• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.1415-1424
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• 2009

Measuring dynamic properties of gravel-sized materials demands large specimens. Due to the difficulties in experiment as well as equipment, the dynamic properties of gravel-sized material has rarely been investigated. To realize free-free end condition more properly and stabilize specimen during testing with new specimen support system, a free-free resonant column testing device, which is capable of testing gravel-sized materials and constraining a specimen in free-free boundaries, is developed. We report the calibration of the equipment and preliminary testing results on Jumunjin sand. The testing data are compared with the previous data obtained from the existing fixed-free resonant column test.

• Journal of The Korean Society of Agricultural Engineers
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• v.56 no.3
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• pp.75-81
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• 2014

Fossil energy is needed for a whole year greenhouse cropping due to climate in South Korea. Because the most of the fossil energy resources is imported, it is necessary to develop technology to be able to reduce the energy cost in order to manage greenhouse profitably. The greenhouse commonly consume less amount of energy as compared to other industrial sectors. Replacement of fossil fuel with solar thermal storage, therefore, can be an economical as well as environmentally sustainable option for greenhouse heating. The fluid flow, heat storage and radiation characteristic of the gravel bed model were analyzed to provide basic data for design of the experimental solar heated greenhouse with underground thermal storage using gravel. The air flow velocity in the gravel storage bed was proven to be affected from the capacity of circulation fan and the circulation method and the positive pressure method was proven to be the best among the different air circulation methods. The initial air temperature of the thermal storage bed of 1.2 m $wide{\times}9$ m $long{\times}0.9$ m deep was $10^{\circ}C$. After the thermal storage bed is heated by air of the mean temperature $4^{\circ}C$ during 9 hours, the temperature has increased about $20.3^{\circ}C$ and the storage of heat was about 33,000 kcal. The important factors should be taken into consideration for design of the solar heated greenhouse with underground thermal storage using gravel are insulation of rock storage, amount of storing heat, inflow rate and direction of inlet and outlet duct.

• Journal of the Korean Geotechnical Society
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• v.21 no.10
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• pp.61-71
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• 2005

Cemented Sand and Gravel (CSG) is a material made by simple mixing of rock-based raw materials such as excavated soil and riverbed gravel together with cement and water. The use of CSG material for cofferdam and large dam is gradually increasing in Japan because a quarry and aggregate plants can be diminished. Also, the CSG method can reduce dam construction cost, construction duration and destruction of environment. In this paper, the basic strength characteristics of CSG, such as compressive strength, modulus of elasticity and stress-strain curve were investigated by unconfined compression test and large triaxial compression test. From the results of the experimental study, the correlation equations between elastic modulus and unit cement, age are proposed.

• Journal of the Korean Geotechnical Society
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• v.33 no.6
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• pp.27-36
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• 2017

Gravel compaction pile method has been widely used to improve the soft ground on the land or sea as one of the soft ground improvement technique. The ultimate bearing capacity of the ground reinforced by gravel compaction piles is affected by the soil strength, the replacement ratio of pile, construction conditions, and so on, and various prediction equations have been proposed to predict this. However, the prediction of the ultimate bearing capacity using the existing models has a very large error and variation, and it is not suitable for practical design. In this study, multiple regression analysis was performed using field loading test results to predict the ultimate bearing capacity of ground reinforced by gravel compaction pile, and the most efficient input variables are selected through evaluation of error by leave one out cross validation, and a multiple regression equation for the prediction of ultimate bearing capacity was proposed. In addition, the prediction error was evaluated by applying artificial neural network using the selected input variables, and the results were compared with those of the existing model.

• The Journal of the Petrological Society of Korea
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• v.26 no.3
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• pp.255-269
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• 2017

Five year term monitoring investigating variation of allochthonous originated gravels are has been conducted in the beach gravel deposit of the Island Dokdo natural reserve which takes purity and uniqueness with enormous attention though a number of areas. The beach gravel deposits near the dock of the Dongdo and near the accommodation facility of the Seodo comprise various types of gravels including basalt, trachyte, and tuff from the Dokdo itself, and granite, rhyolite, gneiss, quartzite, marble, and concrete from elsewhere. The types of the allochthonous gravels on the basis of the study in 2011 and in 2016 shows no difference, so is the ranking of abundance of the allochthonous gravels; granite-concrete-gneiss in turn on the Dongdo, concrete-gneiss-granite in turn on the Seodo. Nevertheless, the relative ratio of the allochthonous gravel area against the total area is decreased. While it is suspected that the disintegrated facility and the influx of material for construction are the main 2 reasons for the contamination by allochthonous gravel, diminished total contamination ratio indicate that supervising allochthonous material has been improved; at least not worse during the 5 years. On the other hand, it is inferred that gradual influence of rockfall also has been made the gravel beach changed. Therefore, consistent rockfall investigation must be inquired.

• Journal of the Korean Geotechnical Society
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• v.29 no.7
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• pp.37-46
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• 2013

Various sizes of gravels are included in the most field soils that are utilized for civil constructions. Especially, the small amounts of gravel are often included in selected soils for backfill materials, earth dams, and subbase ground. In such cases, the small amounts of mixed gravel and its shape may influence the determination of dry density of soils, which results in an inaccurate degree of compaction for soils in the field. In this study, a dry density of sand with various gravel contents (0, 10, 17, 23, 29 and 33%) and three different sizes (2.0-2.36, 3.35-4.75, 5.6-10.0 mm) was experimentally investigated for compacted or loosely packed conditions. The loosely packed sand with gravels was simulated by pouring sand into compaction mould and its density was determined. When a 33% of gravel content was mixed with sand, its dry density increased up to 15-20% for compacted specimen and 20-23% for loosely packed specimen. When a gravel content and size were the same, a dry density of compacted specimen was $0.1-0.16g/cm^3$ higher than that of loosely packed specimen. Even though the same gravel content was used, a dry density of sand with big gravels was $0.04-0.08g/cm^3$ higher than that of sand with small gravels for compacted specimen and $0.03-0.05g/cm^3$ for loosely packed specimen.

