Visualized cyclic triaxial tests on sand liquefaction using digital imaging technique

A modified CKC cyclic triaxial apparatus is used to monitor the evolution of granular soil microstructures during cyclic triaxial tests. Micro digital screening techniques are used to capture the change of microstructures of sand samples during liquefaction induced by cyclic loading. Digital images at certain stages of the tests are cut from the videos and further processed by self-developed software named GeoDIP. The microfabric evolutions including particle orientation, contact normal and number of contacts are analyzed. Labeled particles are traced to study the micro mechanism of soil deformation. It is found that there is no preferred orientation of the long axes of particles in liquefied samples. The main direction of contact normal between particles orients vertically whether the sample is liquefied or not. The samples experience a significant loss of contact number during liquefaction, but the number regains a lot after post-liquefaction drainage. Soil particles exhibit obvious translational motion before liquefaction, but start to move relatively and rotate when liquefaction occurs. The results of this study can not only explore the micro mechanism of sand liquefaction, but also provide an experimental basis for numerical modeling of sand liquefaction.liquefaction, but the number regained a lot after post-liquefaction drainage. Soil particles exhibited obvious translational motion before liquefaction, but start to move relatively and rotate when liquefaction occurs.