Improved method to calculate the critical conditions for drying out sandy soils around power cables

A numerical model has been developed, with which it is possible to calculate the critical thermal conditions at which drying out in sandy soils starts. This model is based on the theory of Philip and de Vries. Comparison of results of calculations with those obtained from extensive experiments on different types of sand shows that there is a reasonable measure of agreement. In particular, this is the result of taking into account both the effect of hysteresis in the relation between water content and suction tension and the effect of temperature upon this relation. It is indicated how the knowledge about these drying-out phenomena can be incorporated in the procedure of determining cable dimensions in practical cases. This knowledge enables quantification of the risk due to thermal runaway, which leads to a more efficient use of buried cables