A large amount of waste is produced by coal-burning power stations. The properties of the waste varies, dependent on the mineralogical contents of the mother rock in which the coal is embedded. The waste quality depends on the method of mining and cleaning. The waste mainly consists of clays, quartz, carbonaceous materials, mica, pyrites, and so on. About 80% of coal-ash is now utilized and the remainder is disposed of at disposal sites. However, the life span of the disposal sites is limited, and it is difficult to find new disposal sites. It is therefore requested that the percentage of utilization of flyash be increased in every field in Japan. So, it is very desirable that cement with flyash added be used as the injection material for natural/artificial openings. From these points of view, in order to clarify to what degree the contents of chemical additives affect the properties of the injected flyash mixture in slurry pipe jacking, different combinations of flyash, additives and water were considered by means of several experiments.