###### Abstract  
This work aims to analyze theoretically and with laboratory tests the sensitivity of high-frequency GPR (Ground-Penetrating Radar) to resin injections used in the building and ornamental stone industries to repair marble blocks before final slab cutting. We simulate uniform fractures in the laboratory using small regular marble blocks and we compare the results of GPR tests with the analytical model of the thin bed reflections. We performed two series of GPR surveys with a 3 GHz antenna, progressively increasing the fracture thickness from 0.25 mm to 16 mm, to analyze the results on two simulated conditions: open fracture and repaired fracture. The repaired condition was simulated by substituting the resin layer with polyvinyl chloride (PVC) sheets because the permittivity of PVC is quite similar to the permittivity of epoxy resin. According to the analytical models, when a thin air-filled fracture is filled with resin, the received signal amplitude is expected to decrease by 33% (26% if resin is simulated with PVC). The results showed a very good match between the predictions and the real data observations when the fracture is thicker than 4 mm. Although the analytical and laboratory results show some deviations when the fracture is thinner than 4 mm, the qualitative trend of the amplitude variations is still consistent with the predictions and the 3 GHz antenna can resolve the change in the filling material down to the minimum tested thickness (0.25 mm). As a result, our findings validate the GPR method as a proper tool for nondestructive quality control of resin injections in marble fractures. m 2022 2021 17 January 20221 17 January 20221 17 January 20221 17 January 20221 17 January 20221 17 January 20221 17 January 20221 17 January 20221 17 January 20221 17 January 20221 17 January 202  
with a nondestructive method is of primary importance to validate the success of the repair operation. Geophysical surveys have always played an important role in different projects that concern natural resources. Wherever high contrasts in the physical properties of the target and its hosting medium are expected, proper geophysical techniques can be successfully applied to provide valuable information about the subsurface conditions, e.g., [7; 8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18]. Among different geophysical techniques, the ground penetrating radar (GPR) method can provide high-resolution results in a variety of applications, e.g., [19; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31; 32; 33]. In recent decades, GPR surveys have been increasingly used in the quarrying industry and stone production to study the depth to different layers, detect faults and fractures and monitor the defects of stones, e.g., [11; 13; 34; 35; 36; 37; 38; 39; 40; 41; 42; 43]. Considering the high potential of the GPR method to enter the quarrying and stone industry, interest is increasing in studying the capabilities of the GPR method to help in different stages of stone production. The need to investigate the effectiveness of the GPR technique for characterizing fractures and determining their aperture and filling material emerged in the last decade and the research is still ongoing [40; 42]. The GPR method has the potential to detect the fractures of stones and monitor their repair conditions to help in optimal production of building stones as well as managing the repair or protection of stones in use. Previous studies have demonstrated the sensitivity of high-frequency GPR antennas to fracture aperture and to different properties of the material hosted within the fractures [44; 45]. However, the objective of these studies was to explore the potential of GPR as a tool for characterizing a fractured rock by determining fracture apertures and hosted materials (e.g., water, clay, sand, air).