Study On Subgrade And Pavement Structural Deformation Characteristics Of High-grade Highway In Permafrost Regions

Permafrost regions of the Qinghai-Tibet Plateau have the natural environment characteristics of high altitude, strong radiation, low temperature, great temperature difference and wide spread various permafrost types. Quickly decay in roadbed pavement performance, plenty of road diseases, such as crack, rut, uneven settlement and so on, lower the use of performance road was caused by these characteristics. This paper combined field test with numerical simulation method to study on the temperature field and displacement field in subgrade and pavement and analyze the road deformation characteristics in permafrost regions.Based on Qinghai-Tibet road G109 and Qingkang road G214 in Tibetan plateau permafrost regions, this paper analyzed the natural environmental conditions characteristics, including radiation, rainfall, frozen soil types along the road and others, summarized and analyzed the subgrade-pavement typical structure and road diseases types in permafrost regions based on the field investigations.Unsteady temperature field, moisture field, stress and deformation field equations with transformation was established. Gonghe-Yushu highway form K629 + 800- K634 + 200 was taken as tset section for selecting the semi-rigid base asphalt pavement, composite asphalt pavement and flexible base asphalt pavement structure to establish a numerical model of subgrade-pavement structure in permafrost regions.Based on the field investigations, to analyze the deflection, pavement deformation and disease distribution characteristics of test section(K629+800- K634+200) of Gonghe-Yushu highway. Considering the bearing capacity and pavement deformation, resistance to deformation of pavement, anti-cracking and other factors, to evaluate pavement performance of test section in permafrost region, the results show that the performance of the composite base asphalt pavement(4% cement stabilized macadam base, 2% cement stabilized macadam base test section) is the best, flexible base asphalt pavement(unbound graded base, geocell test section) follow.This paper established subgrade and pavement structure numerical calculation model, and simulated temperature, moisture content, load and displacement boundary conditions of test section. Numerical calculation of the displacement deformation of the subgrade and pavement structure, and comparing with the field investigation results to validate the established numerical model of subgrade and pavement structure is correct and reasonable.Numerical calculation and analysis of temperature field variation characteristics of the semi-rigid asphalt pavement, composite base asphalt pavement and flexible base asphalt pavement structure, the results show that the composite base asphalt pavement structure works best in improving zero freezing line and reducing the melting of frozen soil. Based on calculation and analysis of different pavement structures displacement field characteristics, it shows that the composite base asphalt pavement deformation less than semi-rigid and flexible pavement in permafrost regions.Calculation and analysis of temperature field, displacement field and road surface subsidence of wide and narrow composite base asphalt pavement, it shows that the wide road structure has obvious decalescence, heat accumulating and heat preservation effect, the wide road structure, which exists within a wide range of high-temperature region in its foundation, greater than the narrow in road structure deformation.