Research On Detection Of Steel Sleeve Compactness By Impact Echo Method

In recent years,the fabricated structure has been paid much attention to and widely used,and its working performance has been paid much attention to.For the structural integrity,the connection between members is very important,the reinforced sleeve grouting connection is one of the important connection methods in common use,and the quality of the connection directly affects the overall quality of the structure,therefore,it is very important for the safety of the structure to ensure the tight grouting connection of the assembled shear wall sleeve.However,there is not a good method to measure the quality of sleeve grouting.Therefore,it is of great significance for the safety and durability of the assembled structure to study a reasonable and feasible non-destructive testing method to detect the plumpness of sleeve grouting connection.Impact Echo method is a mature and effective nondestructive testing method,which is widely used to detect the defects of prestressed pipes and concrete.In this paper,the Impact Echo method is used to detect the grouting sleeve of different grouting defects,and the signal is analyzed according to the detection:1.This paper summarizes the detection methods of steel sleeve grouting,and focuses on the development history of Impact Echo method and the current situation of steel sleeve grouting detection,analyzes its propagation principle,and proves the feasibility of this method.The steel grouting sleeve was preliminarily tested,and the Impact Echo detection signals of different working conditions of the control group were studied.The time domain waveform and the thickness frequency of the spectrum curve of the specimen were mainly analyzed.The results of test data analysis show that it is feasible to detect the grouting defects of sleeve by using the Impact Echo method.The grouting sleeve with dense cavity and defects can be judged from the fluctuation uniformity and disorder degree of the time-domain waveform of the specimen.The inner part of the sleeve can be detected by analyzing the propagation path of stress wave,the propagation time of stress wave and the thickness frequency the quality of grouting compactness.2.In order to study the material characteristics of the grouting sleeve,the layout of the reinforcement around the sleeve and the four kinds of special defects that may appear in the actual grouting operation,several grouting compactness tests are designed.The results show that: the material characteristics will affect the Impact Echo detection signal,and the sleeve material has little effect on the Impact Echo detection signal,while the polypropylene(PP)fiber grouting material and glass fiber reinforced plastic(GFRP)bar have their own plastic properties,which reduce the thickness frequency value of the sleeve with the same grouting density,and the high strength concrete(UHPC)can accelerate the propagation speed of stress wave,The results show that the thickness frequency of the specimen increases;the reinforcement around the sleeve will increase the thickness frequency,and the increase of the thickness frequency is related to the number of reinforcement around;the thickness frequency of the specimen with uniform grouting defect and longitudinal grouting defect is mainly related to the defect degree,and the thickness frequency of the specimen with 25% defect degree is greater than that of the specimen with 50% defect degree The thickness frequency of specimens with circumferential and oblique grouting defects is 75% of the thickness frequency,which is mainly related to the degree of filling the sleeve section with defects.3.The wavelet packet energy value analysis is carried out for the signal of the specimen detected by the Impact Echo method.The results show that the energy proportion of wavelet packet in the frequency band of the Impact Echo method is quite different.In addition to the high-strength concrete group,the energy proportion is mainly distributed in 42,44,45 and 47 frequency bands,the energy proportion of other groups is mainly distributed in 37-40 frequency bands;according to the distribution of wavelet packet energy proportion in different frequency bands,the empty sleeve with grouting density of 0 can be well judged,and it is difficult to distinguish the sleeve with grouting density of 50% and the sleeve with grouting density of 100%;the grouting density is high The energy distribution frequency band of sleeve specimen with compactness of 0 is smaller than that of grouting compactness of 100%,sleeve grouting compactness of 50% and dense concrete;for sleeve with special defects,it is difficult to distinguish the degree of defects from the energy frequency band of wavelet packet;the value of wavelet packet energy ratio has little relationship with the compactness of specimen,the degree of defects and the location of measuring points.4.In order to further verify the feasibility of the Impact Echo method to detect the sleeve grouting quality,the engineering measurement was carried out.The results show that: the Impact Echo method for the same concrete strength grade of shear wall detection,the thickness frequency value of concrete dense area is relatively stable,the signal test is good;there are grouting not dense sleeve in different layout of sleeve,the thickness frequency will drift to low frequency;Impact Echo method for different strength of concrete detection results are different,mainly in the concrete The larger the soil strength is,the greater the thickness frequency is.The frequency drift of double empty sleeve is larger than that of single empty sleeve in the same concrete strength level.The frequency drift of empty sleeve in the same concrete strength level is larger in the Impact Echo method.