Prairie Wetlands Seasonally Frozen Ground Study On Mechanical And Deformation Characteristics Of Embankment

Combined with Lang-Chang highway engineering, based on indoor model test andnumerical simulation, this paper made a research on the force and deformation characteristicof grassland seasonal frozen soil subgrade, the main research results are as follows:(1) Laboratory model test results indicate that, it suggested that when subgrade heightwas2m, the isolation layer should be set in1.0~1.5m under road surface, namely0.5~1.0munder subgrade surface, and20cm high over surface water, with10~20cm thickness.(2) Numerical simulation analysis showed that, it suggested that when the frost heave ofsubgrade fill happens in winter, the internal temperatures of subgrade appear axiallysymmetrical distribution along the subgrade central axis. Subgrade fill produces thaw collapsedue to sunshine difference in the two subgrade slope sides, so the internal temperatures ofsubgrade appear asymmetrical distribution along the subgrade central axis in summer, andwith climate warming, the subgrade frozen layer gradually thaws downward from up.(3) Numerical simulation analysis showed that，Thaw collapse is most unfavorable toseasonal frozen subgrade stability. When subgrade thaw collapse occurred, the settlementdeformation is larger and gradually decreases downward from pavement, the largestsettlement of pavement and base as a whole reaches to100mm, and the subgrade andfoundation settlement linear decrease with depth. Setting isolation layer in the contact ofsubgrade and foundation can effectively enhance subgrade stability, and considering theinfluence of ground water lever, the isolation layer should be0.1~0.2m above ground.(4) Laboratory model test results indicate that, it suggested that increasing subgradeheight contributes to increasing its strength and stability, but it cannot guarantee expected thedry and wet state of subgrade, and will bring about increasing project cost, destroying prairiewetland ecological environment, therefore, it’s not an option. For prairie wetland seasonalfrozen subgrade, to ensure its stability, if not setting isolation layer, the subgrade heightshould be above1.5m, after setting isolation layer, the subgrade height is generally about1.0m.