Numerical Analysis Of Soil Arching And Geogrid For Geogrid-Reinforced And Pile-Supported Embankments

The geogrid-reinforced and pile supported embankments is a global force system, which is composed of filled materials, geogrid reinforced cushion, pile and pile cap, soil among the piles.and the underlying soils. The vertical loads can be transferred to the rigid piles by soil arching and the geogrid reinforced cushion within the embankment, reduces the pressure on the soil among piles, thus effectively reduces the total and differential settlements of the soft ground. In practice, geogrid-reinforced and pile-supported embankments has been widely used in various fields, such as highway, railway, airport runways and the construction of harbor etc.In this dissertation, based on the embankment section of DK205+870 in ChaoShan railway station, study on the settlement rules of the geogrid-reinforced pile-supported embankments, the soil arching effect within the embankment and the major factors which influence it, and the effect by using geogrid reinforcement. The main contents and results are as follows:(1) The state of the art of geogrid-reinforced and pile-supported embankments are outlined, and its definition and composition, failure mode, deformation rules and working mechanism are summarized.(2) The first section of the ChaoShan railway station were selected for the numerical simulation to study the settlement laws of the geogrid-reinforced and pile-supported embankments, and numerical results shows that the vertical load of the embankment can be effectively transferred to the underlying soils, significantly reduces the pressure on the soil among piles, and effectively reduces the amount of compression of the soft soil and the total settlement of the soft ground, while improving the displacement field and stress field of the soft ground, has a significant strengthening effect.(3) A numerical simulation has been conducted to study the development laws of the soil arching effect into the embankment interactions by the height of the fill, and the results suggested that the pile-subsoil relative displacement and the pile-soil stress ratio increased with the height of the embankment fill, so the filling height of the embankment is more higher the degree of soil arching effect playing is more better.(4) By a large amount of computations with the established numerical model, six major factors, such as the size of pile caps, the pile spacing, the internal friction angle, the cushion modulus and thickness, the tensile stiffness of geogrid, which influence on the soil arching effect were systematically analyzed. The numerical results show that, if the size of pile caps is too large or too small the soil arching will be affected, if the pile spacing is closer, the pile-subsoil relative displacement is very small, it's restrict to the soil arching effect, if the pile spacing is larger, it will impact on the differential settlement at the top of the embankment, embankments with larger internal friction angle has a better effect of soil arching, cushion modulus and thickness increase can enhance the soil arching effect, but not very effective, geogrid tensile stiffness increase can enhance the soil arching effect, but compared with the size of pile caps and pile spacing it has little effective.(5) The numerical analysis shows that the geogrid reforcement can significantly reduces the level displacement of the ground surface and the lateral displacement of the soft ground, but for using to reduces the settlement of the soft ground it almost invalid.