Steel sheet piles, soldier piles and soil cement walls are used for the temporary earth retaining walls needed in a range of construction work. After the final retaining wall or other formal structures are built, the corresponding temporary structure is either removed or left as it is. This procedure extends the construction period, intensifies the effect on the surrounding ground and structures, and increases the costs of construction. Furthermore, it is difficult to build a final structure in front of a temporary earth retaining wall between railway tracks, or in other small spaces in urban areas where there may be insufficient space for construction work. A method of utilizing temporary earth retaining walls effectively is therefore required.
   The RTRI thus proposed a method for constructing final retaining walls using temporarily built earth retaining walls (Fig. 1). For this purpose, the RTRI studied the structure of a temporary earth retaining wall with a view to using it as part of the final structure, and also studied a method of designing the final structure and its details in consideration of the state when it is temporarily set up. As this method uses the temporary wall effectively as an integral member of the final structure, it is economical and convenient in that the entire final structure does not need to be built separately. Construction costs are also cut by 20 to 50% compared with conventional methods depending on conditions at the site. Since the final structure is built at the location of the temporary earth retaining wall, it can be located away from tracks, allowing effective utilization of land.
   This method has been used by JR companies to leverage the benefits it offers.