Feasibility of Using Expansive Soil As Embankment Fill in the Construction of Nanning Outer Ring Expressway: A Demonstration Study

The proposed Nanning outer ring expressway crosses the region of widespread distribution of expansive soil. If using the design proposal of displacing soil, more than 1.4 million cubic expansive soils will be abandoned to considerably increase the construction investment and seriously damage the ecological environment. Therefore, Guangxi Communications Planning Surveying and Designing Institute and Changsha University of Science and Technology corporate to generalize the new treatment technology of expansive soil embankment. And the use of expansive soil as embankment fill is based on the fact expansive soil is sealed with nonexpansive soil or geosynthetics and expansive soil fill is not in direct contact of water. The various soil properties testing and road performance testing were carried out to determine whether the Nanning expansive soil can be directly used as embankment filler or not. In terms of testing results, the analysis demonstrations are performed on the strength, deformation and compactability of the expansive soil. The results show that all the expansive soils can be directly used to fill the subgrade of Nanning outer ring expressway except one whose consistency is not satisfying the requirement. The theoretical basis and design parameters are provided for implementing the physical treatment plan.