Based on first-order kinetics of hydrolysis process, biodegradation of municipal solid waste （MSW） is assumed to obey a first-order decay equation which can take the direct effect of water content on biodegradation ...Based on first-order kinetics of hydrolysis process, biodegradation of municipal solid waste （MSW） is assumed to obey a first-order decay equation which can take the direct effect of water content on biodegradation into account. Hydraulic model is an unsaturated-saturated flow model using mass conservation equations for fluids. Mechanical compression of MSW is ex- pressed by a stress-age coupled compression model. Through above models, a one-dimensional （I-D） bio-hydro-mechanical coupled model is established to analyze solid-liquid-gas interactions in landfilled MSW. Values of all the model parameters for current typical Chinese MSW are determined. Numerical analysis of a hypothetical waste sample in a closed system shows that gas pressure and gas concentration is extremely large which might cause severe gas explosion problem. Total gas production is about 267.0 m3 per wet ton of fresh wastes. For another hypothetical landfilled MSW layer, the coupled model predicts a dis- sipation of gas pressure during passive gas collection process. Annual gas production is large at the beginning of biodegradation, and then decreases with time. Surface settlement of the wastes increases quickly initially and then becomes stable with a compression strain of about 0.32 after 20 years.展开更多
When the shield tunnel passes through the gas-bearing strata,gas and water leakage may occur depending on the sealing performance of the segment joints.This process involves the complex multiphase seepage flow phenome...When the shield tunnel passes through the gas-bearing strata,gas and water leakage may occur depending on the sealing performance of the segment joints.This process involves the complex multiphase seepage flow phenomenon in unsaturated soil.In this study,a fully coupled solid-liquid-gas model of the GIL Utility Tunnel was established to investigate the influence of the high-pressure gas on the mechanical properties of the tunnel segments and joints.The constitutive model of the Extended Barcelona Basic Model was imple-mented to simulate the effect of the seepage process on soil deformation.The results show that significant upward displacement occurred in the gas reservoir and its overlying strata,and the maximum displacement reached 30 mm.In addition,during the leakage of the gas and the water,an increase in the average soil effective stress was observed.It would induce a reduction in the suction and expansion of the yield surface.The tunnel tended to be stable from 20 years onwards,thus the soil deformation due to the water leakage only occurred at the early stage.In addition,the joint opening under the most unfavorable internal force combination was 0.69 mm,and the correspond-ing bolt stress was 119.5 MPa,which is below the yield limit.The results of this study help to understand the influence of high-pressure gas on tunnel safety and the sealing performance of the joints.展开更多
A solid/liquid/gas unified model has been developed to investigate the gradient composition formation during the plasma deposition manufacturing(PDM) composite materials process. In this model,an enthalpy porosity mod...A solid/liquid/gas unified model has been developed to investigate the gradient composition formation during the plasma deposition manufacturing(PDM) composite materials process. In this model,an enthalpy porosity model was applied to deal with the melting and solidification of the deposited layer,and a level-set approach was introduced to track the evolution of the free surface of the molten pool and the deposited layer. Moreover,complicated physical phenomena occurring at the liquid/gas interface,including forced convection heat loss,heat emission and plasma heat source,have been incorporated into the governing equations by source terms. In this study,the numerical experiment of nickel base alloy powder deposited on the medium steel substrate by PDM technique was implemented based on the staggered grid and SIMPLEC algorithm. Concentration gradient distribution of the solute material at the composite material interface,fluid flow and temperature distribution in the molten pool and the deposited layer have been investigated in detail.展开更多
