Study On Thawing Settlement Remediation Of Permafrost Subgrade Based On Low Exothermic Polymer

Under the background of global warming,roadbed thawing diseases in permafrost regions will be more serious.In response to the actual needs of existing roads in permafrost regions in my country,a study on the thawing settlement of existing road subgrades in permafrost regions based on low exothermic polymers has been carried out.The road non-destructive monitoring technology is used to evaluate the effect of grouting repair,a variety of sensors are used to record and analyze the influence of polymer grouting-diffusion-expansion process on the road structure.The finite element method is used to study and analyze the effects of different grouting schemes on the heat preservation,seepage prevention and suppression of subgrade thawing settlement of the frozen soil subgrade,and the results are verified by field test data.It aims to provide a theoretical basis and reference for the application of polymer grouting repair technology to the treatment of hidden road diseases in permafrost regions.The main research contents and results are as follows:1.Based on Fourier’s law and numerical unit model,the Abaqus finite element analysis software is used to establish a three-dimensional polymer element model of the first type and the third type of superimposed boundary conditions.The results show that the thermal conductivity of the low exothermic polymer grouting material is positively correlated with the density of the material;fitting results obtained polymer grouting material thermal coefficient prediction formula for the density of the material,to provide reference for polymer construction site.2.The sensor records and analyzes the influence law of the whole process of polymer grouting on the road structure.The analysis shows that the grout will give priority to filling the void areas of the pavement structure.The grout spreads between the structural layers in an elliptical shape,and the driving direction of the roadbed is further affected by the grout;the polymer grouting has less disturbance to the frozen soil roadbed during the whole process.Two hours after the grouting is finished,the soil returns to its initial temperature.Therefore,it is feasible to repair roadbed diseases in permafrost regions based on low-heat polymer,and the road can be blocked for a short time after grouting.3.Based on COMSOL Multiphysics finite element software,establish a fully coupled numerical model of water and heat for permafrost roadbed,and verify the feasibility of the model with field monitoring data.The calculation results show that the polymer grouting layer can effectively prevent the intrusion of heat insulation into the soil,reduce the amount of water migration in the soil of the roadbed,reduce the ice content of the soil by about 15%,and inhibit the frost heave and thaw settlement of the roadbed.The best protection effect is superimposed grouting under the semi-rigid road base,the bottom of the roadbed backfill and the lower part of the upper limit of permafrost.4.Use the road surface non-destructive testing technology to evaluate the polymer repair effect,and monitor the changes of the roadbed soil after grouting through sensors.The analysis shows that the polymer grouting technology can effectively repair the mild subsidence of the frozen soil roadbed.The loose and empty areas of the roadbed are repaired,and the roadbed deflection is reduced by about 20% on average.The soil temperature and humidity in the polymer grouting area are more stable than those in the non-grouting area,which is consistent with the simulation results.