The Research On The Settlement Controlling And Geotechnical Centrifuge Tests Of Piled Embankment In Collapsible Loess Ground Of High-speed Railway

At present, high-speed railway that is developed quickly abroad and domestic has advantages in mass transportation due to lower energy consumption, safety, slight pollution and not affected by climate. The high speed running of train needs a smooth and stable foundation. The subgrade which is the foundation of track system must maintain the designing parameters of track within a standard under the operating condition, and this means that a high quality of stability for the settlement of subgrade is needed. Therefore, development of high-railway demands a subgrade that possesses such engineering properties as higher strength, greater rigidity, more stable and durable, lower strain and homogenous in longitudinal. The investigation of the settlement of high embankment of the high-speed railway after construction which is concerned by the engineers all the time becomes the main control factor of the high speed railway subgrade.The piled embankment is one of the new techniques of foundation treatment, which is popular abroad and at home in recent years. Both the vertical reinforcement body (piles and pile caps) and the horizontal reinforcement body (Geosynthetic-Reinforced mat) are used in piled embankments. This kind of structure combines the superiority of the vertical reinforcement and the horizontal reinforcement, such as little settlements, rapid construction, good stability and low cost. Therefore the piled embankments are used wider and wider in modern domestic and foreign railroads and highway construction.So far, the application of piled embankment just starts in China, and the piled embankment is only restricted in the soft soil ground in domestic and foreign projects application and fundamental research, not yet promoted to collapsible loess ground processing project. In view of the prominent merit of piled embankment, this article will attempt to use it in collapsible loess, and conduct the research to it.Geotechnical centrifuge modeling test is the test method that studying the prototype character by simulating the same stress with the prototype in model. Nowaday geotechnical centrifuge tests had arose abroad attention in the world, and many reseachers study the complicated geotechnical engineering by the geotechnical centrifuge test. With the development of the geotechnical engineering in our nation, lots of problems appear ceaselessly which make the methods of laboratory study and numerical analysis are not sufficient to solve it. The geotechnical centrifuge test turns into the new and efficiency experimental way. So study the application of geotechnical centrifuge modeling test in geotechnical engineering have the important meaning on theory and practice value.This paper main study some problems as follows by means of geotechnical centrifuge tests in Tongji University. (1) Geotechnical centrifuge tests through simulate pit permeability test of undisturbed collapsible loess and remolded collapsible loess to analyse the relations between collapse settlement and time.(2) This test through survey the relative displacement between pile and soil around the pile to infer the phenomenon of negative skin friction of pile and neutral point of pile.(3) According to the surveying the settlement of collapsible loess ground in loading of high-speed railway to analyse influence to the settlement of collapsible loess ground on different position, different depth of subgrad with time.(4) In terms of different bearing stratum in collapsible loess ground this paper analyse the influence tohe settlement of collapsible loess ground, especially to the settlement after construction on changing pile spacing and length of pile, pile caps with time.