Simulation Study On Frost Heave Of Subgrade In Seasonal Frozen Area Based On FLAC3D

The subgrade in seasonal frozen soil area is affected by the freeze-thaw cycle,and the subgrade will undergo frost heaving,which will cause uneven settlement of the road.The subgrade frost heave affect the driving safety,and increase the maintenance and repair costs of the road.Therefore,the subgrade frost heave and safety issues in seasonal frozen soil areas deserve attention.Based on FLAC3D,this paper simulated the frost heave problem of subgrade in seasonal frozen soil area.Obtained the frost heave coefficients through the indoor frost heave tests,and modified them to give a method to modify the frost heave coefficient.At the same time,performed the indoor thermal parameter tests to obtain the thermal parameters such as the thermal conductivity and specific heat capacity which used in the simulation.The subgrade model has been established to analyze the frost heave characteristics of the subgrade at different temperatures.Based on the daily average temperature in winter in Harbin,the subgrade model has been subjected to the full frost heave numerical simulation in winter,and the displacement and temperature fields of the subgrade were obtained.The main research work was as follows:(1)The basic theory of the FLAC3D temperature module has been described,including the energy equation,thermal strain formula and heat conduction formula,and the key parameters required for numerical simulation have been determined,that were: the frost heave coefficient,thermal conductivity and specific heat capacity of the material.(2)Through the indoor frost heave tests,the frost heaving coefficients of three kinds of soils in seasonal frozen soil regions at different moisture contents,different dry densities,and stepwise decreasing temperatures have been obtained,and the corresponding original data of frost heaving coefficient of the roadbed frost heave simulation has been provided.The laboratory tests of thermal parameters of differenttemperatures of specific sample have been carried out to obtain the thermal conductivity,specific heat capacity and thermal conductivity coefficient;consulted the literature to obtain the mechanical parameters of the roadbed model.(3)Through FLAC3D simulation of indoor frost heave tests under multiple working conditions,comparing the simulation and test results,the frost heave coefficients were corrected,and the corrected frost heave coefficients were obtained again through the FLAC3D simulation test.The simulation and test results were closer.More accurate frost heave coefficients and correction methods have been given.(4)Established the roadbed model,and carried out different temperature freezing simulations on the roadbed model,and analyzed the frost heave characteristics of the roadbed under different negative temperature freezing.According to the winter temperature in Harbin,the above parameters have been used to simulate the frost heave of a roadbed during the full freezing period in Harbin,and the general law of the displacement and temperature field of the roadbed have been obtained.