• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.480-480
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• 2018

전 세계적으로 자연 친화, 하천생태계 보전, 친수하천 등을 조성하기 위한 대대적인 하천 정비사업이 활발히 진행 중에 있다. 최근 홍수로 인한 제방 붕괴에 대응하기 위한 제방의 안정화 및 개선을 위한 방법으로 기존의 시멘트와 같은 혼합물질을 사용하지 않고 환경 친화적이고 지속 가능한 대안에 대한 수요가 증가되고 있는 추세이며 현재 노후화 된 불안정 제방에 대한 보강대책을 수립해나가는 과정으로써 친환경 신소재를 활용하여 제방을 보호하는 연구가 수행되고 있다. 제방사면에 적용되는 신소재는 바이오폴리머를 활용한 재료로써 공동연구기관 카이스트에서 개발된 환경 친화적인 물질로 미생물에 의해 유도된 고인장 및 인체 무해성 등의 특성을 갖고 있으며 경제적 타당성인 측면에서 시멘트와 비교 분석 되어야 하고 실제 현장에서의 적용 가능성, 신뢰성 및 내구성 검토 등 성능을 보장하기 위한 지속적인 연구가 필요한 상황이다. 이에 본 안동하천실험센터에서는 중규모 제방을 직접 제작하여 수리모형실험을 통한 친환경 신소재 활용 제방의 안정성 및 성능 평가를 실시하였다. 수리실험 조건은 카이스트에서 제시된 레시피를 기반으로 먼저 분말형태의 바이이폴리머를 물과 희석하여 만들어진 바이오폴리머 용액을 흙과 혼합한 뒤 제방표면에 직접 미장작업을 수행하여 실험조건에 따라 일정한 두께(1cm, 3cm, 5cm)로 피복하였다. 이후 월류 붕괴 실험이 가능한 3 - 5일 정도의 양생기간을 거쳐 실험을 진행하였다. 실험결과는 다수의 고프로(GoPro) 및 비디오 카메라 등 다양한 영상장치를 이용하여 픽셀기반의 영상분석기법을 활용한 시간 흐름에 따른 제방 사면에서의 붕괴규모를 산정하여 신소재의 피복 두께에 따른 제체의 붕괴 거동 및 안정성을 평가하였으며, 또한 제방 파괴부에서의 흐름 상황 및 유속이 붕괴 발달에 미치는 영향을 분석하기 위하여 PIV 분석을 실시하였다. 이번 연구의 최종목표는 지속적인 예비실험을 수행하여 월류 및 침투, 파이핑 등 파괴 인자 별 신소재의 성능 개선 및 개발된 새로운 공법에 대한 효과 검토를 통한 최적안을 도출함으로써 향후 실규모 실험실증을 통한 신소재 시공 및 공법에 대한 현장적용 가능성 검증을 거쳐 최종적으로 신소재 제방 공법 설계 기술, 신소재 및 공법 표준안, 제방공법 안정성 평가 가이드라인 등을 제시하고자 하며, 이러한 실험데이터를 축적함으로써 실제 제방 붕괴 시 비상대처계획 수립에 필요한 기초자료로 활용이 가능할 것으로 사료된다.

• Journal of the Korean Geotechnical Society
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• v.23 no.10
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• pp.97-107
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• 2007

Accurate evaluation of the slope stability by assuming failure block as the entire slope is considered to be apposite for the small scale slope, whereas it is not the case for the large scale slope. Hence, appropriate estimation of a failure block size is required since the safety factor and the joint strength parameters are the function of the failure block size. In this paper, the size of failure block was investigated by generating 3-dimensional rock joint system based on statistical data of joints obtained from research slope, such as joint orientation, spacing and 3-dimensional joint intensity. The result indicates that 33 potential failure blocks exist in research slope, as large as 1.4 meters at least and 38.7 meters at most, and average block height is 15.2 meters. In addition, the data obtained from 3 dimensional joint system were directly applicable to the probability analysis and 2 and 3 dimensional discontinuity analysis.

• The Journal of Engineering Geology
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• v.25 no.1
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• pp.115-129
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• 2015

The cut-slope of a large-sectional tunnel portal is recognized as a potential area of weakness due to unstable stress distribution and possible permanent displacement. This paper presents a case study of a slope failure and remediation for a large-scale cut-slope at a tunnel portal. Extensive rock-slope brittle failure occurred along discontinuities in the rock mass after 46 mm of rainfall, which caused instability of the upper part of the cut-slope. Based on a geological survey and face mapping, the reason for failure is believed to be the presence of thin clay fill in discontinuities in the weathered rock mass and consequent saturationinduced joint weakening. The granite-gneiss rock mass has a high content of alkali-feldspar, indicating a vulnerability to weathering. Immediately before the slope failure, a sharp increase in displacement rate was indicated by settlement-time histories, and this observation can contribute to the safety management criteria for slope stability. In this case study, emergency remediation was performed to prevent further hazard and to facilitate reconstruction, and counterweight fill and concrete filling of voids were successfully applied. For ultimate remediation, the grid anchor-blocks were used for slope stabilization, and additional rock bolts and grouting were applied inside the tunnel. Limit-equilibrium slope stability analysis and analyses of strereographic projections confirmed the instability of the original slope and the effectiveness of reinforcing methods. After the application of reinforcing measures, instrumental monitoring indicated that the slope and the tunnel remained stable. This case study is expected to serve as a valuable reference for similar engineering cases of large-sectional slope stability.

