Research Of Alarming Rail Temperature Of A Curved CWR Track Stability Considering Parameter Randomness

In recent years,CWR (Continuously Welded Rail) track has been rapidly developed not only in China but around the world, because of its advantages like riding quality, comfort and less maintenance. However, as the CWR track cannot move freely under thermal loading, the track may buckle when the thermal loading is too large. Accidents have shown that track lateral stability is still confronted with severe problems especially in CWR track on curves. In order to reduce these accidents and the collateral damage, it is critical to predict and monitor the track lateral stability at elevated rail temperatures, but there is not enough scientific background for the early rail temperature prediction or alarming. For this reason, this thesis will carry out the study on the early warning of CWR track stability.Based on the tested data in Jing-Cheng railway line. FE models for stability were developed which are more corresponding to the field conditions. Considering the randomness of key influencing parameters, analyses on force^ deformation and track lateral stability were conducted. And on this basis, probability analysis of reliability is carried out through Monte-Carlo method.The relations for the failure probability and temperature increase above neutral temperature under several operational conditions are given, alarming thresholds are proposed referenced by current practical experience. Main conclusions are as follows:(1) After maintenance,there is a non-uniform drop of the ballast lateral resistance. After no maintenance, mass machine work and operations of track-lifting, it is concluded that the ballast lateral resistance all follows the normal distribution through test, and it follows the type I extreme value distribution after both no maintenance and operations of track-lifting.(2) Regardless the randomness of ballast lateral resistance, compressive loads in the rails tend to move the curved track outward compared to tangent.Once considering the randomness of ballast lateral resistance, before temperature increment, the alignment is smooth at the beginning, followed by a non-uniform deflection with temperature increase which is closer to the field test.(3) It is important to consider the randomness of the parameters when studying the stability of CWR. The stress and deformation will be closer to the practical results when the randomness of the CWR track is considered with temperature increment.But it also increases a number of the stability uncertainties, therefore, only considering the use of safety factor has certain limitations when studying the alarming rail temperature threshold.(4) According to the sensitivity analysis, the ballast lateral resistance is the most sensitive parameter which is negatively correlated with the rail lateral displacement. The RAW (ratio of amplitude to wavelength) and change of neutral temperature are less sensitive and have positive correlation with the rail lateral displacement.(5) It is recommended the use of reliability index for the CWR track stability temperature prediction of two warning yellow-red level mechanism. Where, the reliability index for yellow warning is 1.5, and for the red warning is 2.0. The warning method and the indicators still need to be perfected to better fit the practical situation.