• Journal of Korean Society for Geospatial Information Science
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• v.25 no.2
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• pp.67-74
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• 2017

The D-InSAR is a technique for precisely measuring the subsidence of subsidence using difference of two SAR images. In order to calculate the subsidence using D-InSAR, a high coherence between master image and the slave image is essential. Since the existing D-InSAR method calculates the displacement based on the total coherence, the accuracy of the subsidence is lowered when the coherence map contains mountains or bare-land. In order to solve this problem, in this study, a point having a temporal coherence and spatial coherence of 0.7 or more was extracted to form TIN, and the subsidence was calculated based on this TIN. In addition, we compared the existing D-InSAR technique with the new D-InSAR technique considering spatial and temporal coherence. As a result, the new D-InSAR technique showed smaller standard deviation, relative variance, variation coefficient and quadrature deviation than the existing D-InSAR technique. It is also easy to grasp the trend of the subsidence.

• Korean Journal of Remote Sensing
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• v.34 no.6_4
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• pp.1545-1553
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• 2018

Recent eruptive activity at Kīlauea Volcano started on at the end of April in 2018 showed rapid ground deflation between May and June in 2018. On summit area Halema'uma'u lava lake continued to drop at high speed and Kīlauea's summit continued to deflate. GPS receivers and electronic tiltmeters detected the surface deformation greater than 2 meters. We explored the time-series surface deformation at Kīlauea Volcano, focusing on the early stage of eruptive activity, using multi-temporal COSMO-SkyMed SAR imagery. The observed maximum deformation in line-of-sight (LOS) direction was about -1.5 meter, and it indicates approximately -1.9 meter in subsiding direction by applying incidence angle. The results showed that summit began to deflate just after the event started and most of deformation occurred between early May and the end of June. Moreover, we confirmed that summit's deflation rarely happened since July 2018, which means volcanic activity entered a stable stage. The best-fit magma source model based on time-series surface deformation demonstrated that magma chambers were lying at depths between 2-3 km, and it showed a deepening trend in time. Along with the change of source depth, the center of each magma model moved toward the southwest according to the time. These results have a potential risk of including bias coming from single track observation. Therefore, to complement the initial results, we need to generate precise magma source model based on three-dimensional measurements in further research.

• Korean Journal of Remote Sensing
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• v.35 no.6_3
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• pp.1235-1249
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• 2019

Kilauea Volcano is one of the most active volcano in the world. In this study, we used the ALOS-2 PALSAR-2 satellite imagery to measure the surface deformation occurring near the summit of the Kilauea volcano from 2015 to 2017. In order to measure two-dimensional surface deformation, interferometric synthetic aperture radar (InSAR) and multiple aperture SAR interferometry (MAI) methods were performed using two interferometric pairs. To improve the precision of 2D measurement, we compared root-mean-squared deviation (RMSD) of the difference of measurement value as we change the effective antenna length and normalized squint value, which are factors that can affect the measurement performance of the MAI method. Through the compare, the values of the factors, which can measure deformation most precisely, were selected. After select optimal values of the factors, the RMSD values of the difference of the MAI measurement were decreased from 4.07 cm to 2.05 cm. In each interferograms, the maximum deformation in line-of-sight direction is -28.6 cm and -27.3 cm, respectively, and the maximum deformation in the along-track direction is 20.2 cm and 20.8 cm, in the opposite direction is -24.9 cm and -24.3 cm, respectively. After stacking the two interferograms, two-dimensional surface deformation mapping was performed, and a maximum surface deformation of approximately 30.4 cm was measured in the northwest direction. In addition, large deformation of more than 20 cm were measured in all directions. The measurement results show that the risk of eruption activity is increasing in Kilauea Volcano. The measurements of the surface deformation of Kilauea volcano from 2015 to 2017 are expected to be helpful for the study of the eruption activity of Kilauea volcano in the future.

• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.6
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• pp.507-520
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• 2014

In this study, the surface displacement was investigated according to the various depth of cover when the tunnel excavation equipment was used in a clay soil. For this the laboratory scaled model test was carried out using the soil sample similar to the in-situ conditions. We carried out four tests according to tunnel depth(1.5D, 2.0D, 2.5D, 3.0D). The distribution of impact due to tunnelling was quantitatively analyzed in the three-dimension by measuring the surface displacement. In addition, the pattern of surface displacements was figured out.

