Application of the Estacade (Cantilever Road) System in Algeria's Kherrata Gorges Despite the Challenging Terrain of a Deep Canyon

This study presents the implementation of the Estacade method, a unique engineering solution applied in the Kherrata Gorges, northeastern Algeria, for road construction in a challenging deep valley where conventional techniques are infeasible, and it details the construction process of this innovative system, initiated in 2014 and completed by the end of 2024. Conventional roads are typically constructed with methods such as excavation, fill, bridges, and viaducts. However, in the Kherrata region, the objective was to widen the RN09 road from a single lane of 3-6 meters to a dual-lane road of 10 meters to alleviate traffic congestion. Given the geomorphological constraints of the deep valley, conventional tunnel or cut-fill methods were unsuitable. Instead, the Estacade System was utilized, involving the placement of 10-meter-long cantilever beams, made of reinforced concrete and steel, perpendicular to the old road. These beams were socketed to the bedrock and overlaid with prefabricated reinforced concrete slabs known as "Predallé," effectively expanding the road width to 10 meters. This method allowed for safe dual-lane traffic without support from the valley floor, presenting significant engineering challenges and highlighting the project's uniqueness.