Study on salt-frost heave characteristics, improvement effect, and curing mechanism of loess-like sulphate soil

Aiming at the obvious salt-frost heave disease of loess-like sulphate soil in seasonal frozen areas, the compaction characteristics, salt-frost heave property and improvement effect of saline soil treated by adding lime, silica fume and lime-silica fume mixture are investigated. The results show that the salt-frost heave and collapse occur alternately and periodically with the freeze-thaw process. In addition, the peak salt-frost heave and thawing residual salt-frost heave increases with the increasing salt content, and the salt-frost heave shows obvious linear accumulation. The composition and dosage of the curing agent, freeze-thaw times and maintenance time have a significant influence on the improvement effect of salt-frost heave. The improvement effect of the lime-silica fume mixture far exceeds that of lime or silica fume alone. Moreover, repeated freeze-thaw cycles have a significant deteriorating effect on reducing salt-frost heave, and the salt-frost heave decreases with increasing maintenance time. The mechanism of curing saline soil by lime-silica fume mixture mainly includes physical filling effect and pozzolanic reaction effect. In particular, the strong pozzolanic reaction between lime and silica fume produces cementing material (CSH), effectively cementing the soil particles and substantially inhibiting the salt-frost heave.