• The Journal of Engineering Geology
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• v.10 no.2
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• pp.18-35
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• 2000

The most dominant type of landslide in Korea is debris flows which mostly take place along mountain slopes during the rainy season, July to August. The landslides have been reported to begin activation when rainfall is more than 200mm within 2days. The debris flows are usually followed by translational slips which occur upper part of mountain slopes and they transit to debris flow as getting down to the valleys. Lithology, location, slope inclination, grain size distribution of soil, permeability, dry density and porosity have been proved as triggering factor causing translational slides. The triggering data taken from mapping are statistically analysed to get landslide potential quantitatively. Rock mass creeps mostly occur on well bedded sedimentary rocks in Kyeongsang Basin. Although the displacement of rock mass creep is relatively small about 1m, the creep can cause severe hazards due to relatively large volume of the involved rock mass. Examples are rock mass creep occurred in the mouth of Hwangryongsan Tunnel, in Chilgok and in Sachon in 1999. Although the direct factor of the creeps are due to slope cutting at the foot area, more attention is required A rotational slide occurring within thick soil formation or weathered rock is also closely related to bottom part of slope cutting. It is propagated circular or semi-circular type. Especially in korea, the rotational slide may be frequently occurred in Tertiary tuff area. Because they are mainly composed of volcanic ash and pyroclastic materials, well developed joints and high degree of swelling and absorption can easily cause the slide. The landslide among the Pohang-Guryongpo national road is belong to this type of slide.

• The Journal of Engineering Geology
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• v.17 no.1 s.50
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• pp.75-87
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• 2007

The recognitions of geometrical characteristics and occurrence conditions are very important to evaluate the land-slides in natural terrains. In this paper, the geometrical characteristics of landslides are analyzed according to a geo-logical condition in three landslides areas. The three landslides areas are classified to the geological condition. The three landslides areas are Jangheung, Sangju and Pohang. The geology of Jangheung area, Sangju area and Pohang area is gneiss, granite, and the tertiary sedimentary rock, respectively. During a heavy rainfall of $150{\sim}588mm$ in these areas, 1,582 landslides have occurred in 1998. The geometrical characteristics according to the geological condition analyzed from the investigation of these landslides. The frequency of landslide is high exceedingly above 90% of a slope attitude, while the frequency is very low below 70%. The frequency of landslide is high exceedingly between $26^{\circ}$ and $30^{\circ}$ of slope angle, while the frequency is very low below $20^{\circ}$. The size of the landslides is ranged from several tens to several hundreds The length is ranged from 5 m to 300 m, and the width is ranged from 3 m to 50 m. Also, the depth is less than 1 m. Therefore, the landslides in these areas have small width, long length and shallow depth. The type of the landslides is changed from transitional slide at the scarp to debris flow at the low part of slope.

• Explosives and Blasting
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• v.29 no.1
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• pp.10-16
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• 2011

To make large slopes or rock structures stable, supporting systems, such as anchor bolt, rock bolt and spiral bolt which are developed recently, are commonly used. In this study, in-situ pull-out tests were carried out to compare the characteristics of rock bolt that is most widely used with ones of spiral bolt that is newly developed. Re-pull-out test for the spiral bolt in which loading and unloading cycles are repeated three times showed that the maximum pull-out load is almost constant irrespective of the number of loading cycles, which may be due to no failure between spiral bolt and filler. On the other hand, the maximum pull-out load for the conventional rock bolt decreases with the number of loading cycles due to the partial failure between rock bolt and filler.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.29 no.5
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• pp.535-541
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• 2011

A debris flow is caused by torrential rain in mountainous regions and carries mixture of fragmental matter from slope failure, deposit soils from a valley floor and a large amount of water. It seriously damages facilities, houses, and human lives in its path. We tried to apply debris flow behavior estimation model developed in foreign country to domestic case. The study area is Inje-county, Gangwon-do and aerial photos and GPS surveying were used to collect information of starting and end point of the landslide and debris flow. The analysis showed that L/H for forecasting the travel distances of debris flows has the mean of 4.93 and standard deviation of 0.98. This model tended to overestimate the scale and extent of debris flows. In Inje-county's case, a debris flow is caused by multiple simultaneous small-scale landslide. This is quite different from the foreign cases in which a large-scale landslide cause a large-scale debris flow. Thus, an empirical model suitable for domestic conditions needs to be developed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5C
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• pp.263-271
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• 2008