Slag movement on SiO2-based prism refractories in different slag systems was observed. The cross section shape evolution mechanism was discussed. Two types of shape evolution appear. For PbO-SiO2 slag whose surface te...Slag movement on SiO2-based prism refractories in different slag systems was observed. The cross section shape evolution mechanism was discussed. Two types of shape evolution appear. For PbO-SiO2 slag whose surface tension improves with SiO2 concentration, slag film flows up along four edges under axial Marangoni shear force and wettability. Then, it flows down along four lateral faces under gravity. Corrosion rate at edges is larger than that on lateral faces due to different SiO2 solubilities of ascending and descending flow. Prism cross section shape changes from square to round. For FetO-SiO2 slag whose surface tension reduces with the increase of SiO2 concentration, slag film flows up under the inflence of wettability. Then, it flows down under Marangoni shear force and gravity. Compared to four edges, slag is mainly up and down on four lateral faces due to larger surface tension and size. So, prism cross section shape keeps square.展开更多
为掌握含气地层中盾构隧道渗漏气引起的地层变形对隧道结构的影响,以苏通气体绝缘金属封闭输电线路(gas-insulated metal enclosed transmission line,GIL)项目中江底富含高压浅层气地层为研究对象,利用自主开发的有限元程序,并采用非...为掌握含气地层中盾构隧道渗漏气引起的地层变形对隧道结构的影响,以苏通气体绝缘金属封闭输电线路(gas-insulated metal enclosed transmission line,GIL)项目中江底富含高压浅层气地层为研究对象,利用自主开发的有限元程序,并采用非饱和弹塑性本构模型,对含气地层不均匀沉降对盾构隧道结构的影响进行了三维固-液-气耦合数值模拟分析。结果表明:排气引起的地层不均匀沉降会导致隧道沉降,产生附加内力。其中,渗气口附近沉降位移最大,含气地层下部由于卸荷效应会有少许回弹;同时,沉降位移最大处所在截面的附加弯矩也最大;越远离含气层的位置,截面附加弯矩越小。展开更多
The mold pressing process was applied to investigate the formability of closed-cell aluminum foam in solid–liquid–gas coexisting state.Results show that the shape formation of closed-cell aluminum foam in the solid...The mold pressing process was applied to investigate the formability of closed-cell aluminum foam in solid–liquid–gas coexisting state.Results show that the shape formation of closed-cell aluminum foam in the solid–liquid–gas coexisting state was realized through cell wall deformation and cell movement caused by primary α-Al grains that slid,rotated,deformed,and ripened within cell walls.During formation,characteristic parameters of closed-cell aluminum foam were almost unchanged.Under proper forming conditions,shaped products of closed-cell aluminum foam could be fabricated through mold pressing.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos.51010008, 10972195)the National Basic Research Program of China ("973" Project) (Grant No.2012CB719800)
文摘Based on first-order kinetics of hydrolysis process, biodegradation of municipal solid waste （MSW） is assumed to obey a first-order decay equation which can take the direct effect of water content on biodegradation into account. Hydraulic model is an unsaturated-saturated flow model using mass conservation equations for fluids. Mechanical compression of MSW is ex- pressed by a stress-age coupled compression model. Through above models, a one-dimensional （I-D） bio-hydro-mechanical coupled model is established to analyze solid-liquid-gas interactions in landfilled MSW. Values of all the model parameters for current typical Chinese MSW are determined. Numerical analysis of a hypothetical waste sample in a closed system shows that gas pressure and gas concentration is extremely large which might cause severe gas explosion problem. Total gas production is about 267.0 m3 per wet ton of fresh wastes. For another hypothetical landfilled MSW layer, the coupled model predicts a dis- sipation of gas pressure during passive gas collection process. Annual gas production is large at the beginning of biodegradation, and then decreases with time. Surface settlement of the wastes increases quickly initially and then becomes stable with a compression strain of about 0.32 after 20 years.
