Investigation of forward-looking synthetic circular array for subsurface imaging in tunnel boring machine application

3-D subsurface imaging in front of tunnel boring machine (TBM) is considered by means of Ground Penetrating Radar (GPR). The performances of two different GPR antenna topologies, i.e., planar array and circular synthetic aperture radar (CSAR) are compared for some typical operation scenarios of TBM, e.g., brutal change of geology, fault and so on. Numerical simulations show that in the presence of soil attenuation planar array over performs CSAR in terms of subsurface imaging quality, especially for the imaging of the area in front of the array center.