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• Development of Digital Image-Based Soil Color Assessment Technologies Development of Digital Image-Based Soil Color Assessment Technologies ▲ Senior Researcher Kwak Tae-young, Department of Geotechnical Engineering Research, KICT Prologue Soil color is widely used as a fundamental indicator for classifying and predicting soil properties, as it is known to be influenced by factors such as mineral composition, organic content, moisture content, and ion concentration, among others. Particularly in the field of agriculture, soil color is utilized as a prominent indicator for classifying soils, and suitable farming practices and crop types are determined based on soil color variations. Additionally, in civil engineering, the color of soil samples collected during soil surveying of a site is recorded in the boring log. This practice is based on the understanding that soils with similar colors in adjacent areas are highly likely to have similar geotechnical properties. Color is typically determined through visual observation. The MUNSELL Soil Color Charts shown in Figure 1 were developed to objectively differentiate observed soil colors based on combinations of hue, value, and chroma. However, the method of determining soil color using MUNSELL Soil Color Charts has the following limitations: ① It is susceptible to the subjectivity of the observer, ② the color of soil samples and the standard color chips can vary depending on environmental conditions like lighting, and ③ the standard color chips are discontinuous, making numerical or statistical analysis challenging. Recently, digital image-based soil color assessment technology has been highlighted as a means of overcoming these limitations. Digital image processing involves a series of computer-based processes to analyze digital images, allowing for rapid and objective soil color determination without the need for observer involvement. Furthermore, since soil color is represented as continuous values in digital image-based systems, it offers the advantage of enabling numerical or statistical analysis. Current Status of Development of Digital Image-Based Soil Color Assessment Technologies Current Status of Development of Digital Image-Based Soil Color Assessment Technologies Variations in Soil Color Due to Changes in Lighting Conditions Figure 2 presents digital images of granitic soils in the Anseong area, captured under lighting conditions simulating natural light. Despite capturing consistently prepared soil samples with the same camera settings, the soil color displayed in the images varied significantly based on the lighting's color temperature and illuminance. Color temperature is a measure of the color of light sources expressed in absolute temperature (K). The lower the color temperature, the redder the light source; the higher the color temperature, the bluer the light source. Illuminance is a measure of the intensity of light received on a specific surface. As illuminance increases, the light source becomes brighter. Soil color exhibited a similar trend to changes in color temperature and illuminance of the lighting. The phenomenon of soil color changing with lighting conditions highlights the clear limitations of previous studies that were not applicable in practical field settings. It is believed that the development of a digital image-based soil color analysis method that can consider irregular lighting conditions would further enhance the universality and applicability of research findings in practical field settings. Development of Digital Image Processing-Based Soil Color Analysis Technology A color system is a method of numerically representing colors, expressing a specific color as a point in a color space. There are various ways to define a color space, depending on the color system used. Some common color systems include RGB, HSV, CIEXYZ, CIExyY, CIELAB, and CIELUV (Billmeyer and Saltzman, 1981). In this study, two color systems, RGB and CIELAB, were utilized for soil color analysis. The RGB color system is the method most widely used in electronic devices such as digital cameras, and represents colors using the three primary colors of light: red (R), green (G), and blue (B). The RGB color system has the advantage of being able to reproduce most colors through a simple combination of the three colors. However, it cannot represent all the colors that the human eye can perceive. To overcome this limitation, the International Commission on Illumination (CIE) proposed the CIELAB color system based on the CIEXYZ color system (CIE, 1978). In the CIELAB color system, colors are expressed as a combination of L*, a*, and b*. L* represents the brightness of the color and ranges from 0 (dark) to 100 (bright). Additionally, a* and b* represent color values, and a* represents which side of red (positive number) and green (negative number) it is closer to, while b* indicates which side of yellow (positive number) and blue (negative number) it is closer to. Color System for Digital Image-Based Soil Color Analysis In an attempt to overcome the limitations of previous researches, the Korea Institute of Civil Engineering and Building Technology (KICT) has developed a digital image processing-based soil color analysis technology that can consider irregular lighting conditions in the field. As shown in Figure 3, a digital image capture studio was established to simulate natural light conditions. Various soil samples, including a single silica-based sand sample and granitic soil collected from four different regions, were photographed under different lighting conditions. Digital image processing was performed on the captured sample images to extract and analyze soil color in various color systems (RGB, CIELAB). In the RGB color system-based soil color analysis, it was observed that as the illuminance of the lighting intensified, the soil color components (R, G, B) also increased. Of the RGB components, green (G), which is known to have the highest correlation with brightness, showed a very high correlation with illuminance. However, red (R) and blue (B) showed relatively lower correlations due to the influence of color temperature. Since soil color represented in the RGB color system is influenced to some extent by both illuminance and color temperature, it was considered challenging to completely exclude (or correct for) the effects of lighting conditions using this system. The analysis of soil color based on the CIELAB color system revealed that L* is influenced only by illuminance, while a* and b* are affected solely by color temperature, and the correlations were high. This is attributed to the fact that L* represents the brightness