Settlement Analysis For Soft Foundation And Prediction Of Post-construction Settlement On High Way

When a highway is built on soft clay, vehicles will bounce when they run through a bridge approach because large settlement different between a bridge and an embankment. Composite foundation which be reinforced the soft clay is widely used in construction projects, and composite foundation has solved many problems, include the different settlement and the phenomenon of the bounce.At the same time, the high speed running of the car needs a smooth and stable foundation. The subgrade which is the foundation of the track system must maintain the designing parameters of the road within a standard under an operating condition, and the means a high quality of stability for the settlement of subgrade is necessary. Therefore, the predicting and the effective controlling of post-construction settlement are the key point of designing and constructing of the highway.With a suggested displacement model, this dissertation takes the interaction of soil and piles into consideration and derives an analytical-function of compressive deformation of stabilized layer of composite foundation under embankment. Analytical-functions are also derived of frictional resistance between pile and soil and of the pile-soil stress ratio. One simple method for computing the deformation is also derived based on the analytical-function of friction resistance.This article is on the base of experiments about one year in the stable observation foundation of the GU-SHENG first level highway. The contrastive result between the improved hyperbolic long-base method and the improved exponential curve method discovered that the improved hyperbolic curve suits to the prediction of the composite foundation, and the improved exponential curve method suits to the prediction of the sand drains.Further analyzed and discovered that there are a lot of factors affecting the foundation subsidence stability, for example: The speed of loading, fill highness, thickness of weak soil layer, the soil parameter of each layer of embankment and ground(such as: modulus of deformation, Poisson's ratio, cohesive force, angle of internal friction) and so on. The role of these factors to the settlement is not independent, but is restricts mutually, plays together. With the aid of the FLAC^3D, analyzed the relation between the fill highness, thickness of weak soil layer and the end settlement of the foundation, which the result discovered that they have the good line relations, and the fill soil higher, the settlement larger; the thickness of weak soil layer thicker, the settlement larger, too.