Detection Method And Cause Analysis Of Internal Cracks For Large Scale Concrete Structure

Impact Imaging Method is a new nondestructive testing method for concrete engineering.It can carry out quick and effective detection for internal cracks and flaws in massive concrete construction,and gets more and more application.It generates elastic waves(longitudinal wave,transverse wave,surface wave,et al)on surface of target concrete structure.Elastic waves are reflected on discontinuous interface(crack,defect and disease)inside structures.By analysis on the amplitude,the physical and mechanical information of discontinuous interface is quantitatively revealed.But this method applying in detection of internal concrete cracks is still in early stage,and some key technical problems to be solved,such as determining the depth of defect,detection accuracy and resolution,et al.In order to clarify the influence on response waveform and detection results,FEM dynamic numerical simulation is carried out on basis of actual engineering model.The detection factors for impact imaging method such as depths,sizes,and relative positions of cracks are further discussed.The key technical problems of determining the depth of defect solved,as well as detection accuracy and resolution.The numerical simulation provided a scientific basis for parameters selection and standardized research.Based on the numerical analysis,the impact image method is applied in the internal cracks detection for pre-stressed concrete retaining walls in a water-diversion project.The data acquisition system and acquisition process are detail stated.Dealt with the acquired waveforms by average amplitude analysis and visualization processing,the plane distribution and buried depth of internal cracks and flaws are revealed in detail.Compared with the statistics data from drilling work on walls,the detection results of impact image method well agree with the drilling work.At last,finite element simulation analysis is conducted on the mechanism of crack developing within concrete structure caused by typical frost heaving.The reasons of damage occurring in this large-scale concrete wall are illustrated.It has important reference value for similar large-scale concrete engineering in future.