Geophysical Measurements Performed at Targu Ocna Salt Mine to Evaluate Subsurface Homogeneity

This paper presents the results of an experimental campaign performed in a mine gallery from Targu Ocna salt mine (Bacau county, Romania) that aimed to assess the potential of various geophysical measurement methods to evaluate the homogeneity of salt layers. The test site contained two different subsurface layer structures: one that has a 7 m layer of rock salt followed by a cavity corresponding to the next exploitation level of the mine, and one that is formed only by solid layers. The specific purpose of the measurements was to emphasize the presence of this cavity. The investigations were performed using the following methods: ground-penetrating radar, electromagnetic ground conductivity analysis and seismic refraction. For each method we present the measurement configurations and the main results. The long term goal of the measurement campaign was to identify a reliable geophysical measurement technique that can be used as reference for future muon tomography-based measurements in salt mines or other types of soil/geological layers.