9.1 Introduction

This Chapter describes some of the civil engineering applications of GPR and considers roads and pavements, concrete structures, bridges and tunnels. GPR has become an established and routine method of inspection of civil engineering structures. Further information can be found by contacting the appropriate national authorities, some of whose websites are referenced.

9.2 Roads and Pavements

Roads and highways carrying vehicular traffic are described as having pavements. In the UK, the word pavement is often loosely used to describe that part of the infrastructure used by pedestrians. In North America, this would be known as the sidewalk. In the following Section, the word pavement should be understood to describe the structure of roads or highways.

GPR systems can be used either hand propelled (Figure 9.1) or alternatively mounted on a vehicle (Figure 9.2). The radar may take the form of a single line survey or may be an array covering one carriageway of the pavement.

Horizontal scale 3 m; vertical scale 0.7 m

Figure 9.1: GPR survey of road pavement showing reinforcing and sub-base layer (courtesy ERA Technology)

Figure 9.2: 8-Channel, 1 m-wide experimental vehicle mounted radar system (courtesy ERA Technology)

Vehicle based systems can survey pavements speedily, economically, safely and with minimum disruption to existing traffic. GPR technology is widely used in Europe and North America. In the UK the Highways Agency routinely contracts radar surveys of the road network, and the TRL, in conjunction with the County Surveyors' Working Party, monitor developments in the technique. In...