Numerical Analysis Of Settlement Of Soft Ground Under Highway Embankment

Since the 1980's, with the rapid development of highway construction, there are more and more roads built on the soft soil. Because of the difficulty in estimating the settlement of soft ground, how to estimate the settlement of soft ground well and truly, especially to estimate the relation between settlement and time is becoming an important problem of highway design. However, compared with the measured results, the results calculated by the ordinary method usually can't meet the demand. So in this thesis, the author introduced the Biot consolidation theory and analyze the settlement of soft ground with the nonlinear Finite Element Method.On the base of the Biot consolidation theory and the principle of Finite Element Method, the author developed a FEM program BP in FORTRAN language. This program includes soil element, reinforcement element, Goodman element and pile element etc. In the program, Duncan-chang model was applied to earth, which can consider the nonlinear relation between the stress and strain. This program can be used to calculate the settlement of various kinds of soft ground under highway embankment, it can also be used to calculate lateral displacement and pore water pressure. In this thesis, the author used this program to calculate one-dimensional consolidation problem, and the results showed that this program was credible.The author used FEM program BP to calculate the settlement of soft foundation under a supposed highway embankment. Comparing Finite Element Method with ordinary method, the author concluded that the Biot FEM can reflect the influence of lateral displacement more truly, calculate the settlement at every moment more suitably, and consider the progress of construction more easily.At last, the author analyzed three engineering cases with FEM program BP. From the results of first two engineering cases, it can be found that the results calculated by BP were very close to the measured results. This proved that the FEM program BP is very credible and practical. On the base of the results, the author concluded the rule of settlement, lateral displacement and pore water pressure along with the load and time. In the third engineering case, the author separately adopted Duncan-chang model and linear elastic model. Compared their results with the measured results, the author found that the Duncan-chang model is more suitable to evaluate the settlement of soft ground.