Using Robotic Technology to Inspect Underground Spaces
▲ Senior Research Fellow Lee Seong-won and Research Specialist Shim Seung-bo, Department of Geotechnical Engineering Research
Complex and Diverse Underground Spaces
The underground space of the city is a familiar place. It has huge shopping malls, serves as a passageway for transportation, and becomes a workplace as well. With the full utilization of underground spaces, the range of human activity has been expanded greatly, but is also naturally accompanied by risks. There are various risk factors such as collapse or flooding that accompany the underground space. The Department of Geotechnical Engineering Research at KICT is researching geotechnical engineering technologies that are essential to civil engineering construction, such as for tunnels and underground spaces, structural foundations, slopes, soft ground, and earthquakes.
“Based on our current progress in research and development, the Department of Geotechnical Engineering Research is working with a focus on four major research subjects. To be specific, when constructing earthworks and foundation structures, they are classified under “development of technologies for automation of quality control,” “development of technologies for advanced management of three-dimensional infrastructure,” “development of technologies for securing safety of earthquake response facilities,” and “development of technologies for utilizing large underground spaces.” Members of the department are dedicated to the research based on expertise in their respective field. With our cutting-edge research achievements, we are leading the development of technologies for South Korea’s underground spaces.” With industrialization progressing in earnest, Korea's underground spaces are also becoming more and more complex. As the highways were built, tunnels through mountains were also constructed in various places, and recently the world's fifth longest undersea tunnel was opened in Boryeong. Research Specialist Sim Seung-bo explains that the underground space in Korea can be largely classified into railway tunnels, road tunnels, undersea tunnels, and utility-pipe conduit tunnels based on characteristics such as shape, size, and use.
“The longest high-speed rail tunnel in South Korea is the Yulhyeon Tunnel, which is 50.25 km long and connects Suseo Station in Seoul to Jije Station in Pyeongtaek. The recently completed Boryeong Undersea Tunnel is one of the undersea tunnels, stretching to a length of 6.93 km. Finally, the most important tunnel is the utility-pipe conduit tunnel. This tunnel contains systems accommodating electricity, communication, heating, water, and conduit pipes necessary for living in the city. This tunnel is called a “lifeline” because it acts like the blood vessels that distribute energy to the body. Such tunnels are classified as national security facilities and are kept inaccessible to the general public.”
Utility-pipe Conduit Accidents Leading to Large-scale Disasters
A fire that broke out in the communication tunnel under the KT Ahyeon branch building on November 24, 2018 was an accident that clearly demonstrated the importance of the utility-pipe conduit tunnel. As a result of the accident, approximately 79 m of the communications tunnel on the first basement floor was burned out, and the Internet, mobile phone, and the wireless communications services provided by KT in the western area north of the Hangang River in Seoul became unavailable.
“Unlike other tunnels, the utility-pipe conduit tunnel takes up space even for the internal accommodation facilities, so the space for people to move is very narrow. That was why it took so much time to extinguish the fire, which soon led to a large-scale accident. Based on the total amount of damage at that time alone, KRW 8 billion in property damage and KRW 30 billion in compensations were incurred. On the day of the accident, text messages were sent out to inform people, but no one could know why their phones were not working because the KT network was cut off.”
It was called a digital disaster situation, where financial transactions and payment systems were cut off as the high-speed internet was unavailable at the time, and an elderly person in his 70s who could not report to 119 for help ended up dying due to the severance of communications. As a result, the scale and impact of direct and indirect damages in our daily life and society from an accident in the utility-pipe conduit tunnel raised the awareness that it could potentially lead to a bigger and more serious disaster than previously anticipated. Accordingly, thorough inspection and management of underground spaces including utility-pipe conduits have become much more important.
“In Korea, infrastructure built during the period of economic development and growth are gradually approaching the end of their life expectancy, resulting in more frequent accidents. Such accidents can inevitably increase with aging, which has prompted us to take a closer look at practical ways to protect the safety of our citizens from such risks.”
Robotic Technology Enabling Autonomous Travel and Inspection
Periodic inspection is the most important means to safely manage underground space facilities. In particular, management through regular precision inspection is required. The conventional inspection method is known to have been carried out in a human-centered manner. Precision inspection is an inspection method where the inspector visually checks the damage point, then measures and records the size of the specific point using a crack gauge or crack detection microscope. In this case, it is said that it is not easy to diagnose the condition objectively because it inevitably involves the subjective judgment of the inspector. In addition, there are disadvantages in that costs are continuously required to improve safety through maintenance by increasing the frequency of inspection. The research team has developed technology for an automated inspection robot that travels inside the tunnel in the place of workers to inspect damage points on concrete structures.
“The development of technology for automated inspection robots is divided into three phases: The phase of developing the core technology for each constituent technology, the phase of integration between constituent technologies, and the phase of on-site testing. In Phase 1, damage detection technology using deep learning as well as damage measurement technology using stereo vision are developed. In Phase 2, an inspection scenario according to the measurement result is implemented by linking the uncrewed moving object and the robot arm. Finally, automated inspection robotic technology is completed through on-site testing so that precision inspections can be performed in a tunnel environment.”
The biggest advantage of automated inspection robotic technology is that it can be used flexibly in maintaining underground spaces based on the convergence of multiple core technologies. The robot is applied with technology for an uncrewed traveling object that can autonomously travel inside the tunnel, technology for the robot arm that can avoid complex internal accommodation facilities, and technology for the artificial intelligence sensor that can detect and measure damage points. This inspection technology was developed to also enable remote control through a wireless network, enabling convenient application by administrators.
"The utility-pipe conduit is an underground lifeline; it is a tunnel that jointly accommodates communications lines, utility lines, and heating and gas pipes. In the past, tunnels and pipelines were laid in a complex urban underground system according to their respective uses, such as communications, utilities, and gas pipelines. To facilitate joint accommodation, it is essential to cut the costs of operating and maintaining utility-pipe conduits. It is expected that operation and maintenance costs can be reduced through the use of automated inspection robotic technology and that various accommodation facilities can be safely and efficiently managed within the utility-pipe conduit tunnel.”
Provision of Safe and Sustainable Infrastructure
The research team plans to continue its research to provide safe and sustainable infrastructure to society. The team will continue to advance this research in various forms and ultimately contribute its best efforts to the perfection of uncrewed and automated technologies for the maintenance of underground facilities.
“In our future society, the aging of our population will be accelerated thanks to the extension of average life expectancy, while the economically active population will decrease accordingly. Under such circumstances, the maintenance of infrastructure relying on the workforce is expected to become more difficult. In response to these issues, we plan to develop the necessary technologies for automation and uncrewed maintenance and to further develop the technologies needed to enable automated damage repair.”
