Fundamental study on development of filling material into tail-void surrounded by acid sulfate soils in tropical regions

In recent years, Japanese government has been trying to export its techniques to developing countries through ODA (Japan Tunneling Association, 1997). Among them, Southeast Asian countries plan the large-scale improvements of sewage in large cities. However, open cut method witch is the most popular method is difficult to be applied, since most ground area is occupied by structures in these areas. From this point of view, application of the pipe jacking method on the construction of infrastructure is expected. The pipe jacking method is relatively reasonable among trenchless construction methods. For application of this method, the acid sulfate soils in these areas have negative impacts on filling materials (one of cement materials) injected into the Tail-void which are over-cutting areas formed to lower the friction between the pipes and the surrounding soils. In this study, it was discussed to apply fly ash and slag which can control the effect of sulfur acid to filling materials. As the results of the experiments, fly ash and slag could reduce the deterioration of filling materials. In addition, the filling materials added slag lowered frictional resistance, compared to the filling materials added fly ash. Filling materials with the lower frictional resistance can more reasonably conduct pipe jacking constructions. Therefore, using filling materials added slag is proper for safety and economy in order to apply the pipe jacking method to Southeast Asian countries.