Test And Application Of GPR Detecting Of Grouting Behind Segment Of The Shield Tunnel Across The River

Through using Ground Penetrating Radar (GPR) to take nondestructive test on the distribution of grouting behind segment of shield tunnel, the second time compensatory grouting can be carried on in time which is aimed to control the final longitudinal settlement of the tunnel. In this paper, combination of larger diameter and the lager thickness on the shield tunnel across the river, based on the experiments in lab, numerical simulation, model testing and in-situ tests, this thesis is focused on the research of the feasibility and key technologies of using GPR in the detection on the distribution of grouting behind segment of the large diameter shield tunnel. Some main conclusions are as follows:1. In the soft soil and structure of the tunnel, using 250 MHz, and 1 GHz 500MHz frequency GPR to detect the Shanghai-Yangtze River shield tunnel, in accordance with metal plates model detection, the permittivity of segment is achieved; using sheet metal model and coaxial probe method for the detection of grouting material; using coaxial probe method for Shanghai typical soft mud soil dielectric constant measurement and analysis. The dielectric constants and velocities of electromagnetic waves in various media are acquired.2. Using the Finite Difference Time Domain (FDTD) method to simulate the test model of by different frequency GPR. Then based on the numerical simulation and the phsical model, the different age grouting, the different filling ways behind the segement and water on the surface of segment were detected by the 250 MHz, 500MHz and 1GHz GPR. Compared by the numerical simulation and the physical model, the result of 500 MHz GPR is better than 250 MHz and 1 GHz, and detecting in the third day of grouting is best. In the construction period, the 500MHz GPR and the third day after grouting are proposed.3. Against the characteristics of the grouting detectiong on the large diameter shield-tunnel, the three corresponding mechanical devices are designed. They are the NDT equipment set on the shield machine, the rapid detection device on an automobile and crawling robot device. In a few years, the possibility of the rapid detection device on an automobile is achieved to satisfing the needs of detection.4. Based on the above researches, the application using both 250MHz and 1G Hz frequency GPR in Xiangyin Tunnel, the Shangzhong Tunnel and Shanghai Yangtze River Tunnel were carried on. The result of 500 MHz GPR is better than the detection of 250 MHz and 1 GHz. In site test, the thickness of the grouting in the through hole of the Shanghai Yangtze River Tunnel Link Passage is 21cm, and the thickness using 500 MHz GPR to detec is about 20 cm to 22 cm, so the result is good.Finally, the problems requiring further studies were discussed.