| Through using Ground Penetrating Radar (GPR) to take nondestructive detection on the distribution of grouting behind segments of shield-driven tunnel, the second time compensatory grouting can be carried on in time which is aimed to control the tunnel's final longitudinal settlement. Based on the experiments in lab, numerical simulation 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 segments of shield-driven tunnel. Some main conclusions are as follows:1. In the lab, using 250M Hz and 1G Hz frequency GPR respectively to detect one of the segments used in Shanghai metro tunnel. Sheet-metal was put on the whole area or part area of the back of the segment. Through finding out the strong reflection and the point of phase inversion on the GPR data, the double passing time of the electromagnetic wave in the segment was achieved. Then the velocity of the electromagnetic wave in the segment can also be obtained which could be used to get the segment's permittivity. Under the test frequency of 1G Hz, the velocity of the electromagnetic wave in the segment is 0.0933m/ns and the segment's permittivity is 10.34. Under the test frequency of 250M Hz, the velocity of the electromagnetic wave in the segment is 0.0834m/ns and the segment's permittivity is 12.95.2. A lab Coaxial Probe Method was firstly proposed for measuring the permittivity of grouting materials and the clay soil in the stratum layer where tunnel was constructed. Then the velocities of electromagnetic wave in these materials were achieved through their permittivity.
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