Quality monitoring of metro grouting behind segment using ground penetrating radar

• Field measurement of the dielectric constant of the concrete segment.
• Laboratory monitoring for dielectric constant of grouting mixture.
• Grouting layer thickness and defects nondestructive testing.

In this paper, a survey of the Nanchang Metro Line 1 is completed to determine the effectiveness of a grout assessment method combines GPR and image processing. Two aspects are used as a basis: one is to estimate the thickness of the grouting layer, and the other is to determine the presence and distribution of any damage. Finite-difference time-domain simulation is used to assist the interpretation of measured data. The results show most grouting layer is approximately 30 cm thick (i.e., the standard 30 cm). Several defects in the grouting layer were also found, primarily voids, crack or fissure.