As a part of field test series, the effect of differences was investigated in the tip shape of the sampling tube (edge angle and inside clearance ratio) on the unconfined compression strength. The influence of the thickness of sampling tubes was also investigated, although it has already been tested in Kinkai Bay, in order to confirm the conclusion in different soil profiles.
　Test results are summarized as follows:
　1) Four kinds of edge angles in the range of 3°to 90°were tested, and the best samples with the least disturbance were obtained with the edge angle of 3°
　2) Inside clearance ratios of 0 and 2% were tested, and the better results were obtained with flat tube of no inside clearance.
　3) The thickness of sample tubes was tested in the range of 1.3 to 3 mm, and no significant difference between them was observed. However, considering also the previous results, tube thickness of 1.5 to 2.0 mm may be recommended for practice, depending on the soil properties.