The spewing of a screw conveyor easily occurs from the earth pressure balance(called EPB)shield in a water-rich sand stratum.This may lead to the collapse of the tunnel face and even serious subsidence of the ground s...The spewing of a screw conveyor easily occurs from the earth pressure balance(called EPB)shield in a water-rich sand stratum.This may lead to the collapse of the tunnel face and even serious subsidence of the ground surface.To understand the spewing mechanism of the shield screw conveyor and explore the critical hydraulic condition of soil spewing in a shield–soil chamber,a simplified theoretical model for the spewing of the screw conveyor was developed based on the equation of groundwater flow in the screw conveyor under turbulent state.Thus,coupling Darcy's law with Brinkman's equation,this model was implemented within the COMSOL Multiphysics framework.The underground water flow in the shield screw conveyor was simulated so as to obtain its velocity and flow rate.Numerical simulations show that the water pressure distribution is concentrated in the lower part of the soil chamber after the groundwater enters the soil chamber.When the groundwater enters the screw conveyor,its pressure gradually decreases along the direction of the screw conveyor.When the water flow reaches the stratum–shield interface,the flow velocity changes markedly:first increases and concentrates at the entrance of the lower soil chamber,plummets and stabilizes gradually,and increases again at the exit.The soil chamber and screw conveyor are significantly depressurized.It is also found that the soil permeability coefficient can be reduced to k<2.6×10^(−4)cm/s through appropriate soil improvement,which can effectively prevent the occurrence of spewing disasters.展开更多
Fatliquor migration within the leather matrix may lead to the formation of fatty spew,oil patches and fogging,posing challenges to the production of high-quality leather.Currently,it lacks a straightforward and effect...Fatliquor migration within the leather matrix may lead to the formation of fatty spew,oil patches and fogging,posing challenges to the production of high-quality leather.Currently,it lacks a straightforward and effective method for analyzing fatliquor migration behavior.This investigation introduces a novel approach for analyzing fatliquor migration by measuring its spreading area on collagen fiber membranes.By applying 300 mg of fatliquor onto 0.5 mm square membranes(10 cm×10 cm),distinct oil spots were observed,enabling analysis of migration behavior.Using stearic acid as a standard reference compound effectively minimized the influence of different leather sections on fatliquor migration.Fatliquors with low molecular weight,low melting point and high aliphatic ester content exhibited obvious migration potential.Organic-tanned leathers and sulfated fatliquors displayed weak interactions,resulting in easy fatliquor migration within the leather.Conversely,metal-tanned leathers and phosphorylated fatliquors demonstrated strong interactions,effectively hindering migration.This research provides valuable practical and theoretical insights for developing effective strategies to prevent and control fatliquor migration in leather production.展开更多
基金National Natural Science Foundation of China,Grant/Award Number:U1261212。
文摘The spewing of a screw conveyor easily occurs from the earth pressure balance(called EPB)shield in a water-rich sand stratum.This may lead to the collapse of the tunnel face and even serious subsidence of the ground surface.To understand the spewing mechanism of the shield screw conveyor and explore the critical hydraulic condition of soil spewing in a shield–soil chamber,a simplified theoretical model for the spewing of the screw conveyor was developed based on the equation of groundwater flow in the screw conveyor under turbulent state.Thus,coupling Darcy's law with Brinkman's equation,this model was implemented within the COMSOL Multiphysics framework.The underground water flow in the shield screw conveyor was simulated so as to obtain its velocity and flow rate.Numerical simulations show that the water pressure distribution is concentrated in the lower part of the soil chamber after the groundwater enters the soil chamber.When the groundwater enters the screw conveyor,its pressure gradually decreases along the direction of the screw conveyor.When the water flow reaches the stratum–shield interface,the flow velocity changes markedly:first increases and concentrates at the entrance of the lower soil chamber,plummets and stabilizes gradually,and increases again at the exit.The soil chamber and screw conveyor are significantly depressurized.It is also found that the soil permeability coefficient can be reduced to k<2.6×10^(−4)cm/s through appropriate soil improvement,which can effectively prevent the occurrence of spewing disasters.
基金financially supported by the National Natural Science Foundation of China(22208227)the Fundamental Research Funds for the Central Universities.
文摘Fatliquor migration within the leather matrix may lead to the formation of fatty spew,oil patches and fogging,posing challenges to the production of high-quality leather.Currently,it lacks a straightforward and effective method for analyzing fatliquor migration behavior.This investigation introduces a novel approach for analyzing fatliquor migration by measuring its spreading area on collagen fiber membranes.By applying 300 mg of fatliquor onto 0.5 mm square membranes(10 cm×10 cm),distinct oil spots were observed,enabling analysis of migration behavior.Using stearic acid as a standard reference compound effectively minimized the influence of different leather sections on fatliquor migration.Fatliquors with low molecular weight,low melting point and high aliphatic ester content exhibited obvious migration potential.Organic-tanned leathers and sulfated fatliquors displayed weak interactions,resulting in easy fatliquor migration within the leather.Conversely,metal-tanned leathers and phosphorylated fatliquors demonstrated strong interactions,effectively hindering migration.This research provides valuable practical and theoretical insights for developing effective strategies to prevent and control fatliquor migration in leather production.
