The Field Test Research And Analysis Of The Overload Preloading Method To Reinforce Large-Area And Deep Soft Soil Foundation

There are large areas of soft soil in the southeast coastal area, which has the characteristics of large thickness as well as the characteristics of high compactness, poor permeability and low bearing capacity. As a result, the foundation will make a large consolidation settlement under the effect of the accepted load and we need to reinforce the foundation in view of this situation. At present, we always use the overload preloading method jointing the plastic drainage plate to reinforce the foundation. However, the current theory calculation formula to calculate the consolidation settlement of the deep soft soil foundation has many limitations. At the same time, there is a lack of agreement on the mechanism of the plastic drain to strengthen the soft soil. Therefore, it’s difficult to control the consolidation time and evaluate the reinforcement effect. Besides, the settlement displacement changes are different along with the engineering geological conditions and the construction ways. Therefore, the subject research about the overload preloading method jointing the plastic drainage plate to reinforce the foundation can play a guiding role in expanding the method in coastal areas.Based on the ground treatment engineering of the wharf yard in the port of Hai-cang, we have analyzed and discussed the settlement displacement law of the soft foundation and the reinforcement effect using the in-situ monitoring, theoretical analysis and the finite difference modeling analysis.After monitoring the construction site for one year, we obtained the settlement curve and the lamination settlement of the soft foundation in heap load areas and proceeded to the field sampling and in-suit test before and after the reinforcement. We draw the conclusion that the plastic drainage plate can obviously increase the consolidation settlement rate of the deep soft soil foundation. The foundation bearing capacity after the reinforcement is estimated165kPa.Combined with practical engineering, we discussed the theoretical method of the deep soft soil foundation, In view of the limitations of the traditional one dimensional and linear elastic theoretical method, we established a peacekeeping multidimensional settlement theory calculation formula. With the comparison of three calculating methods and the measured curve, we drew the conclusion that the multi-dimensional nonlinear theory method can be closer to the actual settlement result of deep soft soil foundation. Based on the theoretical analysis, we put forward the improvement of there traditional settlement prediction models of hyperbolic curve, index curve and increasing curve by setting different consolidation parameters for the soft soil with different loads and by fitting measured curves in sections. The index curve improved by the test can predict the settlement of the deep soft basement accurately. In contrast, the predicted settlement result of the standard hyperbolic curve is always bigger than the actual settlement value.With the FLAC3D finite element analysis software, we established a numerical model and verified the accuracy of model with the engineering test. We discussed the influence of the loading method and loading rate, the over-consolidated scale layer and the residual soft soil layer located in the bed bottom to the soft soil consolidation settlement and developed four models. The conclusions of the present research are given as follows. The scale-based uniform loading can reduce the. settlement of the soft basement efficiently. The existence of the over-consolidated scale layer has a notable effect on the settlement of the soft basement and it is practically significant for protecting and using the over-consolidated scale layer. What’s more, the residual soft soil layer located in the bed bottom influences the stability of the foundation and it should be cleaned to the greatest extent.