Acoustic emission induced by sand liquefaction during vibration loading

Abstract The article deals with the study of poorly graded sand samples of different grain content subjected to liquefaction. Eleven parameters of acoustic emission (AE) were studied during the process of sand liquefaction. The research results show the V-shaped behavior of the AE parameters that correspond to the three-stage sand behavior associated with the changes in its stress state as follows: the behavior of AE in phase A is due to microfractures/displacements between sand grains caused by an increase in pore pressure before the liquefaction point. Phase B (the stage of AE silence just before the liquefaction point) reflects the equality between pore pressure and cell pressure. Phase C (the stage of increase in AE parameters’ values) is explained by intense friction between sand grains during their movement caused by liquefaction. Despite the obvious signs of the V-shaped behavior of the AE excitation relative to the liquefaction point, changes in the AE parameters depend on the composition of the sand.‎ The results show that the change in the sand composition from the poorly graded dune sand to "extremely poorly graded sand" significantly increases the time for the creation of the liquefaction state while the larger the grain size, the longer the time needed to reach the liquefaction state. The last finding is explained by the increase in soil hydraulic conductivity, which complicates the conditions for the increase in pore pressure and hence makes longer the time till the liquefaction state is reached.