Traffic-load-induced Plastic Deformation Of Soft Subsoil

With the development of urbanization, the popularity of the design of low embankment and the increase of the speed and the load of traffic, people pay more and more attention on the problem of traffic-induced settlement. The existing models of calculating the traffic-induced settlement are mostly based on the emprical equations in the framework of undraind cyclic tests. As a result of this, the coupling relationship between the accumulated shear strain and the dissipation of excess pore pressure has not been considered. Thus, in this thesis, the cyclic model which can consider vertical consolidation and combined vertical and radial consolidation is presented and the model is applied to two cases. At last, the method "gate-type cement mixing piles" is proposed to solve the problem of differential settlement at the bridgehead.With respect to the proposed cyclic model, the plastic strain comprises two parts:plastic volumetric strain and plastic shear strain. In the calculation of plastic volumetric strain, the dissipation equation with a source term, which couples consolidation theory with the experimentally-achieved cumulative pore pressure model under undrained condition, is adopted. In the calculation of plastic shear strain, the hardening factor of plastic volumetric strain is taken into consideration. In the proposed models, the strain increment cofficient A is based on the hardening factor of plastic volumetric strain while the strain increment cofficient A is a constant in the traditional experimental models.In the dynamic analysis of soils under traffic, the FLAC3D is adopted. Then the proposed models are applied to the history cases, which conclude that the settlement induced by the plastic shear strain accounts for about70%of the traffic-induced settlement.About the proposed method "gate-type cement mixing piles", the continuous cement mixing piles should be constructed at the both sides of the foot of the slope and the length of piles is variable according to the distance from the birdgehead. Geomembrane is used between the layer of subgrade and the subsoil. The beneficial effects of the designs above is to control the horizontal deformation of subsoil and delay the consolidation settlement of subsoil.