Comparison and Analyses of Numerical Simulation and in Situ Observed Data of Subgrade Subsidence of Beijing-Tianjin Intercity Railway

Research purposes: There are a lot of soft soils in the Tianjin section of Beijing-Tianjin Intercity Railway.The main reasons for the soft soil formation are the alluvion and accumulation of lake marsh.According to the lithologic classification,most of these soft soils are clay,silt and sand soil and a few of them are sludge and mucky soil.As the soils contain much water with big void ratio,the subsidence of subgrade subsidence is large under the loads of the embankment and the train.For satisfying the requirement of ballastless track for the construction-post subsidence of subgrade,the subgrade base is reinforced with CFG pile.As the stressed situation of composite subgrade is complicated,it is difficult to predict the construction-post subsidence of subgrade.In this paper,the construction-post subsidence of the subgrade is predicted by making the comparison and analyses of numerical simulation and in situ observed data.Research conclusions:(1) The numerical simulation and in situ observed data are used to compare and analyze the subsidence law of composite subgrade and it can be seen that the compression of soil between piles appears in 1/4~1/6 ranges of the pile bottom and the entry volume of pile end is up to 20%-30% of the total subsidence volume.(2) It can be seen from the subsidence-depth distribution curve that the compression depth of the soil body under the pile end is one tine of plane distribution width of pile.(3) The max.subsidence volume and construction-post subsidence calculated with finite element method are very close to the observed data and the difference of construction-post subsidence predicted with finite element method is smaller than that with experience formula.So the finite element method is worth using widely in calculation of subsidence.