Abstract
Japanese National Railways developed a new construction method of an underpass beneath the railway banking using a horizontal pipe jacking in 1976. But in earlier time, it was one of important problems to estimate its thrust when one wants to carry out this work. Thereafter, the author found that the thrust depends upon the characteristics of the ground, the shape of an element to be jacked, that of a cutter head and so on, proposed a formula to estimate this value and proved its practicability comparing the estimated value with that measured. The author also carried out the experiments to find out the effects of a few conventional methods to cut down the thrust on this construction method quantitatively and succeeded to enlarge the jacking length.
