Extended Inspection Cycle for Manhole Iron Covers Installed on RoadsNTT Access Network Service Systems Laboratories


    This section introduces a technology for reducing inspection operations by constructing a deterioration estimation model based on statistical analysis of inspection data and grouping according to deterioration characteristics.

    Background and existing issues

    The deterioration speed of manhole iron covers installed on roads will vary considerably depending on the installation environment, but all manholes are currently inspected uniformly every five years. there is a demand for proper maintenance and management in accordance with the deterioration characteristics of manholes iron covers.

    Advantages of this technology

    • By quantifying the risk of deterioration, it is possible to prioritize inspection of manhole iron covers with high risk, and to detect defective equipment at an early stage.
    • With 70% of conventional periodic inspections being able to detect manhole iron covers that are susceptible to deterioration, group management is realized based on their degradation characteristics.

    Use Scene

    • This allows for efficient maintenance of manhole covers installed on roads.

    Explanatory chart

    Technical explanation

    Using the description variables "Inspection data (wear amount, inspection year, etc.)," "Equipment data (manhole type, manhole iron cover shape, etc.)," and "Installation environment data (exclusive locations, public/private category, etc.)," the combined conditions that correlate with the target variable "Manhole iron covers prone to degradation (wear speed of 0.1 mm/year or more)" were extracted, and a model for estimating degradation was built.
    Based on the deterioration estimation model, we were able to find more than 99% of the manhole iron covers that deteriorate rapidly, at 70% of the number of conventional inspections.Therefore, We defined the remaining 30% as a group that is less likely to deteriorate, and developed a technology to reduce inspection operations by setting the inspection cycle to 10, which corresponds to the progress of deterioration.
    In addition, by quantifying the risk of wear deterioration, it has become possible to preferentially inspect mahole iron covers with high risk, enabling early detection of defective equipment.

    Department in charge

    NTT Access Network Service Systems Laboratories - Civil Engineering Project

    Related content