Research On Deformation Law In Concrete Subgrade Bed Of High Speed Railway In Cold Region And Its Engineering Countermeasures

The Beijing-Shenyang Passenger Dedicated Line is an important part of the eight-vertical and eight-horizon main skeleton railway network of China.Due to its special geographical environment,there is no good solution to the problem of frost heave deformation of the high railway base in cold regions.To control the frost heave deformation of the subgrade to ensure the safe and stable operation of the high-speed train,the concrete subgrade structure is adopted along the line foundation,that is,the concrete is used instead of the AB group filler in the subgrade area to reduce the occurrence of frost heave deformation from the root source.High-speed railway has strict requirements on track deformation.One of its most remarkable features is the high smoothness of the track.The high-speed railway concrete subgrade structure in the cold area will generate stress and deformation under the influence of environmental temperature changes,which may bring hidden dangers to the safe and stable operation of the high-speed train.Therefore,the warpage deformation law of concrete subgrade structure in cold area is studied,the deformation characteristics of concrete subgrade are summarized,and scientific and reasonable engineering treatment measures are put forward,which provides technical support for improving the maintenance and repair of high-speed concrete subgrade line in cold area.Besides,it provides theoretical guidance for the design and construction of high-speed railway foundation engineering in cold regions,which has important practical significance and economic value.Based on the theory of heat conduction,this paper studies the temperature field distribution and warpage deformation of high-speed railway concrete subgrade structure in cold area under ambient temperature through on-site monitoring and finite element simulation analysis.The main research work is as follows:(1)Based on the measured data of ground temperature of DK347+710 subgrade concrete subgrade section of Beijing-Shenyang Passenger Dedicated Line,the variation law of ground temperature amplitude with depth is studied,and the distribution law of temperature and the variation of freezing depth of high railway base in cold area are analyzed.(2)According to the long-term monitoring data of warpage deformation of concrete subgrade in Beijing-Shenyang Passenger Dedicated Line,the variation of warpage deformation of concrete subgrade under ambient temperature is studied.(3)Assuming that the concrete subgrade plate only has a temperature gradient in the thickness direction,the finite element software ABAQUS is used to establish a numerical model of the high-speed railway foundation structure.According to the fourier heat conduction equation,the heat transfer analysis of the concrete subgrade plate under this condition is carried out,and the concrete is passed through the site.The measured data of the warpage deformation of concrete subgrade is compared to verify the correctness of the established finite element model.(4)Using ABAQUS to establish the subgrade structure model under different working conditions,and to explore its influence on the warping deformation of concrete subgrade.The results show that the ambient temperature conditions and the length of concrete subgrade have a great influence on the warpage deformation.When using concrete subgrade structure,not only the length of concrete subgrade should be controlled,but also the insulation measures should be taken.(5)In order to reduce the influence of warping deformation on track smoothness,the countermeasures for dealing with warping deformation of high-speed concrete subgrade structure in cold regions are put forward.