Research On Grouting Compactness Detection Based On Spectrum Analysis And Wavelet Packet Entropy Technology

During the construction of prestressed concrete bridges,poor quality of cement slurry,blockage of bellows channels,improper grouting operations by construction personnel,and many other factors will cause the channels to be not compacted,and even large-area void defects.The quality of the channel grouting directly affects the service life of the bridge.In this paper,finite element software is used to simulate the process of hole grouting compactness detection under different defect conditions,and the time-domain data is analyzed by frequency spectrum and wavelet packet entropy calculation.The main conclusions are as follows:(1)First,five finite element models with different defect diameters under different plate thicknesses are established.The time-domain data is analyzed by frequency spectrum,and the relationship between the frequency and the grouting compactness suitable for evaluating the concrete strength of C55 with a slab thickness of 0.2m to 0.4m is fitted.The results show that as the defect diameter decreases(the degree of compactness increases),the frequency will increase,and the spectrum analysis method has certain limitations on the detection ability of smaller defects.Secondly,a finite element model with a regular defect boundary of 0.316 m is established.The relationship between the frequency and the grouting compactness suitable for evaluating the concrete strength of C55 under the 0.316 m plate thickness is fitted.The results show that as the regular defect boundary increases(the compactness increases),the frequency is will increase.Thirdly,in view of the irregular shape of grouting defects in actual engineering,a finite element model with a plate thickness of 0.316 m with irregular defect boundaries was established.The results show that spectrum analysis cannot distinguish the working conditions of irregular defect boundaries under the same defect boundary.After comparative analysis with the test results,it is proved that the two fitting formulas have certain feasibility in actual engineering.(2)A tunnel grouting compactness test was carried out on a bridge in Hebei Province.The calculation result of the frequency and grouting compactness fitting formula for evaluating the strength of concrete with a thickness of 0.2m to 0.4m as C55 and the frequency and grouting compactness fitting formula for evaluating the strength of 0.316 m concrete as C55 Calculation results,Compare and analyze with the test results respectively.It is proved that the two fitting formulas have certain feasibility in actual engineering.(3)Taking the finite element model as the research object,calculate the wavelet packet entropy value under various working conditions.The results show that in the working conditions of different defect diameters,the entropy value increases with the decrease of the defect diameter,and it can identify smaller defects than the frequency spectrum analysis.In the working condition of regular defect boundary,the entropy value increases with the increase of the defect boundary.In the working condition of irregular defect boundary,the entropy value still increases with the increase of the irregular defect boundary,which realizes the distinction of the irregular defect boundary working condition at the same defect boundary.