• 한국방재학회:학술대회논문집
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• 2010.02a
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• pp.33.2-33.2
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• 2010

고층건물의 최상층 수평변위는 해당 건물의 안전성 및 사용성 평가에 중요한 지표가 된다 이러한 건물의 수평변위는 주로 풍하중에 기인한다 본 논문에서는 이러한 구조반응을 풍하중에 기인한 풍속데이터로부터 직접 추정하기 위해서 인공신경망(Artificial Neural Network, ANN)을 도입하였다 이에 대한 적용성을 판단하기 위해서 고층건물을 형상화한 모형테스트를 실시하고 풍향, 풍속, 변위 값을 얻었다. 이후 인공신경망에 적용시켜 실제 실험 데이터와의 비교를 통해 타당성을 검토하였다.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.04a
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• pp.303-306
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• 2002

변위가 발생한 해안도로 옹벽에 대한 원인을 규명하기 위하여 기반암과 매립부 지반에 대한 조사를 실시하였다. 연구지역에서 지질구조선의 발달은 관찰되지 않고 지표에서 기반암의 거동은 낙석의 형태로 나타난다. 기반암은 생교란작용의 유무에 따라 상, 하부지층이 구분되며 하부 지층은 신선한 상태로 이완된 불연속면은 나타나지 않는다. 변위는 옹벽의 이음부에 집중되며 옹벽의 운동방향은 우향이동과 좌향이동이 반복되며 최초 변위 발생지점 (시 점부)에서 멀어짐에 따라 장력에 의한 확장 (벌어짐)이 우세하며 종점부에서 회전운동이 수반된다. 이음부의 확장과 회전은 최초 발생 지점에서 응력이 전달되는 과정에서 나타난 것으로 해석된다. 매립부 지반의 전기비저항탐사에서 상부의 매립층은 높은 전기비저항을 가지는 것에 반해 하부는 매우 낮은 전기비저항 값을 보여준다. 이는 매립부의 하부지반이 해수면 이하에 위치하여 해수와 같은 유체의 영향을 받으나, 상부는 유체의 영향을 거의 받지 않는 것으로 추정된다. 반면 최초 변위가 발생한 지점의 매립부 지반은 하부와 같이 낮은 전기비저항 값을 보여준다. GPR 탐사에서 최초 변위 발생 지점에서 매질의 이완 내지 공동으로 추정되는 구조가 관찰된다.

• Journal of Korean Tunnelling and Underground Space Association
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• v.8 no.4
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• pp.289-305
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• 2006

This paper presents the effect of excavating methods on tunnel behavior. As part of this study, it is preliminarily focused on the comparison of two different excavation methods, center diaphram (CD) method and ringcut (RC) method. Especially, the purpose of this research is to study the behavioral mechanism of two tunnels which share the same construction environment but different excavating method. Two numerical analysis models with the same tunnel section and material properties are compared in this study, and they are analyzed by 3D finite element analysis. In each model, face stability, crown displacement, ground settlement, and shotcrete-lining stress are computed, then the general behavior of CD method and RC method is studied. The results indicate that the CD method tends to be effective in controlling tunnel displacement while the RC method is more effective in controlling ground settlement. Design implications of the findings from this study are discussed.

• Korean Journal of Remote Sensing
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• v.26 no.2
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• pp.143-151
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• 2010

We carried out studies on InSAR techniques for time-series deformation monitoring using multi-temporal SAR. The PSInSAR method using permanent scatterer is much more complicate than the SBAS because it includes many non-linear equation due to the input of wrapped phase. It is conformed the PS algorithm is very sensitive to even PSC selection. On the other hand, the SBAS method using interferogram of small baseline subset is simple but sensitive to the accuracy of unwrapped phase. The SBAS is better method for expecting not significant unwrapping error while PSInSAR is more proper method for expecting local deformation within very limited area. We used 51 ERS-1/2 SAR data during 1992-2000 over Las Vegas, USA for the comparison between PSInSAR and SBAS. Both PSInSAR and SBAS show similar ground deformation value although local deformation seems to be detected in the PSInSAR method only.

• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.4
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• pp.373-386
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• 2014

This paper concerns the deformation behavior of tunnels crossing weak zone during excavation. A three dimensional finite element model was adopted in order to conduct a parametric study on the orientation of weaj zone in terms of strike and dip angle relative to the tunnel longitudinal axis. The results of the analyses were then analyzed so that the tunnel displacements in terms of the ratios between the crown settlement and springline displacement can be related to the orientation of the weak zone. The results indicate that the displacement ratios between the tunnel crown and springline tend to quantitatively change when a weak zone exists near or ahead of the tunnel suggesting that the displacement ratios can be effectively used to predict the weak zone during tunnelling. Practical implications of the findings are discussed.

• Disaster Prevention Review
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• v.20 no.1
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• pp.28-34
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• 2018