of the color, while a* and b* are indicators of hue. Based on the analysis of the relationship between L* and illuminance, as well as a* and b* with color temperature within the CIELAB color system, I proposed the following soil color correction equations according to varying lighting conditions. In this context, I and T represent the illuminance and Color temperature received by the soil, respectively. aL and fL denote the slope and intercept of the linear regression equation between the L* value of soil color and Illuminance, while aa and fa represent the slope and intercept of the linear regression equation between the a* value of soil color and color temperature, and ab and fb signify the slope and intercept of the linear regression equation between the b* value of soil color and color temperature. For dry soil, it was confirmed that the slopes (i.e., aL, aa, ab) in Equations (1) to (3) are similar, regardless of the type of sample. Ultimately, the following correction equation was proposed. Through the proposed method, it is possible to correct the soil color of soil samples captured under arbitrary lighting conditions to the desired soil color under specific lighting conditions. More detailed correction procedures are described in Baek et al. (2023). Epilogue The KICT is currently developing a digital image-based soil color analysis technology that can consider irregular lighting conditions in the field. As shown by the results of an analysis of captured images, it appears that the impact of irregular lighting conditions on soil color can be eliminated (or corrected) based on the CIELAB color system. Using the analysis results for dry soil samples, a lighting condition correction equation has been proposed. In addition, currently, analyses are being conducted for soil samples containing water. Once the analysis for water-containing unsaturated soils is completed, it will become possible to acquire soil color quickly and easily from digitally captured soil images in the field, regardless of moisture content, enabling statistical analysis. Department of Geotechnical Engineering Research Date2023-10-11 Hit 275
• Firefly Sensor Developed for the Monitoring of Ground Failures Firefly Sensor Developed for the Monitoring of Ground Failures ▲ Department of Geotechnical Engineering Research, KITC - Smart Sensor and System Developed to Detect Symptoms of Ground and Structural Failure - Field-deployable, Fast, and Accurate Technology that Contributes to Public Safety The Korea Institute of Civil Engineering and Building Technology (KICT) has developed a smart detection sensor (Firefly Sensor), which can detect signs of ground and structural failure, along with a real-time remote monitoring system. The technology was developed jointly with Disaster Safety Technology Co., Ltd., KICT's first research affiliated company, and EMTAKE Co., Ltd., a Korean venture company. The developed Firefly Sensor can be easily mounted in various high-risk areas where ground failures are a concern, with a spacing of 1 m to 2 m. In addition, it can detect deviations as small as 0.03° in real-time, surpassing the 0.05° threshold of the slope inclinometer criteria set by the Korea Forest Service for slope collapse. When a sign of collapse is detected, an immediate alert is triggered using LED illumination. The LED alert utilizes high-efficiency optical transmission lens technology, enabling managers and workers on site to visually confirm the alert, even at a distance of 100 m during daylight hours. Site conditions can be simultaneously and remotely monitored from the control room in real time, facilitating additional measures such as sharing the risk situation with related institutions. In addition, the sensor offers easy installation, resulting in more than a 50% cost savings compared to the installation and operation expenses of conventional measurement sensors. It offers the advantage of operating for a full year without battery replacement, thanks to its ultra-low power design. Additionally, the sensor is designed to operate reliably in extreme temperatures ranging from -30°C to 80°C, and is considered especially suitable for regions with distinct seasonal variations. The Firefly Sensor is equipped with an algorithm technology that prevents malfunctions by analyzing and assessing risks based on the installation location. This means that it can be utilized in a range of locations that includes construction and civil engineering sites, aging buildings, cultural heritage and fortress structures, steep slopes, areas prone to landslides, tunnel construction, mines and underground structures, bridges, dams, areas where erosion protection is needed, and more. Currently, the Firefly Sensor is being operated in pilot installations that include Jeju Lava Cave, water treatment and sewage plants in Incheon, cut slopes and mountain slopes along national highways, the KINTEX station section of the GTX-A route, construction sites for apartment complexes in Daejeon and Damyang-gun, and LG chemical factories. It has also been incorporated into the design of the extension project for the 2023 Sin Bonding Line. It is expected that its application in national infrastructure construction projects, including in the demolition of buildings, will increase. This achievement would not have been possible without the support of the Ministry of Science and ICT, specifically as part of the KICT's main project (Regional Cooperation Project) entitled "Development of Jeju-type Ground Subsidence Response System for Road Safety Operation (2020-2022)." Department of Geotechnical Engineering Research Date2023-06-27 Hit 395
• Using Robotic Technology to Inspect Underground Spaces 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.” Department of Geotechnical Engineering Research Date2022-03-28 Hit 826