Investigation and analysis of the debris flow characteristics such as basin topography, geologic conditions of initiation location and triggering rainfall are required to systematically mitigate debris flow hazard. In this paper, 48 debris flows which had caused some damages to the highway in the past 5 years are investigated and their characteristics of basic topography and triggering rainfall are analyzed. Debris flows are found to occur in small basins having the area of $0.01{\sim}0.65km^2$ range and mostly initiated by the surficial failure of natural slope having the inclination of 29~55 degree during the intense rainfall. As for the triggering rainfall, rainfall of 2 to 5 year recurrence frequency are found to be able to trigger the debris flow and magnitude of debris flow in a basin could depend on the rainfall intensity and cumulative amount.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.93-93
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• 2022

최근 이상기후로 인하여 우리나라 산림에 태풍 및 국지성 호우가 빈번히 발생하고 있다. 이로 인해 사면재해가 많이 발생하고 있으며 그 중 호우로 인한 많은 양의 물과 함께 토석 및 부유물이 중력에 의해 경사면을 따라 흐름 형태를 보이는 토석류 재해는 속도가 매우 빠르고 파괴적이며 그 결과는 비참하기까지 하다. 더구나 인구밀도가 낮은 산지 계곡부 뿐만 아니라 도시지역에서도 토석류 재해가 빈번히 발생하며 국내 및 해외에서도 토석류에 의한 피해사례는 자주 볼 수 있다. 이러한 토석류 재해의 피해를 줄이고자 토석류의 유동성을 저감시키기 위한 대책구조물의 시공이 많이 이루어지고 있으며 최근에는 투과형 구조물 중 하나인 원통형 기둥구조물을 그룹 형태로의 시공하는 경우가 늘어나고 있다. 토석류와 대책구조물 간의 상호작용은 월류(overflow), 쳐오름(run-up), 역류(backwater) 등의 복잡한 흐름 거동을 보인다. 하지만 원통형 대책구조물에 대한연구가 많이 이루어져 있지 않고 대규모 실험 또한 비용이 많이 소요되고 실행하기도 어렵다. 이 연구는 오픈소스 소프트웨어인 OpenFOAM을 사용하여 원통형 대책구조물의 설치 조건에 따라 토석류 흐름에 미치는 영향을 분석하였다. 짧은 시간 내에 흐름이 발생하고 비뉴튼 유체 특성을 갖는 토석류의 유효전단응력이 난류전단응력에 비해 상당히 크므로 난류의 영향은 무시하였다. 계산된 수치모의의 결과를 같은 규모로 시행한 실험결과와 비교분석 및 검증하였다. 공학학적 문제에 적용 가능하도록 비교적 낮은 해상도의 계산 격자를 사용했지만 실험에서 보여지는 토석류의 흐름거동을 양호하게 재현했으며 원통형 대책구조물의 배치조건에 따라 토석류 선단부 유속의 감소 정도 및 시간에 따른 흐름깊이 변화를 분석할 수 있었다. 이 연구는 다양한 조건을 가지는 토석류 흐름을 해석하는데 유용하게 활용할 수 있으며, 추후 복잡한 실제지형 조건을 고려하는 연구를 통하여 적용성을 확보하고자 한다.

• The Journal of Engineering Geology
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• v.19 no.3
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• pp.331-344
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• 2009

Large landslides occurred since 1990 on natural terrain, Korea were reviewed with the existing data to characterize them in terms of the condition of rainfall, geology and geometry. Ten landslide areas over the nationwide are selected for this study. Among them, five areas consist of granite basement, four areas of granite and metamorphic rocks and the remaining an area of gabbro. The basement lithology on which landslides most dominantly occurred is granite, on which 58% of landslides among the total 3,435 are taken place, the next dominant one is metamorphic rocks where 24% of landslides are occurred, and the remaining 18% are on the areas of volcanic and sedimentary rocks which are partly distributed in some areas. The landslide occurrences may depend on the rainfall intensities rather than durations. We applied the theories of Caine's threshold and Olivier's final response coefficient to the Korean cases. The rainfall conditions at the landslide areas were all satisfied enough with the landslide triggering conditions suggested by Caine and Olivier. The triggering mechanism and type of landslides may largely depend on the weathering and geomorphic characteristics of basement lithology. The granite areas are characterized by being relatively shallow but consistent weathering profiles and almost no outcrop, and therefore, shallow translational slides are dominant. Whereas metamorphic areas are characterized by consisting of steep slope, weathered outcrops on ridges and partly on flanks and irregular weathering profiles, and relatively large debris flows are dominant.