For precise estimation of the point bearing capacity of open end piles, it is important to predict how large plugging effect will develop during pile driving. A series of model tests have been conducted to study on the applicabihty of cone penetration test for the examination of the plugging effect of open end piles. Test results revealed that the vertical distribution of cone penetration resistance was wholly different according to if the plugging effect developed enough or not. In case of open end piles suffciently plugged, the cone penetration resistance in the center of ground inside the pile had a tendency to increased in proportion as the depth of cone increased. However, in case the plugging effect did not develop sufficiently, the reduction of cone penetration resistance was observed at the depth of bottom tip of the pile. Moreover, it is noteworthy that the distribution of cone penetration resistance around suffciently plugged open end pile was extremely similar to that around the closed end pile.
　In the present paper, the results of cone penetration tests will be introduced in detail, subsequently, applicability of cone penetration test will be discussed.