Study On Subgrade Frost Heave Mechanism And Line Regularity Control Technology Of High-speed Railway In High-cold Regions

The high-speed railway in the alpine region has a very high demand for the railline smoothness.The special climate characteristics of the seasonal frozen soil area in northeast China lead to the problem of the irregularity of the high-speed railway under the action of frost heave.Therefore,it is very important to study the frost heave mechanism of high-speed railway subgrade and the control technology of track irregularity.Relevant research can provide support for the construction and operation of high-speed railway in seasonal frozen soil area,ensure the safety of high-speed train operation,and hope to contribute to the development of seasonal frozen soil theory.Based on the high-speed railway projects such as Harbin-Dalian railway and Harbin-Qiqihar railway,this paper studies the frost heave characteristics and mechanism of fillers from the micro and macro perspectives,and researches the frost heave characteristics of coarse-grained soil fillers by means of field investigation,model test,field test,numerical analysis and theoretical derivation.On this basis,taking the subgrade track structure system of railway in cold area as the research object,this paper reveals the influence of frost heaving on the line,establishes the control standard of subgrade frost heaving,puts forward the frost heaving modification method of coarse-grained soil filler for high-speed railway,and evaluates the application effect of frost heaving cement stabilized crushed stone subgrade for Harbin-Qiqihar passenger dedicated line.The main research work and innovation achievements are as follows:(1)The mechanism of frost heaving of high speed railway subgrade filler in high cold area is revealed.As there is no systematic study on the mechanism of frost heave of coarse-grained soil filler,so this paper based on X-CT scanning and image reconstruction technology,the structural state and water distribution characteristics of micro frost heaving filler are analyzed.Through the development of experimental model,the hydrothermal characteristics of coarse-grained soil frost heaving are studied.It is found that the contribution of fine particle content to frost heave is greater than that of water content,and the contribution of water content to frost heave depends on the content of fine particles.(2)The transfer law of frost heave deformation of high-speed railway subgrade is put forward.Based on the coupled analysis model of subgrade frost heaving CRTS ? slab ballastless track structure track geometric irregularity transmission,the paper forecasts the frost heaving time-space distribution curve,reveals the influence law of frost heaving on the smoothness of each layer and the track surface irregularity,analyzes the uneven frost heaving effect,and evaluates the influence regulation of subgrade frost heaving on driving safety,comfort and line operation reliability law.When the wave amplitude ratio(wavelength / amplitude)of frost heave increases,the deformation of track structure and subgrade tends to be the same;when the wave length is fixed,the influence of frost heave on the stress of track slab and base slab basically shows a linear growth trend.(3)The control standard of Subgrade Frost Heave based on static and dynamic analysis is established.Because the static and dynamic irregularity of the track is significantly affected by the local deformation of the uneven Subgrade Frost heave,based on the influence of frost heaving on the structure and driving,the frost heaving degree is divided into three areas by two critical curves.When the frost heaving degree is located in area I,the track irregularity can be controlled by the allowable deviation of amplitude in the management standard for geometric state acceptance of high speed railway track.When the frost heaving degree reaches to area II,it is necessary to focus on checking the off seam under the board at the frost heaving position and making small-scale repair,measures shall be taken immediately to ensure the safety of the line in case of frost heave in area III.(4)The method of frost heave modification of coarse-grained soil filler for high-speed railway is put forward.Because only the adjustment of the fastener itself may not meet the control requirements of frost heave,it is necessary to study the frost heave characteristics of the subgrade bed itself when dealing with the problem of frost heave deformation.The effects of particle size and cement content on frost heave performance,unconfined compressive strength and permeability coefficient of graded crushed stone are studied.It is concluded that when the cement content is 3%,the frost heave rate of the sample decreases significantly.Compared with the unmodified filler,the frost heave rate of the modified coarse-grained soil filler decreases to one fifth of the original.When the cement content reaches 5%,the frost heave resistance of the material can be improved obviously.It is suggested that the graded crushed stone with 3% fine-grained soil content and 3% cement content should be selected as the filler for the non permeable foundation bed,and the graded crushed stone with 3% ? 5% cement content should be selected as the filler for the permeable foundation bed.(5)The service characteristics of cement stabilized gravel bed with frost proof expansion are evaluated.Because the anti freezing effect of the Modified Cement Stabilized Graded Crushed Stone Foundation needs to be further evaluated in the actual project,this paper combines the static subgrade deformation and frost heave monitoring with the dynamic detection of the dynamic inspection vehicle,the frost heaving characteristics of cement stabilized crushed stone subgrade bed are evaluated,and the emergency treatment measures for special frost heaving sections are described.The evaluation results show that the frost heave can be restrained effectively and the uneven frost heave control standard can be satisfied.