Effect of Specimen Preparation Method on Grain Arrangement and Compressibility in Sand

Abstract

Effects of methods of specimen preparation on fabric and compressibility were investigated in a medium grain-sized sand. The effect of vibratory compaction was compared with the effect of pluviation by characterizing the particle arrangements and measuring compressibility in a specially fabricated oedometer. The lateral stresses during compression were also measured. Specimens densified by vibration in layers had random grain orientation up to 100 percent relative density. When vibration was continued beyond the time interval needed for achieving 100 percent relative density, the grains acquired a preferred orientation. Pluviated specimens had randomly oriented grains at both low and high densities. The loose, pluviated specimens were much more compressible than the dense specimens prepared by the same procedure. The dense specimens when prepared by vibration were less compressible than the pluviated specimens. The lateral stresses were higher in the loose pluviated specimens than in the dense pluviated specimens during loading. On unloading, the same trend was present initially but reversed at lower axial loads. This trend was also measured in the specimens prepared by vibration.

Effects of soil fabric on behaviors of granular soils: Microscopic modeling

“…-Long axes distribute randomly [37] Static compaction (slow loading) (D r = 90%) -Long axes distribution showed a weak bimodal preferred orientation at nearly 45°from horizontal Dry pluviation (D r = 62%) -Long axes concentrate in the horizontal direction Monterey #0 Sand -Uniform medium sand -Rounded and somewhat elongate particle -Length to width ratio = 1.39 -D r = 53-106% Dry pluviation (D r = 53%, 106%) -Long axes distribute randomly for both loose and dense specimen [38] Vertical vibratory compaction (D r = 97%, 104%)…”

Regolith simulant preparation methods for hardware testing

“…It was shown that relative density has an impact on their mechanical properties. In Mahmood et al (1976), it was also observed that for a given relative density achieved, the manner it is achieved affects the physical properties of the prepared GM. Indeed, vibration and pluviation techniques were used to obtain the same relative density of a well-sorted, medium grain size quartz and feldspar beach sand.…”

“…The influence of relative density on a granular material's mechanical properties has clearly been established. The effect of relative density on the results of sand compression tests is reported in Mahmood et al (1976). The variation of internal angle of friction with relative density of five Martian soil simulants is illustrated in Perko et al (2006).…”

“…This would facilitate system performance comparison. In Mahmood et al (1976), authors conclude on the need to specify relative density and preparation method of granular materials in standardized tests. Additionally, tests conducted with carefully prepared regolith simulants can be used to calibrate numerical simulations or develop analytical models.…”

Estudo em câmara de calibração do comportamento de fundações por estacas helicoidais em areia muito compacta

“…3.5.4.6.2 Tensões no solo durante a moldagem Outro fator que influencia o resultado final é a tensão no solo durante a moldagem. Mahomood et al (1976) estudaram a compressibilidade das areias preparadas a partir de 2 métodos: chuva de areia no ar e vibração. Propositalmente, os autores eliminaram a variável "partículas angulares e alongadas", utilizadas por ODA (1972) ao trabalharem nos ensaios com a areia de Monterey nº0 de grãos arredondados e pouco alongadas.…”