Preparation of a Large Size Granular Specimen Using a Rainer System with a Porous Plate

摘要

In this study, a rainer system capable of forming a large homogeneous granular specimen is introduced. A series of laboratory tests is carried out in order to study the performance of the proposed system. The features of the rainer system used in this study are the adoption of a porous plate and the air-pluviation without changing the deposition intensity. Without a porous plate, the rainer induces an insignificant density increase with increasing drop height, providing a dense to very dense specimen. However, the rainer with a porous plate produces a medium dense to dense specimen, with a drastic density increase at drop heights of 10-40 cm and a progressively reduced rate of density increase at larger drop heights. It is shown that the density obtained by using a porous plate rainer with a 70 cm drop height is similar to that achieved by using a conventional rainer with a 10 cm drop height. It is concluded that the use of a conventional rainer that adopts a porous plate significantly widens the range of density achievable even without an alteration in the deposition intensity. It is also concluded that using the rainer with a porous plate significantly improves the vertical and horizontal homogeneities of the specimen. The relative density evaluated from the measured cone resistance appears to provide a reasonable estimation at depths of 40-80 cm. The profile of shear wave velocity measured using bender elements seems to accurately reflect the vertical non-uniformity of the specimen.