Verification Conducted for Quantitative Assessment of Sewer Pipe Wall Thinning Due to Corrosion Using AI and Robotics

NTT Docomo Solutions, Inc. Kyoto Prefecture Basin Sewerage Office Tmsuk Co., Ltd. NTT Docomo Solutions, Inc. (Headquarters: Minato-ku, Tokyo; hereinafter "NTT Docomo Solutions"), in collaboration with the Kyoto Prefecture Basin Sewerage Office (Location: Nagaokakyo, Kyoto) and Tmsuk Co., Ltd. (Headquarters: Kyoto, Kyoto; hereinafter "Tmsuk"), conducted a study and verification (hereinafter "this verification") from April to December 2025 aimed at advancing inspection operations for basin sewer pipelines in Kyoto Prefecture. In this verification, data acquired by mounting LiDAR on a multi-legged robot for sewer pipe inspection developed by Tmsuk was processed using AI (patent pending) developed by NTT Docomo Solutions. This AI estimates the original pipe wall shape at the time of installation and performs differential analysis against the current wall shape. As a result, the team successfully quantified and visualized the depth and extent of wall thinning caused by corrosion in sections of the target sewer pipes. Additionally, using past pipeline inspection data held by Kyoto Prefecture, the team analyzed the applicability of existing degradation prediction models to the sewerage sector. The results showed that the analysis aligned with the trends that sewer managers had previously identified through empirical observation, such as sections prone to rapid degradation and the factors contributing to such deterioration. While the standard service life of a sewer is 50 years, approximately 7% of the roughly 500,000 km of sewer pipelines nationwide had exceeded their service life as of 2022, and this figure is expected to reach approximately 42% by 2043 (*1). The inspection and renewal of these pipelines present significant financial and technical challenges for local governments. Furthermore, in response to recent road cave-in accidents caused by aging sewers, the Ministry of Land, Infrastructure, Transport and Tourism is revising its sewer inspection guidelines, considering increases in the scope and frequency of inspections and the addition of quantitative evaluation criteria. As these revisions increase the burden of inspection, sewer managers are required to appropriately prioritize repairs. However, conventional visual or image-based inspections can identify surface conditions like cracks or the presence of corrosion, but they cannot quantitatively grasp the depth or extent of corrosion, making it difficult to judge the urgency and priority of repairs. Against this backdrop, NTT Docomo Solutions, the Kyoto Prefecture Basin Sewerage Office, and Tmsuk conducted this verification. 【Overview and Results of the Verification】 ■ Implementation Period April 2025 – December 2025 ■ Objective Quantitative evaluation of wall thinning and degradation prediction for basin sewer pipelines in Kyoto Prefecture. ■ Roles of the Three Parties NTT Docomo SolutionsResearching technology to realize quantitative assessment of wall thinning using AI and data analysis, conducting degradation prediction and factor analysis using accumulated inspection data, and planning/executing this verification.Kyoto Prefecture Basin Sewerage OfficeSelecting target pipelines based on knowledge accumulated through managing wide-area trunk lines, providing verification fields and accumulated inspection data, and evaluating the results of this verification.TmsukProviding the multi-legged sewer inspection robot and technical support for data acquisition.