PURPOSE: To reduce the penetrating resistance of each excavation shaft and stabilize the direction of penetrating.
CONSTITUTION: Five or more excavation shafts 11-15 are laid in line while their excavating regions overlap partially, and in the condition thus arranged, all excavation shafts 11-15 are driven for penetrating simultaneously. With this method of shaft penetration, a guide hole H is in advance bored in the ground 10 in each of the excavating regions of those two 11, 15 of the shafts 11-15 which are positioned on the outer sides. Then all shafts 11-15 are driven for penetrating while such an arrangement is kept with the lefthand group of shafts 11-14 and the righthand group of shafts 13-15 that the bottom of any excavation shaft is always positioned lower than the bottom of the excavation shafts lying inside of this excavation shaft concerned.
Megumi Ashida
Nishijima Yoshiharu
