Verifying Jet Grouting Consolidation through 3D Seismic Tomography: A Viaduct on the Naples-Bari Railway

This study examines the application of 3D seismic refraction tomography for verifying jet grouting consolidation beneath a railway viaduct. While traditional bidimensional seismic methods typically yield insufficient resolution for complex subsurface structures, our investigation demonstrates the superior capabilities of volumetric imaging. The study comprised two phases: a preliminary assessment on approach areas and detailed assessments of the operational viaduct. The results demonstrate that 3D seismic tomography provides higher resolution compared to conventional approaches, effectively delineating treated zones through significant P-wave velocity contrasts. Anomalously high velocities detected beneath structural elements confirmed successful soil densification, while velocity gradients at treatment boundaries revealed permeation phenomena extending beyond designed intervention areas. This research establishes 3D seismic tomography as an effective non-invasive methodology for evaluating jet grouting interventions in critical infrastructure applications, offering comprehensive volumetric characterization that enables quantitative assessment of treatment efficacy, enhanced spatial resolution without interpolation artefacts, precise delineation of treated/untreated interfaces, and the ability to extract multidirectional sections from unified datasets. Such advanced geophysical approaches represent valuable analytical tools for quality control in geotechnical engineering, particularly for complex foundation treatments.