• The Journal of Engineering Geology
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• v.29 no.3
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• pp.289-302
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• 2019

As the occurrence of ground subsidence near the excavation site increases recently, studies are being conducted to predict the possibility of ground subsidence prior to excavation. In this study, the ground subsidence risk rating for pre-excavation (GSRp) developed by the previous study was applied to actual excavation sites to verify its applicability. The final results for the evaluation of the ground subsidence risk level for five excavation sites revealed that GSRp scores were calculated between 40 and 79 points and classified mainly into grades II (Good Ground)~III (Fair Ground). In order to verify the evaluation method, the obtained GSRp grades were compared with the measured horizontal displacements. The horizontal displacements measured in five excavation sites were between 25% and 47% of the allowable displacement, which were well agreed with the low subsidence risk level obtained from GSRp calculation. It is expected that the GSRp method can be used as an evaluation tool for predicting the risk of ground subsidence before excavation if GSRp is verified and supplemented through the additional research for the poor soil with the high risk of ground subsidence.

• Journal of the Korean GEO-environmental Society
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• v.22 no.11
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• pp.23-29
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• 2021

Recently, ground subsidence has been steadily occurring mainly in downtown areas, threatening the safety of citizens. Under the road, various underground facilities such as water supply pipe, sewage pipe, and communication pipe are buried. Due to the aging of these underground facilities and the reckless development of the underground, it is acting as a cause of ground subsidence. Although there is a result of analyzing the risk of ground subsidence according to the deterioration of the existing pipeline, there is no result of analyzing the risk of ground subsidence using the density of pipelines indicating ground disturbance. Therefore, in this study, the density of the underground space was analyzed using the data of six types of representative underground pipelines in Seoul, and a study was conducted on whether there is a correlation with the ground subsidence. As a result, it was found that the density of underground facilities is high in the area where the ground subsidence occurred, indicating that the density of pipelines have an effect on the ground subsidence.

• Journal of the Korean GEO-environmental Society
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• v.23 no.8
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• pp.5-10
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• 2022

Ground Subsidence has been continuously occurring in densely populated downtown. The main cause of ground subsidence is the damaged underground facility like sewer. Currently, ground subsidence is being dealt with by discovering cavities in ground using GPR. However, this consumes large amount of manpower and cost, so it is necessary to predict hazardous area for efficient operation of GPR. In this study, ◯◯city is divided into 500 m×500 m grids. Then, data set was constructed using the characteristics of the underground facility and ground subsidence in grids. Data set used to machine learning model for ground subsidence risk grade prediction. The purposed model would be used to present a ground subsidence risk map of target area.

• Progress in Superconductivity and Cryogenics
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• v.11 no.1
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• pp.49-54
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• 2009

This paper presents the numerical simulation results on the moving type electrodynamic suspension (EDS) simulator and static type EDS simulator using high-Tc superconducting (HTS) levitation magnet. The levitation force of the EDS system is formed by the reaction between the moving magnet and the fixed ground conductor. The possible two ways to simulate the EDS system were simulated in this paper by using finite element method (FEM). The first way was the moving type simulator which consists of the fixed HTS magnet and the moving ground conductor. The second way was the static type simulator which consists of the fixed magnet, the fixed ground conductor and the ac current supply system. To verify the characteristics of high speed EDS system with the moving type simulator heavy, large and fast moving ground conductor is needed. The static type simulator can get the characteristics of the high speed EDS system by applying equivalent ac current to velocity, therefore it does not need large moving part. The static type EDS simulator, which can consist of an HTS magnet, the fixed ground conductor(s), an AC power supply and the measuring devices, also test the effect of the shape of the ground conductor easily. The plate type ground conductor made stronger levitation force than ring type ground conductor. Although the outer diameter 335 mm ring type ground conductor (Ring3) was larger than the outer diameter 235 mm ground conductor (Ring2), the levitation force by Ring2 was stronger than that by Ring3. From the calculation results on this paper, the consideration of the magnetic flux distribution according to the levitation height should be included in the process of the ground conductor design.

