Research On Influence Of Subgrade Frost Heave On High-speed Railway Subgrade On Geometric Smoothness And Mechanical Properties Of Double Block Ballastless Track Structure

With the improvement of China's high-speed railway network,a large number of railway lines have been built in seasonal frozen soil areas,and a number of operating lines in the northwest and northeast regions have experienced severe subgrade frost heaves,which has caused irregularities and local cracking in ballastless track structure.Under the condition of deformation exceeding the limit,it will affect the safe and stable operation of the train.In severe cases,it is necessary to reduce the speed of the train,which increases the cost of line operation management and maintenance and repair.This paper combines the Menyuan to Haomen section of Lanzhou-Wulumuqi high-speed railway with severe frost heave to carry out corresponding research,and firstly conducts on-site survey and manual monitoring of the frost damage of this section,then analyzed the frost-heaving characteristics of the soil and frost-heaving changes in this section,and determined the frost heave conditions for studying the effect of subgrade frost heave on ballastless track.On this basis,ANSYS finite element software is used to establish the frozen soil subgrade temperature field-deformation field coupling model,the subgrade frost heave deformation transfer model,and the high-speed train-track-subgrade system coupling model.Based on the research and analysis of the effects of the subgrade frost heave on the deformation and stress of the CRTS I double block ballastless track structure,the research results have important theoretical and practical significance for the prevention and treatment of frost heave of high-speed railway subgrade.The main research work is as follows:(1)Investigated the environmental characteristics of the subgrade with severe frost heaves.It is believed that the conditions of the region such as climate,moisture,and soil quality have promoted the emergence and development of the subgrade frost heaves.The soil samples were subjected to particle sieving and orthogonal tests to analyze the gradation composition and the effects of different water content,fine particle content and compaction degree on the extent of frost heave.Using the artificial level monitoring method,the overall frost heave deformation of the embankment,culvert and transition section and the change rule of frost heave over time were statistically analyzed.(2)By combining local meteorological data and field observation data,the boundary conditions and initial conditions of the temperature field of the roadbed were determined,and a two-dimensional temperature field model was established to analyze the distribution characteristics of the temperature field and the change law of the soil freezing depth in different periods.Frost heave rate test and melt compression test determined the mechanical parameters such as the linear expansion coefficient of the soil at different temperatures.The temperature field results were applied as loads in the deformation field,and the distribution of the deformation subgrade temperature-deformation coupling field was analyzed.(3)Based on the monitoring and statistics of the frost heave deformation of the subgrade on this road section,the characteristics of the uneven frost heave curve of the subgrade and the calculation conditions under different frost heave wavelengths,frost heave peaks and frost heave positions were determined.Using the finite element method,a frost-heave deformation transfer model for the roadbed considering the nonlinearity of reinforced concrete is established,which analyzes in detail the effects of different frost heave wavelengths,frost heave peaks and frost heave peak longitudinal positions of the subgrade on the deformation law of double-block ballastless tracks,interlayer separation and structural stress characteristics.(4)Based on the vehicle-track coupling dynamics principle,the physical model is simplified into a mathematical model under a half-vehicle structure,and a parametric language programming function was used to establish a high-speed train-track-subgrade system coupling model.The main dynamic performance indicators that affect the safety and comfort of operating trains,such as displacement and wheel load reduction,were compared and analyzed for the dynamic response of the system under typical frost heaves,different frost heave wavelengths,and peak frost heave conditions.(5)Summarized the commonly used frost heaving remediation measures for subgrade in seasonal frozen soil areas in the current stage,combined with the characteristics of the frost heaving section of the Lanzhou-Wulumuqi high-speed railway,a variety of remediation measures for the surface freezing damage of the subgrade bed were proposed from the aspects of surface water,surface cracks,cracking of expansion joints,and thermal insulation measures.