Application of a non-destructive method in the analysis of the homogeneity of a concrete foundation in a tunnel structure

This paper presents the application of the pulse echo test (PET) method at 22 positions of a foundation element with a height of 1.4 m, aiming at a non-invasive assessment of the quality of the produced concrete. Additional verification was carried out through destructive testing by coring at positions 1 and 21, where the parameters of bulk density, moisture content, porosity, and compressive strength were analyzed. Correlation analysis indicated a negative relationship between porosity and strength, as well as between moisture content and strength, with a high reliability of the regression relation (R² ≈ 0.85). Despite the limitations of the PET method for shorter elements, proper calibration and combination with destructive procedures allow for reliable interpretation. The obtained results confirm the stability of the reflectograms, uniform pulse velocity, and mechanical integrity of the concrete mass, thereby confirming the technical validity of the foundation and the applicability of the methodology in similar infrastructure projects. Keywords: non-destructive methods, tunnel, ultrasonic testing, PET method, destructive testing