Verification Conducted on Quantitative Assessment of Wall Thickness Reduction Due to Sewer Corrosion Using AI and Robots

NTT DOCOMO Solutions, Inc.

Kyoto Prefectural Basin Sewerage Office

Tmsuk Co., Ltd.

NTT DOCOMO Solutions, Inc. (Head Office: 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; hereinafter, Tmsuk), conducted an investigation and verification (hereinafter, this verification) from April to December 2025 aimed at advancing inspection operations for basin sewerage pipelines within Kyoto Prefecture. In this verification, an AI (patent pending) developed by NTT DOCOMO Solutions was applied to sewer pipe data acquired by a multi-legged robot, developed by Tmsuk and equipped with LiDAR, for traveling inside sewer pipes. The AI estimates the pipe wall's original shape at the time of installation and performs a differential analysis with its current shape. As a result, they succeeded in quantitatively identifying and visualizing the depth and extent of wall thickness reduction due to corrosive deterioration in a section of the sewer pipe targeted in this verification. Furthermore, using past pipeline inspection data held by Kyoto Prefecture, they analyzed the applicability of existing deterioration prediction models to the sewerage sector. The results of this analysis were partially consistent with the trends that sewer managers had empirically sensed regarding sections prone to deterioration and its contributing factors.

The standard service life for sewers is considered to be 50 years. However, of the approximately 500,000 km of sewer pipelines nationwide, about 7% had exceeded their service life as of 2022, and this proportion is expected to reach about 42% by 2043. *1 The inspection and renewal of these sewer pipelines have become a financial and technical challenge for local governments. In recent years, in response to a series of road cave-ins caused by aging sewers, the Ministry of Land, Infrastructure, Transport and Tourism has been revising its sewer inspection guidelines, considering an increase in the scope and frequency of inspections and surveys, and the addition of quantitative evaluation items. As these guideline revisions increase the inspection workload, sewer managers are required to appropriately prioritize repairs for numerous pipelines. However, conventional visual and image-based inspections can confirm surface conditions like the presence of corrosion and cracks but cannot quantitatively grasp the depth and extent of corrosion, making it difficult to judge the urgency and priority of repairs.

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

[Overview and Achievements of this Verification]

Implementation Period

April 2025 - December 2025

Purpose

Quantitative evaluation of wall thickness reduction and prediction of pipeline deterioration for basin sewers in Kyoto Prefecture.

Roles of the Three Parties

NTT DOCOMO Solutions

Development of technology to achieve quantitative assessment of wall thickness reduction using AI and data analysis, implementation of deterioration prediction and factor analysis using accumulated inspection data, and planning/execution of this verification.

Kyoto Prefectural Basin Sewerage Office

Selection of target pipelines utilizing knowledge accumulated from managing wide-area trunk lines, provision of verification fields and accumulated inspection data, and evaluation of the verification results.

Tmsuk...