Rapid and economical evaluation of concrete tunnel linings with impulse response and impulse radar non-destructive methods

Concrete tunnel linings, whether pre-cast or cast in place, are designed to distribute external soil pressures as uniformly as possible through the tunnel shell. To this effect, the contact between the lining and the surrounding soil is usually assured by grouting the annular space between. Any voiding in the grout at this interface negates the purpose of the grout. This paper describes the use of non-destructive testing to examine the efficiency of tunnel lining grouting programmes, with particular emphasis on results obtained by the impulse response and impulse radar methods. The rail, water supply and sewer tunnels discussed in this article vary in diameter between 1 and 5 m, and emphasis is placed on the rapid results obtained by these methods.