An Instrument For Defect Detection Of Sleeve Grouting Based On Impact Echo Method Develop And Test The Influencing Factors

Prefabricated buildings,as a new construction technology of green and environmental protection,have been developing rapidly in China.However,the existing defect detection instruments are mainly conventional defect detection,and there are few kinds of detection instruments for sleeve grouting defects.Among many methods for detecting sleeve grouting defects,the impact echo method is not interfered by the external environment and specimen material,and can be detected only at a single point and a single side.Therefore,this method can be used as an ideal method for detecting sleeve grouting defects.In order to more accurately detect the grouting defects of sleeve,the application principle of impact echo method in the grouting defects detection of sleeve is first described.Based on this method,a special grouting defect detection system is developed and its detection function is tested.Then,in order to study the effect of the test method based on the impact echo principle on the detection of sleeve grouting defects,the instrument was used to detect the specimen model containing typical sleeve grouting defects.Finally,finite element method is used to simulate the influence factors of detection results.The research results are as follows:(1)In the sleeve grouting defect detection,the thickness frequency measured in the dense area of concrete is basically consistent with the theoretical value;The thickness frequency of survey line with grouting defects is less than that without grouting defects.The measured value of double-row sleeve is slightly less than that of single-row sleeve.The accuracy of measurement results is higher when measuring the thickness frequency of the measuring line with two kinds of grouting quality.(2)Influencing factors of detection results In the simulation study,the detection accuracy of ranging is relatively high within the appropriate range.The grouting sleeve and internal reinforcement have little influence on the thickness frequency.The thickness frequency obtained from the single row of sleeves for grouting defects is significantly reduced compared with the working condition of compacting concrete.The thickness frequency offset value obtained from the grouting defect of the double-row sleeve is basically the same as that obtained from the single-row sleeve.If the sleeve is in a plum shape arrangement,the adjacent sleeve has little influence on the test result of the test sleeve.When the offset distance of the survey line is within the radius of the sleeve,the measured thickness frequency still decreases significantly.If the sleeve is set horizontally and the grouting defects are small,the impact load isapplied on the side of the specimen model.The measured thickness frequency is basically the same as the measured results under the grouting compaction condition,and the defect identification effect is poor.If applied to the bottom of the model,defects can still be identified.