Preparation of Reconstituted Sand Specimens

Review and assessment of sand sample preparation techniques from both theoretical and experimental viewpoints are presented. Sample densities obtained by air pluviation are shown to be sensitive to rate of pouring and drop height. Terminal velocity is reached at a very small drop height, and homogeneous samples of the same initial density tend to be formed by pluviation of uniform sand in water. Uniformly dense samples obtained by vibration of loose pluviated samples show no detectable difference in behavior when compared to samples densified by control of drop height only. Effective confinement during densification by vibration appears to prevent formation of a loose top layer. A loose top layer in an otherwise dense sample leads to a marked decrease in liquefaction resistance. Preparation of triaxial sand samples by pluviation in water is recommended because it results in initially saturated specimens, and homogeneous samples of desired densities can be replicated without difficulty.