Study On The Non-destructive Detection Method In Highway Subgrade Based On Rayleigh Wave Theory

Seismic wave mainly include P-waves and S-wave when it propagate in elastic media. Because of it exist the entire elastic space, these waves are called body wave. In comparison, another wave exist nearby elastic interface, it only distributes nearby elastic interface in energy, so was called surface wave, seismic surface wave plays an important role in Seismic wave. In earthquake, Rayleigh wave is very serious to damage building, but if we handling of the propagation features and laws of Rayleigh wave, it can be serve for engineering construction. Rayleigh wave was firstly defined theoretically in 1887 by British scholar Rayleigh. It is low frequency, low velocity (the velocity of Rayleigh wave is the velocity of S-wave 0.95 fold), strong amplitude. In stratified medium, Rayleigh wave has frequency dispersion, that is wave velocity vary with frequency (or wavelength), there are relativities between the velocity of Rayleigh wave and the velocity of S-wave, these open up bright prospects of Rayleigh wave applications.The paper is begining from propagation features of Rayleigh wave, it is discussing the propagation features and laws of Rayleigh wave in homogeneous medium and stratified medium, these lay a theory foundation for Rayleigh wave applications. Secondly, the paper systemly analysising the present extract method of Rayleigh wave at home and abroad. The effect of general two-dimensional filtering(f-k filed filtering)depending on the choice of filter, sample interval and sample points.The method must use multichannel recording(In the ordinary 6 channels) to obtain dispersion curve, thereby reduce the transverse and the longitudinal resolution of Rayleigh wave exploring, so it is hard to meeting the demand of highly accurate detecting. The paper emphatically elucidates extract method of Rayleigh wave inτ—p filed, extract method of Rayleigh wave based on the coefficients Threshold judging of wavelet transform. Through serious researching, Rayleigh wave extract by the two methods can overcome defects of general two-dimensional filtering multitrack weighted average, unable detecting small-scale and local anomaly, and resolve the problem of Rayleigh wave dispersion curve calculating in the event that transverse mutations of medium. Thirdly, through improvement on dispersion curve calculating method, divide the frequency interval that is needed calculating logarithm value, to augment the interval of high frequency Segment and reduce the interval of low frequency Segment, improves the deep resolution and exploration depth significantly. Fourthly, making mathematical model and index statistics of highway subgrade quality testing, geting reasonable interlated factors by least squares technique, it is the Obtaining Approaches of undetermined coefficients of relational expression between volume weight, bearing capacity, intensity and the velocity of S-wave, depth. Establish the theoretical base to implement interpretation of Rayleigh wave testing form determination on the nature to quantitative. Fifthly, through check experiment research, implement extracting Rayleigh wave that is qualified to adjacent channel dispersion curve calculating from transient Rayleigh wave records effectively, removing the average effect of general mthod, herefore greatly enhancing the longitudinal and the transverse resolution and testing accuracy of Rayleigh wave, true responsing the underground local and surge anomaly in small-scale.Sixthly, through the paper research, we develop "Rayleigh wave data processing and interpretation software". Combining the application of highway testing to verify the software is fitness, certify through Rayleigh wave method can test subgrade compactness> foundation capacity and composite foundation capacity, and CT imaging to testing the quality of deep mixing pile, providing a convenient method for highway quality non-destructive detection.The paper is study on the non-destructive detection method in highway subgrade based on Rayleigh wave, through theoretical analysis^ numerical simulation> physical simulation and application experiment contrast, obtaining the following consequents:1. Usingτ—p tranform method to extracting Rayleigh wave successfully,meets the need of calculating adjacent channel dispersion curve, therefore greatly enhancing the cross direction resolution and accuracy. Resolve the problem of general two-dimensional filtering method can't accurately detect small-scale and local anomaly.2. Using Threshold judging of wavelet transform method to extracting Rayleigh wave successfully, improving the cross direction resolution of Rayleigh wave, resolve the problem of Rayleigh wave detecting in the event that croosdirection Surge of medium.3. Through changed frequency interval method, using fourier transform value integration to calculating dispersion curve directly, improving the deep resolution of Rayleigh wave significantly.4. Through making mathematical model and index statistics of Rayleigh wave method detect highway subgrade quality, geting reasonable interlated factors. Establish the theoretical base to implement interpretation of non-destructive detection form determination on the nature to quantitative.5. Developing "Rayleigh wave data processing and interpretation software". Certify through Rayleigh wave method can test subgrade compactness> foundation capacity and composite foundation capacity, and CT imaging to testing the quality of deep mixing pile. Implementing the conversion from theoretical research consequents to practical application.