Study On The Application Of Fast Non-destructive Testing Method For Compaction Quality Of Railway Subgrade

Compaction quality of the subgrade is a significant link to ensure its engineering character and stability.Besides the well-graded filler and reasonable construction technology,compaction quality inspection is one of the key to guarantee the subgrade quality.With the methods of the compaction quality inspection developing,traditional detection methods has been widely applied in the railway construction practice,but they also have lots of disadvantages:the detection needs much time to detect the embankment quality,it requires a lot of manpower because of heavy instrument,it is greatly influenced by the environment and operators,it works less efficiently,it maybe damage subgrade structure in the detection and so on.How to realize the rapid and non-destructive inspection on the compaction quality of railway subgrade is a far-reaching significant subject to the railway's construction and it's operation management.In this paper,according to the shortcomings of the traditional subgrade compaction quality inspection methods,the rapid and nondestructive detection methods are discussed by means of field test and analysis of experimental data:the geological penetrating radar(GPR)method and detecting method of multichannel transient Rayleigh wave in consideration of time difference phases between channels,improving the detection methods of subgrade compaction quality.The main contents are as follows:(1)Describing the application situation of the GPR and Rayleigh wave method,the traditional detection method of compaction quality of subgrade and their respective advantages and disadvantages,summarizing the advantages of two types of nondestructive testing method,GPR and Rayleigh wave method,in subgrade compaction quality inspection.It also introduces the basic theory and principle of GPR and Rayleigh wave method,including the requirement of setting the working parameters.(2)Simulating the electromagnetic wave to the GPR by using GprMax2D and MATLAB software.Forward simulation mainly includes various subgrade defects,summarizing the characteristics of subgrade defects and establishing the gallery of quality defects.It is significantly vital to interpretate the map of subgrade quality defects,measured by GPR method.(3)In this paper,time difference phase between channels is put forward,and the basic principle and advantages of the multichannel transient Rayleigh wave method in consideration of time difference phases between channels are discussed.(4)Detecting subgrade compaction quality using the GPR method in the field of railway and setting different subgrade defect areas.Through GPR scanning,editing and processing of radar profiles by Radan7 software.We can achieve the gray-scale maps of detecting area and electromagnetic wave waveform,analyzing the characteristics of defects in the gray-scale maps and comparing with the gallery of subgrade defect defects established by forward simulation,and then analyze the existing problems of the quality of roadbed construction.(5)Detecting subgrade compaction quality using the multichannel transient Rayleigh wave in consideration of time difference phases between channels in the field of railway.Comparing the tranditional surface wave method used widely with the multichannel transient Rayleigh wave method in consideration of time difference phases between channels and analyzing the surface wave velocity-depth curve can highlight the advantages of the surface wave method in consideration of time difference phases between channels.According to the velocity-depth curve coordinates,the wave velocity profile of the subgrade can be generated,and we can evaluate the effect of the subgrade compaction through the wave velocity distribution in different depth.