In Situ Test and Numerical Analysis of Traffic-Load-Induced Cumulative Settlement of Alluvial Silt After Treatment with Burnt Lime

Abstract

Alluvial silt is widely distributed in the Yellow River basin, especially in its largest alluvial plain, the Yellow River delta. In this area, owing to the wet and soft characteristics of the alluvial silt, cumulative settlement often occurs under traffic loads. To reduce the settlement, various methods are applied to improve the subgrade bearing capacity in this area. Among them, the use of calcium oxide (burnt lime) to treat shallow subsoil is a common selection. However, the effect and mechanism of this method have not been fully determined. Therefore, a large integrated device was developed for an in situ test so that the comparative analysis of the short-term settlement of the natural and burnt-lime-treated ground under traffic loads can be achieved. For the long-term cumulative settlement, a numerical method using a cumulative deformation model was applied to analyze the settlements after 10 years. Furthermore, the numerical method respectively predicted the settlement after 1 and 2 years to compare with the in situ test. The in situ test results demonstrate that the wave impedance of the alluvial silt subsoil treated with burnt lime grows and both the dynamic stress caused by wheel load and the excess pore water pressure are reduced. These indicated that the short-term cumulative settlement was significantly reduced after the alluvial silt subsoil was treated with burnt lime. Moreover, the results obtained by the numerical method are similar to those in the in situ test. For the long-term cumulative settlement, the calculation results of the numerical method indicated that the use of burnt lime to treat the ground is effective. In detail, 10 years later, the settlement of the burnt-lime-treated ground decreased by about 1/5.