| The main problems for an engineer to build high-grade highways on soft soil foundations are concerned with the settlement and stability of the soft soil foundations. Soft soil will have different engineering characteristics because of their different formation. In the soft soil area along the sea of the south China, there are many successful examples and good treatment measures dealing with the construction of high-grade highways. However, there are a few reports on the construction of high embankment on silt soft foundation in the river and lake areas just by making use of the synthetic treatment for the shallow soft clay foundation. The paper is based on a practical project which has some special features such as deep mud foundation, bad engineering performance of soil, short construction time, fast loading for filling, general shallow treatment measures, all of which makes the paper more representative. The main work of the paper includes monitoring ground deformation in the period of construction, on-site monitoring data analysis, curve line fitting of settlement and numerical analysis of the stability. It also summaries the characteristics and regulars of the deformation for roads in Jin Gang-based construction project and has played a guiding role for the future use.For the purpose of the research, we select K2 +850 cross-section as the research object. We burry a static leveling meter, a settlement plates, a pore pressure meter, the cement side piles and Chilodonella to measure the process of settlement, excess pore water pressure, the lateral displacement of the ground slope and uplift, as well as the lateral displacement of the embankment.We also use three methods, i.e. method of index, method of hyperbolic and method of Poisson to fit the settlement data obtained from the measurement and present three fitting curves of consolidation settlement of the foundation. By contrast analysis, we find that the fitness effects of curves depend largely on the loading process for filling embankment and the shape characteristics of actual settlement curve. After fitting analysis, we also find that the fitting curve from method of exponential function is in a good agreement globally with the observing results. Less good result is the method of index, and that of Poisson.We also adopt the finite element analysis to evaluate the stability of the highway under the circumstance of gradation loading. According to indoor experiment results about the shear strength of soft soil test and compression test, we compare both the vertical and horizontal displacements with the measurement results, and the results are satisfactory. At the same time, it can be seen from the simulation results that the anti-pressure landslide prevention and pine wood piles have played an active rule in limiting the level of the right lateral foot formation and maintaining the stability of embankment. The comparison of the calculated results with the measured data shows that the method adopted in the paper with the use of finite element analysis for the evaluation of soft clay foundation fill embankment stability under the gradation loading is reasonable.
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