Settlement Prediction And Calculation Of Embankment On Soft Ground

To the settlement of highway, if it could not be calculated and controlled strictly, the phenomenon of rip on road surface and deviation between bridge and its support will come up before long, which not only threaten the safety of transport but also cause the larger waste of manpower and material resources. The following research work has been deployed around the kernel problem of settlement calculation and prediction of embankment on soft ground:(1) Research on models and methods for embankment settlement predication. For the multistage loadings of embankment, the logistic curve model to embankment settlement predication is put forward by error analyses and comparisons. Moreover, in view of the existence of rheological effect, the empirical model, which can consider rheology of soft soil, is advanced.(2) Research on the practicability of FEM for embankment settlement calculation. To meet the need of settlement calculation with FEM when absence of laboratory triaxial test data in common road engineering, methods of determining the five parameters included in tangential elastic module through soil routine tests and the related emendation coefficient are given. At the same time, one approximately substituted formula for tangential poisson ratio is also developed, which is suitable for both sandy soil and cohesive soil.(3) Research on main parameters modification of Duncan-Chang model based on the improved BP network. Firstly, with the nonlinear FEM program, the detailed analyses of eight parameters' influencing degree to settlement for Duncan-Chang model are done. The several ones that have more lager sensitivity to embankment settlement are found out. Then, aimed at the traditional three-layer BP network's shortages: easily getting into local minimum value and slow convergence, the modification combined momentum method with self-adaptation study velocity is made, and one improved BP network is put forward. Finally, According to the results from above sensitivity analyses, the nonlinear model main parameters of each natural layer in roadbed are approximately rectified using the improved BP network technology founded on its stronger nonlinear mapping capacity and the settlement measurements.(4) Research on considering stress history and lateral deformation in 1-Dmethod for embankment settlement calculation. For av e~p method, the modification coefficient M, from influence of soil stress history is put forward. Then, aimed at the e~lgp method and so on, by lots of nonlinear FEM calculation, the different settlement revised formulas M2 are given for uniform and non-uniform roadbed cases. Integration of these two sides could let the results of layerwise summation method (LSM) be more accuracy, which can consider not only soil stress history but also soil lateral deformation and soil nonlinear properties even.(5) Research on the application of meshless method for embankment settlement calculation. Radial Point Interpolation Meshless Method with unequal-rank Polynomial Basis is selected and its shape function formed manner is discussed. Then, the mainly solved equations for plane strain Biot consolidation problem with this method are given. Moreover, the according calculation program is written. Afterwards, the nonlinear calculation of embankment settlement by using this new method is carried out, and the results are more satisfying.