Testing Research And Settlement Analysis Of Soft Ground Road Embankment Improved By DJM Pile

In order to enhance road embankment stability and control settlement deformation. DJM composite ground is widely used to reinforce the embankment constructed on soft soil. At present, some useful result of calculation theory and test research on the embankment deformation have achieved, however, the characteristic of DJM composite ground is very complex, the mechanism of the stress-deformation theory of DJM composite ground isn't thoroughly understood yet. and the number of uncertain influence factors of design parameter is too much to be considered. So there still exits much disparity between theoretical result and measured result. And traditional design method canl satisfy the need to predict the highway post-construction settlement. Considering that the load was added in steps, dynamic design based on in-sile test parameter is an effective and practical method.Based on the author's experience of DJM composite ground engineering, and two projects of highway DJM composite ground, it systemically analyzed and summarized the in-site test result as well as the settlement deformation, pore water pressure dissipation, deep horizontal displacement, stress ratio, stress of pile. etc. It also compares the in-site test results of DJM composite ground with or without rigid bearing stratum, and draws many practical conclusions.According to the prior achievements, based on pile deformation test data, it puts forward a method that combined the Mindlin's solution with Boussinesq's solution to calculate the superimposed stress of DJM composite ground, and then uses the superimposed stress to calculate the settlement by layer-wise summation method. By a nonlinear elastic and viscoelastic FEM model, based on in-site test data, the back-analysis method of the direct optimal multiple parameters are adopted to calculate the road embankment settlement of typical project. The result indicates that the nonlinear elastic model is appropriate for better foundation condition, while the viscoelastic model is appropriate for worse foundation condition. According to the uniqueness of back analysis solution, it is put forward a method for the back analysis of layer-wise and section-wise iteratively. which is showed advantage by the calculation result.It is approved that Gray Model is consistent with Asaoka model in mathematics, which placed the theoretical base of Gray theory's application to settlement prediction. Considering on that the prediction model adopted static parameter have low precision, based on GM. this paper established a settlement prediction method with time-dependent parameter. Engineering example was analyzed, which indicated that the settlement prediction model adopted time-dependent parameter has much higher precision than the tradition model. At the end. it is provided a method to select appropriate model predicting the settlement by least square method.