• Characterization of Construction Materials using X-ray CT Characterization of Construction Materials using X-ray CT Research Supervisor: Kim, Kwang Yeom (Research Fellow, kimky@kict.re.kr) ■ Overview The Korea Institute of Civil Engineering and Building Technology possesses platform technologies related to the evaluation of materials based on multi-tube industrial X-ray CT devices and CT imaging for the X-ray CT (computed tomography) imaging assessment of construction materials. Through the use of such technologies, while quantifying the features for various construction materials, it also suggests new methodologies for acquiring and evaluating new information on materials, which was not possible in the past. Using this new evaluation method, 3D penetration images inside of materials provided by the X-ray CT device were integrated with material analysis technologies to overcome the limitations of past construction material analysis methods in order to procure new engineering technologies with high added value. By using this new material evaluation method, this technology will provide critical analysis services, and furthermore, can be used to derive international standards for the characterization of materials. The research achievements of this project were assessed to be high, and in 2016, this marked the first time in the nation that a government funded research institute won the DESTRESS project, a joint international research project of EU Horizon2020. This is a joint research project with European partners, and the purpose of this project is to develop and prove geothermal reservoir formation technologies. ▲ Multi-tube industrial X-ray CT device ■ Background and Need for Research In recent years, there has been growing international interest in the characterization of materials using X-ray CT. X-ray CT filming and analysis has the advantage of enabling quantitative evaluation, in addition to the ability to observe internal material features that could not be measured through existing methods using X-ray CT. Micro CT is a method that uses the characteristic of an X-ray, in which the energy dissipation of the X-ray changes according to the density of materials. Using this characteristic, it is possible to extract key information for evaluating the distribution of components inside materials, pore sizes, pore quantity, etc. The aim of this study was to procure platform technologies that could be utilized in key areas such as long-term behavior assessment of construction materials and performance evaluation of structures using such new evaluation methods of materials. ▲ DESTRESS International Joint Research Achievemen ■ Research Contents X-ray CT-based material evaluation technologies procured through the research are as follows. ● Development of phase separation techniques based on statistics processing ● Statistical analysis-based material anisotropy analysis ● Porosity analysis using SPF ● Particle form analysis technology ● Construction of dynamic behavior evaluation system within X-ray CT chamber ▲ Research achievements and data sharing platform ■ Research Achievements The purpose of this study is to quantify observations on materials through X-ray CT imaging evaluations of construction materials. Various image evaluation technologies were developed to this end, and this has led to a number of academic accomplishments and industrial property rights such as domestic and international patents, publications in international SCI theses, etc. ● First government funded research institute to participate in the Horizon2020 project ● Presentation at internal academic conference, by invitation with all expenses paid for ● Won joint international research project (British Swansea and Swiss NAGRA) and signed MOU ● 7 cases of supporting small and medium companies related to X-ray CT technologies ● Total of 2,620 cases of DB construction ● Start-up business creation and technology transfer (ECME) ● 13 theses in SCI and SCIE-level journals, and 5 domestic theses ● Registered 8 domestic patents and 1 international patent (Japan), 2 international patents pending (US, Japan), 13 SW registration, 11 cases of press PR ● Appeared on YTN Science show and 10 cases of press PR ● Efficient use of DB and service PR by operating homepage ▲ DB and service model packaging for each material ■ Expected Effects Through the results of this study, it was possible to visualize the interior of specimens using a means that was not possible in the past, and it is judged that it will be possible to procure material evaluation technologies and application results in a new dimension. This technology enables an analysis of quantified results by observing the interior without deforming or destroying materials, and is therefore expected to result in cost savings of billions of won every year, by reducing both working time and expenses. Furthermore, it is also expected to create profits by winning international orders, which will improve the international status of Korean companies, and also will enhance national safety by supporting status assessments of shielding materials for nuclear power generators. In particular, it is judged that the analysis technologies procured in this study will contribute significantly to carrying out international joint research derived from this study, and that in the future, this technology will be used by the international community for large projects and additional joint international research. In addition, it is judged that the informatization of X-ray CT images and the physical features of various materials and the construction of a DB will provide support not only for the public sector, but also for the private sector in relevant industries. Department of Geotechnical Engineering Research Date2017-09-07 Hit 1690
• [2015] World’s First Microbial Biopolymer based Construction Material for Geotechnical Engineering Practices Project Leader: Chang Il-han (Senior Researcher, ilhanchang@kict.re.kr) The ‘microbial biopolymer-based geotechnical engineering construction material technology’ being developed by KICT is the world’s first attempt of theoretically investigating the characteristics and geotechnical engineering behavior of soils treated by microbial biopolymers generated by microorganisms and developing a new construction material and its utilization method to apply biopolymers in geotechnical construction areas. Currently, high strength biopolymer-soil composites with a compression strength of 25MPa or higher are developed through phased strength improvements. Xanthan gum, Gellan gum and Casein were selected as potential biopolymers to be used as construction material, and the intellectual property rights in Korea and other countries have been secured. The technology is expected to reduce CO2 emission (use of cement) in construction and lead the future ecofriendly geotechnical construction market. Research Background and Necessity Ordinary cement which is the most widely used soil binder in geotechnical constructions, emits massive carbon dioxide (0.95ton CO2 / 1ton cement) that it takes up to 8% of the whole global CO2 emission. Following the Paris Agreement signed in 2015, it is becoming more important to develop materials to replace cement for eco-friendly geotechnical construction in order to meet the mandatory reduction of greenhouse gases. The biopolymer is an eco-friendly biological byproduct generated by microorganisms or bacteria and consumes large amounts of carbon dioxide during production while offering outstanding tensile strength. The study of using biopolymers for geotechnical construction was