Long-term strength of frozen saline soils

Grounds and foundations, underground structures

There are many experimental methods for determining the strength of frozen soils. However, the experimental period is always much shorter than the period of infrastructure facilities operation on permafrost. Hence, one of the main tasks of the frozen soils mechanics is the development of methods for prediction of long-term strength. The aim of the research is selection of equations for long-term strength prediction of frozen saline soils. The selection is carried out based on spherical template indenter test (STI) using artificial samples of two soil types (fine sand, loam) with different salinity (from 0.07% to 1.42%), water content and temperature (-2°C, -4°C,-6°C). There were 200 experimental tests. Two approaches with 10 empirical equations and time analogy method were used for long-term strength prediction. As a result, only four equations satisfied the selection criteria and can be used for the long-term strength calculations. Our studies have shown the possibility of using the time analogy method for saline frozen soils. Calculated values of equivalent cohesion for a saline-time analogy as well as for a temperature-time analogy were within confidence interval: 90% and 80% of values respectively.