Centrifugal Model Test Study On Thermal Melt Stability Of Widened Subgrade In Permafrost Area

As the western region development and the discrepancy of the Tibetan vehicles increases,more plateau highway has obvious insufficiency,overwhelmed on the Qinghai-Tibet,along with the implementation of the " One Belt and One Road " policy,the western highway traffic infrastructure construction is imperative,using the secondary road upgrading is also an important construction comparison and selection scheme.The roadbeds of the Qinghai-Tibet Plateau are mostly frozen soil with high ice content,the sensitivity of the soil to freezing and thawing is significant,affected by many factors such as light intensity,temperature cycle fluctuations,and heat accumulation effects of the roadbed,the temperature in the soil is variable and the cracks are more developed,the problem of heat-melt stability is extremely complicated,widening on the frozen soil subgrade will further affect the heat-melt stability of the subgrade,and the development pattern of longitudinal cracks will also be greatly changed.Therefore,it is necessary to study the stability of widened subgrade thermal melting in permafrost regions,and to reveal its generation mechanism and evolution process,the research results have important engineering significance for widening the thermal stability of subgrade in permafrost regions and the prevention of roadbed disasters.Based on the research background of widening subgrade engineering in the permafrost region on the Qinghai-Tibet Plateau,this paper analyzes the temperature evolution and differential thawing mechanism of frozen soil subgrade through indoor centrifugal model tests;the temperature change process and longitudinal crack development pattern of roadbed and permafrost region under roadbed under different working conditions were studied by means of Fiber Bragg Grating test,so as to provide a basis for guiding engineering practice.The main research results are as follows:(1)Designed and produced a centrifugal model test system for testing the temperature field and longitudinal crack development domain of frozen soil widening subgrade,and the temperature field and deformation field of subgrade space in different fillers and different forms under temperature cycle fluctuation and sunny-shady slope effect were tested.(2)By analyzing the results of centrifugal simulation test of the frozen soil widened subgrade,the distribution law of temperature field of roadbed broadening with permafrost in different forms is revealed,and the water transfer law of roadbed broadening with permafrost,the temperature difference under sunny-shady slope effect,and the evolution process of temperature between roadbed and permafrost active area are studied.(3)Based on the test technology of fiber Bragg grating,the differential settlement of roadbed under sunny-shady slope effect is systematically analyzed,and the development law of differential settlement of roadbed soil and new and old roadbed under different fillers and different forms of permafrost is revealed.(4)Combined with the development law of temperature and settlement of permafrost subgrade,this paper analyzes the longitudinal cracks in the test and reveals the development characteristics of longitudinal cracks.Comparative analysis shows that the appearance of longitudinal crack is closely related to the range of temperature change,heat transfer route and the development trend of melting plate in the subgrade.