• Journal of the Korean Geosynthetics Society
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• v.14 no.2
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• pp.71-79
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• 2015

This paper describes vegetation based soil-media hydroseeding measures that have been previously applied as slope revegetation methods show problems such as insufficient binding force, drying, and insufficient organic matter. In particular, in the case of slope faces in regions where scattering is severe, a vicious circle exists in which remarkably low vegetation cover rates and increases in withering rates over time lead to further decreases in vegetation cover rates, which lead to further increases in erosion and scattering. Therefore, in the present study, environment friendly soil stabilizers were applied for resistance against erosion or scattering and engineering evaluations such as long-term immersion tests and flow resistance tests were conducted to determine appropriate mixing ratios. According to the results of long-term immersion tests utilizing environment friendly soil stabilizers and existing greening soil based materials, 100% collapse occurred at 30 hours and 40 days in the case of soil stabilizer mixing ratios of 0% and 2%, respectively. While the original form of the samples remained intact until the experiment was completed in the case of mixing ratios exceeding 4% indicating that 2% or higher soil stabilizer mixing ratios could affect the maintenance of forms even under extreme conditions. In addition, artificial rainfall tests were conducted on 40, 45, and 55 degree slope faces to evaluate the structural stability of vegetation based materials. Flow resistance tests were conducted on soil stabilizer mixing ratios of 0, 4, 8% to evaluate erosion resistance capability. Based on the results of the tests, environment friendly soil stabilizers applied for prevention of scattering or resistance against erosion by rainwater are considered to provide large effects to reduce losses and loss rates showed a tendency of decreasing rapidly when soil stabilizers were mixed.

• Journal of The Korean Society of Agricultural Engineers
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• v.62 no.5
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• pp.93-103
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• 2020

In this study, we estimated soil moisture values using the Deep Neural Network(DNN) scheme at the mountainous regions. In order to test the sensitive analysis of DNN scheme, we collected the measured(at the soil depths of 10 cm and 30 cm) soil moisture and DNN input(weather and land surface) data at the Pyeongchang-gun(relatively flat) and Geochang-gun(steep slope) sites. Our findings indicated that the soil moisture estimates were sensitive to the weather variables(5 days-averaged rainfall, 5 days precedent rainfall, accumlated rainfall) and DEM. These findings showed that the DEM and weather variables play the key role in the processes of soil water flow at the mountainous regions. We estimated the soil moisture values at the soil depths of 10 cm and 30 cm using DNN at two study sites under different climate-landsurface conditions. The estimated soil moisture(R: 0.890 and RMSE: 0.041) values at the soil depth of 10 cm were comparable with the measured data in Pyeongchang-gun site while the soil moisture estimates(R: 0.843 and RMSE: 0.048) at the soil depth of 30 cm were relatively biased. The DNN-based soil moisture values(R: 0.997/0.995 and RMSE: 0.014/0.006) at the soil depth of 10 cm/30 cm matched well with the measured data in Geochang-gun site. Although uncertainties exist in the results, our findings indicated that the DNN-based soil moisture estimation scheme demonstrated the good performance in estimating soil moisture values using weather and land surface information at the monitoring sites. Our proposed scheme can be useful for efficient land surface management in various areas such as agriculture, forest hydrology, etc.

• The Journal of Engineering Geology
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• v.16 no.4 s.50
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• pp.359-371
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• 2006

In this study, the soil characteristics are analyzed using the result of various soil tests as an object of the soil layer of natural slopes in landslides areas composed with gneiss, granite, and the tertiary sedimentary rock. To investigate the soil characteristics according to landslide and non landslide areas, soils are sampled from Jangheung, Sangju and Pohang. The landslides at three areas are occurred due to heavy rainfall in same time. The geology of Jangheung area, Sangju area and Pohang area is gneiss, granite, and the tertiary sedimentary rock, respectively. On the basis of the landslide data and the result of soil test, the soil characteristics at the landslide area and the differentiation between landslide area and non landslide area are analyzed. However soil characteristics have a little differentiation to geological condition, the uniformity coefficient and the coefficient of gradation of soils at the landslide area is larger than those of soils at the non landslide area. Also, the proportion of fine particle of soils at the landslide area is higher. The plastic limit of soils sampled from the granite and the sedimentary rock regions is larger than that sampled from the gneiss region. However the liquid limit is irrelevant to the geological condition. Also, the consistency of soils at the landslide area is smaller. The natural moisture content of soils in the sedimentary rock regions is larger than that of the granite and gneiss. It is mainly influenced by mineral composition, soil layer structure, weathering condition, and so on. The soils sampled from landslide area have higher porosity and lower density than those from non landslide area. It means that the soils of landslide area have poor particle size distribution and loose density. Therefore, the terrain slope with poor distribution and loose density is vulnerable to occur in landslides. Also, landslides are occurred in the terrain slope with high permeability. The permeability is mainly influenced by the soil characteristics such as particle size distribution, porosity, particle structure, and the geological origins such as weathering, sedimentary environment. Meanwhile, the shear strength of soils is little difference according to the geological condition. But, the internal friction angle of soils sampled from the landslide area is lower than that of soils from the non landslide area. Therefore, the terrain slope with low internal friction angle is more vulnerable to the landslide.

