Calculation And Predicting Inverse-analysis Of Soft Clay Ground Settlement

Along with the development of our country's infrastructure, more and more high quality highways have been emerging in many areas such as soft clay ground, airdrome, etc. For the soft clay deformation, although there have been plenty of systematic achievements on the calculation theory and testing method have been made, but as the characteristic of soft clay is very complicated, and especially as creep characteristic of the soft clay is the key role toward the project quality. The current calculation methods based on one-dimensional consolidation theory have not met the project's needs. So it is necessary to make in-depth study on the settlement calculation theory and the prediction method on the final settlement.Starting with the soft clay-engineering characteristic and its settlement deformation mechanism, this paper has analyzed the advantage and disadvantage of the present settlement calculation methods, including its application conditions. On the basis of the previous achievements and the settlement observed data, considering the obvious creep characteristic, visco-elastic-plastic creep model, which reflects the saturated soft clay's nonlinear deformation characteristic, has been proposed in this paper, with the consideration of the primary and secondary consolidation settlement. The soft clay visco-elastic and visco-plastic deformation is also depicted respectively.Because of the high sensitivity of the soft clay, it is difficult to get the original sample and make experiments. Based on the feature of subgrade construction and with the analysis of the observed settlement data, a series of stress-strain isochrones are arranged in this paper. The respective linear and nonlinear model parameters are determined according to these isochrones' elastic-plastic deformation segment. Considering the feature of subgrade deformation, the off set limit and the settlement calculation depth are discussed in this paper. According to the model, the correspand program is complied, through which settlement of the Tang Jin freeway subgrade hasbeen analyzed by nonlinear finite element method. The result is much closer to the observations than that of specification calculations.Starting from the aspect of practical engineering application, a calculation formula of the predicting inverse-analysis for the saturated soft clay ground settlement is established according to the Merchant one-dimensional consolidation theory, and the relevant program is compiled. According to the observed results and the corresponding settlement calculation results, the objective function is established by using the Least Square Method. With the pattern search method, the optimal estimate of the needed inverse-analysis parameter has been gained. Through this estimate, one more precise prediction for the soft clay ground afterward settlement can be made to guide the design and control the construction.