Long-Term Performance of a Highway Embankment Built with Lightweight Aggregates

This paper presents the results from a field and numerical studies performed to understand the long-term performance of a bridge approach embankment designed with lightweight, expanded clay and shale (ECS) aggregates to mitigate the settlements on a soft soil foundation. The ECS aggregates and traditional select fill were used to build southern and northern approach embankments, respectively, for a bridge on State Highway 360 in Arlington, Texas. An extensive series of laboratory tests were conducted to obtain the engineering behavior of ECS and the select fill materials before the construction. These properties were then used in the finite element modeling to simulate the embankment sections to verify the long-term performance. The embankment sections were instrumented with vertical inclinometers to monitor the lateral movements for more than four years. This data was used to validate the numerical models with an acceptable amount of accuracy. Then a parametric study was conducted for varied heights of embankments, thicknesses of foundation soil and also compression/recompression indices of foundation soil to develop design charts. The numerical, as well as field data, indicate that there is a two-thirds reduction in settlement of the foundation soil with the use of the lightweight material. The pre-consolidation pressure and the overconsolidation ratios govern the settlement behavior of the foundation soil due to lightweight embankments. The design charts can be useful in either predicting the embankment settlements for a given ECS embankment configuration or determine the allowable height of the ECS embankment for a specified settlement value when constructing in similar foundation soil encountered in this study.