Thermal resistivity of soil

The thermal resistivity of the soil has a significant impact on cable ampacity of buried cables, especially when directly buried without backfill. The lower the thermal resistivity, the higher the cable ampacity for the same conductor temperature $\theta_c$.

If the thermal resistivity of soil is unknown, the values from the reference operating conditions in IEC 60287-3-1 are recommended. Or else, the IEEE Standard 442 provides values for some materials and a paper by O.E. Gouda from 2010 lists values for some tested type of soils.

The table lists the thermal resistivities calculated from the thermal conductivities of typical soils surrounding pipelines as given in the Subsea Engineering Handbook by Yong Bai and Qiang Bai, 2012.

Soil typeminmeanmax
Peat (dry)5.882
Peat (wet)1.852
Peat (icy)0.529
Sand soil (dry)2.3261.7861.449
Sand soil (moist)1.1491.0470.962
Sand soil (soaked)0.5260.4630.413
Clay soil (dry)2.8570.2991.923
Clay soil (moist)1.4491.2821.149
Clay soil (wet)0.9620.7690.641
Clay soil (frozen)0.938
Gravel (sandy)0.398