文摘When the shield tunnel passes through the gas-bearing strata,gas and water leakage may occur depending on the sealing performance of the segment joints.This process involves the complex multiphase seepage flow phenomenon in unsaturated soil.In this study,a fully coupled solid-liquid-gas model of the GIL Utility Tunnel was established to investigate the influence of the high-pressure gas on the mechanical properties of the tunnel segments and joints.The constitutive model of the Extended Barcelona Basic Model was imple-mented to simulate the effect of the seepage process on soil deformation.The results show that significant upward displacement occurred in the gas reservoir and its overlying strata,and the maximum displacement reached 30 mm.In addition,during the leakage of the gas and the water,an increase in the average soil effective stress was observed.It would induce a reduction in the suction and expansion of the yield surface.The tunnel tended to be stable from 20 years onwards,thus the soil deformation due to the water leakage only occurred at the early stage.In addition,the joint opening under the most unfavorable internal force combination was 0.69 mm,and the correspond-ing bolt stress was 119.5 MPa,which is below the yield limit.The results of this study help to understand the influence of high-pressure gas on tunnel safety and the sealing performance of the joints.
基金Supported by the National Natural Science Foundation of China (Grant No. 50474053)the High Technology Research and Development Program of China (Grant No. 2007AA04Z142)
文摘A solid/liquid/gas unified model has been developed to investigate the gradient composition formation during the plasma deposition manufacturing(PDM) composite materials process. In this model,an enthalpy porosity model was applied to deal with the melting and solidification of the deposited layer,and a level-set approach was introduced to track the evolution of the free surface of the molten pool and the deposited layer. Moreover,complicated physical phenomena occurring at the liquid/gas interface,including forced convection heat loss,heat emission and plasma heat source,have been incorporated into the governing equations by source terms. In this study,the numerical experiment of nickel base alloy powder deposited on the medium steel substrate by PDM technique was implemented based on the staggered grid and SIMPLEC algorithm. Concentration gradient distribution of the solute material at the composite material interface,fluid flow and temperature distribution in the molten pool and the deposited layer have been investigated in detail.
基金Projects(U1738101,51804023)supported by the National Natural Science Foundation of ChinaProjects(FRF-TP-18-007A1,FRF-MP-18-007)supported by Fundamental Research Funds for the Central Universities,ChinaProject(2019M650489)supported by China Postdoctoral Science Foundation
文摘Slag movement on SiO2-based prism refractories in different slag systems was observed. The cross section shape evolution mechanism was discussed. Two types of shape evolution appear. For PbO-SiO2 slag whose surface tension improves with SiO2 concentration, slag film flows up along four edges under axial Marangoni shear force and wettability. Then, it flows down along four lateral faces under gravity. Corrosion rate at edges is larger than that on lateral faces due to different SiO2 solubilities of ascending and descending flow. Prism cross section shape changes from square to round. For FetO-SiO2 slag whose surface tension reduces with the increase of SiO2 concentration, slag film flows up under the inflence of wettability. Then, it flows down under Marangoni shear force and gravity. Compared to four edges, slag is mainly up and down on four lateral faces due to larger surface tension and size. So, prism cross section shape keeps square.
文摘为掌握含气地层中盾构隧道渗漏气引起的地层变形对隧道结构的影响,以苏通气体绝缘金属封闭输电线路(gas-insulated metal enclosed transmission line,GIL)项目中江底富含高压浅层气地层为研究对象,利用自主开发的有限元程序,并采用非饱和弹塑性本构模型,对含气地层不均匀沉降对盾构隧道结构的影响进行了三维固-液-气耦合数值模拟分析。结果表明:排气引起的地层不均匀沉降会导致隧道沉降,产生附加内力。其中,渗气口附近沉降位移最大,含气地层下部由于卸荷效应会有少许回弹;同时,沉降位移最大处所在截面的附加弯矩也最大;越远离含气层的位置,截面附加弯矩越小。
基金financially supported by the National Natural Science Foundations of China (No.51371104)
文摘The mold pressing process was applied to investigate the formability of closed-cell aluminum foam in solid–liquid–gas coexisting state.Results show that the shape formation of closed-cell aluminum foam in the solid–liquid–gas coexisting state was realized through cell wall deformation and cell movement caused by primary α-Al grains that slid,rotated,deformed,and ripened within cell walls.During formation,characteristic parameters of closed-cell aluminum foam were almost unchanged.Under proper forming conditions,shaped products of closed-cell aluminum foam could be fabricated through mold pressing.
