Research On Deformation Of Geogrid Reinforced Soil On The Transition Section Of Road And Bridge In Seasonally Frozen Region

Seasonally frozen soil and permafrost are widely distributed in northern China and the Qinghai Tibet Plateau.The expansion of frozen soil causes problems in the construction and use of buildings.However,the complexity of frozen soil itself is difficult to be explained by simple theory.As a multi-phase media,frozen soil contains four different media: liquid phase,gas phase,solid and ice.The interaction mechanism is extremely complex.Temperature changes and moisture migration have the greatest impact on frost heaving.Taking the Dehui bridge-subgrade transition section as the research object,a reliable hydro-thermo-mechanical coupling model is established.The frost heave deformation is analyzed by numerical simulation.The geogrid is used to strengthen the soil,and the effect of geogrid on frost heave deformation is analyzed quantitatively.The main work is as follows:(1)The influence factors of temperature field and moisture field are discussed respectively.The equations of temperature field and moisture field are established by introducing solid-liquid ratio and relative saturation to control equations of temperature field and moisture field.Through the finite element software COMSOL Multiphysics,the equations are solved numerically,and the reliability of the numerical simulation is verified based on the Zhangye loam freezing experiment,and the result has a good fit.(2)The discrete land surface temperature is fitted in the form of sine functions summation.Taking the transition section of fill road and bridge of Dehui Bridge as the object,the model is established to analyze the distribution and change law of variables in temperature field and moisture field.Through numerical solution,the freezing depth of roadbed is1.82 m to 1.92 m,and the maximum vertical displacement of roadbed centerline is15.13 mm.(3)A numerical simulation method of frozen soil engineering with volume ice content as field variable is proposed,which connects the hydrothermal field with the stress field.The ABAQUS software is used to simulate the road-bridge transition section affected by freezing,and the Mohr-Coulomb elastoplastic constitutive model is used to calculate the frost heave.The results show that the maximum displacement of the track centerline of the road-bridge transition section is 6.52 mm,which is more in line with the reality than the linear elastic model.Quantitative analysis of subgrade deformation characteristics under different reinforcement schemes.Laying geogrid can effectively control the deformation of road-bridge transition section,and the reinforcement effect increases with the decrease of reinforcement spacing,and becomes more obvious with the increase of elastic modulus.This study provides a solution method for the frost heave process of the road-bridge transition section in the seasonal frozen region,and realizes the quantitative analysis of the reinforcement performance in the frost heave process,which is expected to be used in design and practice.