Study On Settlement Characters Of Composite Foundation Under Train Load

In recent years, there is a dramatic development in constructing high-speed railways in China. During this process, subgrade settlement has been one of the most unfavorable factors limiting high qualified high-speed railways'construction. To date, CFG pile composite foundation is a widely used technic in dealing with railroad subgrade settlement problem in soft soil zone. With the continuously increasing the speed, train load is likely to have an adverse impact on railway subgrade and underlying CFG pile composite foundation. Therefore, studying the settlement characters of CFG pile composite foundation under train load is of practical significance.Considering the engineering background of Wuhan test section in Wuhan-Guangzhou Passenger Transport Line, CFG pile composite foundation settlement observation data during construction has been collected. Curve of time versus dynamic soil pressure caused load induced by different speed trains. Based on these data, CFG pile composite foundation settlement characters under train load has been deeply analysed. The Main work of the study is as follows:1. After train load is equivalent to ZK dynamic load, CFG pile composite foundation settlement, caused by train load, was calculated theoretically using compound modulus method and layer-wise summation method.2. Basing on the geology and subgrade data, subgrade settlement simulating models were built by finite difference software FLAC3D.3. Changing situation and distribution rule of CFG pile composite foundation settlement in embankment-filling stage, heap-preloading stage and unloading-placing stage, were simulated with FLAC3D, and the results were compared with actual settlement observations to verify the reliability of constructed model.4. Using measured dynamic soil versus time curve, CFG pile composite foundation settlement characters and dynamic decreasing characteristics, under load induced by different speeds trains and different embankment heights, were studied with FLAC3D simulation model.5. Considering the low embankment engineering background in test section, CFG pile composite foundation reinforcing scheme was proposed against the most unfavorable load combination in this research.