• Journal of Korean Tunnelling and Underground Space Association
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• v.25 no.2
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• pp.87-99
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• 2023

Ground excavation inevitably causes ground displacement of adjacent ground, and structures and facilities exposed to ground displacement may suffer various damages. Therefore, in order to minimize the damage and damage to adjacent structures and facilities caused by excavation, ground displacement (settlement and horizontal displacement) in the adjacent ground caused by excavation must first be predicted. There is many ground displacement information induced by general braced cut excavation, but the information is not enough for circular shaft excavation. This study aims to provide information on the estimation of ground settlement caused by circular shaft excavation through the case analysis of circular shafts and comparison with braced cut excavation. From this study, it was found that the use of the settlement criterion of braced cut excavation as the settlement management criterion for circular shaft excavation is a conservative approach in terms of safety. But when considering the economic aspect, it may result in overdesign of the wall and therefore, a more reasonable settlement criterion can be needed for circular shaft excavation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1C
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• pp.53-61
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• 2006

This study is aimed at to examine the stress redistribution mechanism for tunneling in an unconsolidated ground with inclined layers through model tests. To make the unconsolidated ground, two dimensional model ground is prepared with aluminum rods and blocks, which are frictional resistance free between testing apparatus walls and ground materials, by establishing the ground materials self-supporting. It is carried out to measure the ground deformation and the stress redistribution for model ground with tunneling by measuring apparatus respectively. For the ground deformation, surface settlements are measured to examine the deformation features during tunnel excavation. For the stress redistribution, the earth pressure acting on both the tunneling part and its surrounding parts is measured to examine their mutual relationship. Based on test results, precise examination is conducted on the stress redistribution mechanism in the unconsolidated ground with inclined layers during tunnel construction.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2007.11a
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• pp.231-234
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• 2007

This paper presents an analysis method of transient ground impedance using the lightning impulse and variable frequency currents. The transient ground impedance strongly depends on the configuration and size of grounding electrodes and the shapes of impulse currents, and the inductance of grounding electrodes has a significant affect on the transient impedance of the grounding system. There are some differences between the effective impulse ground impedance which was introduced some papers and the transient ground impedance. The transient ground impedance measured from the peak value of impulse voltage and the peak value of impulse current is more reliable than the effective impulse ground impedance.

• 한국방재학회:학술대회논문집
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• 2007.02a
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• pp.433-436
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• 2007

We analyzed the sloped ground safety factor, which is not presented in the design specification, using a computational analysis program L-Pile Plus 13.8. To achieve this we chose a required parameter set and a level ground safety factor presented in the design specification, and then determined its values comparing with the change of the safety factor according to the parameter. Using these parameters, we estimated the sloped ground safety factor for the slope of 35 degrees considering the improvement value of the slope presented in the design specification. As a result of this analysis, we obtained the smaller safety factor by about 0.7 times than the case of the level ground and verified that a number of concrete poles fail to assure 1 degree of the safety factor. We, therefore, concluded that an adjustment of the embedment depth is required in the case of the sloped ground.

• Korean Journal of Applied Biomechanics
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• v.12 no.1
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• pp.115-124
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• 2002

The purpose of this study is to analyze the ground reaction force of arm landing on arm and leg during sports aerobics. Subjects of this study were total 10 players of 5 males and 5 females who have are domain sports aerobics medalists more than the third place in national tournaments. The subjects jumped between the two ground reaction force analyzers, while landing their right hand on the front platform(#1) and their right leg on the rear platform(#2), and the data frequency was set to 200Hz. Findings of this study are as follows; More than 3 times of impact peak force of vertical reaction force acted on arm joint than on leg joint. And, when ground reaction force on foot increased, ground reaction force on hand decreased. 3 impact peaks of curve of ground reaction force were found - Impact Peak 1 incurred on the time the palm lands on the ground, Impact Peak 2 absorbing shock secondarily on wrist joint, and Active Peak incurred on the time of holding the weight while pushing out the severly bent elbow joint.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.45-56
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• 1999

There have been many coal mines abandoned since late 1980s in Korea. Due to the abandoned mines, there have been ground subsidences in some area where are under ground reinforcement works now. So, this study shows the general phenomena of mining subsidence and the procedure of ground reinforcement. In general the procedure for ground reinforcement is as below, 1) obtaining information from inquiries and observations, 2) satellite image analysis and surface geological mapping, 3) analysis of maps of coal mines, 4) geophysical survey and boring test and 5) selection of reinforcement method. The case of reinforcement design at Chul-am area, Kangwon Province is introduced in this article.