Research On Application Of Sound Source Identification Technology In Geotechnical Testing

Sound source identification technology has been gradually applied to the structural damage testing of rail transit engineering.Some researchers at home and abroad have carried out research on the application of sound source identification technology under operating conditions such as rails,steel structures,and geotechnical engineering.some successful technical experience.In this paper,the timbre index is selected through correlation analysis,and then the identification method is clarified by means of simulation calculation and measured percussion sound feature extraction of soils with different compaction degrees,and the standard value is proposed.Finally,this method is applied to the field rolling process.Sound source recognition technology realizes real-time,continuous and complete compaction quality control of indoor and outdoor soils.The application of this technology can greatly improve construction efficiency and engineering quality.At the same time,this technology can be extended to other types of geotechnical and structural testing.It is of great practical significance to study and promote the identification technology of students.Starting from the characteristics of the tapping sound in the geotechnical inspection,the MIRtoolbox sound toolbox was selected,and the correlation analysis was performed between the sound index in the toolbox and the target working condition,and the sound index that could characterize the soil compaction degree and the cavity and non-cavity state of CFST was obtained.The granite residual soil commonly used in backfilling projects in Guangdong is selected,and soil columns with different compaction degrees are made indoors,and the sound and acceleration signals are excited and collected by a force hammer.Through the normalization analysis,the index with strong correlation is used for fitting,and then the timbre index extracted from the percussion sound and its standard value are used to identify the degree of soil compaction.Compared with the traditional geotechnical compaction detection and continuous compaction control technology,this technology has wider application and can be applied to other types of detection.The analysis and research results of this paper are as follows:(1)Through simulation calculation,the natural vibration frequency of soil obtained by the equation of soil motion and energy method is used,and it is found that the natural vibration frequency of soil is closely related to that.On the basis of correlation analysis,a sub-band spectrum to characterize soil compaction is proposed.centroid indicator..By making nine soil samples with different degrees of compaction indoors,hammering the soil with different hammering forces,and analyzing the sound of the collected sounds,it is found that the bands of 1200 Hz?4200 Hz in the spectrum diagram increase with the degree of compaction.Great and steady growth.The test shows that when the hammering force is 55±5 N,the correlation between the centroid of the subband spectrum and the degree of compaction is the strongest,the correlation coefficient reaches 0.81,and the fitting equation is y=38x-1048.Subband spectral centroid analysis is performed using this equation and the acquired sound to inversely predict soil compaction.At the same time,it is found that the impact of the hammer force has little effect on the centroid index of the subband spectrum.When the soil compaction degree increases from 76 % to 100 %,the centroid value of the subband spectrum increases from 1500 Hz to 3000 Hz.The results show that the greater the degree of soil compaction,the greater the centroid value of the percussion sound.At the same time,when the hammering force is 55±5 N,the correlation coefficient between the centroid of the acceleration signal neutron band spectrum and the compaction degree reaches 0.78,which can also characterize the soil compaction degree.(2)After filtering the sound signal and acceleration signal during the multi-pass rolling process on site,it was found that the spectral cloud map after filtering at 1200 Hz has regular bands with obvious changes.The centroid of the subband spectrum was extracted and analyzed for the acoustic signal and the acceleration signal,respectively.It was found that the eigenvalues of the centroid of the acoustic subband spectrum and the eigenvalues of the acceleration subband spectrum could well represent the soil compaction degree during the on-site rolling.With the gradual compaction of the subgrade soil,its compaction degree increases,and the index values also increase.The centroid index value of the sound subband spectrum is increased from 1500 Hz to 2000 Hz,and the index value of the acceleration subband spectrum centroid index is increased from 3000 Hz to 4000 Hz.(3)A method of identifying the cavity defects of concrete filled steel tubes by using the timbre index "fluctuation intensity(F index for short)" is proposed,and the hammer sound analysis was carried out for different materials respectively.The F index value in the percussion sound of pure steel pipe is greater than 3900,and the average value is4387;the F index value in the percussion sound of pure concrete is less than 2800,and the average value is 2699.When the CFST column is in a compact state,the F value is between 2800 and 3200,and the average value is between 3052 and 3125,which is less than 3200.When the cavity is in the center or at the end,the F value is between 2800 and 3200.Between 3168 and 3570,the average value is between 3343 and 3430,and the F value when the cavity is at the end is relatively larger,greater than 3300.For CFST specimens and columns,knocking on the hollow positions of both,it is found that the greater the knocking force,the greater the F index value,the greater the hole diameter ratio,and the greater the F index value;the larger the steel pipe diameter,the smaller the F index value.