Research Of Prediction Method For Subgrade Settlement On Railway Passenger Dedicated Line

Scientific and rational prediction of post-construction settlement is a key link of ballastless track construction. The subgrade settlement magnitude of railway passenger dedicated line is quite small and large relative fluctuation, whether the curve fitting method used widely in prediction of large settlement of subgrade on soft ground is suitable for this settlement condition is still a problems needing further research, therefore, combining the real engineering, developing well stability, high precision, convenient settlement prediction methods based on analyzing systematically and selecting optimally has important academic meanings and engineering values.Relying on the settlement and deformation evaluation of Wuhan-Guangzhou railway passenger dedicated line, facing to the construction of railway passenger dedicated lines, aiming at the case of small settlement but large relative fluctuation of subgrade under ballastless track, the suitability of curve fitting method in settlement prediction of subgrade under ballastless track has been studied synthetically by using the field observation data of subgrade settlement of Wuhan-Guangzhou railway passenger dedicated line, and then a new prediction model has been proposed to guide settlement evaluation directly.The main work and results in the thesis are as following:According to the field observation data of Wuhan-Guangzhou railway passenger dedicated line, the prediction methods widely used in engineering such as hyperbolic method, three-point method, Asaoka method, exponetial method and the developed hyperbolic method applied successfully in related engineering in German are selected to evaluate experimentally and the suitbaility of each prediction method is analyzed, then, the magnitude of prediction error and the effects of different time starting point and different segment to prediction accuracy are studied by comparision of field observation data and prediction data.The result of optimum comparison and selection shows that three-point method can reflect the settlement trend, with higher correlation coefficient, smaller prediction error and more sensitive to abnormal data, it can timely detect the problematic section with abnormal settlement trend, so three point method is recommended as the optimal method for subgrade settlement prediction of Wuhan-Guangzhou railway passenger dedicated line.With higher correlation coefficient and more suitable, the developed hyperbolic method will not bring serious distortion of prediction results, whose prediction error only is a little larger than three-point method. So the developed hyperbolic method is recommanded as second-class method to necessarily verfy the prediction result of three point method. The exponential curve method has been improved by introducing the seleting points thought of three-point method into exponential curve model. Analysis of engineering examples shows that the improved exponential curve method has good stability and not special requirement to three-point seleting. So the improved exponential curve method can be used to subgrade settlement prediction of railway passenger dedicated line.The three-point mehod based on hyperbolic model is proposed by introducing the basic idea of three-point method into hyperbolic method. Analysis of engineering examples shows that the new method has more advantages than hyperbolic method and three-point method. The new method can obtain higher prediction accuracy if seleting longer time interval or later time starting point.Considering the characteristics of field observation data fluctuating between upper and lower envelope curve, the closed interval of final settlement has been obtained through theoretical derivation. The control conditions of stability for three point method based on hyperbolic model are proposed and its scientific rationality is verified through combining theoretical derivation with engineering practtice. Finally, the software framework and implementing steps for three-point method based on hyperbolic model and an overall conception for settlement analysis evaluation system based on network platform have been proposed.