Screw Plate Insertion in Sand
Laboratory measurements of the depth of penetration at the end of each revolution of a 30-mm-diameter screw plate were made when the insertion was carried out with no vertical thrust applied to the screw plate. The tests were carried out to a depth of 150 mm in a dry, uniformly graded sand with a wide range of densities and two values of surcharge pressure. The results showed that, except for sand with a relative density less than about 30%, the penetration per revolution decreases significantly with increasing depth and decreases more rapidly as the density increases. After insertion, loading tests were carried out using the screw plate; the results show a large increase in apparent modulus at the higher values of density. Measurements of elastic modulus were also made when the screw plate was inserted under the control of a threaded rod having the same pitch as the screw plate and with a flat disk buried in the sand.