Research On Key Construction Technology Of Permafrost Swamp Wetland Subgrade In High Altitude And Cold Region

The swamp wetland in the high altitude and cold region is very different from that in general area.The main reason is that there are permafrost layers under the turf and peat layers.The swamp wetland and the underlying frozen soil constitute a symbiotic system,which is interdependent,resulting in a great particularity of subgrade construction in this area.The research is supported by the project of highway S224 from Erdaogou military station of 109 fork to Zhiduo.The key construction technology of permafrost swamp wetland subgrade in alpine and high altitude area is studied based on the field investigation,indoor tests and numerical simulation.Based on the existing researches,this paper summarizes the formation reasons and the engineering characteristics of permafrost wetland.Meanwhile,the common subgrade diseases were summarized,and the influencing factors were analyzed.The thermal conductivity of swamp wetland turf layer was tested and analyzed,since it is the key factor affecting the temperature field of subgrade.The results show that the turf layer has good thermal insulation.The permafrost wetland is classified by combining the degree of swamp development with road construction.With the help of UAV low altitude aerial survey technology,the swamp wetland model was established,and the micro geomorphic parameters of the surface of wetland model were extracted by Image-Pro Plus software.Combined with the underlying permafrost type and the development degree of turf layer,the swamp wetland is classified by three-level indexes.In order to analyze the influence of different construction methods-whether or not to remove the surface turf-and different construction seasons on the subgrade temperature field of permafrost swamp wetland,the finite element analysis software COMSOL Multiphysics is used to establish the temperature field model of permafrost swamp wetland subgrade.The temperature field inside the subgrade is calculated for 10 years to analyze the law and characteristics of the subgrade temperature.On this basis,it is recommended to adopt the construction method of not removing the surface turf,and it is better to carry out the subgrade construction in autumn.Combined with the test road paving in typical swamp wetland section,the construction technology and process of permafrost swamp wetland subgrade in high altitude and cold region are summarized.