• Journal of The Korean Society of Agricultural Engineers
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• v.49 no.3
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• pp.79-88
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• 2007

This paper suggests a hierarchial method to select the target sites for the nonpoint source pollution management considering factors which reflect the interrelationships of significant outflow characteristics of nonpoint source pollution at given sites. The factors consist of land slope, delivery distance to the outlet, effective rainfall, impervious area ratio and soil loss. The weight of each factor was calculated by an analytic hierarchy process(AHP) algorithm and the resulting influencing index was defined from the sum of the product of each factor and its computed weight value. The higher index reflect the proposed target sites for nonpoint source pollution management. The proposed method was applied to the Baran HP#6 watershed, located southwest from Suwon city. The Agricultural Nonpoint Pollution Source(AGNPS) model was also applied to identify sites contributing significantly to the nonpoint source pollution loads from the watershed. The spatial correlation between the two results for sites was analyzed using Moran's I values. The I values were $0.38{\sim}0.45$ for total nitrogen(T-N), and $0.15{\sim}0.22$ for total phosphorus(T-P), respectively. The results showed that two independent estimates for sites within the test water-shed were highly correlated, and that the proposed hierarchial method may be applied to select the target sites for nonpoint source pollution management.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.4
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• pp.19-27
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• 2012

The objective of this study was to test the pollutant reduction effect by the silt fence and vegetated ridge through field monitoring. The experiment plots were established with two replication and three treatments. Each plot was designed with 5 m width, 22 m length, and 3 % slope. Flumes with the floating type stage gages were installed at the outlet of each plot to monitor the runoff. For a rainfall monitoring, tipping bucket rain gage was installed within the experiment site. Cultivated crops were spring daikon and autumn chinese cabbage. Analysis of variance (ANOVA) indicated that the water quality concentration from three experiment plots were not significantly different in 5 % of significant level. The monitoring results showed that the average pollution loads reduced by silt fence compared to control were SS 75.33 %, TN 40.87 %, TP 56.58 %, BOD 52.12 %, COD 36.07 %, TOC 34.99 %; by vegetated ridge compard to control were SS 65.27 %, TN 81.80 %, TP 54.26 %, BOD 67.09 %, COD 46.55 %, TOC 43.30 %. Analysis of Spearman's rank correlation coefficient showed that BOD-SS and SS-Turbidity were highly related at the silt fence and vegetated ridge plots. In all plots, SS-Turbidity and TP-TN relations were relatively high. The monitoring results showed that the silt fence and vegetated ridge were effect method to reduce the pollutant loads from the field runoff. Long-term monitoring is required to obtain more quantitative reduction effect for diverse crops and to increase the reliability of results.

• Journal of the Korean Geotechnical Society
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• v.30 no.6
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• pp.5-21
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• 2014

It has been pointed out that the collapses of unsaturated road embankments caused by earthquake are attributed to high water content caused by the seepage of the underground water and/or the rainfall infiltration. Hence, it is important to study influences of water content on the dynamic stability and deformation mode of unsaturated road embankments for development of a proper design scheme including an effective reinforcement to prevent severe damage. This study demonstrates dynamic centrifugal model tests with different water contents to investigate the effect of water content on deformation and failure behaviors of unsaturated road embankments. Based on the measurement of displacement, the pore water pressure and the acceleration during dynamic loading, dynamic behavior of the unsaturated road embankments with about optimum water content and the higher water content than the optimum one have been examined. In addition, an image analysis has revealed the displacement field and the distributions of strains in the road embankment, by which deformation mode of the road embankment with higher water content has been clarified. It has been confirmed that in the case of higher water content the settlement of the crown is large mainly owing to the volume compression underneath the crown, while the small confining pressure at the toe and near the slope surface induces large shear deformation with volume expansion.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.27 no.4
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• pp.421-428
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• 2009

In Korea, the change of river flux due to seasons change is so considerable because of the mountainous terrain with the sharp slope and leaned rainfall. This unfavorable natural condition and the difficulties in precise grasping of the river status made the water resource management difficult so that the necessity of the precise river management has been continuously increased. In this study, a precise river-region DEM using the latest equipments of ALS and MBES is constructed. After acquiring DEM from each senor on the river region, a single DEM was generated by combining them. Also, the field inspection was carried out in the overlapped region of ALS and MBES in order to verify the quality of DEM. The verification of DEM was carried out by comparison between TINs obtained from the combined result of ALS and MBES and the surveying result from total station at more than 10 points in the selected two test areas. As a result, NO.1-area's RMSE of 0.322m and 0.113m are obtained for NO. 1 and NO. 2 areas, respectively. The result of this study shows the feasibility of DEM construction for river region using ALS and MBES as seen in the case of NO. 2 area. At the same time, it was appeared that a better method on the data fusion should be developed as seen in the result of NO. 1 area.

• Journal of Korean Society of Forest Science
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• v.113 no.1
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• pp.14-30
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• 2024

This study characterized areas at risk of land creep by focusing on a site that has undergone this phenomenon in Ulju-gun, South Korea. Land creep in the area of interest was catalyzed by road expansion work conducted in 2022. The site was examined on the basis of its geological features, topography, effective soil depth, soil hardness, electrical resistivity, and subsurface profile. It consists of a slope covered with sparse vegetation and a concave top that retains rainwater during rainfall. Compositionally, land creep affected the shale, sandstone, and conglomerate formations on the site, which had little silt and more sand and clay compared with areas that were unaffected by land creep. An electrical resistivity survey enabled us to detect a groundwater zone at the site, which explains the softness of the soil. Finally, the effective soil depth at the land creep-affected area was 30.4 cm on average, indicating deep colluvial deposits. In contrast, unaffected sites had an effective soil depth of 24.7 cm on average. These results should facilitate the creation of systems for monitoring and preemptively responding to land creep, significantly mitigating the socioeconomic losses associated with this phenomenon.