In this study, the internal erosion of fine particles (suffusion) in a compacted pumice sand with a large amount of non-plastic fines was visualized using X-ray CT scanning, and the microstructural changes that support the tendency of clogging of pores and increasing in shear strength associated with suffusion were successfully captured. The following conclusions were obtained: (1) suffusion occurs around large localized pore spaces, and (2) when suffusion progresses due to water permeation, the fine particles migrated and trapped at the bottleneck of the pore network, resulting in decrease of hydraulic conductivity due to clogging and increase of shear strength resistance angle by reinforcement of the soil skeletal structure. These observations are consistent with the test results obtained in previous studies on shear strength characteristics of the pumice sand with/without suffusion experience.

X-ray CT,Compaction,Suffusion