initiated as a means to drastically improve soil strength with a small amount of resources. ▲Conceptual diagram of microbial biopolymer-based soil strength improvement ▲Micro-scale interaction of biopolymer/soil bonding Research Contents This study investigated the inter-particle bonding mechanism between biopolymers and soils through theoretical and experimental studies on various biopolymers and soil types to develop a new microbial biopolymer-based geotechnical construction material and its site implementation methods. As a result, the optimal biopolymer/soil mixing condition is discovered, while a biopolymer/soil mixture that does not dissolve in the water is developed. Based on the results, an industry-academia-institute collaboration is in progress to develop commercialization technologies such as ecofriendly soil architecture, cement-free soil packaging, eco-friendly slope protection/reinforcement, soil erosion restraining, and ground injection/ mixing. In addition, key technology to prevent desertification using biopolymer is currently under development with support from the National Research Foundation of Korea to present alternative technology to cope with climate change. ▲Applicable areas of biopolymer geotechnical construction material Research Results This study is the world’s first attempt to utilize microbial biopolymers for geotechnical engineering practices. In addition to the academic study of investigating the biopolymer/soil bonding mechanism, the development of commercialized technology that can be applied in geotechnical construction is ongoing. As such, research results have been published in many international journals and intellectual property rights in Korea and other countries were obtained to lead key original technologies. In addition to commercialization, KICT expects royalty income from technology transfer. • Two prototypes (cement-free biopolymer-soil packaging; block/panel prototype) • 8 research papers published in international SCIE • Three domestic patents related to biopolymer construction material and its field application • Two pending international patents related to application in biopolymer geotechnical construction ▲Conceptual diagram of biopolymer/soil in-situ mixing and construction ▲View of biopolymer/soil packing test (Oct. 2015) Utilization and Impact This study is related to the development of new eco-friendly material to reduce or substitute the use of existing soil treatment materials such as cement in geotechnical construction and its application and is expected to lead the next-generation sustainable construction market. The technology can be applied not only in conventional geotechnical construction areas (reinforcement, retaining, soil packaging, etc.) but also in restraining of soil erosion and preventing the expansion of desertification to cope with climate change. As such, it is expected to be applicable in broad overseas markets. Since the biopolymer-based geotechnical construction material can be produced anywhere in the world, if the microorganism, nutrient and culture conditions are right, it can be used as an alternative material in regions (Africa and Southwest Asia) that are short of cement. Adopting the concept of ‘local binder’, the technology is expected to find demand in developing countries. ▲Prototype of biopolymer / soil architectural material (Sep. 2015) ▲Conceptual diagram of biopolymer application in combat desertification Department of Geotechnical Engineering Research Date2016-10-07 Hit 1544
• Special Bridge Safety Inspection Technology Utilizing Robots Special Bridge Safety Inspection Technology Utilizing Robots ▲ Senior Researcher Seo Dong-woo, KICT Department of Structural Engineering Research Prologue Most of the structures currently constructed as special bridges in Korea (collectively referring to cable-stayed bridges on which the measurement system is built) are constructed in the form of cable-stayed bridges or suspension bridges. Since the service life required for special bridges is more than 100 years, the stability, durability, and usability of the structure must be secured (KSCE, 2006). Damage to cables, which is one of the key deficiencies in special bridges, is a major factor reducing bridge safety and shortening service life. Cable damage is caused not only by environmental factors (climate, load, earthquake, etc.) but also by unpredictable accidents such as fire or collision. If a bridge in public use must suspend its operation due to cable damage, the economic and social losses are enormous (Na et al., 2014). In Korea, there was an accident in which one out of a total of 144 construction materials was completely broken and two were partially damaged by a cable fire at Seohae Bridge (cable-stayed bridge) (Gil et al., 2016). Although studies aiming to develop various inspection technologies for the safety and maintenance of cables are being conducted, there is a limit to the applicability of these technologies to special bridges, especially to cables, which are large facilities, due to limitations in the mobility and accessibility of equipment. To address this, efforts to develop a cable inspection robot capable of non-destructive testing are ongoing (Kim et al., 2014). To apply the inspection robot to cables, it is necessary to secure its field usability by using a wireless system and minimizing dead-weight. In this article, I would like to introduce a cable inspection robot equipped with an electromagnetic sensor to improve the driving stability, which was pointed out as a disadvantage of existing inspection robots, and to detect whether the inside of the cable is damaged. Design and Specifications of Cable Inspection Robot In making the cable inspection robot, we focused on the applicability of large diameter cables over 200 mm and securing the robot's driving stability. Figure 1 shows the 3D image of the cable inspection robot and its main devices. The dimensions of the robot are 510 mm × 610 mm × 710 mm, and the weight is reduced to 12.8 kg. In addition, to improve durability, the frame of the robot was made of aluminum. A high-resolution IP camera (1920 × 1080 pixels) was installed to take pictures of the exterior of the cable, enabling real-time cable shot images to be transmitted with a wireless Wi-Fi router. Furthermore, the movement distance of the robot could be calculated using an acceleration sensor and a rotary encoder. Three driving motors (IG-32GM, DC12) and urethane wheels were installed so that the robot can move on the cable while minimizing its shaking during climbing. In addition, a variable diameter adjustment part (140-300 mm) was made to improve the adhesion between wheel and cable. The wireless remote control of the