• Journal of the Korean Geosynthetics Society
• /
• v.23 no.2
• /
• pp.1-7
• /
• 2024

Various innovative technologies and methods are being applied to ensure the stability of steep rock slopes. However, there are design limitations concerning site ground conditions, leading to discrepancies between the designed and actual ground conditions during construction. In the case of the retaining wall in Yeosu, where the study area is located, although the construction of a 5-stage retaining wall is planned, at the current completion of the second stage, cracks on the upper part of the wall, settlement in the front of the wall, and seepage have been observed. After the completion of stages one and two, issues regarding cracks and settlement on the upper part of the wall and seepage in the front of the wall were discovered. Thus, there was a need to reevaluate the results of the existing stability assessment. It was confirmed that the issue was due to groundwater leakage, attributed to the lack of clear assessment of the colluvial soil layer during the initial design stage. Therefore, to conservatively reflect groundwater level conditions, a groundwater level contour was positioned at the top of the wall to conduct a slope stability assessment. The assessment results indicated that the safety factor during the rainy season exceeded the required value of 1.3, with a calculated safety factor of 1.31. However, during seismic events, the safety factor was determined to be 1.12, falling short of the required safety factor of 1.3. Therefore, it is suggested that the existing retaining walls constructed during stages one and two undergo reinforcement using methods such as micro-piles with grouting, and additional work should be carried out to ensure a clear assessment of the colluvial soil layer.

• The Journal of Engineering Geology
• /
• v.26 no.1
• /
• pp.51-61
• /
• 2016

New building methods are needed to aid increased inner-city redevelopment and industrial construction. A particular area of improvement is the efficient use of cut slopes, with the minimization of associated problems. A retaining wall of precast panels can resist the horizontal earth pressure by increasing the shear strength of the ground and reinforcing it through contact with the panels. Precast panels allow quick construction and avoid the problem of concrete deterioration. Other problems to be solved include the digging of borrow pits, the disposal of material cut from the slope, and degradation of the landscape caused by the exposed concrete retaining wall.This study suggest the methods of improvement of an existing precast panel wall system by changing the appearance of the panels to that of natural rock and improving the process of adhering the panel to a vertical slope. The panels were tested in the laboratory and in the field. The laboratory test verified their specific strength and behavior, and the field test assessed the panels' ground adherence at a vertical cutting. Reinforcement of the cutting slope was also measured and compared with the results of 3D numerical analysis. The results of laboratory test, identified that the shear bar increase the punching resistance of panel. And as a results of test construction, identified the construct ability and field applicability of the panel wall system adhered to in-situ ground. In addition to that, extended measurement and numerical analysis, identified the long-term stability of panel wall system adhered to in-situ ground.

• The Journal of Engineering Geology
• /
• v.24 no.3
• /
• pp.373-381
• /
• 2014

It is difficult to predict the magnitude of a rockfall with respect to the shape, volume, and weight of the rock mass, as a rockfall exhibits erratic behavior that depends on the slope geometry, such as the height and dip of the slope. In this study, a field survey was conducted on the slopes of Ulleung-Do, South Korea, where rockfalls frequently occur along coastal roads, to classify the mode of rockfalls and estimate their magnitude. This study also analyzed the effects of rockfall behavior on roads by applying a simulation technique. Agglomerate and trachytic rocks distributed across the study area produce rockfalls in a differential weathering rockfall mode and a toppling rockfall mode. In terms of rockfall weight, trachytic rockfalls were 2-3 times heavier than agglomerate rockfalls. An analysis of rockfall behavior from the simulation indicates that the impact energy on the road exceeded the absorbing energy of a standard rockfall protection fence; however, the rockfall was secured when a ring-net was applied.

• Journal of Korean Society of Forest Science
• /
• v.88 no.2
• /
• pp.240-248
• /
• 1999

On the basis of data obtained from five forest roads collapsed due to a heavy rainfall of 1995 in Chunchon, Kangwon-do, this study was carried out to evaluate and predict the fill slope failure of forest roads with four factors of forest road structure and those of location condition by using Quantification theory(II). The results were summarized as follows ; In the structure factors of forest road, the fill slope failure was mainly occurred in longitudinal gradients less than $2^{\circ}$ or more than $4^{\circ}$, distance of surface-flow longer than 80m, fill slope length greater than 6m, and fill slope gradients steeper than $35^{\circ}$. In the factors of location condition, the failure was mainly occurred in ridge portion of road position, weathered rock and soft rock of constituent material, slope gradients in the range from $35^{\circ}$ to $45^{\circ}$, and concave and convex of longitudinal slope forms. The priority order for factors influencing on fill slope failure was ranked by fill slope length, constituent material, road position, and so on. And the rate of correct discrimination by analysis of fill slope failure was estimated at the high prediction of 86.5%.

