals between applications, and xd the dosage of the pesticide.展开更多
基金Project(2023YFC2907600)supported by the National Key Research and Development Program of ChinaProjects(42077267,42277174,52074164)supported by the National Natural Science Foundation of ChinaProject(2024JCCXSB01)supported by the Fundamental Research Funds for the Central Universities,China。
文摘Non-pillar mining technology with automatically formed roadway is a new mining method without coal pillar reservation and roadway excavation.The stability control of automatically formed roadway is the key to the successful application of the new method.In order to realize the stability control of the roadway surrounding rock,the mechanical model of the roof and rib support structure is established,and the influence mechanism of the automatically formed roadway parameters on the compound force is revealed.On this basis,the roof and rib support structure technology of confined lightweight concrete is proposed,and its mechanical tests under different eccentricity are carried out.The results show that the bearing capacity of confined lightweight concrete specimens is basically the same as that of ordinary confined concrete specimens.The bearing capacity of confined lightweight concrete specimens under different eccentricities is 1.95 times higher than those of U-shaped steel specimens.By comparing the test results with the theoretical calculated results of the confined concrete,the calculation method of the bearing capacity for the confined lightweight concrete structure is selected.The design method of confined lightweight concrete support structure is established,and is successfully applied in the extra-large mine,Ningtiaota Coal Mine,China.
基金The National Natural Science Foundation of China(No. 11162015)the Natural Science Foundation of Ningxia Hui Autonomous Region (No. NZ1106)
文摘To better design and analyze concrete structures, the mechanical properties of concrete subjected to impact loadings are investigated. Concrete is considered to be a two-phase composite made up of micro-cracks and solid parts which consist of coarse aggregate particles and a cement mortar matrix. The cement mortar matrix is assumed to be elastic, homogeneous and isotropic. Based on the Moil-Tanaka concept of average stress and the Eshelby equivalent inclusion theory, a dynamic constitutive model is developed to simulate the impact responses of concrete. The impact compression experiments of concrete and cement mortar are also carried out. Experimental results show that concrete and cement mortar are rate-dependent. Under the same impact velocity, the load-carrying capacity of concrete is higher than that of cement mortar. Whereas, the maximum strain of concrete is lower than that of cement mortar. Regardless of whether it is concrete or cement mortar, with the increase in the impact velocity, the fragment size of specimens after experiment decreases.
基金Project(51904104) supported by the National Natural Science Foundation of ChinaProject(2020JJ5174) supported by the Natural Science Foundation of Hunan Province,China+2 种基金Project(2019M662780) supported by China Postdoctoral Science FoundationProject(19C0746) supported by Scientific Research Fund of Hunan Provincial Education Department,ChinaProject(2021-2843) supported by College Student Innovation and Entrepreneurship Training Program of Hunan Province,China。
文摘Phosphogypsum(PG)is a potential resource for rare earth elements(REEs).Several studies have been carried out on REE leaching from PG.However,few in-depth studies have investigated the kinetics of this leaching process.In this study,the leaching kinetics of REEs from PG in nitric acid at different temperatures were explored in depth.The experiments show that the maximum leaching recovery for ΣREE was 58.5%,75.9%and 83.4%at 30,60 and 80℃,respectively.Additionally,among La,Ce,Y and Nd,Y had the highest leaching rate.A new shrinking core model(SCM)based on the dissolution reaction of a cylindrical solid particle with interfacial transfer and diffusion across the product layer as the rate-controlling step was deduced and could well fit the leaching process of REEs from PG.The activation energies for the leaching of La,Ce,Y and Nd were determined on the basis of the new cylindrical SCM.In summary,the cylindrical SCM was a more suitable fitting model than the spherical SCM,and the interfacial transfer and diffusion across the product layer were the rate-controlling step for REE leaching from the PG sample.
文摘A set of equations is suggested to describe the kinetics of degradation of organic compounds applied tosoils and the kinetics of growth of the involved microorganisme:where x is the concentration of organic compound at time t, m is the number of forcroorganisms capableof degrading the organic compound at time t, while j, k, f and g are positive constaats. This model cansatisfactorily be used to explain the degradation curve of organic compounds and the growth curve of theinvolved microorganisms.
文摘The factors influencing on soil expansion are reviewed in the paper. A mechanics model to determine swelling potential of expansive soils is presented. The mechanics model is based on the softening of expansive soil following absorption of water. The constitutive relationships of the mechanics model include the relationship among swelling under free load, swelling under load, and vertical pressure, and the relationship of swelling under free loading and swelling pressure. A concept of additional compression modulus is introduced and the method determining the modulus is proposed. Finally, the predicted results of swelling potential using the mechanics model compare well with the measured data.
文摘Heavy metals are well recognized as potential health hazards as they can neither be degraded nor biologically detoxified. This experimental study aims to investigate the possible use of Libyan local soil, Ashkida soil, mined in the Southern Province of Libya as a low cost adsorbent to remove copper ions from aqueous solutions. In this work, the effects of various parameters such as adsorbent dosage, initial concentration of copper, agitation rate, contact time and solution pH level on the adsorption efficiency are investigated through batch experiments at room temperature. The results indicate that the optimum conditions for copper removal from aqueous solutions are 60 minutes contact time, 10 g/L adsorbent dose and 500 rpm agitation rate at natural pH value. The results are fitted to Freundlich, Langmuir, Temkin and Dubinin-Radushkevich isotherms. A satisfactory agreement between the experimental data and the model-predicted values is expressed by the correlation coefficient, r^2, and the total mean error, E%. Freundlich model offers the best representation of adsorption process revealing a monolayer adsorption capacity, qmax, of 27.03 mg/g. A comparison of kinetic models applied to the adsorption of copper ions on the adsorbent is evaluated by simple first order, pseudo first order and pseudo second order kinetic models. Kinetic parameters, rate constant, equilibrium sorption capacities and related correlation coefficients for each kinetic model are determined revealing that the pseudo second order kinetic model is in a better correlation with the experimental data in comparison with the other isotherms.
文摘This paper deduces a kinetic model for microbial degradation of pesticides in soils:where x is the concentration of pesticide at time t, so the initial concentration of the pesticide, me the initial number of pesticide-degrading microorganisms, M the carrying capacity for the microorganisms, μ the specific growth rate of the microorganisms, and k the rate constant for the pesticide degradation.In periodic applications of pesticides, this model can be used to continuously describe every degradation curve. Whether a lag phase occurs or not, we can obtain the minimum residue of the pesticide (xe):xe=xdexp(-kMr)/[1-exp(-ker) ]where r is the regular time internals between applications, and xd the dosage of the pesticide.
