Grout Saturation In Prestressed Duct Two-dimension Simulation In GPR Field And Application

The grouting of the prestressed duct is a full concealed engineerings, it is difficult to ensure quality of the grouting of prestress duct in construction. After the construction is completed, it is difficult to exactly evaluate quality of the grouting and remedy in time. If the quality of grouting of prestressed duct is not high, there are the void, not dense and water-filled hole in grouting duct, which gives the chloride, water and oxygen to the existence of space. When all conditions exist, they will corrode steel strand. Once the steel strand corroded, it will seriously affect the security and durability of bridge. Therefore the study of the quality of grouting in pre-stressed duct is full of great theoretical and practical significance. Ground-penetrating-radar which has the advantages of economy, non-destructive, fast and intuitive and so on plays an important role in detecting and evaluating the quality of grouting of the prestressed duct.To begin with The thesis introduce the theory on the wave propagation and finite difference time domain, according to them, we build there mathematical and physical models which consist of void,void filling water and no void model. We simulate the model which we build using finite difference time domain method in two dimensions. The simulation results show that the void causes strong refrected signal, The polarity of reflected signal amplitude is the same with the polarity of incident wave amplitude. The void filling water causes strong refrected signal. The polarity of reflected signal amplitude is in contrast with the polarity of incident wave amplitude. The void doesn’t cause multi-refrected-wave while the void filling water doesn’t cause multi-refrected-wave. On the basis of the theory of radar detection, methods and the grouting technology, we research main influence factors and detective keys on GPR detecting grout saturation. According to the characteristics of the reinforced concrete precast beams, we build some models that the some kinds void in the metal corrugated pipe which is under the single layereinforced bar and between two layers of reinforced bar. We simulate the models which we build using finite difference time domain method in two dimensions. We find it is too difficult to find the reflected signal of void between the signal of reinforced bar and metal corrugated pipe. Because the signal of reinforced bar conceal or cover up the signal of void. We subduct the signal of reinforced bar and metal corrugated pipe with the method of wave subduction. It is helpful to resolve the signal of the void. The signal of void in the GPR image is more obvious than before it is processed. By changing the permeability, we build void medal in grouting different magnetic permeability of concrete in metal corrugated pipe. We simulate with finite difference time domain method in two dimensions the models which we build. We also do wavesubduction.The simulation results show that we can find the reflected signal which void causes. After we detected prestressed beams of some bridges using the GPR and parts of them is verified by opening the window or the drill hole. We analyzed and summarized typical characteristics of the defects in the radar images. It is a reference basis for detecting.Theoretical research and engineering practice show the results we simulate the models of the void in grouting duct and filling magnetic concrete with finite difference time domain are the same with the position of detect in GPR field. So it is good to detect grout saturate of grouting duct with GPR in Practice.