Passenger Dedicated Line Composite Foundation Ballastless Track Subgrade Settlement Control And Computational Analysis Study

Passenger dedicated railway construction has entered a period of rapid development in China, and it is becoming an objective requirement to develop vigorously ballastless track for constructing the passenger railway. As the own structural limitations of ballastless track, it is very strict in deformation of subgrade. The settlement of post-construction on passenger railway is required less than 15mm, even of road foundation no settlement. As a matter of fact, the settlement control is the core problem to pave ballastless track on the subgrad of passenger dedicated line. Basing on the fomer fruit and combing with the engineering practice of Wuhan-Guangzhou passenger dedicated line, some researches are done on the subgrade settlement of ballastless track for passenger dedicated railway, by the means of the theoretical analysis, in-suit testing and numerical simulation. The research work of the paper involves several aspects as follows:(1) According to the basic characteristics of subgrade of ballastless track for passenger dedicated line, the technical requirements of ballastless track paved on soil subgrade are discussed. The concept that the subgrade of ballastless track for passenger dedicated line should be designed and constructed as geotechnical structures is put forward.(2) According to the correlation experiment regulation and construction standard, the static loading tests of the cement flyash gravel piles (CFG piles for short) composite foundation are carried out to detect the effects of strengthening. The construction control of subgrade settlement is completed effectively, based on the filling technology of the test section of roadbed and monitoring in site of subgrade settlement in Wuhan-Guangzhou passenger dedicated line.(3) According to the working and reinforcing mechanism of the CFG piles composite foundation, the settlement computing model is set up, while the influence factors of the settlement computing are also introduced. And then some settlement computing methods are discussed in particular. (4) Based on the giving geological data of the road section DK1268+599.38-DK1268+913 of the Wuhan-Guangzhou passenger dedicated line, and considering piles and soil as different materials, the magnitude of settlement prior to and after the foundation reinforced are calculated and the einforcement effect of CFG piles composite foundation is studied by using FLAC finite difference programs. After that, the influence degree of different design parameters of CFG piles on subgrade settlement is analyzed with the the orthogonality analysis method. And the reasonable pile length and distance of the road section are given in this paper, according to the change of subgrade settlement under the condition of different pile length and distance.(5) Based on the basic principle of prediction of grey theory, the same interval GM (1,1) model and grey Verhulst model are developed. And then the settlement is predicted for three typical sections (DK1268+769,DK1268+787 and DK1268+835) of Wuhan-Guangzhou passenger dedicated line. The prediction results are tested by the relative error to in-suit testing results, so that prediction effect of grey theory model to settlement of subgrade of passenger dedicated railway is analyzed.