Amplitude-based GPR imaging to detect subsidence under a reinforced concrete floor slab

This paper presents the development of different amplitude-based GPR imaging techniques aiming to improve the detection of subsidence and settlement phenomena in a reinforced concrete floor slab, and the underlying anthropic filling, servicing a manufacturing facility. GPR is a non-invasive method that provides a high-resolution imaging of the subsoil while covering a wide area in a relatively short period of time (saving time and money). The purpose in this study is to detect internal damage and failure affecting the structural stability of the foundation system. GPR measurements were performed using a ground-coupled antenna of 500 MHz central frequency. Additionally, traditional invasive tests such as sample drilling and penetration tests were carried out closest to the most important anomalies interpreted with GPR in order to validate the results obtained. The approach developed herein has demonstrated to be an efficient tool that can be successfully used to detect settlement of reinforcement and subsidence in critical areas.