• Proceedings of the Korean Geotechical Society Conference
• /
• 2006.03a
• /
• pp.1100-1109
• /
• 2006

In this study, two different technologies which can measure temperature simultaneously at many points are introduced. One is to use a thermal sensor cable that is comprised of addressable thermal sensors connected in parallel within a single cable. The other is to use an optic fiber with Distributed Temperature Sensing (DTS) system. The difference between two technologies can be summarized as follows. A thermal sensor cable has a concept of 'point sensing' that can measure temperature at accurate position of a thermal sensor. So the accuracy and resolution of temperature measurement are up to the ability of the thermal sensor. Whereas optic fiber sensor has a concept of 'distributed sensing' because temperature is measured by ratio of Stokes and anti-Stokes component intensities of Raman backscatter that is generated when laser pulse travels along an optic fiber. It's resolution is determined by measuring distance, measuring time and spatial resolution. The purpose of this study is that application targets of two temperature measurement techniques are checked in technical and economical phases by examining the strength and weakness of them. Considering the functions and characteristics of two techniques, the thermal sensor cable will be suitable to apply to the assessment of groundwater flow, geothermal distribution and grouting efficiency within 300m distance. It is expected that the optic fiber sensor can be widely utilized at various fields (for example: pipe line inspection, tunnel fire detection, power line monitoring etc.) which need an information of temperature distribution over relatively long distance.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.21 no.6
• /
• pp.607-613
• /
• 2008

A monitoring system for the subway structures using prestrained FBG sensors fixed with partially stripped fibers was developed. The sensor packages had pre-strain controllable fixtures. Tensile and compressive strain of the structure could be measured without slip. The FBG sensor system was applied to the concrete lining structure in Taegu subway. Near the structure, the narrow tunnel construction, for the electric power cables and telecommunication cables, started. We wanted to measure the deformations of the subway structures due to the construction by the FBG sensor. The applied sensors had the gauge length of 1 meter to overcome the inhomogeneity of the concrete material with enough length. In order to fix tightly to the structure, the partially stripped parts of the sensor glued to the package and slip phenomenon between fiber and acrylate jacket was prevented. Prestrain of the sensor was imposed by controlling the two fixed points with bolts and nuts in order to measure compressive strain as well as tensile strain. The behavior of subway lining structure could be monitored very well.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2009.09a
• /
• pp.117-129
• /
• 2009

This paper studied the safety management network system of infrastructure which constructed smart sensors, closed-circuit television(CCTV) and monitoring system. This safety management of infrastructure applied to bridge, cut slop and tunnel, embankment etc. The system applied to technologies of standardization guidelines, data acquirement technologies, data analysis and judgment technologies, system integration setup technology, and IT technologies. It was constructed safety management network system of various infrastructure to improve efficient management and operation for many infrastructure. Integrated safety management network system of infrastructure consisted of the real-time structural health monitoring system of each infrastructure, integrated control center, measured data transmission using i of tet web-based, collecting data using sf ver, early alarm system which the dangerous event of infrastructure occurred. Integrated control center consisted of conference room, control room to manage and analysis the data, server room to present the measured data and to collect the raw data. Early alarm system proposed realization of warning and response within 5 minute or less through development of sensor-based progress report and propagation automation system using the media such as MMS, VMS, EMS, FMS, SMS and web services of report and propagation. Based on this, the most effective u-Infrastructure Safety Management System is expected to be stably established at a less cost, thus making people's life more comfortable. Information obtained from such systems could be useful for maintenance or structural safety evaluation of existing structures, rapid evaluation of conditions of damaged structures after an earthquake, estimation of residual life of structures, repair and retrofitting of structures, maintenance, management or rehabilitation of historical structures.

• Tunnel and Underground Space
• /
• v.21 no.1
• /
• pp.20-32
• /
• 2011

Failure aspects of cut-slope, which induce the sequential collapses during the excavation stage, have been analyzed. Slope rock structures are investigated by examining the orientations and positions of discontinuity planes calculated based on the BIPS image inside the boreholes. Drilled core log has been also used to identify the structural defects. Clay minerals of swelling potentials are detected through XRD analysis. Numerical analysis for slope stability has been performed by utilizing the joint shear strength acquired from the direct joint shear test. Cut-slope collapse characteristics have been studied by investigating the posture of failure-prawn joint planes and the stability of tetrahedral blocks of different sizes. Cross-section analysis has been also performed to analyze the cut-slope behavior and to estimate the amount of reinforcement required to secure the stability of cut-slope. Behavior of reinforced cut-slope is also investigated by analyzing the slope monitoring data.

• Tunnel and Underground Space
• /
• v.34 no.4
• /
• pp.267-282
• /
• 2024

This study aims to develop a wireless communication system for long-term monitoring of high-level radioactive waste disposal facilities. Conventional wired sensors can lead to a deterioration in buffer quality and management difficulties due to the use of cables for power supply and data transmission. This study proposes the adoption of a wireless communication system and compares the received signal strengths within bentonite using modules such as WiFi, ZigBee, and LoRa. Increases in dry density of bentonite and distance between transceivers led to reduced received signal strength. Additionally, using the low-frequency band exhibited less signal attenuation. Based on these findings, a conceptual design for a wireless network-based THM integrated sensor system was proposed. Results of this study can be used as foundational data for long-term monitoring of disposal facility.