• The Journal of Engineering Geology
• /
• v.17 no.3
• /
• pp.483-494
• /
• 2007

The properties of fracture system on road-cut slopes along the Busan-Ulsan express way under construction are investigated and analyzed. Fracture spacing distributions show log-normal form with extension fractures and negative exponential form with shear fractures. Straight line segments in log-log plots of cumulative fracture length indicate a power-law scaling with exponents of -1.13 in site 1, -1.01 in site 2 and -1.52 in site 3. It is likely that the stability and strength of rock mass are the lowest in site 1 as judged from the analyses of spacing, density and inter-section of fractures in three sites. In contrast, the highest efficiency of the fracture network for conducting fluid flow is seen in site 3 where the largest cluster occupies 73% through the window map. Based on the field survey data, this study modified weighting values of the RMR system using a multiple regression analysis method. The analysis result suggests a modified weighting values of the RMR parameters as follows; 18 for the intact strength of rock; 61 for RQD; 2 for spacing of discontinuities; 2 for the condition of discontinuities; and 17 for ground water.

• Explosives and Blasting
• /
• v.24 no.2
• /
• pp.41-50
• /
• 2006

Excavation by explosives blasting necessarily involves noise and vibration, which is highly prone to face claims on the environmental and structural aspects from the neighbors. When the blasting carried out in the vicinity of a structure, the effect of blasting vibration on the stability of the structure should be carefully evaluated. In the conventional method of evaluation, an equation for blast vibration is obtained from test blasting which is later used to determine the amount of charge. This method, however, has limitations in use since it does not consider topography and change in ground conditions. In order to overcome the limitations, dynamic numerical analysis is recently used in continuum or discontinuous models, where the topography and the ground conditions can be exactly implemented. In the numerical analysis for tunnels and rock slopes, it is very uncommon to simulate multi-hole blasting. A single-hole blasting pressure is estimated and the equivalent overall pressure at the excavation face is used. This approach based on an ideal case usually does not consider the ground conditions. And this consequently results in errors in calculation. In this presentation of a case study, a new approach of using blast waves obtained in the test blast is proposed. The approach was carried out in order to improve the accuracy in calculating blasting pressure. The stability of a structure in the vicinity of a slope blasting was examined using the newly proposed method.

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

• Tunnel and Underground Space
• /
• v.31 no.6
• /
• pp.534-548
• /
• 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 Geomorphological Association of Korea
• /
• v.18 no.3
• /
• pp.65-81
• /
• 2011

The landforms based on granite and basalt in Gosung, Gangwon province were analysed. Some part of this area experienced volcanic activities while most of the area was experiencing erosion of weathered mantle(saprolites) of mesoic granites during cenozoic period. Two different lithologies affect the mode of landscape evolution. The basalt covers the mountain tops as a 'cap rock' with flat surfaces. It shows relatively fresh rock surface with cliff or steep slops at the boundary with weathered granite. The blocks detached from the cliff accumulated at the foot of the cliff(talus) or moved and filled the valley(block streams). These debris slopes cover the deeply weathered granites. In the case of Oeum Mt. and Duibaekjae, the number of point of origin of the basalt flow is not clear. The orientation of blocks from block stream coincides with slope aspects and it can be assumed that the bolcks were moved by solifluction. The landscape change of the block streams are dominated by removal of weathered material from beneath of the valley rather than removal of bedrock blocks themselves.

• Journal of the Korean Geosynthetics Society
• /
• v.17 no.1
• /
• pp.139-152
• /
• 2018

This study is an analysis of slope failure examples of cut sedimentary hills during construction road in Kyoungsang Basin, especially Yangsan Fault system (Ilkwang-Dongrae fault). This area involved a lot of hillslope failures compared to other areas during road construction. The exposed failure slopes were first face-mapped, and then back analyzed based on the limit equilibrium method to assess the shear strength parameters of discontinuity (bedding). The results of this analysis indicate that the shear strength parameters of discontinuity (bedding) are significantly smaller than those used in the design stage and presented in the existing works. The filling in the bedding and emerging groundwater may be decreasing strength parameters. Especially, the clay in the bedding plays a key role in the effect of the shear strength. The study also suggests that the bedding angle and the internal friction angle are proportional to each other. Using this relationship and knowing the bedding angle, the friction can easily be estimated.