• Journal of Korean Society of Forest Science
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• v.104 no.4
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• pp.588-597
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• 2015

This study was carried out to identify the reasons of the landslide by land creeping in South Korea in order to provide basic information for establishing the management plan for prevention. Total 29 sites of landslide areas caused by land creeping were observed in South Korea. Among them, the soil-composition of most frequent landslide areas occurred by land creeping was colluvium landslide as 75.9% (22 sites), followed by clay soil landslide as 10.3% (3 sites), bedrock landslide as 6.9% (2 sites), and weathered rock landslide as 6.9% (2 sites). According to the types of parental rocks, the investigated landslide areas were divided into 3 types: 1) metamorphic rocks including schist, phylite, migmatitic gneiss, quartz schist, pophyroblastic gneiss, leucocratic granite, mica schst, banded gneiss and granitic gneiss, 2) sedimentary rocks including limestone, sandstone or shale and mudstone, 3) igneous rocks such as granite, andesite, rhyolite and masanite. As a result, it was noticed that the landslides occurred mostly at the metamorphic rocks areas (13 sites; 44.8%), followed by sedimentary rock areas (12 sites; 41.4%), and igneous rock areas (4 sites; 13.8%). Looking at the direct causes of the landslide, the anthropological activities (71%) such as cut slopes for quarrying, construction of country house, plant, and road, farming of mountain top, and reservoir construction were the biggest causes of the landslides, followed by the land creeping landslides (22%) caused by geological or naturally occurred (22%), and cliff erosions (7%) by caving of rivers and valleys.

• Journal of the Korean GEO-environmental Society
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• v.18 no.7
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• pp.13-20
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• 2017

Soil nailing is ground reinforcement method using the shear strength of ground and the pullout shear resistance force of nail. It is mainly used for reinforcement of cut slopes, earth retaining structures and retaining walls, etc. It may be designed considering the pullout resistance of nail in the case of earth retaining structure and retaining wall, but it should be designed considering not only pullout resistance but also shear and bending resistance in the case of slope. However, conservative designs considering only pullout resistance are being done and most of the studies are about increasing pullout resistance by improving of material, shape and construction method of nail. Actually, Shear bending deformations occur centering on the active surface in ground reinforced with the nail. The grout with relatively low strength is destroyed and separated from the reinforcing material. As a result, the ground is collapsed while reducing the frictional resistance rapidly. Therefore, it is necessary to develop the method to increase the shear resistance while preventing separation of nail and grout body. In this study, an experimental study was conducted on new soil nailing method which can increase shear resistance by forming protrusions through pressurized grouting after installing a packer on the outside of deformed bar.

• Journal of the Korean GEO-environmental Society
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• v.11 no.12
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• pp.47-56
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• 2010

The construction of new roads and the consistent extension of already-existing roads or the line-shape revision of those roads are increased with the governmental investment to SOC facilities currently. Accordingly, the road cut slopes are in the trend of rapidly increasing. As the road slope has increased, a lot of human and property damages has entailed consequently and in the local case, numerous studies have carried out aiming at minimizing this damages caused by the rockfall and landslide. In general, standard falling rock prevention facility has employed for most of the local road slope based on "Guide for Installation and Management of Road Safety Facilities" published by MLTM(the Ministry of Land, Transport, and Maritime Affairs) but profound doubt has raised as to whether this rockfall prevention facility would function properly enough to prevent rockfall efficiently without any damages in case of actual occurrence of rockfall. In addition, it is a reality that in most cases, such work is relied on overseas technology as a whole as the local technical level is low and in case of rockfall prevention net, it is judged that a study on rockfall prevention net that is able to endure more powerful rockfall energy is required as the problem including net bursting is taken place as a result of enough bearing force being failed to be demonstrated due to its partial weak point(not uniformly made). Under this background, in this study, three kinds of model depending on mesh size of expanded metal that is considered to have an adoptability as rockfall prevention net, as target are selected and characteristics depending on mesh size of expanded metal is intended to be researched through a pull-out test performance by using pull-out test equipment rockfall prevention net.

• The Journal of Engineering Geology
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• v.12 no.2
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• pp.137-150
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• 2002

Recently, plane failure mode occurred frequently along the bedding plane having low angle dip about 20 degree when cutting slopes were constructed in sedimentary rock region of the Gyeongsang Basin. Landslide of the Whangryeong Mountain which was occurred at Busan Metropolitan City in 1999 belongs to the category mentioned above. Reconstruction for cutting slope of the Whangryeong Mountain has finished in 2000 and final grade of reconstructed cutting slope is 1:2.0. To analyze slope failure mode for landslide of the Whangryeong Mountain, various analyses were performed such as in-situ investigation and test, drilling, laboratory test, aerial photograph interpretation, X-ray diffraction analysis, and slope stability analysis using Stereographic Projection and Limit Equilibrium methods. As the result, it is identified that tension cracks had been developed one year before the landslide took place. The tension crack semis to be formed by merging several joint sets. It appears that failure blocks broke down along the sliding planes of different layers. Risk of plane failure is conformed as a result of stability analysis using Stereographic Projection and Limit Equilibrium methods in case that greenish gray tuffaceous shales, regared as sliding planes, are weathered. From now on, a detailed investigation is needed for the thin layers which is sensitive to weathering, and stability analysis for this layer is performed at cut slope construction site having similar geological condition.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.9
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• pp.382-389
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• 2019