robot uses IEEE 802.11 an/ac 5 GHz 2×2 MIMO to achieve a communication distance of 10 km and a data transmission rate of up to 867 Mbps. Damage to the steel wire of cables is detected with an electromagnetic sensor. As shown in Figure 2, the principle applied is that the polarity is divided again at the damaged area when the cable breaks or gets damaged. As shown in Figure 3, the sensing device mounted on the inspection robot for cable damage detection consists of pipe diameter adjusting units that can be adjusted according to the cable diameter and a roller for moving on the cable surface. Also, the electromagnetic sensor for detecting cable damage is inserted in the middle of the roller part. Performance Evaluation of Cable Inspection Robot Indoor and outdoor tests to evaluate the driving performance of the cable inspection robot were conducted as shown in Figure 4. One cable-stayed bridge with a history of cable accidents was selected as a test bed bridge for field tests of bridges currently in public use. The bridge is a short-span earth-anchored steel composite cable-stayed bridge with a span length of 400 m and a width of 23.9 m, on a four-lane road (two ways). The field cable (200 mm) had an inclination angle of 27.3 degrees, and the indoor test was conducted at 45 degrees. With the verification test, the climbing speed (19 cm/s) and the descent speed (20 cm/s) were evaluated, and it was confirmed that the robot is effectively controlling its speed when the speed increases due to slipping that may occur during the descent. It was also confirmed that the driving speed was constant regardless of the inclination angle. In addition, real-time images of the cable surface were taken with three cameras in the field test, and as shown in Figure 5, it was confirmed that visual inspection of the cable was possible. No communication-related problems occurred during the performance verification test. The cable damage detection test was conducted indoors. The cable specimen used in the indoor test is a type of cable currently used in bridges, and the inner cable consists of 20 pieces of one bundle composed of seven 1.57 mm strands. For the cable sheathing, the same High-Density Polyethylene (HDPE) tube used in the driving capability test was used. To detect cable damage, damage types were artificially simulated as shown in Figure 6. Cut damage was subdivided according to the degree of cross-sectional cut into 30%, 50%, and 100% cut (break). For disengagement damage, the case where the cable protruded to the outside in a tidy state was reproduced. For disconnection, one cable was made short. Figure 7 shows the results of the test conducted indoors. In the graph, the X-axis is time and the Y-axis is the electromagnetic sensor measurement. It can be seen that the phase of the electromagnetic sensor measurement changed by 180 degrees at the point where damage (cut) took place. On the other hand, it was confirmed that the phase of the electromagnetic sensor measured value did not change during disconnection, but the magnitude of the magnetic field increased. To secure the reliability of the experimental results, it is considered that additional experiments are needed, with more diverse damage types and repeatability than those conducted in this study. Epilogue This article introduced the development of a cable inspection robot capable of measuring large-diameter cables over 200 mm. The developed cable inspection robot has expanded its field applicability by improving its driving ability, driving stability, and wireless communication performance. The possibility of detecting damage to the inside of the cable using an electromagnetic sensor was verified through an indoor test. However, it is considered necessary to further improve inspection efficiency by developing an analysis algorithm that in addition to detecting the presence of cable damage can determine the degree and type of damage through additional tests. If facility maintenance technology using inspection robots is continuously advanced and applied, it is expected that it will greatly contribute to facility safety management. This cable inspection robot was developed with budget support by the Ministry of Land, Infrastructure, and Transport. It has been handed over to the Korea Authority of Land & Infrastructure Safety and is being used for the maintenance of general national highway special bridges. Department of Structural Engineering Research Date2022-09-27 Hit 534
• Development of Nondestructive Evaluation Technology for PSC Structures (PSC Stethoscope) Development of Nondestructive Evaluation Technology for PSC Structures (PSC Stethoscope) ▲ Senior Researcher Park Kwang-yeun, KICT Department of Structural Engineering Research The Aging of PSC Structures and Need for External PS Tendon Nondestructive Testing Whether at home or abroad, in countries where civilization has progressed rapidly, a number of bridges containing the essence of civil engineering technology have been built, allowing logistics and passengers to quickly cross rivers and valleys. In South Korea as well, befitting a civilized country, many bridges have been built and are playing numerous roles. These bridges enable convenient crossing of the Han River to bind the Gangbuk and Gangnam areas into a single city, overcome mountain valleys to greatly increase accessibility to mountainous regions, and connect islands to the mainland. It is found that 38% of these bridges were built using pre-stressed concrete (PSC) structures. Given the fact that a large number of bridges have been built since the 1980s and 1990s when Korea's economy grew rapidly, it can be assumed that the development of safety diagnosis technology for PSC structures older than 30 years is urgent. As the name suggests, the pre-stressed tendon (PS tendon) plays the most critical role in the PSC structure. PS tendons can be broadly classified into external PS tendons and internal PS tendons. For example, regarding external PS tendons, there was a case of enormous economic and social loss in 2016 due to corrosion of external PS tendons on Jeongneungcheon Viaduct, the inner ring road in Seoul, raising public awareness of the need for safety diagnosis (Figure 1). State of External PS Tendon Nondestructive Testing Technology Taking the Jeongneungcheon Viaduct case as an opportunity, the Korea Institute of Civil Engineering and Building Technology (KICT) conducted the KICT Blind Test (2016), targeting domestic and foreign nondestructive testing technologies to investigate the technology that can assess the integrity of external PS tendons. The integrity of the external PS tendon can be checked using three indicators: sectional damage, stress, and voids. However, for