Abstract
Metro systems in urban cities demand rapid inspection methods, in order to identify critical structural defects in a timely manner. However, traditional inspection methods are only specific to one kind of structural defect, which reduces the overall efficiency of inspection. This study proposes an integrated solution for rapidly acquiring and identifying two kinds of structural defects (surface defects and cross-sectional deformation) in a metro tunnel, using a cart equipped with non-metric cameras. The integrity and rapidity are considered in formulating a systematic design for the development of the acquisition device. Methodologies based on image processing and photogrammetry are proposed to identify the structural defects of the metro tunnel. A series of on-site tests validate that the proposed method has enough speed and has acceptable accuracy in detecting critical structural defects of metro tunnels. The cost and efficiency analysis shows that the proposed method is competitive, which will greatly improve the efficiency and reduce the costs of the inspection of metro tunnels.
Highlights
Metro systems are an important type of infrastructure in large cities
To overcome the shortcomings of the existing devices and methods, this study proposes an integrated device for rapid acquisition and identification of two kinds of structural defects of metro tunnels
The proposed device and methods were validated in several tunnels of Shanghai Metro. These metro tunnels were all constructed by the shield tunneling method and they are all buried in soft soil
Summary
Metro systems are an important type of infrastructure in large cities. Accidents caused by untimely inspection have recently attracted the attention of researchers, owners and administrations [1–5].It has been widely recognized that the structural defects of metro structures (mainly tunnels) should be frequently inspected, in order to avoid the risk of disruption due to late intervention [6–13].the time required for inspection leads to the unavailability of transport infrastructures.The inspection of metro tunnels is tense and urgent, as the time period of inspection is restricted to only several hours, due to daily operating pressures. The time required for inspection leads to the unavailability of transport infrastructures. The time period available for inspecting structural defects is only 2 h for the Shanghai Metro, which has an operating mileage of 705 km The proposed device and methods were validated in several tunnels of Shanghai Metro. These metro tunnels were all constructed by the shield tunneling method and they are all buried in soft soil. These tunnels are circular tunnels, assembled by segmental linings with a inner diameter of
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