As a nondestructive testing technology, radar has been widely used in tunnel lining quality inspection. 19) The precautions for radar detection are ().

In the process of tunnel construction, the quality inspection is mainly based on longitudinal wiring, supplemented by circumferential (horizontal) wiring. Two-lane longitudinal survey lines should be arranged at the vault, left and right arches and left and right side walls of the tunnel respectively, and 5~7 survey lines can be arranged according to the inspection requirements; For three-lane and four-lane tunnels, two survey lines should be added at the arch waist of the tunnel, and the defective lining should be encrypted.

Longitudinal wiring adopts continuous measurement. When special location or conditions do not allow, spot survey can be used. The distance between measuring points should not be greater than 200mm, and the mileage should be marked every 5~ 10m.

The antenna must keep close contact with the measured lining surface (except air-coupled antenna), and the antenna cannot be separated from the structural surface or tilted at any end. The basic requirement of the allowable degree of the antenna not being closely attached is that the reflected target can be clearly distinguished, otherwise the detected paragraphs should be re-detected in time.

The antenna should move evenly and at a constant speed of 3 ~ 5 km/h.