The Research On The Vehicle-borne GPR Detection Technology Of The Railway Subgrade Defects

Quickly and accurately locating and effectually remedying the hidden railway subgrade defects are considerably significant for the railway transport efficiency and security. Among a number of exploration methods, ground penetrating radar (GPR) is the first choice for the railway bed detecting because of its advantages of celerity, non-destruction and high-resolution. For the existed GPR system, in order to realize the quick detection of the quality of the railway bed by the vehicle-borne way, there still remains special research on several technical details such as the coupling mode of the antennas, the identity of radiation, the processing of the interference brought by sleepers.In the first part of this paper, we analyze the shaping mechanism and the geological and geophysical features of the railway bed defects, and state the fundamental principles of railroad bed GPR detecting. In the next part, for the developed railway vehicle-borne GPR detecting system in heavy haul railway, we accomplished systemic experiment and investigation towards the main capability of antennas such as the shielding effect, the radiation features and the coupling effect, which provide the basis for the collocation of vehicle-borne GPR antennas and the selection of the acquisition parameters. In addition, on account of the features of the railway vehicle-borne GPR data, the use of the band-pass filtering algorithm in single-dimensional wavelet transformation can suppress the noise outside the main frequency range and the instrument's own low-frequency trailing; the spatial filtering in two-dimensional wavelet transformation can suppress the regular interference like reflection from the track and the direct coupling waves; the time-space filter screen can suppress diffracted waves and multi-diffracted waves caused by sleepers; the complex signal analysis of wavelet along with migration imaging can make radar enhance the identification characters of the hidden trouble signals. Finally, combined with an instance of the GPR detecting, a piece of measured vehicle-borne GPR data from the Shuo-Huang railway was analyzed and processed, which offers signal features from the response of GPR and judging foundation to synthetically identify the defects of ballast bed and foundation bed such as ballast capsule, fluctuation or subsidence in foundation bed and mud pumping.This project receives the support of the National High Technology Research Developing Program of China (863 Program) named'The Research on the Detection and Enhancement Technology of Bridge and Subgrade in Heavy Haul Railway'(project No.2009AA11Z101). As a part of the sub-project called'The Investigation of Vehicle-borne GPR Detecting System in Heavy Haul Railway', this paper provides technique support for the installation and implementation of railway vehicle-borne GPR detecting system and the data interpretation by the study on the key technology of the vehicle-borne GPR detecting.