• 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.

• International Journal of Highway Engineering
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• v.19 no.6
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• pp.147-153
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• 2017

PURPOSES : This research aims to estimate the occurrence of hydroplaning on roads based on the road alignment types and rainfall intensity in Seoul. METHODS : Three types of data were used for estimation of hydroplaning in this study. The Inner Circulation Road (12.5 km) to the Bukbu Expressway (7.4 km) in Seoul was selected as the test road and data was collected for road information using a probe-vehicle. Precipitation was observed from Automatic Weather System in Seoul. These data were interpolated by applying Inverse Distance Weighted Methodology for hydroplaning estimation. Finally, the water depth information of the roads was observed using an RCM411 device. RESULTS : This study demonstrated that the cross slope with small-angle-tilt or vertical section with large-angle-tilt are the primary factors causing hydroplaning on the roads. The flow velocity on steep slope is high; however, large drainage lengths result in hydroplaning on the roads. CONCLUSIONS : This result can contribute towards the reduction of car accidents on rainy days. Furthermore, information regarding hydroplaning can be delivered to drivers more rapidly and precisely in the future.

• Proceedings of the Korean Geotechical Society Conference
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• 1993.06b
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• pp.19-44
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• 1993

The purpose of this paper is to study the design and the construction for the most economic and safe slope stability analysis. The approach to the purpose Iies in analyzing the characteristic on direction and distance by the sample value for the geotechnical parameters using the semi-variogram concept. Based on the result, we derive the Kriging system equation from the stochastical concept and solve the equation to find the weighting factor which is applied both the point estimation and the block estimation in the particular position. Comparing and analyzing the various methods. we find the best reliability, which is more accurate than any other.

• Korean Journal of Environmental Agriculture
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• v.28 no.2
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• pp.113-124
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• 2009

Severe sediment-laden problem has been the hot issue in Korea. It was assumed that agricultural activities and landslides were the primary causes of these problems in watersheds. The USLE-based systems have been widely used in soil erosion studies. However the GIS-based USLE modeling system has limitation in USLE L factors. In this study, the SATEEC L module was developed to reflect the slope length segmentations in the fields. The SATEEC L module was applied to the study watershed to analyze the effects of using the SATEEC L module on estimated sediment. As shown in the comparisons between SATEEC estimated sediment with SWAT values, the SATEEC GA-SDR module derives the SDR with reasonably acceptable accuracies. However, it is worthy to note that the soil erosion using the SATEEC L module for the study watershed was lower than that without using the SATEEC L module by 25%, although the SATEEC estimated sediment values with and without using L module match the SWAT sediment values with similar accuracies. This is because the SATEEC GA-SDR module estimates lower SDR in case of greater soil erosion estimation without the L module and greater SDR in case of lower soil erosion estimation with the L module. This indicates that the SATEEC input parameters, especially L factor, need to be prepared with care for accurate estimation of SDR at a watershed scale and for accurate evaluation of BMPs in the watershed.

• The Journal of Engineering Geology
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• v.18 no.1
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• pp.17-26
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• 2008

In this study, the design method of slope reinforced by the earth retention systems were systematically developed, and the flow chart of design procedure fur each system were constructed to design the slope rationally. The proposed design method is composed of 5 steps such as field condition investigation step, slope design step, landslide occurrence prediction step, slope failure scale estimation step and reinforcement countermeasure selection step. The quantitative standard of slope failure scale was established based on the arrangement of various overseas standards which is estimating the slope failure, and the analysis of slope failure scale which is occurred in the country. The slope failure scale is classified into three categories the small scale of slope failure is less than $150m^3$ of slope failure volume, the middle scale of slope failure is from $150m^3$ to $900m^3$ and the large scale of slope failure is more than $900m^3$. The earth retention system could be selected by the proposed slope failure scale based on the slope failure volume. Meanwhile, the design methods of earth retention system such as piles, soil nails and anchors were developed. The optimal countermeasure for slope stability could be proposed using above design methods.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.5
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• pp.103-109
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• 2008

Precipitation on slope is separated into infiltration and outflow according to physical properties of soil and slope. However, the slope analysis is assumed that all precipitation are percolated. So, groundwater level is excessive tend to be calculated. In this paper, NRCS model and Horton models that have a suitability were used for agro-type analysis of Seoul station after precipitation was separated into infiltration and outflow. Also, gradient of slope was analyzed about seepage behavior and underground water level aspect through numerical analysis. After inclination correction, the estimated infiltration was compose of slopes much applied by domestic design standard. The change of groundwater level is appeared greatly as agro-type goes from D type to A type in the analysis results.

