Study on the disintegration characteristics of expansive stiff clay: with consideration of expansion-disintegration interaction

The disintegration of expansive stiff clay will cause irreversible damage and deterioration of mechanical properties of the soil. The latest studies show that the disintegration is related to the swelling capacity of soil. In this study, a series of hydration disintegration tests and swelling pressure tests were performed on compacted Nanning expansive stiff clay samples with different initial water contents and dry densities. The observed disintegration process of all samples could be divided into initial, rapid and residual disintegration stages, among which the rapid stage dominated the whole process. By introducing relevant indicators to quantify the disintegration process, it was found that at a given dry density, the average disintegration rate of the sample decreased with increasing initial water content; while at a given water content, it decreased with increasing initial dry density. Such phenomena coincided well with the obtained evolution of swelling pressure at different initial water contents and dry densities. Based on these findings, the expansion-disintegration interaction mechanism of expansive stiff clay was finally analyzed from the perspectives of microstructure and hydration cracking. The initial conditions of the compacted samples determine the volume of inter-aggregates pores and thus the water transfer rate in soils, which affects the formation of hydration cracks. The cracking is induced by tension failure due to the expansion gradient formed during the hydration of sample, destructing the soil integrity to facilitate the disintegration. The disintegration, in turn provides preferential water infiltration channels to accelerate further soil expansion and hydration cracking. Such interactions proceeded until the completion of sample disintegration.