Research On Insulation Material And Structure Of Tunnel Arch In High Altitude Cold Region

The frost heaving disaster of the tunnel in the cold region of high altitude is frequent.With the continuous progress of the research,it is difficult and limited to set up the drainage structure of the tunnel in the cold region of high altitude,so the application of new materials and the study of new structure will be the key development direction of drainage and insulation design.In this paper,the thermal insulation materials and structural forms of the invert in the cold region of the tunnel at high altitude were studied.From the perspective of new materials and new technology,the feasibility analysis of filling the invert with foamed concrete was carried out,high-performance foamed concrete was developed,and the thermal insulation structure and layout scheme of the invert in the cold region of the tunnel with new materials were proposed.Combining the construction requirements of the invert arch filling in the cold area tunnel and the basic characteristics of the foam concrete,the feasibility analysis of the inflating foam concrete material in the invert arch is carried out in this paper,including the material deformation,construction technology,strength and other factors.The high strength foam concrete was developed through the mix ratio design,and the strength characteristics of the developed foam concrete were obtained.The relationship function between the compressive strength and density of the foam concrete at low temperature and low pressure was given,and the differences of the concrete under different atmospheric pressures were analyzed.In accordance with the climate characteristics of high altitude and cold regions,the freeze-thaw cycle experiment was carried out in this paper,and the degradation characteristics of freeze-thaw cycle of foam concrete with different densities were analyzed.The thermal conductivity of foam concrete was measured by a self-developed thermal conductivity testing device,and the change law of thermal conductivity of foam concrete with density was obtained.The experimental results reflect the advanced nature and adaptability of the developed high-performance foam concrete as a filling material for the invert.Based on the differential equations for controlling the temperature field of the tunnel surrounding rock,this paper established a discrete calculation model for the temperature field of the tunnel arch,concrete filling layer and lower surrounding rock.The example analysis shows that the foam concrete filling layer in the insulative thermal insulation structure plays a significant role in antifreeze and thermal insulation.Finally,based on the concrete test and the theoretical calculation results of the heat transfer of the surrounding rock of the tunnel,this paper gives the buried plan of the thermal insulation structure and drainage structure of the tunnel arch,and analyzes the distribution law of temperature field under different schemes of drainage structure with the help of finite element calculation software.The numerical calculation results show that the layout plan of the inverted arch thermal insulation structure and drainage structure proposed in this paper meets the requirements of thermal insulation and antifreeze,reduces the buried depth of the central drainage ditch,reduces the construction risk,and promotes the development of new materials and structures in drainage and thermal insulation.