A series of compression tests of silica sands have been carried out in a square box. Silica sands have been filled and smoothed in the box and compressed by a punch 2mm shorter in width than the box, and the distributions of pressure, friction stress, internal stress, deformation, strain etc. have been measured under loading and unloading. The pickups, i. e. the pressure cell, the friction cell, the inclination cell and the internal stress cell have been developed by the authors to measure them. The mean pressure on the punch surface has been raised up to 111kgf/cm2. The following conclusions have been obtained:
(1) Thed eveloped pickups have shown good performance. It has turned out thatt here is a problem on the measurement of internal stress with sharp gradient.
(2) The pressure distribution is lower in the middle and higher by 20% on the both ends below the lower surface of the punch. The direction of friction turns reversely at some parts on it. The pressure distributes almost uniformly (40-50% of the mean pressure on the punch surface) on the side of the box. It is higher in the middle and lower on the both side on the bottom.
(3) The internal stress cell is transmitted almost vertically except near the both sides.
(4) The vertical displacement can be explained by the square law (σ∝ε2). It distributes horizontally uniform and vertically exponential. The strain is maximum at the ends of punch and decreases near the bottom. The strain distribution is not uniform.
(5) On the way of unloading, the stress decreases not proportional to the mean pressure on the punch surface but slowly in the beginning of unloading. The principal axes rotate in some region. The residual stress remains on the bottom and the sides. The recovery of deformation is about 3% under unloading.
(6) The use of a simple slip-line solution as a rough approximation can be justified in some cases.
