Contributions > Radjai Farhang

Three dimensional coupled DEM-LBM approach is utilized to investigate the internal signature of `compaction' state versus `liquefaction-like' state of a granular bed composed of spherical particles fully immersed in a fluid while being subjected to a pressure standing wave. A wide parametric space covering large range of packing fraction, pressure wave properties (frequency and magnitude) and relative density were explored and a very promising but `non-trivial' insight results were obtained. Two granular beds were used: a frozen bed to focusing on the pressure wave changes in the bed and, a free bed to investigate, at short and long term, the microstructure of the granular bed changes that should enable to identify whether we are in a `compaction' or in a `liquefaction-like' state. For the fluid point of view in the granular bed regarding the forcing signal, the
pressure wave attenuation in the granular bed shows a strong dependency on the packing fraction while the forcing frequency plays a role in the phase shift. Non effect on the attenuation in the pressure wave magnitude were observed. The microstructure changes at long term on the free bed shows that the `liquefaction-like' state is more favorable of lower-pressure wave magnitude combined in certain measure with lower particles relative density: this corresponds at the sample level to a lower bed effective stress. The `compaction' state is found to be more favorable of higher-pressure wave magnitude combined in certain measure with higher-particles relative density; contrary to the `liquefaction-like' state, the `compaction' stat correspond to a higher bed
effective stress. The analysis of the granular bed contact network revealed that the descriptor of the `liquefaction' versus `compaction' state lies in the variation in its anisotropy while an unclear observed variation in packing fraction, coordination number or effective bed stress should not be used as descriptor key.