Rationality of frost susceptibility of soils

The frost heave and thaw weakening are the critical issues for the infrastructures in cold regions. How to reasonably assess the frost susceptibility of soils has been a hotspot in cold-region geotechnics. The frost susceptibility has been studied for about one hundred years since Casagrande (1931) proposed fine content as a main index to evaluate the frost susceptibility of soils. In most cases, the frost characteristics defined by fines content are clear and very simple, and work well in guiding the engineering construction in cold regions. However, the recent studies show that: (1) The frost heave occurs frequently in the subgrade which is designed and constructed absolutely according to the existing frost susceptibility criteria. (2) The current frost susceptibility criteria vary greatly in different countries and regions with different accuracies. (3) The vapour flow can lead to considerable frost heave in coarse-grained soils, which is not considered in the existing frost susceptibility. The above issues challenge the existing frost susceptibility. It is worth to analyze whether the concept of frost susceptibility is reasonable or not as well as its evaluation system. This study tries to analyze the advantages and disadvantages of the existing frost susceptibility criteria. The main findings are: (1) The reliability of the existing frost susceptibility is generally low, within the range of 50% to 80%. (2) The existing frost susceptibility criteria are not suitable to the case that the frost heave in coarse-grained soils is caused by vapour transfer. The freezing environmental factors should be considered in defining the frost susceptibility. (3) The existing frost susceptibility may be suitable to indicate the thaw weakening property of soils. The outcome of this study is helpful to replenishing the classification of frost susceptibility criteria. It would be of great significance to frost disaster prevention in cold regions.