Experimental Study On Nondestructive Testing Of GFRP Anchorage Quality For Earthen Sites

Technology of GFRP anchoring has occupied an important position in the consolidation and conservation of earthen sites,and its anchoring quality affects the safety of the earthen sites.Therefore,it is particularly important to inspect the quality of anchorage construction and safety during service.However,due to the earthen sites are cultural relics,the current methods of pulling detection are far from meeting the requirements for earthen sites.And the application of acoustic frequency stress wave non-destructive testing technology is still in its infancy in the GFRP bolt anchoring system of earthen sites,and due to the diversity of media in the anchorage system of earthen sites,the propagation of the stress wave and the identification of the inversion are complicated.Many questions remain unclear,which restricts the application of the acoustic stress wave method in the GFRP bolt anchoring system of earthen sites.Based on the field investigation of GFRP bolt anchoring construction in earthen sites,Through the indoor model test,combined with filtering,Fourier transform and Hilbert Huang signal processing methods,this paper studies the non-destructive testing of GFRP bolt anchoring system in earth sites,,It mainly includes the following research results:(1)Through the study of indoor models with different exposed sections and anchor slurry at the bottom of the bolt,the influence of exposed length and depth of anchor slurry at the bottom of the bolt on the detection signal of the acoustic stress wave method is obtained.The length threshold of the exposed section is given as an anchorage parameter for nondestructive testing.(2)Through the study of the nondestructive testing of the anchor model slurry age,the relationship between the age and the time-frequency characteristics of nondestructive testing such as consolidation wave velocity and fundamental frequency was obtained,and the difference in time-frequency characteristics of the slurry age between the partial hole model and the complete model was clarified,laying a foundation for quality control during anchoring construction;(3)By setting complete models of different anchoring lengths and combining signal processing methods such as Fourier transform and Hilbert-Huang,the identification method of the anchoring length of the grouting complete anchoring model using the Hilbert-Huang time-spectrum was clarified.Provides a more systematic inversion scheme for the detection of the anchorage and anchorage length of GFRP bolt anchoring at earthen sites;(4)By analyzing the detection signals of two typical defect anchoring models of partial hole model and the complete model,the inversion method of the anchor length of the partial hole anchoring model and the time-frequency characteristics of grouting defect anchoring systems are obtained,combined with HHT signal processing method clarifies the inversion method of grouting defect position in the anchoring system.In addition,using the difference between the bottom reflection time of the complete model and the grouting defect model,a method for inverting the size of the grouting defect is given.It provides a basis for the detection of grouting defects in the GFRP anchoring system of earthen sites.