Laterally Cantilevered Space Frame for the Roadway Widening in Steep-Sloped Mountainous Areas

Conventional approach for widening of roadway in steep-sloped mountainous area requires deep cuts and high fills that involve massive excavation and retaining efforts. In most cases, such construction activities on slope are difficult, costly, and unsafe. In the landslide-prone area, it is often impractical and undesirable because it would lead to potential slope instability and initiates new landslides during the service period. To provide a more practical and inexpensive alternative, a laterally cantilevered space frame consisting of single-column bents and ground tieback anchors was developed for hillside roadway widening. In this space frame system, the ground anchors are used as integral structural components attached to the column top to resist overturning. Under vertical loading, the anchor–structure interaction in this frame system can generate a nailing effect on the slope at the column base. Since this interaction can effectively convert surcharge loadings such as structure weight and traffic load into clamping pressure on the slope, loading-induced complications to the slope instability can be removed. This system offers significant advantages over the conventional approach. These advantages include a substantial reduction in working area and excavation required, low life cycle costs resulting from reduced construction work and potential maintenance needs, and minimized environmental impact due to limited alteration on the existing slope condition.