With the purpose of testing the effectiveness and feasibility of Ground Penetrating Radar ( GPR) in settling a common construction quality problem which is the thickness estimation of backfill grouting, we conduct a field experiment in Shanghai. A shield tunnel segment, with half of its outer surface covered by a wooden box, is put vertically on the ground. We inject the concrete grout into the box until over 80 percent space of the box is filled. Static measurements by GPR 400 MHz frequency antenna on the internal surface of the segment show that direct wave and coupling wave are stacked together which is regarded as the time zero point. Contrastive analysis of Average Canceling method ( AC) and Principal-Component Analysis ( PCA) reveals that PCA performs better than AC in removing direct wave and highlighting effective signals. The inner structure and interfaces of the segment, grouting and other objects in the back can be distinguished from processed radargram, and that travel time of electromagnetic wave in the grouting become shorter than that a week before, which is caused by the loss of moist in the solidification process of concrete. This demonstrates the proposed technique can provide dynamic change information of back-filled grouting layer and supervise shield tunnel quality.

LOKASI: Ruang Koleksi Umum
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