stress, no organization possessed the related technology, regardless of location at home or abroad, and for voids, only one French company (Advitam) applied for and demonstrated a detection rate of about 73%. Among the three indicators, cross-sectional damage is the most important and direct indicator. Of the ten local and foreign companies that applied for related nondestructive technology, only two companies, Tokyo-Rope of Japan and Instron of Russia, showed valid results, and none of the Korean companies demonstrated valid results. As for the technology of the two companies, which showed valid results, we came to the conclusion that it would be difficult to apply it in the field unless the cost, usability, size, and weight of equipment were improved. Development of Nondestructive Evaluation Technology for PSC Structures (PSC Stethoscope) For this reason, the KICT initiated a study to develop a proprietary technology that can inspect cross-section damage, stress state, and voids by conducting nondestructive testing of external PS tendons. The cross-sectional damage and stress use the magnetic properties of the external PS tendon made of metal, and the presence or absence of voids is inspected by applying radar technology. In this article, I would like to briefly introduce a technology for nondestructive testing of sectional damage, which is the most important indicator to assess the integrity of PS tendons. Underlying Concept of Nondestructive Testing Sensor Figure 2 shows the conceptual diagram of the developed electromagnetic sensor installed on the external PS tendon. Although the external PS tendon (the red-brown part in Figure 2) is actually paved with ducts and grouts, the magnetic properties of the duct and grout are almost the same as that of air (or vacuum). Therefore, it can be assumed that there is no magnetic property. The electromagnetic sensor is largely made up of three parts: the primary coil (yellow part in Figure 2), the secondary coil (orange part in Figure 2), and the fixing frame (purple part in Figure 2). The fixing frame is made of plastic that does not respond to magnetic fields. The primary coil is a kind of electromagnet that generates a magnetic field inside the sensor by flowing electricity, and the magnitude of the generated magnetic field is a function of the cross-sectional area of the external PS tendon, a metal component that penetrates the inside of the sensor. The secondary coil is wound to wrap the external PS tendon several times, and if the magnetic field inside the sensor is changed by varying the current applied to the primary coil, an induced current proportional to the magnetic field change is generated in the secondary coil. Using this principle, when AC electricity having a sine wave shape of constant amplitude is passed through the primary coil, AC electricity having an amplitude positively correlated with the cross-sectional area of the external PS tendon is induced in the secondary coil. Therefore, the cross-sectional area of the external PS tendon can be estimated by analyzing the amplitude of the induced AC electricity. The cross-sectional area of the metal component decreases when the external PS tendon is broken or rusted (iron oxide does not respond to a magnetic field). So, it is possible to estimate corrosion and break from the reduction in the cross-section. Development of Sensors Optimized for Field Work As can be seen from Figure 2, the sensor using this principle should have a closed circuit that wraps the external PS tendon. Tokyo-Rope of Japan and Instron of Russia, who were introduced earlier, also share the concepts and basic ideas mentioned above (of course, if you look at the details, they are quite different). However, Japanese and Russian technologies require winding work or equivalent work at the site, as shown in Figure 3, to make a closed circuit wrapping the external PS tendon, which takes a considerable amount of time. Consequently, workability is poor. In addition, since the sensor condition changes every time it is installed, the reliability of the sensor is lowered, and it is disadvantageous to work in the narrow passageway inside the bridge because all the sensor parts must be carried separately to be moved. On the other hand, the electromagnetic sensor developed by the KICT is divided into two, as shown in Figure 4, so with a little mastery, it can be installed within one to two minutes. Furthermore, it was ensured that the reliability of the sensor does not decrease, no matter how many times it is repeatedly installed, by composing the main junction with a highly reliable ready-made connector. The total weight is 5 kg and each side weighs about 2.5 kg, so it is not too heavy for a person to carry. If this sensor is installed as shown in Figure 5 and scanned at an appropriate speed along the external PS tendon, the change in the cross-sectional area can be inspected by performing a nondestructive test for the concerned section. Decision-making Technology Using Signal Processing and Artificial Intelligence Figure 6 shows the results applied to the specimens made to test the developed non-destructive equipment. The cross-sectional area simulating the damage as well as the damaged section are schematized at the top of the Figure. The result, measured by the same process as in Figure 5, is shown as the green line in Figure 6, but it is difficult to distinguish with the naked eyes because the amplitude change is insignificant. When the measured signal goes through several stages of signal processing, such as amplitude demodulation, to help assess the integrity of the external PS tendon using the measurements from the magnetic sensor, the result shown in the red line in Figure 6 can be obtained. In the red line, it can be seen that the change according to the damage to the PS tendon is clearly distinguished. However, a lot of experience is needed to distinguish whether these changes are caused by damage or noise. In addition, it is difficult to obtain information about the extent of the damage. To solve this problem, we developed an algorithm that uses a shallow FRP nerve sensor to specify the location of the damage, as shown in the blue dot in Figure 6, and predicts the ratio of the damage cross-section and even the length of the damage. Moreover, a number of specimens, as shown in Figure 7, were made and used to study artificial intelligence. Epilogue The KICT has developed a technology for nondestructive testing of the external PS tendon, a major element of the PSC structure, to prevent situations such as the Jeongneungcheon Viaduct that occurred in 2016 from being repeated. This technology uses the principle of nondestructive testing of the