| The high smoothness of the track is the premise to ensure the high-speed and safe operation of the train.With the continuous increase of China’s railway operation mileage,the intensity of track maintenance work is gradually increasing.It is known that some railway subgrade fillings contain weak expansive soil,which has the characteristics of water absorption expansion and water loss shrinkage.Therefore,the railway weak expansive soil subgrade is prone to shrinkage and settlement in the environment of continuous high temperature and less rain,which causes rapid and large changes of track geometry(called track deformation).The sudden and violent deformation of the track brings great difficulties to the track maintenance.At present,it has caused the speed limit operation of trains in some sections in summer,which seriously interferes with the transportation order.Aiming at the problem of track deformation caused by weak expansive soil subgrade settlement,this paper mainly completes the following work on the basis of mileage deviation correction of track inspection vehicle detection data:(1)Analyze the characteristics and reasons of the unique changes of track geometry in the subgrade section of weak expansive soil.By comparing the changes of track geometry caused by settlement of weak expansive soil subgrade section and non-expansive soil subgrade section,the unique characteristics of track geometry size change in the weak expansive soil subgrade section are analyzed.Combined with the expansion and contraction characteristics of expansive soil,the reasons for the unique change of track geometry of weak expansive soil subgrade section are analyzed.It provides a theoretical basis for the identification and prevention of settlement diseases of weak expansive soil subgrade.(2)Predict the peak changes of surface and alignment irregularity after track deformation.The settlement of weak expansive soil subgrade will mainly cause the great changes of surface and alignment value.This paper summarizes the empirical prediction model of subgrade settlement,obtains the modified exponential curve model and hyperbolic model,and puts forward the parameter fitting method of modified exponential curve which can be used for unequal interval observation data.Through the verification of 28 track deformation positions of weak expansive soil subgrade section by rail inspection vehicle test data,it is concluded that the modified exponential curve can better fit the change process of surface and alignment after weak expansive soil subgrade deformation.(3)Predict the time of sudden deformation of track at different mileage position in weak expansive soil subgrade section.Temperature data as well as rainfall monitoring data and track inspection vehicle data along the railway are used to propose a cumulative climate utility index that integrates temperature and rainfall to quantify the moisture changes in the subgrade.Then a track deformation date prediction model based on temperature and rainfall data is proposed to determine whether the shrinkage deformation of the weakly expansive soil subgrade will occur in high temperature period and predict the time when the track will start to deform.Using the temperature,rainfall,and track inspection vehicle data of 2016 and 2017 on the weakly expansive soil subgrade section from k283+860 to k298+436 of the Hankou-Danjiangkou Railway,the parameters in the track deformation date prediction model are estimated.In addition,the dates of track deformation caused by the shrinkage deformation of the weakly expansive soil subgrade during the high temperature period of 2018 are predicted and compared with the actual dates of track deformation.The results demonstrated that the predicted deformation dates matched 92.9% of the actual ones,indicating that the track deformation date prediction model established in this study,combined with the temperature and rainfall data,accurately predicted the dates when the track began to deform due to shrinkage deformation of the weakly expansive soil.Figure:40,table:11,reference:63... |
