Mechanical tests were carried out on compacted specimens of Kira converted into pebble form by crushing and mixing with lime with the objective of effective utilization of fine particle silica sand Kira, which is a by-product of the ceramics industry, as a geomaterial. Furthermore, the mechanical behavior was reproduced using the SYS Cam-clay model, which describes the mechanisms of the soil skeleton structure (structure, overconsolidation, and anisotropy), and was explained based on the concept of skeleton structure. The following are our major conclusions for the present research.

1) Fine particle silica sand Kira is a silty sand with a silt fraction of about 65%. The undrained shear behavior of Kira produced from the slurry state resembles the shear behavior of sand. Furthermore, by reproducing the mechanical behavior using the SYS Cam-clay model, we found that the rate of loss of overconsolidation with shear was about the same as the rate of decay/collapse of the soil structure.

2) By reproducing the mechanical behavior of the improved soil obtained by mixing lime into Kira without temporary storage using the SYS Cam-clay model, we found that mixture of lime into Kira changed the evolution rule parameters and slowed the rates of decay/collapse of structure and loss of overconsolidation. Curing had no effect on the evolution rule parameters, raised the initial degree of structure, and increased the initial overconsolidation ratio.