Lightning protection of buildings constructed in wet ground and near the seashore

Many international standards related to lightning protection permit or even demand a connection between the grounding of a building's electrical circuit and that of the lightning rod. The concept is that the earthing disperses the lightning current in the ground and the connection to the building's network of conductors minimizes the potential difference and hence any magnetic field. The composition and moisture content of the earth are not, however, homogeneous; its electrical resistivity changes horizontally and in depth. Depending on the importance of the site, and taking into account explosion hazards and fire-sensitive zones in industrial buildings, and the probability of lightning strikes, typically one of three existing categories of lightning protection is applied. These categories do not, however, foresee the peculiarities of buildings constructed in wet or waterlogged ground or along the shores of great rivers, lakes and seas. Concrete in dry ground is a good insulator, but concrete buried in wet ground has a resistivity that might not exceed several hundred Ω m. Between the pedestal grounded in water or boggy soil and the soil lightning can engender a high-voltage discharge provoking an electrohydraulic impact (Yutkin effect), immediately creating a pressure of tens or hundreds of thousands of atmospheres at the place of discharge. In consequence, the foundations of the buildings constructed in wet or waterlogged ground or along shores of great bodies of water are likely to be badly damaged. In this paper an experimental study demonstrates the reality of such damage.