Experimental Study On Detective Technology Of Subway Tunnel By Vehicle-mounted GPR

The safety of operating metro tunnel is very important.First of all,because the subway project in which the environment is special,after the subway operation,the subway tunnel disease has a strong concealment,difficult to diagnose and to manage,secondly,the subway tunnel detection can not destroy its original structure and the normal operation of the subway.So the subway engineering structure of the non-destructive testing,health diagnosis methods are more and more attention by engineering and technical personnel.Vehicle-mounted ground penetrating radar(GPR)technology,a long-distance detection method with air-launch antenna,is a fast nondestructive testing technique in the field of tunnel structure health assessment,which has changed the traditional hand-held GPR antenna measurement method.In this paper,the vehicle ground penetrating radar system is applied to the health inspection of the subway tunnel.Analyze the conditions and working principle of the subway tunnel.Through the field test and analysis of the subway tunnel,the conclusions are followes:(1)The detection of the subway tunnel constructed by the mine method can detect the integrity of the tunnel lining surface.The variation of the lining section,the channel structure of the lining surface,the thickness of the lining(Initial support and secondary lining thickness),the stratigraphic texture(grouting reinforcement formation)and the disturbances or collapses of surrounding rock can be detected by using the medium frequency vehicle ground penetrating radar 300MHz air coupling antenna in the vehicle boundary;detection of subway tunnels constructed by mine method using 1200MHz high frequency air coupling antenna within the vehicle boundary,can be detected within a certain range of tunnel lining thickness and surface conditions.The test proves the validity and feasibility of the vehicle ground penetrating radar system in the mine subway tunnel detection.(2)Using the medium frequency vehicle ground penetrating radar 300MHz air coupling antenna in the vehicle within the limits of the shield tunnel construction method of the subway tunnel detection,the antenna from the lining surface of about 80cm,can detect the integrity of the lining lining surface,pipe slice and tube Behind the grouting.When the 1200MHz high frequency air coupling antenna is used to detect the subway tunnel constructed by the shield method within the vehicle boundary,the distance of the antenna is about 60cm from the lining surface.The effect of the bottom interface is obvious,and the radar image is easy to analyze.The appropriate treatment method can be used to reduce the effect of the steel mesh on the electromagnetic wave.The test proves the validity and feasibility of the vehicle ground penetrating radar system in the subway tunnel detection by the shield method.(3)When use vehicle-mounted ground penetrating radar detects the subway tunnel,the antenna is located within the boundaries of the subway tunnel vehicle and can detect the surrounding rock state in the 2.0m deep range from the lining surface under rapid detection conditions.This paper provides a new detection method for the detection of subway tunnels.The method of vehicle ground penetrating radar can improve the detection efficiency of subway tunnels,improve the labor intensity and working environment of inspectors,and ensure the safety of the inspectors.To provide security for the operation of the subway.