Evaluation Of Grouting Sleeve Based On Air-Coupled Impact Echo

At present,prefabricated building has a good development momentum in China.Compared with traditional cast-in-place construction,it has obvious advantages of energy saving and material saving.Precast concrete structure develops rapidly,but there are many factors restricting its development,among which the connection between precast members is one of the key factors.Grouting sleeve is the most common assembled structural joint.In the field operation of grouting of the sleeve,there are many uncertain factors that will cause the grouting to be not compact and the connection quality cannot be guaranteed.In this paper,based on the traditional impact echo detection method from the perspective of gas-solid coupling,air as a medium of coupling between sensors and components under test,carried out based on the coupling impact echo with the sleeve based on air filling defect detection and evaluation to explore the shear wall components,from the numerical simulation of signal processing,experimental exploration of sleeve grouting defect analysis,the main contents are as follows:1.Summarizes the traditional grouting sleeve detection means,and the theoretical background of the development of the shock echo method,by means of numerical simulation based on the coupling of the air impact echo detection method in the applicability of the socket defect detection is studied,based on the established 20 cm thick belt sleeve shear wall model,found that the acoustic pressure signal frequency domain frequency peak and traditional contact point results are basically identical to the collected signals,are about 9270 Hz,subtle differences in the signal results exist only 10 Hz.The feasibility of this method in the detection of sleeve defects is proved.2.Combining numerical simulation with experimental research,the influence of the size of the sleeve,the size of the small ball and the position of the measuring point on the frequency signal was analyzed.It is found that under the same sleeve arrangement condition,the larger size of the sleeve will make the peak frequency of the signal in the frequency domain shift to the lower frequency,and the signal amplitude of the corresponding peak frequency will decrease due to the reflection of the sleeve.When the size of the ball is small,the peak signal energy based on the reflection of the cylinder wall in the frequency domain signal is high,and when the size of the ball is large,the peak value of the corresponding diffraction phenomenon in the frequency domain signal is high.For the selection of the location of the measurement point,when the horizontal distance of the measurement point is controlled within 10cm,the amplitude of the frequency domain can be observed obviously and the diffraction peak of the main frequency will not be misjudged due to the influence of other peaks in the frequency domain.When the height is within 10cm,the energy attenuation of the diffraction peak frequency signal is small,and there is basically no significant attenuation when the height is within 5cm.It is more suitable to take the horizontal distance and vertical height of 3cm for the comprehensive analysis of the position of the measuring point.3.Considering the direct waves and the influence of environmental noise of the detection signal,respectively from the Angle of physical method and signal processing,and found that the spherical wave after come into contact with the insulation baffle,the vast majority of the energy absorbed by the baffle reflection and,but there are still a small number of sound energy transmitted to a partition occurred before and after the top diffraction phenomenon,form a partition vertex centered new spherical wave,the baffle height setting is associated with noise and direct the frequency of the sound wave is strong,when the sound absorbing gluing board is selected and the height of the sound insulation board is set above 10cm,over 70%of the direct acoustic energy can be effectively shielded.In the signal processing method,the post-microphone array filtering method is better than the single-channel spectrum subtraction method,which does not need to estimate the spectrum of the noise signal,and is also effective in the case of complex noise signal operation,and does not require the frequency domain signal to carry out inverse transformation,and there is no consideration of speech distortion caused by the difference of phase spectrum.4.The judgment index based on the offset value is too small compared with the peak frequency itself,which is too sensitive as a judgment index in the actual detection.However,in the actual detection,uncertain factors such as environmental noise and striking force will affect the spectrum component and the size of the peak frequency.Therefore,a judgment index based on reflection and thickness frequency amplitude is proposed,the error rate was only 3.3%in 30 test points.Based on the improved evaluation indexR_A,the identification of sleeve grouting defects can be effectively improved in the detection.