Verification of Quantitative Assessment of Wall Thinning Due to Sewer Corrosion Using AI and Robots

NTT Docomo Solutions, Inc. Kyoto Prefectural Basin Sewerage Office Tmsuk Co., Ltd.

NTT Docomo Solutions, Inc. (Headquarters: Minato-ku, Tokyo; hereinafter, NTT Docomo Solutions), in collaboration with the Kyoto Prefectural Basin Sewerage Office (Location: Nagaokakyo City, Kyoto Prefecture) and Tmsuk Co., Ltd. (Head Office: Kyoto City, Kyoto Prefecture; hereinafter, Tmsuk), conducted research and verification (hereinafter, 'this verification') aimed at improving the efficiency of inspection operations for basin sewerage pipelines in Kyoto Prefecture from April to December 2025. In this verification, an AI (patent pending) developed by NTT Docomo Solutions was applied to sewerage pipeline data acquired by a multi-legged robot for sewerage pipeline inspection developed by Tmsuk, equipped with LiDAR. This AI estimates the pipe wall shape at the time of new construction and performs differential analysis with the current pipe wall shape. As a result, in some sections of the target sewerage pipes, the depth and range of wall thinning due to corrosive degradation were successfully quantitatively identified and visualized. Furthermore, using past pipeline inspection data held by Kyoto Prefecture, the applicability of existing degradation prediction models to the sewerage field was analyzed. The analysis results showed some consistency with trends that sewerage administrators had empirically felt regarding sections prone to degradation and factors contributing to degradation.

While the standard service life of sewerage systems is considered to be 50 years, approximately 7% of the roughly 500,000 km of sewerage pipelines nationwide had exceeded their service life as of 2022, and this proportion is expected to reach approximately 42% by 2043. *1 The inspection and renewal of these sewerage pipelines pose financial and technical challenges for local governments. Furthermore, in response to a series of road subsidence incidents in recent years caused by aging sewerage infrastructure, the Ministry of Land, Infrastructure, Transport and Tourism is advancing revisions to sewerage inspection guidelines, considering increasing the scope and frequency of inspections and surveys, and adding quantitative evaluation items. With the increase in the scope and frequency of inspections and surveys due to these guideline revisions, sewerage administrators are required to appropriately determine repair priorities for numerous pipelines. However, conventional visual and image-based inspections can confirm surface conditions such as the presence of corrosion or cracks, but they cannot quantitatively grasp the depth and extent of corrosion, making it difficult to judge the urgency and priority of repairs.

Against this background, NTT Docomo Solutions, the Kyoto Prefectural Basin Sewerage Office, and Tmsuk conducted this verification.

### [Overview and Results of This Verification] ### ■ Implementation Period April 2025 - December 2025 ### ■ Purpose Quantitative evaluation of wall thinning and degradation prediction for pipelines in basin sewerage systems within Kyoto Prefecture. ### ■ Roles of the Three Parties

NTT Docomo Solutions Examination of technology to achieve quantitative understanding of wall thinning using AI and data analysis technology, implementation of degradation prediction and degradation factor analysis using accumulated inspection data, planning and execution of this verification.

Kyoto Prefectural Basin Sewerage Office Selection of target pipelines utilizing accumulated knowledge from managing extensive main pipelines, provision of verification fields and accumulated inspection data, evaluation of verification results.

Tmsuk Co., Ltd. ...