Application of Ground Penetrating Radar and Electrical Resistivity Tomography for Recognizing Cavities in Critical Urban Areas

Abstract

Large areas behind the historic quay walls and bridges in Amsterdam city center are prone to soil mobilization and cavity (sinkhole) formation due to intensified infrastructure developments and extreme groundwater level fluctuations caused by climate change. We carried out a geophysical survey to investigate a sinkhole formed under the Muntplein (Amsterdam, The Netherlands). The surface trace (hole) of the sinkhole was triggered by a heavy vehicle passing over the street which lies in the vicinity of a quay wall and behind the abutment of the Muntsluis bridge. The application of ground penetrating radar (GPR) and electric resistivity tomography (ERT) provided continuous data of the shallow subsurface which enabled the detection of the backfilled cavity, its southwest (SW) extension, the bridge abutment-to-soil transition, key utility lines and the presence of two potential targets for further investigation. A follow-up geotechnical assessment supported by hydrographic survey in the canal validated our findings and substantiated our first interpretation (i.e., sinkhole in development). The paper demonstrates the applicability of non-invasive electromagnetic (EM) methods to rapidly detect cavities in critical urban areas, and, thus, to de-risk climate-smart infrastructure developments.