Highway construction across heavily mined ground and steep topography in southern China

Due to rapid expansion of the highway network in southern China in recent years, abandoned mine areas have been increasingly considered for highway construction. It is particularly challenging to carry out the assessment and remediation of mining subsidence effects on highway infrastructures, including high-filling embankments, deep-cutting slopes, and bridges. This article describes the subsidence mechanisms of abandoned mines with longwall workings and room-and-pillar systems, and also the potential geohazards and risks associated with abandoned mines. A hazard zonation criterion adopted for highway design and construction in China is introduced, as well as the possible remedial measures that can be carried out for various highway infrastructures. In the case study, grouting was used to fill cavities and stabilize the voids, and a two-layered geogrid was incorporated in the sub-base and embankment to avoid subsidence or sudden collapse of the ground. The remedial measures applied to deep-cutting slopes involved grouting, an anchor, or grid beam, employed either alone or in combination. In addition, a reinforced soil-piled embankment was utilized to reduce differential settlement at the transition zone between a bridge abutment and embankment. Based on the experiences gained, recommendations for future projects are given.