A series of compression tests were carried out with silica sands put in a square box with every one of patterns with various dimensions set on its bottom to analyse the mechanism of compression of granular materials. The distribution of the pressure and the friction stress on the inner surface of the box, the lower surface of the punch, and the upper surface and the side of the pattern was measured using the pressure cells and the friction cells developed by the authors. The following conclusions were obtained:
(1) The pressure on the inner side surface of the box is approximately as large as half the mean pressure on the lower surface of punch.
(2) The maximum values of pressure occur around the center of of punch and the ends of the upper surface of pattern. These increase with the increase of the height of pattern.
(3) The normal and the friction stress are hardly transmitted to the side of pattern. They decrease with the decrease of the distance between the pattern and the inner side surface of the box.
(4) The inclined side of the pattern increases the pressure and the friction stress on this surface.
(5) The pressure cells and the friction cells used have shown the performance good enough to measure the stresses.
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