Detection Test And Visual Analysis Of Small Irregular Cavity Model In Tunnel Lining Structure

In the process of tunnel construction,due to the influence of geological conditions,construction technology and cyclic load,the quality defects of tunnel lining structure such as voids,cracks and water leakage are inevitable.If these defect areas are not identified in time and effectively treated,it will cause significant security risks to the tunnel.The existing nondestructive testing technology can only qualitatively judge the void area and cannot describe its contour characteristics,nor can it realize the quantitative analysis of small irregular void area.In this paper,the ground penetrating radar nondestructive testing technology is used to detect small irregular cavity model.After preprocessing the obtained original radar feature response image,the true contour of the irregular shape cavity model is restored.And using the optimized wavelet transform modulus maxima method to identify irregular cavity GPR signal feature points;finally,all the signal feature points on the contour of the irregular cavity model are serialized to quantify the geometric size of the irregular cavity model and realize the threedimensional visualization of the model.The specific research contents are as follows:(1)The sand box simulation detection experiments of five different shapes and different depths of cavity models were carried out.The Reflexw signal analysis software was used to process the original signal of irregular cavity GPR.The characteristics of time-distance profile images of GPR with different shapes of cavity models were analyzed,and the waveform characteristics and imaging rules of electromagnetic wave signals were summarized.(2)The migration methods suitable for ground penetrating radar signal are compared and selected.The irregular cavity signal after pretreatment is migrated and positioned.The RGB color value of Jet color map is selected as the reference,and the starting and closing pass numbers of the strong signal reflection area are selected to identify the transverse size of the ground penetrating radar signal of the irregular cavity model,so as to calculate the transverse boundary range of the irregular cavity profile.(3)By comparing various kinds of wavelet basis functions with different properties,the optimal wavelet basis suitable for the quantitative analysis of irregular cavity model GPR signal is found and used as the wavelet basis function of wavelet transform modulus maxima method.The optimized wavelet transform modulus maxima method is used to identify the ground penetrating radar signal feature points of irregular cavities and identify the longitudinal size,so as to calculate the longitudinal boundary range of the profile profile of irregular cavities.(4)Based on the horizontal and vertical feature points of the picked irregular cavity GPR signal,AutoCAD software is used to reconstruct all the feature points in two dimensions to form a two-dimensional plane image,and several two-dimensional planes are fitted in threedimensional space form on SoildWorks software to form a three-dimensional visualization image of the irregular cavity.The conversion process of cavity signal from one-dimensional state to two-dimensional and three-dimensional visualization is completed.In this paper,the small irregular cavity of tunnel lining structure is taken as the research object.Based on ground penetrating radar technology,the size quantification and threedimensional visualization recognition of small irregular cavity model are realized by means of migration and positioning,singular feature point extraction and three-dimensional combination analysis of feature information in the detection data of irregular cavity model in the simulation test.The purpose is to improve the detection level and detection accuracy of small irregular cavity of tunnel lining structure,and bring reference and practical value for the quality evaluation of tunnel lining structure.