• Geomechanics and Engineering
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• 제13권6호
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• pp.893-906
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• 2017

Automatic large scale soil model generation is very critical stage for earthquake hazard simulation of urban areas. Manual model development may cause some data losses and may not be effective when there are too many data from different soil observations in a wide area. Geographic information systems (GIS) for storing and analyzing spatial data help scientists to generate better models automatically. Although the original soil observations were limited to soil profile data, the recent developments in mapping technology, interpolation methods, and remote sensing have provided advanced soil model developments. Together with advanced computational technology, it is possible to handle much larger volumes of data. The scientists may solve difficult problems of describing the spatial variation of soil. In this study, an algorithm is proposed for automatic three dimensional soil and velocity model development of southern part of the European side of Istanbul next to Sea of Marmara based on GIS data. In the proposed algorithm, firstly bedrock surface is generated from integration of geological and geophysical measurements. Then, layer surface contacts are integrated with data gathered in vertical borings, and interpolations are interpreted on sections between the borings automatically. Three dimensional underground geology model is prepared using boring data, geologic cross sections and formation base contours drawn in the light of these data. During the preparation of the model, classification studies are made based on formation models. Then, 3D velocity models are developed by using geophysical measurements such as refraction-microtremor, array microtremor and PS logging. The soil and velocity models are integrated and final soil model is obtained. All stages of this algorithm are carried out automatically in the selected urban area. The system directly reads the GIS soil data in the selected part of urban area and 3D soil model is automatically developed for large scale earthquake hazard simulation studies.

• Nuclear Engineering and Technology
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• 제54권11호
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• pp.4253-4264
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• 2022

Since the implementation of the phosphate project in Bled El-Hadba (BEH) deposit, western region of Tébessa, no detailed study has been conducted to assess the natural radioactivity distribution and the associated radiological risk parameter for this open-pit mine. For the sake of determining a credible premining reference database for the region of interest, 21 samples were collected from different geological layers of the above-mentioned deposit. Gamma Spectrometry was applied for measuring radioactivity using a high resolution HPGe semiconductor detector. The obtained activity results have shown a significant broad variation in the radioactive contents for the different phosphate samples. The total average concentrations (in Bq·kg^-1) for ²²⁶Ra, ²³⁸U, ²³⁵U, ²³²Th and ⁴⁰K computed for the different type of phosphate layers were found to be 570 ± 169, 788 ± 280, 52 ± 18, 66 ± 6 and 81 ± 18 respectively. The mean activity concentrations of the measured radionuclides were compared to other regional and worldwide deposits. The ratios between the detected radioisotopes have been calculated for spatial distribution of natural radionuclides in the study area. Based on the aforementioned activity concentrations, the corresponding radiation hazard parameters were assessed. Correlations between the obtained parameters were drawn and a multivariate statistical analysis (Pearson Correlation, Cluster and Factor analysis) was carried out in order to identify the existing relationships.

• Geomechanics and Engineering
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• 제13권4호
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• pp.671-683
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• 2017

Groundwater control is a significant issue in most underground construction. An estimate of the inflow rate is required to size the pumping system, and treatment plant facilities for construction planning and cost assessment. An estimate of the excavation-induced drawdown of the initial groundwater level is required to evaluate potential environmental impacts. Analytical and empirical methods used in current engineering practice do not adequately account for the effect of the jointed-rock-mass anisotropy and heterogeneity. The impact of geostructural anisotropy of fractured rocks on tunnel inflows is addressed and the limitations of analytical solutions assuming isotropic hydraulic conductivity are discussed. In this paper the unexcavated Zagros tunnel route has been classified from groundwater flow point of view based on the combination of observed water inflow and numerical modeling results. Results show that, in this hard rock tunnel, flow usually concentrates in some areas, and much of the tunnel is dry. So the remaining unexcavated Zagros tunnel route has been categorized into three categories including high Risk, moderately risk and low risk. Results show that around 60 m of tunnel (3%) length can conduit the large amount of water into tunnel and categorized into high risk zone and about 45% of tunnel route has moderately risk. The reason is that, in this tunnel, most of the water flows in rock fractures and fractures typically occur in a clustered pattern rather than in a regular or random pattern.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2005년도 제7회 특별심포지움 논문집
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• pp.43-54
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• 2005

