A CALIBRATION OF AN AIR PLUVIATION SYSTEM USED TO RECONSTITUTE LARGE SPECIMENS OF SAND

Abstract

In physical modeling of geotechnical problems, the difficulty in preparing uniform deposits of granular soil or simulating the in-situ soil conditions increases as the size of the testing box increases.  Special care should be provided to the soil preparation process in order to maintain trusted results in a repeated manner. In addition to striving to obtain reliable results, the method used, including the time spent and human effort expended, must be taken into consideration. In this study, a carefully designed and fabricated air pluviation apparatus is used to rain the sand uniformly and homogeneously over the area of the box. Many distinctive features were adopted in the design of the apparatus, such as emptying the box and restoring the sand automatically and getting rid of the dust outside the testing room, which both contribute positively to the health and productivity of the workers and to the quality of the job. In order to prepare a calibration database for a specific type of sand, a series of calibration tests was carried out to measure the density of sand with respect to the height of drop (HD) and the opening size of the perforated plate. It is found that the value of critical HD that achieves the maximum density depends on the porosity of the perforated plate, with a direct relationship between them. The porosity is also the critical factor that determines the density of sand at a certain value of HD. The obtained density can be increased by reducing the opening sieve size for a specific drop height.