Research On Settlement Prediction And Analysis Of High Speed Railway During Operating Period

Abstract:High speed railway has high standards towards safety, comfort and smoothness, which need to strictly control post-construction settlement. High speed railway have to go through various complicated regions such as mountains, rivers and cities et al, engineering geology situations varies, and can be easily influenced by all kinds of natural and human factors, thus the influence factors are too hard to indentify. Thus, Based on the project of "High Speed Railway Ballastless Track Pile Raft Consolidation of Composite Foundation Characteristics and Settlement Control Mechanism Research" and "The Settlement Law and Control of High Speed Railway Soft Soil Foundation" supported by National Natural Science Foundation, and "Construction Safety and Settlement Monitoring Technology of Shanghai-Nanjing Intercity Railway" supported by Railway Technology Research and Development Program, Combining with Beijing-Shanghai and Shanghai-Nanjing high speed railway settlement field test results, through the field monitoring and theoretical analysis, mainly researched influence of regional subsidence, foundation pit excavation and dewatering, and pile-raft composite foundation, and proposed the corresponding calculation method, conclusions are as follows:(1) The paper analyzed the factors that may influence settlement, proposed regional subsidence dynamic network, take network input index of the bench marks and working bench marks, history settlement data as delay feedbacks. Applied the trained model into the subsidence funnel area of CangZhou city, compared to other regular prediction methods, the results show that dynamic networks can predict the trend of settlement more precisely with a consideration of regional subsidence, has a rather high predicting precision.(2) We introduced the random medium theory into the foundation pit excavation and dewatering surface settlement calculation, discussed critical parameter value like the influence angle of stratum, improved settlement calculation method, used the viscoelasticity model to reflect the elastic and viscous deformation of soil skeleton during pumping, calculated the ground surface settlement caused by weight loss, seepage and excavation, applied the theoretical formula into existing line post-construction settlement.(3) Combining with Beijing-Shanghai and Shanghai-Nanjing high speed railway settlement field test results, using Layered settlement instrument, settlement plate and single point settlement instrument to monitor the whole cross section deformation and subgrade filling, analyzed the deformation features and bearing mechanism of pile-raft composite foundation.(4) Based on the field test data, under the assumption of adjacent soil uneven (parabola) distribution under the raft, established the foundation reaction model, analyzed the load transfer mechanism of CFG pile-raft composite foundation, on the basis of load transfer method, we established unit differential equation, thus proposed the pile-raft settlement calculation method considering the pile-soil-cushion combined action, and compared to field test and model test results.