The Testing Technology Of Sleeves Grouting Defect Based On The Impact-Echo Method

Assembly building can protect the environment,shorten the construction period and reduce energy consumption effectively,building industrialization is the inevitable direction of transformation and upgrading of construction enterprises.It is the only way for the development of China's construction industry.At present,the stress steel bar in the fabricated concrete structure is usually connected by grouted sleeve in China and the quality of the grouting in the sleeve will directly affect the safety of the assembled structure.If the grouting is not dense,it will lead to the failure of the effective connection of the stress steel bar,so that the whole structure is difficult to achieve the same structure performance and there will be potential safety problems.With the continuous popularization and application of the assembled concrete structure in our country,it is urgent to develop an effective method to detect the sleeve grouting defects.As a mature detection method and the most promising nondestructive testing technology,impact-echo method has been widely used to detect the concrete defects and tendon ducts defects.Theoretical analysis,experimental research,field test and numerical simulation are used to analyze the defects of sleeve grouting based on impact-echo method.The main contents are as follows:1.The development and application status of impact-echo method are summarized.The response characteristics of grouting sleeve shear wall are analyzed based on the theory of impact-echo method and the feasibility of the method to detect sleeve grouting flaw is proved.2.Model experiment was designed with considering the grouting defect types and sleeve arrangement forms that may appear in the construction site.The result shows that impact-echo method has better detection effect for single row and double row sleeves,it is possible to determine whether the sleeve is dense according to the characteristics of thickness frequency to low frequency drift.What is more,the frequency drift of defective sleeve with different arrangement is different.For double row sleeves,if there is only one sleeve defect,the location of the defective sleeve can not be accurately located.The proportion of the tested defects is approximately the same as that of the designed defects,which basically meets the requirements of the testing accuracy.Comparing test signals of shear walls with sleeve holes and pure shear walls,the sleeve walls and the internal anchorage bars have little effect on thetest results.There is no reflection frequency of significant defect found in the spectrum of the test.3.In order to further verify the feasibility of the impact-echo method to detect the grouting defects in the sleeve,field measurements were carried out.The results show that the impact-echo method is effective in detecting sleeve grouting defects.The test results of the sleeve hole near the free boundary are greatly affected by the boundary conditions,so that the thickness frequency of the sleeve is equivalent to 0.86 times of the thickness frequency of the shear wall.The existence of the bottom fixed boundary condition makes the thickness frequency of the dense region of the location smaller than the thickness frequency away from the boundary position and the frequency drift of the thickness is about 4.5% relative to the dense zone.4.The grouting sleeve's typical conditions were simulated,including the wall of the sleeve,the sleeve anchor within the steel bar,the sleeve arrangement form,sleeve size,and impact time effect on the signal.The theory of numerical simulation results and experimental values of the high degree of coincidence.For double row sleeves,if only a single sleeve is defective,the location of the defect can be determined from the frequency amplitude.With the increase of the sleeve size,the thickness frequency is getting smaller and smaller.In the spectrum,no obvious defect reflection frequency is found.When the impact time is decreased,the reflection frequency of defects is relatively obvious in the spectrogram.5.This paper makes a comprehensive summary of the research results and discusses the future research directions.