Study On Geopolymer Foam Materials And Thermal Insulation Performance In Deep Roadway

With the gradual exhaustion of coal resources,deep mining is inevitable,and the deep thermal environment and artificial control have gradually become an important problem to restrict the sustainable development of energy resources.Traditional artificial mine cooling only considers the cooling loads of underground surrounding rock,equipment and personnel,which leads to the problems of large capacity and high energy consumption of the system.In this paper,from passive cooling and energy saving parts,the physical and mechanical properties and change laws of heat insulation materials suitable for underground tunnels are studied.The change of temperature of surrounding rock and heat exchange between the heat flow and the wind flow are analyzed.The change laws of air flow temperature in the underground tunnel under different conditions are studied as well.Firstly,we study the physical and mechanical properties of fly ash based geopolymer foam materials and their changing rules.The results show that the compressive strength is high when the water cement ratio is 0.4 and the proportion of Na OH is 10%.The compressive strength and thermal conductivity increase nonlinearly with the increase of dry density,and the compressive strength and thermal conductivity can be increased in different degrees with different additional fibers.The influence of coarse and fine aggregate on the strength and thermal conductivity is different.The surface spraying hydrophobic agent has little effect on the strength and thermal conductivity,but the direct addition of hydrophobic agent to the slurry can significantly affect the strength and thermal conductivity.The hydrophobicity of the sample surface can significantly reduce the water absorption of the sample and reduce the influence of external thermal and humidity environment on the thermal conductivity of the insulation material.Analytical and numerical simulation methods are used to study the temperature field of surrounding rock and laws of convection heat transfer.Results show that the thermal insulation layer can significantly reduce the surrounding rock temperature near wall of the roadway,and the heat flow density decreases significantly with the increase of the thickness of the heat insulation layer and the decrease of the thermal conductivity of the heat insulation material;the greater the thermal coefficient is,the greater the heat flux is;the convective heat transfer coefficient has little effect on the heat flux;the convection heat of per unit length increases as the equivalent radius of the roadway increase.When insulation layer is laid partially,the greater the laying range of the heat insulation layer is,the smaller the heat exchange between the tunnel and the wind flow.Extinct lower temperature distribution of the surrounding rock exists at the location of the insulation layer compared to case without that.Based on CFD,the variation of surrounding rock temperature field and inner air temperature in the tunnel,with periodic inlet wind,are analyzed.Under periodic wind temperature,the surrounding rock temperature fluctuates periodically with the wind flow temperature,and the amplitude and phase lag of the temperature wave decrease and increase with the increase of the surrounding rock depth.With constant airflow temperature,inside the tunnel,the airflow temperature is high near the wall of the roadway and low at the middle of axis.the surrounding rock temperature of the roadway increases linearly along the axial direction,and the airflow temperature at the axis increases approximately linearly.With the 100 mm insulation layer laid,the reduction of temperature rise in 500 m roadway and 2000 m roadway was 30% and 40% per 100-meter respectively.