Methodologies for the Use of Ground-Penetrating Radar in Pavement Condition Surveys

Ground-Penetrating Radar (GPR) is a non-destructive geophysical technique to detect subsurface changes in pavements. After adequate processing and meticulous interpretation of the collected data, the technique enables to detect deficiencies (voids, insufficient bond between layers), buried utilities (cables, conduits, pipes) and reinforcements, or to determine homogeneous zones and appropriate locations for core sampling or test trenches. In combination with deflection measurements and core sampling, GPR allows to estimate the thickness and spatial distribution of pavement layers more accurately and, hence, to obtain more reliable moduli from backcalculations. However, choosing the appropriate type of GPR system and operating it requires a certain amount of knowledge, experience, and skills.

Based on its experience from measurements performed on roads and, under controlled conditions, on its indoor test site at Wavre, BRRC has prepared this publication as a practical guideline and useful instrument for GPR users. It makes recommendations for choosing the equipment as well as for collecting, processing, and interpreting the data. The measurement procedure is described in chapter I; the data procession procedure is presented in chapter II. Additionally, the procedure for estimating layer thickness from reflection amplitude and propagation time is explained in appendix I, whilst the procedure for determining homogeneous zones is discussed in appendix II.