Study On Continuously Reinforced Concrete Pavement In Permafrost Region

As one of the three largest permafrost countries in the world,China has a large area of permafrost,accounting for more than two-thirds of the land area.After the construction of Expressway in permafrost region of Qinghai-Tibet Plateau,the total heat absorption area and total volume heat capacity will increase greatly,the permafrost temperature of subgrade and base will rise,and the artificial upper limit of permafrost will move down.Thermal thaw settlement deformation of subgrade structure will easily occur,which seriously affects the service life of pavement structure.In this paper,finite element method(FEM)is used to simulate the temperature field of wide roadbed and the change law of thawing deformation.Different asphalt pavement structures are proposed to calculate stress characteristics based on thawing characteristics.CRCP pavement structure is proposed to calculate stress characteristics.(1)The distortion of embankment in permafrost regions is caused by the coupling effect of temperature field,water field and stress field of permafrost embankment.Firstly,based on a large number of research literature,the temperature field and water field inside the frozen soil embankment were studied,and the equation of water-heat coupling was put forward.Then,based on the elastic-plastic constitutive model of frozen soil,a moisture-heat-stress coupling model of frozen soil embankment was studied.(2)Considering climatic environment and the characteristics of embankment in permafrost regions,calculatingparameters,boundary conditions and initial conditions of temperature field were put forward.A moisture-heat-stresscoupling model was constructed based on theory.And,the temperature contour map,the curve of temperature along the depth over time and the graph of annual maximum thaw depth over time were compared in this paper.The influence of different embankment heights on temperature field of embankment in permafrost region was also studied.Then,the settlement characteristics of permafrost embankment were studied through the deformation field calculated by finite element software COMSOL.The results show that the temperature distribution of subgrade varies with the height of subgrade and with the increase of time,the melting deformation at the central line of subgrade and the foot of subgrade slope increases,and the increase at the central line of subgrade is faster.(3)According to the characteristics of permafrost regions and the research at home and abroad,three kinds of pavement structures commonly used in permafrost areas were proposed.Then finite element software COMSOL was used to calculate the additional stress of thawing settlement of different pavement structure combinations.The sensitivity analysis of the factors affecting the additional stress of thawing settlement,such as the material modulus and thickness of cushion,base,surface and gravel layers,was carried out.According to the results of calculation and analysis of additional stress of pavement thawing settlement,the main influencing factors of additional stress were selected to provide reference for the design of pavement structure thawing settlement in permafrost regions.(4)A typical structure form of continuous reinforced concrete pavement in permafrost regions was proposed.The finite element model of continuous reinforced concrete pavement in permafrost regions was established by COMSOL finite element software.,The model was simplified appropriately according to the relevant characteristics of permafrost regions.According to different influencing factors,the stress characteristics of continuous reinforced concrete pavement structure combination in permafrost regions were studied.It provides a reference for the structural design of continuously reinforced concrete pavement in permafrost regions.