cross-sectional area made of metal with the application of electromagnetism and enables the repair and reinforcement of the PSC structure by detecting breaks and corrosion of the external PS tendon in advance. We not only developed sensors but also developed technology to help decision-making by improving the usability of sensors and applying signal processing and artificial intelligence to measured signals. The usability of the sensor is continuously improving through close communication with the companies currently in demand. Also, in the case of signal processing and artificial intelligence to help decision making, the algorithm is being enhanced and the accuracy is increased by adding learning data. We are also developing technology for the nondestructive testing of cables in cable bridges using the same principle. If the technology introduced here is completed and enters the bridge maintenance market, it will be possible to prevent huge economic losses through preemptive maintenance of bridges and to help avoid social losses caused by inconvenience to many people. Department of Structural Engineering Research Date2022-06-27 Hit 591
• [2015] Participation in international joint research (Horizon 2020) for field demonstration of geothermal power generation using original X-ray CT-based analysis technology Project Leader: Kim Kwang-yeom (Research Fellow, kimky@kict.re.kr) KICT was invited to be a research partner for ‘investigation of geothermal reservoir characteristics’ by the Helmholtz Centre Potsdam GFZ in Germany, the global leading research institute in deep geothermal development. KICT became the first Korean research institute to undertake an EU research project (Horizon 2020) with about USD 28.7 million budget. Horizon 2020 is the eighth stage of the EU R&D Framework Program and is also the largest international joint research program with a budget of 80 billion EU dollor from 2014 to 2020. The main objective of the project KICT involved is to secure key technologies and to verify them for commercialization of an enhanced geothermal system (EGS), a currently worldwide hot issue. Introduction of EGS As the development of new and renewable energy has become an urgent issue due to climate change and energy resource depletion, geothermal energy is becoming more important as a source of clean energy. Unlike other new and renewable energies, the deep geothermal energy is the only clean energy source that can collect sustainable energy very little constrained by external conditions such as time, space and weather. EGS is particularly a key issue worldwide, and there are active technology developments and investments to efficiently increase the economic factors and energy collection. ▲Conceptual diagram of EGS Research Background and Necessity KICT was invited to the Horizon 2020 project as the result of its participation in ‘geothermal power generation demonstration project’ and an ongoing EGS project in Pohang. The project has attracted worldwide attention because it involves Asia’s first construction of an EGS power plant. EGS power generation is the method of producing electricity using thermal energy stored 4~5km underground. Water is used to transport underground thermal energy to the ground, and an artificial reservoir should be created to enable water circulation. The reservoir creation is the key technology of geothermal power generation. KICT has been developed CT image processing algorithms to numerically analyze characteristics of materials especially construction materials based on an X-ray CT system. KICT recently developed a statistical algorithm that can investigate characteristics of microstructures that are not visible on CT images. This technology provides KICT the chance of invitation by GFZ to join the collaborative study on EGS development technologies. Using leading know-how and industrial X-ray CT based analysis, KICT plans to investigate the behavior of artificial reservoir generation, which is a key technology for EGS development. ▲X-ray CT system in KICT to be applied for geothermal study Utilization and Impact KICT is the first Korean government-funded research institute to be invited to the Horizon 2020 project, and the invitation is a result of KICT’s strong push to grow into a world-class institute (WCI) through international cooperation. KICT has been actively cooperating with GFZ of the Helmholtz Group in German which served as the coordinator of Horizon 2020 DESTRESS project. As a result, KICT was invited to participate in the DESTRESS project and to perform hydraulic stimulation experiments and analysis using X-ray CT. Participation in the Horizon 2020 project attended by major global institutes in geothermal power generation is an opportunity for KICT to apply its unique world-class technology in EGS sites in Korea and Europe. Moreover, the formation of a key international network is expected to increase the status of KICT in Korea and to establish the grounds for continuing international cooperation in the future. ▲Analysis of hydraulic fractures using X-ray CT Department of Geotechnical Engineering Research Date2016-03-01 Hit 1283
• [2014] Shield Tunnel Construction Technology Using Steel Strands Prestressing Force Project Leader : Ma Sang-joon (Research Fellow, sjma@kict.re.kr) ‘Shield tunnel construction technology using steel strand prestressing force’ makes it possible to safely and quickly complete tunnel construction by solving problems related to bolt assembly methods generally used for shield tunnel construction. KICT developed technology makes it possible for the first time in the world to increase clamping force using steel strand prestressing force when assembling segments in the process of shield tunnel construction. Unlike previous bolt assembly methods, the steel strand goes through seven segment rings interconnected as a net to increase structural stability. The technology also reduces overall construction costs for shield tunnels by reducing joint material costs and improving construction speed. Research Results In this study (compared to the previous bolt assembly method) the development of the segment assembly method uses a steel strand prestressing force resulted in a 10% improvement in clamping force, 2% reduction in entire construction costs for the shield tunnel and a 50% material cost reduction. Commercialization process was based on development technology transfers that provided results such as the registration and application of industrial property rights and revenue creation from engineering fees. • Completion of a technology transfer for steel strand assembly for shield tunnels (fixed engineering fee USD 9 thousand, ordinary engineering fee 2.5%, KCC Engineering & Construction