A new sand raining technique to reconstitute large sand specimens

Abstract Sand raining is among the popular techniques used in the laboratory for preparing sand samples. Factors like the deposition intensity (DI) and the falling height (HF) affect the produced relative density (RD) in this technique. Studies showed that the RD increase as the HF increases. This is, however, applicable up to a critical HF beyond which the RD seems unaffected. According to previous experiments, the maximum RD achieved using the sand raining is about (70 ± 5)%. The preparation of samples with higher RD is a prerequisite required in many experimental models. In the present article, a new raining system, which is capable to prepare sand samples with a very high RD and with a fast sand flow, is introduced. The new system was used to examine the relationship between the HF and the RD under different trapped air pressures and using rain nozzles with three different opening diameters. The new system was found appropriate for reconstituting SP-SM with very dense specimens (RD > 99%) with achieving higher DI values and a reduction in preparation time of more than 90% in comparison to the classic raining technique. It is time-saving and very suitable to reconstitute large model soil specimens effectively and quickly.