Recent design practice of reinforced earth walls for high-speed rail transportation: A state-of-the-art and way forward

The reinforced earth retaining wall is an engineered earth block to support the earth and various infrastructures. It consists of earth reinforcement, facing walls, and backfill structural elements. The wall is more advantageous with its multiple aspects than the conventional retaining wall, such as cost-effectiveness, energy consumption, carbon emission, flexibility, and stability under heavy loads. Although reinforced earth retaining has a long history in conventional types of railway projects, Japan took the first position to design and build the wall on the High-speed railway. Until today, several kilometres have been designed and constructed on High-speed railways in various countries. The design of the reinforced earth wall includes safety and serviceability aspects. They are reflected in the external stability analysis, internal stability design, overall deformation analysis, drainage design, and connection design. The sources of the strength of the reinforced earth wall are the stiffness of the earth reinforcement, the internal strength of the backfill, the interaction between the earth reinforcement and the backfill, and the connection mechanism between the earth reinforcement and the facing wall. Due to the continuous advancement of technology, improvements in structural elements, construction methods, and design methods are required. The design method was improved from the allowable stress design to the limit state design method, and improvements were made in the structural elements and their interaction to enhance the wall's stability. Furthermore, researchers are stepping up to utilize artificial intelligence and algorithms in the design and construction process of the RER wall. This review aims to summarize the state of knowledge collected from different literature and design codes to provide information for professionals and researchers on the scientific field status and design practice of the reinforced earth retaining wall on high-speed railway projects.