A novel folding process is proposed using a repeated cold-die forging and annealing to form a sterling silver ring. Sterling silver plate was cut into a doughnut shape, and lattices with 0.43-mm line-width were imprinted on it. The sample was folded by forging using dies with slopes of $45^{\circ}$, $60^{\circ}$, and $75^{\circ}$ and annealing. For comparison, samples were also fabricated without annealing. Strain was identified by measuring the length of lattices. Vernier calipers, a Vickers hardness tester, an optical microscope, and a UV-VIS colorimeter were used to determine the size, hardness, microstructure, and body color. Without annealing, cracks occurred. However, successful deformation was possible when annealing was used. The results of macro strain measurements show that the outer diameter and width decreased, while the inner diameter and thickness increased after the final process. The maximum strain was increased 0.128 toward the parallel direction. The Vickers hardness decreased after annealing and increased after the folding process. The microstructure results showed that the grain size increased after annealing but decreased after folding. The color difference based on the Lab index was under 10 for all processes. Eventually, a doughnut-shaped silver plate was successfully deformed into a ring shape by the folding process.

• Tunnel and Underground Space
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• v.31 no.6
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• pp.534-548
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• 2021

In this paper, the feasibility of generating solar power near an abandoned quarry is examined with the objectives of resolving the essential problems that quarries encounter, such as rockfalls and space usage issues. On an abandoned quarry site in Sadang, Seoul, Republic of Korea, two different PV installation methods were analyzed. The first is attaching PV directly on the quarry slope. Since there are no corresponding safety standards and precedents for installing solar panels directly on slopes, the power generation potential was calculated by using topographic data and reasonable assumptions. The surface area of cut slope section was extracted from the Digital Elevation Model(DEM) via ArcGIS and Python programming to calculate the tilt and power capacity of installable panels. The other approach is installing PV as a rockfall barrier, and the power generation potential was analyzed with the assumption that the panel is installed in the direction of facing solar irradiation. For the derivation of power generation, the renewable energy generation analysis program SAM(System Advisor Model) was used for both methods. According to the result, quarries that have terminated resource extraction and remain devastated have the potential to be transformed into renewable energy generation sites.

• Journal of the Society of Disaster Information
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• v.20 no.2
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• pp.270-283
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• 2024

Purpose: Considering the rising frequency of earthquakes in Korea, it is crucial to revise the rainfall thresholds for landslide triggering following earthquake events. This study was conducted to provide scientific justification and preliminary data for adjusting rainfall thresholds for landslide early warnings after earthquakes through soil physical experiments. Method: The study analyzed the change in soil shear strength by direct shear tests on disturbed and undisturbed samples collected from cut slopes. Also, The study analyzed the soil strength parameters of remolded soil samples subjected to drying and wetting conditions, focusing on the relationship between the degree of saturation after submergence and the strength parameters. Result: Compaction water content variation in direct shear tests showed that higher water content and saturation in disturbed samples led to a significant decrease in cohesion (over 50%) and a reduction in shear resistance angle (1~2°). Additionally, during the ring shear tests, the shear strength was observed to gradually decrease once water was supplied to the shear plane. The maximum shear strength decreased by approximately 65-75%, while the residual shear strength decreased by approximately 53-60%. Conclusion: Seismic activity amplifies landslide risk during subsequent rainfall, necessitating proactive mitigation strategies in earthquake-prone areas. This research is anticipated to provide scientific justification and preliminary data for reducing the rainfall threshold for landslide initiation in earthquake-susceptible regions.

• Journal of Korean Society of Forest Science
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• v.112 no.4
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• pp.426-441
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• 2023

This study investigated the predictive accuracy of a model of landslide displacement in Jecheon-si, where a great number of landslides were triggered by heavy rain on both natural (non-clear-cut) and clear-cut slopes during August 2020. This was accomplished by applying three flow direction methods (single flow direction, SFD; multiple flow direction, MFD; infinite flow direction, IFD) and the degree of root cohesion to an infinite slope stability equation. The application assumed that the soil saturation and any changes in root cohesion occurred following the timber harvest (clear-cutting). In the study area, 830 landslide locations were identified via landslide inventory mapping from satellite images and 25 cm resolution aerial photographs. The results of the landslide modeling comparison showed the accuracy of the models that considered changes in the root cohesion following clear-cutting to be improved by 1.3% to 2.6% when compared with those not considered in the area under the receiver operating characteristics (AUROC) analysis. Furthermore, the accuracy of the models that used the MFD algorithm improved by up to 1.3% when compared with the models that used the other algorithms in the AUROC analysis. These results suggest that the discriminatory application of the root cohesion, which considers changes in the vegetation condition, and the selection of the flow direction method may influence the accuracy of landslide predictive modeling. In the future, the results of this study should be verified by examining the root cohesion and its dynamic changes according to the tree species using the field hydrological monitoring technique.

