#Japan #Tokyo #road safety #NISUI CON #Campbell Scientific

Introduction

In a significant move to enhance road safety, NISUI CON, a construction consulting firm headquartered in Shinjuku, Tokyo, and Campbell Scientific Japan (CSJ), based in Saitama, Japan, have collaborated to create an advanced 'Road Collapse Detection System.' This innovative system aims to detect the occurrence and growth of cavities that can lead to road collapses, a problem that became particularly urgent following a serious incident in January 2025 in Yashio City, Saitama.

Development Background

The road collapse incident in Yashio City has spurred a national focus on preventing such events. The Ministry of Land, Infrastructure, Transport and Tourism conducted special investigations, identifying numerous areas requiring urgent attention. In these 'Urgency Level I' sites, immediate action is necessary, yet the time-consuming processes of inspection, design, budgeting, and commissioning can hinder prompt responses from authorities. As a result, a temporary safety assurance mechanism has become essential until permanent repairs can be made.

Roles in Development

NISUI CON's Contributions

NISUI CON has taken the lead by configuring measurement points based on the mechanics of road collapses, determining the installation and construction methods for the sensors, conducting soil experiments, and developing the cloud-based monitoring system.

CSJ's Contributions

On the other hand, CSJ supplies the pressure sensors using a vibrating wire technique, along with unique signal conversion technology, building the measurement and communication systems, and developing on-site data collection and communication devices.

System Overview

The system utilizes pressure sensors installed underground near sewage pipelines to measure changes in soil and pore water pressure. When a cavity associated with the pipeline reaches the sensor installation location, the pressure change is detected, indicating potential hazard for road collapse.

Cavity Detection Method

In locales with localized damage to pipelines, sensors are installed approximately 1 to 2 meters above the pipeline to detect cavities as they expand upward toward the surface. Depending on the sensor's position and the condition of the pipeline, cavities can often be detected prior to manifestation of road collapse at the surface. The 'early warning detection' feature effectively signifies the cavity's reach to the sensor location before any surface depression occurs.

Importance of Early Detection

According to reports from the Investigation Committee on the Causes of Road Collapse in Yashio City, it is suggested that years could pass between cavity formation and surface collapse. This emphasizes the need for proactive measures.

System Features

1. Deep Underground Measurement: Sensors are embedded into boreholes to measure critical changes in deep soil pressures, capturing pressure alterations due to cavity expansion at sensor locations.
2. Long-Distance Cable Measurement: The pressure sensors based on the vibrating wire method possess high resistance to noise, facilitating measurements even over long distances.
3. Remote Monitoring via LTE Communication: Measurement data is wirelessly sent to the cloud through communication equipment installed on the ground, functioning independently with solar power and batteries for continuous operation. This allows for remote management of detection alerts, trends, and equipment status checks.

System Positioning

It is essential to note that this system serves as a supplementary monitoring tool during the period prior to pipeline repairs and does not ensure definitive prediction or prevention of road collapse. Based on measurement outcomes, actions such as inspections and traffic restrictions are to be determined by road and sewage administrators concerning field conditions.

Experimental Validation

Recent experiments within the National Institute for Land and Infrastructure Management have confirmed the capability of sensors to detect pressure changes correlating with cavity growth.

Future Developments

Looking ahead, the data gathered from experimental soil will be utilized in real-world testing. This includes monitoring sensor behavior during groundwater changes and seismic activity, and exploring construction methods that reduce costs through the application of penetration tests in cavity investigations. Through such developments, NISUI CON strives to mitigate the risks associated with road collapses, contributing towards a safer and more sustainable society.

About NISUI CON

Founded in 1959, NISUI CON specializes in water-related construction consulting, including water supply, wastewater, and river projects throughout entire watersheds. The company has been dedicated to addressing various social issues surrounding water management since its inception.