Experimental Study On Comprehensive Test Of Grouting Density Of Bridge Prestressed Pipeline

Modern long-span bridges that cross barriers such as river valleys and urban roads generally use post-tensioned prestressed concrete structures.The post-tensioning bridge realizes the prestressing effect through the construction process of pre-embedded prestressed pipeline,tensioned prestressed steel bar,poured cement mortar and sealing anchor.Pipeline grouting,which is one of the key construction processes,may result in poor grouting due to unreasonable ratio of grouting material and improper grouting process,which seriously affects the bearing performance and durability of the bridge.Therefore,a reliable pre-stressed pipe grouting compactness detection technology is needed to ensure the safe construction and use of prestressed bridges.Among the non-destructive testing techniques used in the engineering field,the ground penetrating radar method(GPR)is widely used in the detection of subgrade pavement and tunnel lining,and has less application for detecting the grouting density of prestressed bridge pipelines.The impact echo equivalent velcity method(IEEV)has certain engineering applications in the field of grouting compactness detection,but there are always limitations such as low work efficiency and inability to locate defect depth.Therefore,in order to effectively improve the detection efficiency and accuracy,this paper combines the GPR method and the IEEV method to carry out comprehensive detection experiments,and analyzes the effect of grouting compactness detection under different working conditions through physical model test,data processing and forward modeling.The limitations of the single detection method and the superiority of the comprehensive detection are clarified.The main work and research results are as follows:(1)The physical model of the concrete beam slab was actually made with reference to the engineering.The model was set with different grouting compactness,different pipe apertures,different pipe spacings and prestressed pipes of different materials.The model was tested using GSSI's SIR-3000 ground penetrating radar and 1600 MHz radar antenna.Using RADAN7 software to process the detection data,it is found that the two methods of exponential gain and deconvolution are more suitable for grouting detection.The two-dimensional radar profile is assembled into a three-dimensional radar image.The two-dimensional and three-dimensional data are analyzed to identify the dense and uncompacted PVC pipe.It is proved that the ground penetrating radar has limitations on the detection of the degree of grouting,the small cavity and the metal pipe.(2)The SBA-HTF detector based on IEEV method performs the location detection of the concrete beam-slab model on the pipe grouting compactness.The frequency domain waveform and the contour map are obtained by using the MEM frequency domain analysis.According to the excellent cycle and the calibration wave velocity in the data,the pipe grouting defects are analyzed.It shows that the IEEV method can accurately detect PVCpipes and metal pipes under the premise of using GPR to locate the pipeline,and can detect tiny holes.(3)The forward modeling of ground penetrating radar was carried out by using Matlab.Based on the principle of finite difference time domain,the model of pipeline grouting disease was established,which truly restored the detection process of ground penetrating radar wave.The simulation results of the grouting compactness test are consistent with the physical model test results,and special working conditions such as debonding of the inner wall of the grouting material,different ages of the grouting material and pipe bleeding diseases are added.The simulation proves that the ground penetrating radar can effectively identify the special working conditions.(4)Through physical testing and forward modeling,it is proved that ground penetrating radar can perform pipeline buried depth and cavity detection,while IEEV can identify small defects and metal pipeline detection.Therefore,this paper proposes a comprehensive detection method for ground penetrating radar global scanning and IEEV accurate detection,which provides reference value for the non-destructive testing integrated technology applied to engineering practice.