Long-Term Settlement Of Soft Soil Ground Induced By Traffic Loadings

With the mass construction and operation of high-speed railway lines through soft soil deposited area, the long-term dynamic stability and especially the post-construction settlement of roadbed due to traffic loads has drawn extensive attention of engineers and researchers. What's more, subgrade settlement after construction is strictly required less than 15mm for high-speed railway of ballastless track, therefore it is a key technique for the roadbed designers to predict and control the long-term settlements of the soft soil ground.Whereas the lack of some targeted and mature researches in this field in china currently, herein,2.5D FE model for track-embankment-ground is built to analyse their dynamic interaction, and the long-term settlement of subgrade ground is solved by incorporating the cumulative deformation model by the laboratory test. Similarly, these related issues above are carried out preliminarily for the subway and highways. The main contents are as follows in this thesis:1. Developments of the train-load-induced dynamic response and cumulative plastic deformation of subgrade, the component and control standards and the existing analytical method of the post-construction settlement of the railway roadbed are summarized, based on the background of Beijing-Shanghai high-speed railway under construction currently.2. The analytical method and principle for dynamic response of soft ground are introduced. Meanwhile, an approach is presented to calculate the long-term settlements of soft ground induced by traffic loadings combined with the cumulative deformation model established through the indoor test on Xiaoshan clay.3. 2.5D finite element model for track-embankment-ground dynamic interaction under moving trainloads is adopted to study the transient vibration and dynamic stress distribution of subgrade and underlying ground. Moreover, the long-term settlements of subgrade ground is solved by the above approach, and the effect from some factors, including train speed and the height and stiffness of the embankment are clarified. Then, the effective depth and impact of foundation treatment are also estimated briefly.4. Track-tunnel-ground interaction numerical model is built to study the spread features of the running subway-train-induced waves in the surrounding ground along the railway line. Moreover, the rale of the long-term settlement of soft ground is analysed, concerning the effect of train speed and the stiffness and depth of the liner structure.5. Pavement-ground interaction numerical model is established to analyse the vibration characteristics of the typical pavement structure of the highways. Moreover, the rale of the subsoil long-term settlement is also given, considering the effects of vehicles speed and the stiffness of the pavement structure.