抄録
An extensive study has been carried out on the shearing conditions of soils given by the penetrati on of various model piercers into the sandy loam and the loam having various densities and water contents.
1) The shear cracks occurred by the penetration were accompanied with the increase of soil water contents the depth of the penetration and the extreme angle of the ball, but were not effected by the densities of soil.
2) The water contents that the shear cracks are difficult to occur in the case of the sandy loam and the loam were 20% and 25% respectively. The shear cracks are also difficult to occur when the depth of penetration was five times of ball diameter.
3) The side shear crack angle that was measured from a level surface was nearly 45°-φ/2 (φ is angle of the internal friction). From these results, it seems most reasonable to conclude that the shear crack occurred by the passive earth pressure.
4) When the ball pierced through the shallow place, the front shear crack occurred by the passive earth pressure.
5) The distance that the ball pressed forward the soil was from three and a half to four times of ball diameter, but it was not related to the depth of the penetration, the density of the soil and the extreme angle of the ball.