시추공을 이용하여 P파 S파의 속도검층 수행시 여러 고려해야 할 사항이 있다. 토양이나 풍화암등 연약층에 설치한 케이싱이 탄성파 측정에 미치는 영향, 사용되는 주파수에 따라 측정되는 탄성파 속도의 변화 등이 있다. 이러한 과제를 극복하기 위해서는 탄성파시험이 설정된 시추공에서는 가급적 케이싱을 설치하지 않고 공벽을 유지하는 시추 기술을 개발, 적용하도록 하고, 속도검층의 목적에 맞는 주파수 대역의 시험법을 적용하도록 해야 하겠다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2004년도 Proceedings of ISRS 2004
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• pp.314-317
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• 2004

The aim of this study was to evaluate the susceptibility from landslides in the Lai Chau region of Vietnam, using Geographic Information System (GIS) and remote sensing data, focusing on the relationship between tectonic fractures and landslides. Landslide locations were identified from an interpretation of aerial photographs and field surveys. Topographic and geological data and satellite images were collected, processed, and constructed into a spatial database using GIS data and image processing techniques, and a scheme of the tectonic fracturing of the crust in the Lai Chau region was established. In this scheme, Lai Chau was identified as a region with low crustal fractures, with the grade of tectonic fracture having a close relationship with landslide occurrence. The factors found to influence landslide occurrence were: topographic slope, topographic aspect, topographic curvature, distance from drainage, lithology, distance from a tectonic fracture and land cover. Landslide prone areas were analyzed and mapped using the landslide occurrence factors employing the probability-likelihood ratio method. The results of the analysis were verified using landslide location data, and these showed a satisfactory agreement between the hazard map and existing landslide location data.

• 한국GIS학회:학술대회논문집
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• 한국GIS학회 2003년도 공동 춘계학술대회 논문집
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• pp.65-70
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• 2003

The weight-of-evidence model one of the Bayesian probability model was applied to the task of evaluating landslide susceptibility using GIS. Using the location of the landslides and spatial database such as topography, soil, forest, geology, land use and lineament, the weight-of-evidence model was applied to calculate each factor's rating at Boun area in Korea where suffered substantial landslide damage fellowing heavy rain in 1998, The factors are slope, aspect and curvature from the topographic database, soil texture, soil material, soil drainage, soil effective thickness, and topographic type from the soil database, forest type, timber diameter, timber age and forest density from the forest map, lithology from the geological database, land use from Landsat TM satellite image and lineament from IRS satellite image. Tests of conditional independence were performed for the selection of the factors, allowing the 43 combinations of factors to be analyzed. For the analysis, the contrast value, W$\^$＋/and W$\^$-/, as each factor's rating, were overlaid to map laudslide susceptibility. The results of the analysis were validated using the observed landslide locations, and among the combinations, the combination of slope, curvature, topographic, timber diameter, geology and lineament show the best results. The results can be used for hazard prevention and planning land use and construction

• 한국환경과학회지
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• 제25권12호
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• pp.1653-1660
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• 2016

Drought is a reoccurring worldwide natural hazard that affects not only food production but also economics, health, and infrastructure. Drought monitoring is usually performed with precipitation-based indices without consideration of the actual state and amount of the land surface properties. A drought index based on the actual evapotranspiration can overcome these shortcomings. The severity of a drought can be quantified by making a spatial map. The procedure for estimating actual evapotranspiration is costly and complicated, and requires land surface information. The possibility of utilizing drone-driven remotely sensed data for actual evapotranspiration estimation was analyzed in this study. A drone collected data was used to calculate the normalized difference vegetation index (NDVI) and soil-adjusted vegetation index (SAVI). The spatial resolution was 10 m with a grid of $404{\times}395$. The collected data were applied and parameterized to an actual evapotranspiration estimation. The result shows that drone-based data is useful for estimating actual evapotranspiration and the corresponding drought indices.

