Influence of freeze–thaw on engineering properties of a silty soil

Freeze–thaw cycling is a weathering process which considerably changes the engineering properties of soils. Therefore, the influence of freeze–thaw must be taken into account for modeling of stress–strain behaviors in stability and deformation analyses for slopes, embankments and cuts in cold regions with soil layers experiencing freeze–thaw cycling. In this paper, freeze–thaw induced changes in the engineering properties of a silty soil, Lanzhou loess, were studied under different freezing conditions and with the dry unit weight from 15.3 to 17.3 kN/m3. The soil samples were subjected to one freeze–thaw cycle. Then changes in dry unit weight, strength parameters, preconsolidation pressure as well as modulus were examined. The changes in mechanical properties along with both the freezing condition and the original dry unit weight, were discussed. It is found that under the same freezing condition, there is a critical dry unit weight, γdcr, in terms of freeze–thaw for some of the engineering properties. When the original dry unit weight was at γdcr, the soil density, the cohesion and preconsolidaiton pressure remained unchanged after freeze–thaw. When the original dry unit weight was larger than γdcr, these three parameters decreased; with the original dry unit weight less than γdcr, these parameters increased after freeze–thaw. However, the modulus always decreased after freeze–thaw.