3Clark M,Gordon M,Forde M C.Issues over High-Speed Non-invasive Monitoring of Railway Trackbed[J].NDT & E International,2004,37(2004):131-139.
4Hugenschmidt J.Railway Track Inspection Using GPR[J].Journal of Applied Geophysics,2000,43(2000):147-155.
5Selig E T.Ballast Deformation:Its Causes and Cures[J].Railway Track and Structures,1998,94(5):25-30.
6Gallagher G,Leiper Q,Clark M.Ballast Evaluation Using Ground-Penetrating Radar[J].Railway Gazette International,2000,(2):188-189.
7Clark M R,Gillespie R,kemp T,et al.Electromagnetic Properties of Railway Ballast[J].NDT & E International,2001,34(2001):305-311.
8Carpenter D,Jackson P J,Jay A.Enhancement of the GPR Method of Railway Trackbed Investigation by the Installation of Radar Detectable Geosynthetics[J].NDT & E International,2004,37(2004):95-103.
9Jack R,Jackson P.Imaging Attributes of Railway Track Formation and Ballast Using Ground Probing Radar[J].NDT & E International,1999,32(1999):457-462.
