In extreme cold regions,a thermal insulation layer(TIL)is commonly employed to mitigate the detrimental effects of frost heaving forces in tunnels.Optimizing the laying scheme of TIL,specifically minimizing frost heav...In extreme cold regions,a thermal insulation layer(TIL)is commonly employed to mitigate the detrimental effects of frost heaving forces in tunnels.Optimizing the laying scheme of TIL,specifically minimizing frost heaving forces,holds considerable importance in the prevention of frost damage.This research developed a two-dimensional unsteady temperature field of circular tunnels by using the difference method(taking the off-wall laying method as an example)based on the law of conservation of energy.Then,the frozen circle and water migration coefficient were introduced to establish the relationship between the temperature field and frost heaving forces,and a reliable methodology for calculating these forces under the specific conditions of TIL installation was developed.Then(i)the influence of the air layer thickness of the off-wall laying method,(ii)different laying methods of TIL,(iii)the TIL thickness,(iv)the thermal conductivity of the TIL,and(v)the freeze-thaw cycles on the frost heaving force were investigated.The results showed that the frost heaving force served as a reliable and effective metric for evaluating the insulation effect in tunnels.In order to avoid frost damage in compliance with the design requirements,the insulation effects from various laying methods were established,in descending efficacy order as follows:off-wall laying,double layer laying,surface laying,and sandwich laying.Our findings revealed that the optimal thickness for the air layer in the offwall laying method was 0.10 m.The insulation effect of materials with a thermal conductivity below 0.047 W/(m·℃)was furthermore found to be good.Under freeze-thaw cycle conditions,it is concluded that to prevent frost damage,the TIL thickness should be the sum of the thickness r1 of the first freeze-thaw cycle without frost heaving forces and an additional reserve value 0.06r1 of the TIL thickness.展开更多
A thermal insulating material is synthesized via a non-steam-cured and non-fired route by using fly-ash, sorel cement and hydrogen peroxide solution as raw material. Properties such as apparent density, compressive st...A thermal insulating material is synthesized via a non-steam-cured and non-fired route by using fly-ash, sorel cement and hydrogen peroxide solution as raw material. Properties such as apparent density, compressive strength, bending strength, thermal conductivity, water resistance, and thermal tolerance of this matrial are studied, some influencing factors on its performance discussed. This material has an apparent density of 360 kg/m3, a compressive strength of 1.86 MPa, a thermal conduction coefficient of 0.072 W/(m·K), a softening coefficient of 0.55, and a thermal tolerant temperature of 300 °C. Test results show that this material is light in weight, of high strength, and good thermal insulation. In addition, neither steam-curing nor sintering is needed in producing it. Further more, large amount of fly ash is used in this material, making it a low cost and environment-friendly building material.展开更多
Encouraged by the porous and stable structure of cold-resist animals’hair or feather,bio-inspired hierarchical structure yarns combining polyacrylonitrile(PAN)nanofibers and polypropylene(PP)hollow microfibers have b...Encouraged by the porous and stable structure of cold-resist animals’hair or feather,bio-inspired hierarchical structure yarns combining polyacrylonitrile(PAN)nanofibers and polypropylene(PP)hollow microfibers have been developed by a modified conjugate electrospinning technology.Physical cross-linking has been built to increase fibers adhesion and construct interlayer support for nanofibrous assembly.The nanofibers and hollow microfibers construct a stable porous structure with porosity of 62%,providing excellent thermal insulating ability[temperature difference(|ΔT|)between skin and yarn surface is 4.9℃]as well as good mechanical property.More interestingly,the water transfer ability(infiltrate the yarn in 10 s)of synthetic fibers has been improved greatly by the combination of thin diameter nanofibers to the yarn.It is believed that the research lays the foundation for bio-inspired engineering technology in the manufacture of thermal comfort.展开更多
基金the financial support provided by the National Natural Science Foundation of China(Nos.52078061,51878074)the Huaihua University Scientific Research Project,China(No.HHUY 2022-26)+1 种基金the Postgraduate Research and Innovation-funded Project of Hunan Province,China(No.CX20220885)。
文摘In extreme cold regions,a thermal insulation layer(TIL)is commonly employed to mitigate the detrimental effects of frost heaving forces in tunnels.Optimizing the laying scheme of TIL,specifically minimizing frost heaving forces,holds considerable importance in the prevention of frost damage.This research developed a two-dimensional unsteady temperature field of circular tunnels by using the difference method(taking the off-wall laying method as an example)based on the law of conservation of energy.Then,the frozen circle and water migration coefficient were introduced to establish the relationship between the temperature field and frost heaving forces,and a reliable methodology for calculating these forces under the specific conditions of TIL installation was developed.Then(i)the influence of the air layer thickness of the off-wall laying method,(ii)different laying methods of TIL,(iii)the TIL thickness,(iv)the thermal conductivity of the TIL,and(v)the freeze-thaw cycles on the frost heaving force were investigated.The results showed that the frost heaving force served as a reliable and effective metric for evaluating the insulation effect in tunnels.In order to avoid frost damage in compliance with the design requirements,the insulation effects from various laying methods were established,in descending efficacy order as follows:off-wall laying,double layer laying,surface laying,and sandwich laying.Our findings revealed that the optimal thickness for the air layer in the offwall laying method was 0.10 m.The insulation effect of materials with a thermal conductivity below 0.047 W/(m·℃)was furthermore found to be good.Under freeze-thaw cycle conditions,it is concluded that to prevent frost damage,the TIL thickness should be the sum of the thickness r1 of the first freeze-thaw cycle without frost heaving forces and an additional reserve value 0.06r1 of the TIL thickness.
基金Project 20062147 supported by the Liaoning Province Natural Science Foundation of China
文摘A thermal insulating material is synthesized via a non-steam-cured and non-fired route by using fly-ash, sorel cement and hydrogen peroxide solution as raw material. Properties such as apparent density, compressive strength, bending strength, thermal conductivity, water resistance, and thermal tolerance of this matrial are studied, some influencing factors on its performance discussed. This material has an apparent density of 360 kg/m3, a compressive strength of 1.86 MPa, a thermal conduction coefficient of 0.072 W/(m·K), a softening coefficient of 0.55, and a thermal tolerant temperature of 300 °C. Test results show that this material is light in weight, of high strength, and good thermal insulation. In addition, neither steam-curing nor sintering is needed in producing it. Further more, large amount of fly ash is used in this material, making it a low cost and environment-friendly building material.
基金This work was supported by the Major Scientific and Technological Innovation Project of Shandong Province,China(No.2019JZZY020218).
文摘Encouraged by the porous and stable structure of cold-resist animals’hair or feather,bio-inspired hierarchical structure yarns combining polyacrylonitrile(PAN)nanofibers and polypropylene(PP)hollow microfibers have been developed by a modified conjugate electrospinning technology.Physical cross-linking has been built to increase fibers adhesion and construct interlayer support for nanofibrous assembly.The nanofibers and hollow microfibers construct a stable porous structure with porosity of 62%,providing excellent thermal insulating ability[temperature difference(|ΔT|)between skin and yarn surface is 4.9℃]as well as good mechanical property.More interestingly,the water transfer ability(infiltrate the yarn in 10 s)of synthetic fibers has been improved greatly by the combination of thin diameter nanofibers to the yarn.It is believed that the research lays the foundation for bio-inspired engineering technology in the manufacture of thermal comfort.