• Magazine of the Korean Society of Agricultural Engineers
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• v.42 no.6
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• pp.72-82
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• 2000

Many lot of books introduce the methods to calculate the time of concentration, and these are described as various forms of formulas. There are few formulas appropriate for our basin characteristics Therefone, there are problems to make excessive or less estimation when these formulas are used. To solve these problems, comparison of formulas and sensitivity analysis for them were made with converting parameters. Finally, Time of concentration was estimated to derive Application limits for 3 watersheds by standardized formulas. In the case of input parameters analysis, SCS formula has the highest value by the length, Kerby by the height and SCS by the slope, respectively, while Kraven formula has the lowest value among them. Concerning the relative sensitivity by Taylor series, the time of concentration showed the constant effect while increasing of the length and slope, and the length was more sensitive than the slope in parameters. Finally the standardization formula developed in this study was applied to derive application limits for 3 watersheds(total 17 subbasins). In this case, Rziha(8 subbasins) and SCS(9 subbasins) formulas were the most similar to observed data of total 17 subbasins respectively. Application limits were about 300~500$\textrm{km}^2$ area, 30~60km length and under 0.01 slope for Rziha formula and about 100~200$\textrm{km}^2$ area, 10~30km length, and over 0.01 slope for SCS formula, respectively.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.09a
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• pp.147-150
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• 2004

Firstly, the precipitation data have to be interpolated for the estimation of water resources. For this purpose, the correlative analysis is made between the topographic variables, which, influence the precipitation phenomena, are classified by elevation(ELEV), slope(SLOPE), distance to the sea(SEA), obstacle (OBST), barrier(BAR), and roughness index(SHIELD), using TOVA(Topographic Variables Extraction Program) and events precipitation during the periods from january the 1st 2000 to December 31 2002. The coefficients of determination show that each event has different topographic influence and ELEV, SLOPE and OBST to the South-West, and SHIELD of every direction have close relationship with the precipitation. The multiple regression model explains 96% of the spatial variation of precipitation.

• The Journal of the Korea Contents Association
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• v.17 no.2
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• pp.535-542
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• 2017

There is a big difference of discharge rate between drought and flood period in Korea since the importance of water resources management has come to the fore. To know a river characteristics, it needs to estimate river discharge accurately. River discharge is calculated using the measured velocity of cross section and the estimated area of watercourse as input parameters into continuity equation. Generally, flow rate over a river is estimated from the relation equation between level and discharge, in this case, there are weakness for only the equal depths and the equal discharge estimated. In the present study, therefore, water surface slope was estimated using measured water level of Seongseo water level observation station and measured water level using ADVM at Gangchang Bridge. And then, we developed the discharge calculation equation using water surface slope. A method to easily calculated flow rate from the measured depth of the two points that are suggested by reflecting water surface slope because natural stream is unsteady flow, not uniform flow or not steady flow.

• Journal of Korea Water Resources Association
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• v.38 no.3 s.152
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• pp.223-233
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• 2005

In this study, a two-dimensional model for identifying areas of erosion and deposition over a basin was developed based on the mass balance principle in a distributed model. The program consists of three steps: (a) estimation of soil erosion; (b) determination of flow amount and direction; and (c) estimation of mass balance. Soil erosion was estimated with USLE. A single-direction (SF) and a multi-direction flow algorithm (MF) were applied to estimate slope length (L). The Maximum Downhill Slope Method (MDS) and the Neighborhood Method (NBH) were used to estimate the slope degree (S). Sediment transport resulting from eroded soil was estimated using Ferro's (1998) and Swift's (2000) sediment delivery ratio (DR). The model was validated by comparing the predicted sediment yields for three basins with measured data. The developed algorithm showed that Ferro's DR method combined with the MDS and MF produced the best agreement with the dredging records of three agricultural reservoir basins in Korea.