A Geophysical Investigation of Imaging Stability Features in Peat

A georadar survey was performed during July 2004 around one of the 40 peat slides that occurred on Dooncarton Mountain near Pollatomish, Co. Mayo, Ireland on the 19th September 2003. Three survey lines were recorded parallel to the slope, while another three survey lines ran above the peat failure and were perpendicular to the first three. A Sensors and Software Pulse EKKO 100 ground penetrating radar was used with antennae frequencies of 100 and 200MHz. The processed radargrams imaged sub-surface layering both in the peat and beneath it. Whilst natural pipes and sub-terrain cracks were also detectable, they required truthing or prior knowledge in order to be accurately interpreted. In comparison, an attempted seismic refraction survey proved ineffective at imaging subsurface layering in the peat soils. The seismic survey did however provide information on the Poisson’s ratio and Young’s modulus of peat and the underlying weather rock layer. In summary, GPR proved to be an excellent tool for imaging both layering and stability features in peat and it can greatly assist stability analysis of peat land areas.