Abstract：A new method is developed for interpreting GPR data to describe trackbed substructure layers and evaluate mud pumping along railway. This new method uses GPR image patterns to identify the substructure layers and types of mud pumping，and includes a new inspection concept called as mud pumping passage. Specifiecations of this new inspection method are outlined in this paper and its application is described for evaluating the railway from Shanghai to Nanjing. Details of the mud pumping results are given along with available repair recommendations.