• Earthquakes and Structures
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• 제25권2호
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• pp.135-148
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• 2023

The structure-soil-structure interaction (SSSI) effect in adjacent structures may affect the liquefaction-induced damage of shallow foundation structures. The existing studies only analysed the independent effects on the structural dynamic response but ignored the coupling effect of height difference and distance of adjacent structures (F) on liquefied foundations on the dynamic response. Therefore, this paper adopts finite element and finite difference coupled dynamic analysis method to discuss the effect of the F on the seismic response of shallow foundation structures. The results show that the effect of the short structure on the acceleration response of the tall structure can be neglected as F increases when the height difference reaches 2 times the height of the short structure. The beneficial effect of SSSI on short structures is weakened under strong seismic excitations, and the effect of the increase of F on the settlement ratio gradually decreases, which causes a larger rotation hazard. When the distance is smaller than the foundation width, the short structure will exceed the rotation critical value and cause structural damage. When the distance is larger than the foundation width, the rotation angle is within the safe range (0.02 rad).

• 한국지리정보학회지
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• 제15권2호
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• pp.57-70
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• 2012

본 연구에서는 지리정보시스템(GIS)을 기반으로 확률강우량과 인공신경망을 적용하여 2006년 태풍 에위니아에 의하여 발생한 강원도 인제 덕적리 지역의 산사태 취약성도 및 미래 위험도를 작성 및 검증하고자 한다. 산사태 취약성 및 위험도와 관련된 요인으로는 지질, 지형도(경사, 경사방향, 곡률도), 토양도(토양 지형, 토질, 토양 배수, 토양 모재 및 유효토심), 임상도(영급, 경급, 소밀도 및 수종) 등을 GIS 기반의 공간 데이터베이스로 구축하였다. 전체 산사태 발생 위치는 694개소이며 이중 50%는 인공신경망의 산사태 발생 지역으로 적용하였으며, 나머지 50%는 취약성도 및 위험도 검증에 활용하였다. 산사태 발생 강우량 임계치는 1일 202mm 및 3일 누적 449mm로 적용하였다. 확률강우량은 1973년부터 2006년까지의 실측 강우량을 정리하여 2106년까지 목표연도별(1년, 3년, 10년, 50년 및 100년) 산사태 취약성도를 작성하였다. 연구결과 연구지역은 강우량의 증가에 의하여 미래 산사태 가능성이 지속적으로 증가하였다. 향후 본 연구는 강우량의 변화에 의한 산사태 위험성 분석에 한 축을 차지 할 수 있다는 점에서 중요성이 있다고 하겠다.

• 지질공학
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• 제26권3호
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• pp.413-422
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• 2016

인구밀도와 기간산업 개발이 급속하게 증가함에 따라 도시지역에서 산사태로 인한 인명손실과 재산손상이 점진적으로 증가하게 되었다. 특히 부산은 한국 내 대도시들 중에서 산지비율이 높기 때문에 과도하게 산지지역을 개발할 수밖에 없다. 본 연구의 목적은 무한사면 모델을 이용하여 부산 황령산 산사태 재해 평가 가능성을 검토하는 것이다. 모든 자료는 ArcGIS 10.0을 사용하여 추출한 주제도와 연관되어 있다. 그 결과 산사태 안전율은 예상대로 지하수위 변화에 반비례한다는 것을 보여 준다. 대부분의 연구지역이 건조 상태에서는 안정된 상태이고, 지하수위가 상승할 때 공극수압이 증가하여 불안정한 지역이 증가하게 된다. 그러나 분석결과 선구조밀도가 높은 기존 산사태 발생지역 중에서 여러 곳이 다른 지역보다 더 안정한 것으로 나타났다. 이렇게 실제상황과 분석결과가 상이하므로 이 문제를 해결하기 위해 부가적인 분석이론이 필요할 것으로 생각된다. 그러므로 새로운 불포화대 침투이론 개발이 시간에 따른 지하수위의 분포를 평가하는데 도움이 될 것으로 생각한다.