Research On Mechanical Characteristics Of Welded Turnouts On Qinghai-tibet Railway In Permafrost Regions

The Qinghai-Tibet Railway plays a very important role in changing the poverty and backwardness of the Qinghai-Tibet Plateau,enhancing the unity and common prosperity of all ethnic groups,and promoting exchanges between Tibet and internal provinces.However,due to the permafrost zone of the Gela Section of Qinghai-Tibet Railway being affected by the environment of high cold and large temperature difference,after several years of operation and trial laying of the seamless track in multiple sections,the seamless track of the Ge’erla section has been gradually realized in 2012.The overall operation is in good condition.However,there is still a buffer zone between the main line of the section and the turnout,which affects passenger comfort and increases disease inspection and maintenance costs.The State Council has put forward the requirements for the entry of EMUs into Tibet in the new era.It requires a higher standard track structure and maintenance level to provide operation guarantee.The use of inter-interval seamless rail is an inevitable choice,and seamless turnout is an inter-interval seamless rail.An important part of the research has important practical significance for the development of research.To this end,the research work is mainly carried out from the following aspects:(1)Design of on-site pavement replacement scheme for seamless turnouts applicable to the Gela sectionAiming at the problems of high temperature difference and high frequency temperature difference in the laying of inter-interval seamless track in alpine regions,based on the laying and safe operation of the Qinghai-Tibet railway inter-interval seamless track,the Yuzhu Peak station is selected as the inter-interval seamless track laying In the test turnout area,according to the actual condition of the line,semi-welded seamless turnouts are used,and the frozen joints are used to weld the turnout area and the main line,and the tensile strength of the joint is tested with a 50 T tension and compression machine;5 pairs of displacement observation piles are buried in accordance with the actual situation on the site;Investigate the highest and lowest rail temperature in the area,and finally determined that the design lock rail temperature is 14±5℃.(2)Establish the finite element calculation model of the seamless turnout track frame to analyze the deformation of the seamless turnout under the conditions of high cold and large temperature differenceBased on the spatial nonlinear finite element method,the 12# seamless turnout track frame calculation model that matches the actual site is established,and the corresponding calculation program is compiled to study the temperature rise,the track irregularity and the long rail displacement under the conditions of applying ground anchor rods.Development Law.Under the action of temperature force,the seamless turnout produces larger lateral deformation at the tip of the switch rail,the heel end of the switch rail,the middle of the guide curve and other unfavorable positions,and the greater the temperature rise,the greater the lateral deformation.The irregularities of the single-track and double-track directions are simulated,and the law of the lateral displacement of the rails is obtained when the temperature rises under different working conditions.When the four-nodes of the double-track and double-sections deviate outward,it is the most unfavorable working condition.The ground anchor tie rods were applied to the switch,guide curve,and frog respectively.The results show that the track strengthening equipment has a significant contribution.When it acts on an unfavorable location,the lateral displacement of that location is reduced the most,and when the double node is at an unfavorable location When ground anchors are applied at the same time,the lateral displacement is reduced the most.(3)Displacement monitoring data analysis of seamless turnout and on-site rail temperature-strain test testAccording to the established semi-welded joint seamless turnout calculation model,the theoretical displacement of the field displacement observation pile placement position at different rail temperatures is calculated,and compared with the field measured data.The field measured data is slightly smaller than the calculated data,indicating that semi-welded Freeze joints are feasible.At the same time,the on-site rail temperature-strain test was carried out in the season when the annual rail temperature of Yuzhufeng station was relatively high.Strain sensors were installed at the rail waists of different parts of the seamless turnout to collect the rail strain increment under the cyclic change of rail temperature and analyze The rail temperature was actually locked at the site,and it was found that the locked rail temperature in the turnout area remained stable,and the change in the increase in strain of the turnout area was consistent with that of the main line long rail,which further verified the feasibility of the semiwelded seamless turnout laying plan.