• Tunnel and Underground Space
• /
• v.28 no.3
• /
• pp.209-231
• /
• 2018

Severe mine disasters have continued to occur around the world. To ensure worker's health and safety and enhance the productivity, a number of studies have been conducted for the development of wireless sensor network (WSN), environmental monitoring, and communication system in underground mines. An increase in development and application of these systems has just begun with the introduction of information and communication technology into the mining industry in Korea, and yet there have been only a few studies that considered the underground mine ventilation system. This study presented the literature review on the development of WSN and environmental monitoring in underground mines, and especially, on 7 subjects in terms of underground mine ventilation. Moreover, studies that especially conducted real-time environmental monitoring were reviewed and categorized by each commercial software commonly utilized for the ventilation network analysis. For the application in domestic underground mines, further issues were discussed regarding research subjects that may be needed in the future and domestic environmental standards that has been used in the underground mine operation. This paper is expected to be useful for the development of WSN-based environmental monitoring and communication system, as well as for related studies in the future.

• Journal of Korean Society for Atmospheric Environment
• /
• v.30 no.3
• /
• pp.233-244
• /
• 2014

The objective of this study was to explore the characteristics of concentration of indoor air pollutants, such as $PM_{10}$, $CO_2$, and $NO_2$, measured by tele-monitoring system in a Seoul Metropolitan underground railway station from January 1, 2008 to December 31, 2012. The annual average concentration of indoor air pollutants actually varied over a wide range and was found to exhibit marked variation with time and measurement sites (tunnel inlet, platform, and concourse). After installing platform screen doors, the average $PM_{10}$ concentration on platform and concourse was decreased by 43.8% and 31.2%, respectively during the study periods. The relationship between the concentration of $PM_{10}$ and meteorological parameters (relative humidity and rainfall) or the Asian dust events was regarded as statistically significant. The correlations between the number of boarding/alighting passengers and $PM_{10}$, $CO_2$, and $NO_2$ were calculated. A p-value of less than 0.01 was regarded as significant except $NO_2$. The I/O ratio of $PM_{10}$ concentration was elevated after a congested time (about 08:00 am). The average I/O ratios of $NO_2$ were observed in concourse and platform on 03:00 am with $1.76{\pm}0.91$ and $1.50{\pm}0.51$, respectively. The average daily variation of standard excess rate of $PM_{10}$ and $NO_2$ concentration in concourse and platform was investigated. The highest standard excess rate was observed on 21:00 (09:00 pm).

• Journal of the Korean Geotechnical Society
• /
• v.22 no.8
• /
• pp.107-118
• /
• 2006

Among a variety of influencing components, time-variant seepage and long-term underground motion are important to understand the abnormal behavior of tunnels. Excessiveness of these two components could be the direct cause of severe damage on tunnels, however, it is not easy to quantify the effect of these on the behavior of tunnels. These parameters can be estimated by using inverse methods once the appropriate relationship between inputs and results is clarified. Various inverse methods or parameter estimation techniques such as artificial neural network and least square method can be used depending on the characteristics of given problems. Numerical analyses, experiments, or monitoring results are frequently used to prepare a set of inputs and results to establish the back analysis models. In this study, a back analysis method has been developed to estimate geotechnically hard-to-known parameters such as permeability of tunnel filter, underground water table, long-term rock mass load, size of damaged zone associated with seepage and long-term underground motion. The artificial neural network technique is adopted and the numerical models developed in the first part are used to prepare a set of data for learning process. Tunnel behavior, especially the displacements of the lining, has been exclusively investigated for the back analysis.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.24 no.3
• /
• pp.27-34
• /
• 2024

The direct and indirect damages caused by fires in underground utility tunnels have a great impact on society as a whole, so efforts are needed to prevent and manage them in advance. To this end, research is ongoing to prevent disasters such as fire flooding by applying digital twin technology to underground utility tunnels. A network is required to transmit the sensed signals from each sensor to the platform. In essence, it is necessary to analyze the application of wireless networks in the underground utility tunnel environments because the tunnel lacks the reception range of external wireless communication systems. Within the underground utility tunnels, electromagnetic interference caused by transmission and distribution cables, and diffuse reflection of signals from internal structures, obstacles, and metallic pipes such as water pipes can cause distortion or size reduction of wireless signals. To ensure real-time connectivity for remote surveillance and monitoring tasks through sensing, it is necessary to measure and analyze the wireless coverage in underground utility tunnels. Therefore, in order to build a wireless network environment in the underground utility tunnels. this study minimized the shaded area and measured the actual cavity environment so that there is no problem in connecting to the wireless environment inside the underground utility tunnels. We analyzed the data transmission rate, signal strength, and signal-to-noise ratio for each section of the terrain of the underground utility tunnels. The obtained results provide an appropriate wireless planning approach for installing wireless networks in underground utility tunnels.

• Tunnel and Underground Space
• /
• v.8 no.1
• /
• pp.37-45
• /
• 1998

In this study, two dimensional and three dimensional numerical analysis were performed with a finite difference code for the safe maintenance of the spillway slope of the Boryeong dam. Results of the geological survey and the stereographic projection analysis on the discontinuities were used as input data for the numerical analysis. As a result, several suggestions were given such as the reinforcement of the local tension zone, the decrease in the angle of the slope, the drawdown of the pore pressure in the slope and the removal of the upper benches. A systematic and long-term monitoring system was also suggested.