In order to find out the leakage of the underground sewage pipeline of Dongda Tong Street in Chengdu, the transient electromagnetic method was used to investigate. The detection area was selected between the two sections of manhole covers of the sewage pipe and was about 20 meters long. Survey line 1 is measured in parallel from directly above the pipeline, and line 2 is separated from line 1 by 0.5 meters. The inversion shows that in the anomaly region with low apparent resistivity at 9-14 meters, the apparent resistivity contour line is confused, which is inferred to be the leakage location. The pipeline robot verified the shooting, which was consistent with the inference. 

Figure 30 Schematic diagram of the model in the survey area Figure 31 Photos in the robot hole

Fig.3 Transient electromagnetic method inversion results