• Journal of the Korean Institute of Landscape Architecture
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• v.45 no.5
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• pp.42-59
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• 2017

To investigate rooting and community forming ability, sod strips of Gramineae such as Miscanthus sacchariflorus (Maxim.) Benth., Miscanthus sinensis var. purpurascens(Andersson) Rendle, Imperata cylindrica var. koenigii(Retz.) Pilg., and Arundinella hirta(Thunb.) Tanaka were planted horizontally at a width of 10~15cm in October 2010 on the bank slope of Kwangju Stream in Korea. Seeds of each species were sown in April 2010 in plastic seedbeds(60cm length ${\times}$ 30cm width ${\times}$ 5cm depth) filled with 4cm of garden soil and grew until October 2010 to form rectangular sod, which then was cut into multiple strips(20cm length ${\times}$ 6cm width ${\times}$ 4cm root depth). Weeds growing on the experiment sites were removed twice a year until those four species had formed a community by 2013. Weeds were not eradicated during 2014 and 2015 to observe whether the community formation can be maintained without weed removal. t-tests on stem numbers and heights in May, July, and September were conducted between 2013 and 2014, and between 2014 and 2015. Stem numbers and heights of the four species in 2014 were significantly decreased(p<0.001) compared with those in 2013 due to weed damage to their growth in 2014. Stem numbers and heights of Miscanthus sacchariflorus(Maxim.) Benth., Miscanthus sinensis var. purpurascens(Andersson) Rendle, Imperata cylindrica var. koenigii(Retz.) Pilg. in 2015 were similar to those in 2014(p>0.05). Stem numbers and heights of Arundinella hirta(Thunb.) Tanaka in 2015, however, were significantly reduced compared with those in 2014(p<0.001) due to weed impact on its growth. After three years of weed removal, a community of each species was formed. Miscanthus sacchariflorus(Maxim.) Benth., Miscanthus sinensis var. purpurascens(Andersson) Rendle, Imperata cylindrica var. koenigii(Retz.) Pilg. were able to establish communities without any further weed removal. Arundinella hirta(Thunb.) Tanaka, however, was not able to maintain its community due to considerable damage to its growth caused by weeds even after three years of weed removal. Miscanthus sacchariflorus(Maxim.) Benth., Miscanthus sinensis var. purpurascens(Andersson) Rendle, Imperata cylindrica var. koenigii(Retz.) Pilg. are more suitable to sod strip plantings on stream bank slopes in terms of the maintenance of community formation without weed eradication. t-test on stem numbers and heights each September during the five year experiment period between sod strip planting and potted plants of the four species were conducted. Stem numbers of strip sod plantings were significantly higher(p<0.001) than those of potted one. Heights of strip sod plantings, however, were significantly lower(p<0.05) than those of the potted samples. Therefore, strip sod planting is more advantageous regarding bank slope erosion protection due to the higher number of stems.

• Journal of Korean Society of Forest Science
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• v.83 no.2
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• pp.246-253
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• 1994

Four Quercus forests in Mt. Mohu were studied to investigate biomass, net production and effective biomass estimation method. Five $10m{\times}10m$ quadrats were set up, ten sample trees were cut and roots of three sample trees were excavated for dimension analysis in each forest. There was little difference in accuracy among three allometric biomass regression models of logWt=A+BlogD, $logWt=A+BlogD^2H$ and logWt=A+BlogD+ClogH, where Wt, D and H were dry weight, DBH and height, respectively. Analysis of covariance showed that there were no significant differences among slopes and intercepts of allometric biomass regressions, logWt=A+BlogD, of four Quercus species. Biomass of Q. acutissima, Q. nariabilis, Q. serrata and Q. mongolica forests were 164.0, 158.9, 115.3 and 118.9t/ha, respectively. Net production of Q. acutissima, Q. variabilis. Q. serrata and Q. mongolica forests were 25.0, 23.2, 14.5 and 12.6t/ha/yr., respectively. The proportion of roots to total biomass and total net production of Q. mongolica forest was higher than that of three other species forests. Net assimilation ratio of Q. acutissima, Q. variabilis, Q. serrata and Q. mongolica forests were 2.87, 2.80, 3.20 and 2.95, respectively. Relatively less leaf biomass of Q. serrata and Q. mongolica forests were the reason why total biomass and total net production of Q. serrata and Q. mongolica forests were less than those of Q. acutissima and Q. variabilis.