Electrical resistivity imaging for detecting soil cracking at the centimetric scale

Electrical resistivity measurements at high resolution (1.5-cm electrode spacing) were performed to detect, from the soil surface, small cracks developing within the soil. We recorded a vertical electrical pseudo-section in a decimetric undisturbed homogenous soil block (silt loam) for different artificial cracking stages. Because of the unusually reduced electrode spacing associated with an air-dried soil surface, a specific Cu/CuSO4 electrode was designed for precision wet contact at given points. The apparent resistivity measurements of the pseudo-section and the interpreted data inverted by using the Res2Dinv software are discussed. The range of interpreted electrical resistivity associated with cracking is considerable, (from 168 to 2185 Ohm m) because the cracks are filled with air that is an infinitely resistant medium. Results showed that even small structures cause perceptible changes in resistivity that can he detected by the electrical resistivity method. Results also showed that specific software is required to predict real crack depth.