Co., Ltd.) • 3 Korean registered research papers and 8 research papers in Korean journals • 1 Korean patent (a device and method for steel strand clamping required to assemble shield tunnel segments, No. 10-1333096) • 1 Korean patent (segment globe for shield tunnels with an island-typed shear key and longitudinal steel strands, No. 10-2014-0184314) • Manufacturing island-typed shear key segments and mold test product, design of a standard cross section for a shield tunnel made of steel strands, and a construction process design manual draft • Conducting international collaborative research for foreign commercialization (Shenzhen Metro and Huidong Design Center in China) Utilization and Impact The demand for underground space that can support effective land-use has resulted in the construction of underground tunnels for subways and roads. A construction method for shield tunnels can minimize construction-related pollution such as vibration and blasting noise and upper ground subsidence compared to previous construction methods such as the NATM tunnel construction method. Advanced European countries have used shield tunnel construction methods for more than 80% of tunnel construction. However, construction costs are high (compared to the previous tunnel construction methods) and such a method cannot be easily applied to a domestic environment with smaller budgets. This development technology is regarded as a construction technology that can improve shield tunnel construction ability and economic feasibility while effectively mitigating problems associated with previous methods of simultaneously assembling shield segments. It is possible to enhance the connectivity and safety of shield tunnels through the improvement of clamping force segments. The construction period can also be reduced by improving construction process precision and construction techniques. It is expected that the application of this development technology will further the application of a shield tunnel construction method with safety and economic feasibility advantages. ▲Clamped steel strand through 4 segments ▲Trial construction for field assembly of developed technology ▲3D modelling of the automatic supplying device for steel strands (interlocked with the shield machine) Department of Geotechnical Engineering Research Date2015-03-31 Hit 1372
• [2014 WBT] Safety-Secured NATM Tunnel Construction Technology [KICT 2014 World Best Technology] Project Leader : Kim Dong-gyou (Research fellow, dgkim2004@kict.re.kr) This technology enables the fast securing of tunnel structure stability and durable tunnel structures. The research objective was the development of high performance tunnel support at lower prices than current tunnel support that can activate opportunities in international markets and secure international technological competitiveness. The absence of safe domestic or international management technology for the construction of a standardized tunnel makes it imperative to develop a safe management system for tunnel construction engineering and provide technology leadership. The domestic standards for tunnel technology engineering and management technology are relatively weaker than general construction projects; therefore, the second objective is to develop technology that can predict tunnel construction hazards and secure a systematic construction management technology. Research Results This research develops advanced technology support for the safe construction required to blast and excavate tunnels as well as element technology to predict the degree of tunnel construction hazard; consequently, the commercialization process has been conducted through the site application of the development technology or technology transfer. Achievements such as revenue based on engineering fees from industrial patents and technology transfers are as follows. • Completion of the technology transfer for the high-performance shotcrete (fixed engineering fee USD 27 thousand, ordinary engineering fee 2%, SilkRoad TND Co., Ltd.) • Site application of high-performance shotcrete (application for 4 areas in the capital area high-speed railroad from Suseo to Pyeongtaek) • Completion of a technology transfer for a high-performance lattice girder support (fixed engineering fee USD 45 thousand, ordinary engineering fee 1%, Se-ahn Co., Ltd.) • Site application of the high-performance lattice girder support (application for Line 9 of the Seoul Subway - No. 918 area and No. 922 area) • Technology transfer and site application of the system for the management of the degree of tunnel construction hazard (fixed engineering fee USD 236 thousand, application for the Gwanak tunnel of the Gangnam Expressway) Utilization and Impact Technology development will enable advanced support to extend the lifespan of tunnels by 50% and help improve public living standards that could be affected by frequent maintenance, replacement costs and carbon dioxide emissions during the construction process. It is possible to obtain orders based on World Best Support Technology instead of obtaining orders based on simple construction technology in the global market. The new-concept safe construction management technology based on R&D will increase public recognition about the construction industry. The expected technological and social ripple effect based on new technology is as follows. • Creation of new industry demands related to new materials based on technology activation from new materials utilization • Carbon dioxide reductions from the use of recycled resources • Expansion into the global tunnel market based on securing high-performance support technology • Development and activation of new technology through the presentation of standard/specifications for advanced support • Protection of private property and lives through the minimization of tunnel construction related disasters and the development of fire response technology • Improvement of credit ratings through the minimization of public petitions related to tunnel construction • Inducement of safe construction through the prior identification of front geological harmful elements that result in tunnel construction collapses • Utilization of collected data and establishment of a database for the results analysis of perforations based on domestic geological conditions in regards to the construction of tunnels in similar geological conditions ▲Construction of high-performance shotcrete ▲Performance verification of high- performance shotcrete ▲High-performance lattice-girder ▲Field application of high-performance lattice-girder Department of Geotechnical Engineering Research Date2015-03-02 Hit 1378

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