EVALUATING THE RESISTANCE TO PENETRATION WITHIN THE SURFACE-LAYER OF SOIL AGGREGATES

Some studies have shown that soil aggregates are not homogeneously bui lt up as commonly assumed. Maximum differences in selected soil proper ties exist between the uppermost layer and the interior of an aggregat e. Evaluation of the strength of this layer by determination of force to penetration yields extremely high values of resistance to penetrati on when using a fine and sharp probe instead of a blunt probe. It is s hown that a very small increase of the soil-metal friction within the range of the sharp tip causes the high value of resistance to penetrat ion. This is normally not the case when using a blunt probe because so il-metal friction, which is subtracted from force to penetration when calculating resistance to penetration, can be measured over the whole depth of penetration.