Feasabiliy of the use of coherent dielectric interfaces as a GPR analysis methodology in the context of coastal masonry: An experimental approach

The durability of coastal masonry structures is the controlling factor in determining the risks of defects propagation in piers, jetties, harbors, seawalls, etc... This work proposes a methodology in adequacy with the problems met on these structures on the field, for the processing and for the interpretation of the data. The methodology proposed aims to be easily implemented by the user in order to obtain results from a GPR investigation on coastal man-made masonry structures. The process uses an initial visualization and selection of coherent dielectric reflectors showing lateral phase continuity which defines their time-space positions and amplitudes. The selection of each reflector from a profile to another is based on a sufficient gridding of the area investigated and on its shape (geometry, intensity and depth). The consistency of the reflectors selected will be demonstrated by their interpolation and mapping. Their amplitudes will be mapped and will enable the user to interpret the relative variability of the reflectors in terms of depth and energy backscattered. The amplitude added to the reflectors 3D positions will provide the key information at this scale of interest. The proposed methodology has been validated and its accuracy discussed, as well as its limitations considering its application. The mapping successfully ensured consistency compared to other ground investigation methods. Thus, this method could be jointly used with other geophysical or geotechnical methods as part of a larger ground investigation. More particularly, the resulting mapping may be used to constrain geotechnical models, image-guided ERT inversion or any other geophysical investigation.