Application of geophysical techniques to identify the causes of roadway instability in conductive ground (Fez region, Morocco)

Road instability in marly formations poses a major threat to infrastructure, as water saturation reduces soil-bearing capacity and promotes landslides and subsidence. To address this issue, this study applies an integrated geophysical approach combining electrical resistivity tomography (ERT) and the very low frequency electromagnetic (VLF-EM) method to identify the subsurface causes of pavement failures on three unstable road sections in the Fez-Meknes region (Morocco). Six ERT profiles were acquired along with VLF-EM surveys and subsequently validated by core drilling. The results reveal pronounced conductive anomalies extending to depths of approximately ۱۵–۲۰. These critical anomalies are characterized by very low resistivity values (ρ ≈ ۱–۵ Ω·m) and interpreted as water-saturated clayey–marly horizons. Moreover, VLF surveys delineate linear conductive zones, while ERT imaging highlights resistivity contrasts and their spatial distribution. Importantly, core drilling confirms that the most conductive zones (< ۵ Ω·m) correspond to plastic clayey marls. Thus, this combined ERT–VLF approach enables the identification of vulnerable areas and supports the design of appropriate drainage and stabilization solutions.

کلیدواژه ها:

Electrical Resistivity Tomography ، VLF-EM ، Road instability ، Landslides ، Marly formations ، Pavement creep ، Drainage