Standard Penetration Resistance in Cohesionless Soils

Abstract

ABSTRACT An extensive number of penetration tests were performed in a laboratory model. The results obtained were compared with field penetration tests in three sites of different characteristics with a view to obtain a general relationship between various penetration devices which are to be used in evaluating the strength of sandy soils. For laboratory tests various sizes of tanks filled with sands of various grading characteristics and of controlled densities were used. The tank used for carrying out the bulk of laboratory tests was not the largest one tried by the author. In fact it was the medium sized tank of 90cm diameter out of the trial tanks used (70, 150 and 200cm diameter). But the results obtained from preliminary investigations showed that there existed a fixed relationship between the findings in this tank and the largest tank (200cm diameter). This latter tank showed from pilot tests to be the most suitable as far as boundary effects concerned. But due to the inherent difficulty in controlling its density through the large number of tests carried out, it was not used. Results obtained from it regarding the relationship observed in controlled pilot tests were used to scale out the 90cm diameter tank results using a correction factor. This factor is deemed to cover for boundary effects in the tank. Laboratory and field results were compared in order to explore the effect of difference in structure between laboratory-filled sands and natural deposits. Besides, the effect of “aging” on laboratory results is clarified. Dynamic penetration tests included the standard spoon test as well as dynamic cones of 1.4, 2 and 3 inches diameter which were driven in a similary way as the spoon. New statistical formulas were derived between various factors which influence soundings in sandy soils.