Application of ground penetrating radar to inspect the metro tunnel

The main constructing methods of metro tunnel include shield tunneling method (TBM) and mining method. The quality of the tunnel constructed by mining method is less stable than by TBM. Various faults may occur during the construction. The tunnel should be inspected by reliable inspecting methods. The inspecting practices in Shenzhen metro indicate that ground penetrating radar (GPR) can be used to exactly inspect the thickness of the second lining, the rebar distribution within the second lining, the dense of the second lining concrete, the cave distribution behind the second lining and so on.