Characteristics Of Railway Subgrade Settlement Research Under Field Test Of Yun-Gui Area Expansive Soil Foundation

High-speed railway provide convenient, comfortable and safety to us, at the same time, the structure of High-speed railway must to be higher requirement. The post-construction settlements and the total settlements of subgrade as the key technology for base design, Further study of settlement characteristics are present in the theory and practice of necessity, This article combine with MiLe test section of Yun-Gui railway, by means of long-term field tests, in-situ tests, indoor physical tests, the pile-soil stress ofand consider expansion of land-based super-consolidation settlement were comprehensively analyzed. main results are following:(1) The pressure of the test section CFG pile reinforced soil there is a slight decrease over time, the authors think, mainly because of the effective stress of soil between piles gradually increasing due to the consolidation of soil, thus increasing the differential settlement of soil pile, arching in piled embankments enhanced, which makes part of the load continues to shift to CFG pile,so the stress of soil reduced.(2) Analysis the layer-divided sinking monitoring data of DK620+230 section, we found the layer-divided sinking of same thickness (about 2m) change not very clear in the region of 8m foundation reinforcement, but in the end the following reinforcement of pile foundation, layered settlement continue to decrease with the foundation depth increases, and the reduced rate increase.(3) Establish an arching model suite to square layout pile-round pile caps, and the theoretical analysis and analytical calculation, obtained the stress of soil under space-arching model and the stress of soil under flat-arching model, and the corresponding load of the pile also be calculated.(4) After the research of pile-soil stress ratio in DK620+230 section of embankment center and the left embankment center, we find that along with an increase in high embankment fill, pile-soil stress ratio is increasing, but fill high reach 6.5m around, pile-soil stress ratio stabilized. Author believe that when the subgrade filling less than 6.5m, the arching in piled embankments is developing after 6.5m soil arching already fully formed.(5) The author calculated the stress on pile and earth between piles under the analysis of arching in piled embankments. And found that the calculated values are very similar to the measured value, consistent with a relatively high degree.(6) natural foundation settlement will be affected significantly with variation of thickness of shallow over-consolidated expansive soil, but the ground settlement will be influenced little by the changes of thickness of deep over-consolidated expansive clay or layer under composite foundation.(7) It is pointed that the settlement calculation gained from over consolidated method is more accurate than normally consolidated method used commonly, and also is more closer to the measured value.(8) In the high-speed railway construction, over consolidated method can be suggested to analyze the settlement of over-consolidated expansive clays, meanwhile, making full use of over-consolidated characteristics of expansive soil in the foundation treatment is reasonable. It can reduce the foundation treatment works and save investment.