Consolidation And Deformation Of Thawing Soil Under Dynamic Loading

At present, a lot of research work on permafrost thawing settlement mechanism and characteristics has been conducted by domestic and international scholars, which is extremely important for engineering construction in cold region. However, these studies mainly concentrated in thawing settlement characteristics under static loading, rarely involves the relationship between dynamic loading and frost heaving and frost boiling and moisture migration, especially without considering the change of pore water pressure on the effect of subgrade settlement. But in practical engineering, only vehicle dynamic load can reflect the external loading condition, while the dissipation of pore water pressure and moisture migration is the key to explain the essence of real thaw settlement phenomenon, which is important for safe operation of the road.Based on the National Natural Fund Project (NSFC)" Theoretical study on dynamic thawing consolidation", focused on the subgrade section of109National Highway in Qinghai Province rubber Hill section, through combination of field investigation and measurement, theoretical analysis, numerical simulation and experimental verification, systematic study has been carried on dynamic thawing consolidation characteristics of permafrost, to further improve the discipline system of permafrost dynamics. The main conclusions are as follows:(1) Aiming at the problem of subgrade frost heaving and frozen soil properties caused by overload, through field investigation and measurement, we study the law of dynamic response of subgrade under dynamic loading with different depth, amplitude and speed. And a long time observation on the dynamic response of subgrade has been carried on.(2) Considering different cooling and melting temperature of soil boundary conditions, we study the law of soil pore-water pressure with lateral confinement in the open system under static and dynamic loading.(3) This paper puts forward the coupling model of the heat-moisture-stress field based on the governing equation of non-stationary heat transfer, moisture movement and the basic differential equations of deformation problem by displacement under axisymmetric conditions.(4) Considering the pore air pressure, the effective stress formula is revised. Considering the permeability coefficient as a function of pore water pressure and pore air pressure, combined with the soil particles, water, ice and gas mass conservation equation and momentum conservation equation, according to the Darcy’s law to express the average velocity of gas and water, an unsaturated high-temperature permafrost thawing consolidation theory model is derived.(5) Using the numerical simulation method, we study law of dynamic melting consolidation of subgrade with high temperature permafrost. Respectively, two models are established to simulate the indoor experiment and the real subgrede structure, a comprehensive analysis of the law of high-temperature permafrost thaw consolidation settlement under different boundary conditions.