Triaxial test for evaluating the compressibility of sandy soil in heavy tamping method

For improvement of deep ground, heavy tamping method is a very popular technique. This technique has been carried out on a wide variety of soil types and conditions. However, its theoretical evaluation has not been fully developed yet, because its mechanism of improvement is too complex. A simplified method for evaluating the degree of improvement is proposed in this paper based on the results of some laboratory tests. Impulsive loading triaxial test apparatus was developed in this study for the purpose of testing soil elements applying the stress increments induced by dropping hammer. Furthermore, the compressibility of sandy soil under various stress increments in both drained and undrained conditions were investigated by using the apparatus. As a result, at first, it was found that in the case of undrained tests, the compaction of soil was produced by dissipation of induced pore water pressure after undrained loading. Secondly, it was concluded than in the case of drained tests, the change of void ratio was induced by both increments of effective mean principal stress and deviator stress.