Numerical Analysis for Steps Excavation Schemes of Old Embankment in Highway-Widening Engineering

Abstract

In expansion and renovation engineering of old highways, due to the different soil material parameters between the new and old embankment, consolidation degree of foundation and other aspects, widening embankments tends to produce superior differential deformation at its junction, leading to the destruction of the subgrade and pavement structure. In engineering practice, step excavation is often used to make the new and old embankment to fit into a whole in their combination, thereby reducing the differential settlement. In order to explore the deformation characteristics between new and old embankments of each construction plans, this article is based on finite element software of PLAXIS to implement elastic-plastic finite element analysis on each excavation scheme at the junction of widening engineering, calculating different deformation between the new and old embankment, and putting forward the reasonable construction scheme through comparative analysis. The finite element calculation results of typical cross-section indicate that the differential deformation is closely related to excavation scheme. The greater amount of unloading and loading at the junction, the larger horizontal and vertical different deformation will produce between the embankments. With excavation methods of small step (step width is 150cm) and big step (step width is 300~450cm), the differential deformation between the new and old embankment is not significant when the height of embankment is less than 5m, big step can be used to facilitate the construction. But when the height of embankment is greater than 5m, method of big step will produce great differential deformation, small step is preferred.