• Journal of The Geomorphological Association of Korea
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• v.23 no.1
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• pp.17-33
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• 2016

Samples from newly exposed outcrop of sedimentary layers forming Jeongdongjin coastal terrace in Gangreung area are collected and analyzed to find the sedimentary environment. The site are located at the gentle hillslope of the terrace surface area. The height of the outcrop is about 8m and the altitude of it's highest part is 68~73m MSL. The lowest part of this out crop is the partly consolidated sand layer with gravel veneer within it. It is found that this part is not in-situ weathered sand stone through the OSL method. This sand layer is overlain by the gravel layer with sand matrix. The shapes of the gravels from this part are mainly 'platy', 'elongated', and 'bladed' by the index of Sneed and Folk(1958). In addition, mean roundness is not so high. It is sceptical to regard this part as marine sediments which are continuously exposed to erosional processes. The boundary between the lowest sand layer and gravel layer showing the abrupt change in forming material without any mixture or transitional zone, so gravels are seemed to deposited after some degree of consolidation of the lowest sand layer. In addition, the hight of the boundary between layers are changed by the place, so the surface of the partly consolidated sand layer is not flat and has irregularity on topography when it buried by gravels. Main part of this out crop is the poorly sorted coarse gravel(22.4mm) with sand matrix($1.36{\phi}$) layer with at least 2m thick covering the relatively fine gravels discussed above. Over 20% of particles have 'very platy', 'very elongated' and 'very bladed' shape and only less than 5% of particles have 'compact' shape, So this particles are also very hard to be regard as marine gravels which are abraded by marine processes. It can be concluded that this gravel layer formed by fluvial processes rather than coastal processes base on the form of the clast and sedimentary structure. The gravel layer is covered by fine($3{\sim}4{\phi}$) material layers of psudo-gleization which showing inter-bedding of red and white layers. Chemical composition of matrix and other fine materials should be analyzed in further studies. It is attempted to fine the burial ages of the sediment using OSL method, but failed by the saturation. So it can be assumed that these sediments have be buried over 120ka.

• Journal of the Korean Geosynthetics Society
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• v.22 no.3
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• pp.1-10
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• 2023

Recently, numerous structures have been constructed near the Nakdong river estuary, with pile foundations embedded in sand and gravel layers. In this study, the side resistance for six drilled shafts embedded in that region was evaluated based on the results of bi-directional and static axial compressive pile load tests. Subsequently, these results were compared with the side resistance calculated using domestic and foreign design codes such as FHWA (1999), KDS (2021), and AIJ (2004). Based on the test results, the evaluated side resistances ranged from 120 to 444kPa. However, the estimated values obtained from the design codes ranged from 69.3 to 170kPa, which were less than 50% of the evaluated values. It was observed that the empirical methods and correlations used in design codes provide a conservative estimation of the side resistance for drilled shafts embedded in sand and gravel layers. It implies that a suitable domestic approach should be developed to accurately estimate the side resistance of pile in sandy gravel and gravel layers near the Nakdong river estuary.

• Journal of the Korean Geotechnical Society
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• v.24 no.6
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• pp.45-55
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• 2008

CFRD (Concrete Faced Rockfill Dam) has been world-widely constructed due to a lot of advantages which it has compared with rockfill dam and recently, sand/gravel materials, Instead of crushed rock materials, are also utilized as a main rockfill material to overcome geological and environmental problems. In Korea, two dams using sand/gravel materials as a main fill material were designed and are being constructed. In this research, the strength and deformation characteristics of the rockfill and sand/gravel materials taken from 2 dam sites were tested by using a laboratory large triaxial testing equipment for a total of 7 cases. From the results of large triaxial and compaction tests, it was observed that two kinds of materials show a little different compaction, shear strenght and deformation characteristics. It could be expected that the shear strength of sand/gravel material was not disadvantageous compared with that of rockfill materials, however, there was some difference between two materials with respect to behavior characteristics. On the other hand, smaller displacements were observed from numerical analysis based on the data from a large triaxial test when the sand/gravel is used as a main fill material compared with the case when the crushed rock material is used as a main fill material. Finally, in spite of a little different shear strength and behavior characteristic between two materials, it was concluded that it will not lead to a significant problem when the sand/gravel material is used as a main rockfill material.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.36 no.2
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• pp.37-49
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• 2024

To date, numerous empirical formulas have been proposed through hydraulic model experiments to predict the wave breaker index, including wave height and depth of wave breaking, due to the inherent complexity of generation mechanisms. Unfortunately, research on the characteristics of wave breaking and the prediction of the wave breaker index for gravel beaches has been limited. This study aims to forecast the wave breaker index for gravel beaches using representative linear-based machine learning techniques known for their high predictive performance in regression or classification problems across various research fields. Initially, the applicability of existing empirical formulas for wave breaker indices to gravel seabeds was assessed. Various linear-based machine learning algorithms were then employed to build prediction models, aiming to overcome the limitations of existing empirical formulas in predicting wave breaker indices for gravel seabeds. Among the developed machine learning models, a new calculation formula for easily computable wave breaker indices based on the model was proposed, demonstrating high predictive performance for wave height and depth of wave breaking on gravel beaches. The study validated the predictive capabilities of the proposed wave breaker indices through hydraulic model experiments and compared them with existing empirical formulas. Despite its simplicity as a polynomial, the newly proposed empirical formula for wave breaking indices in this study exhibited exceptional predictive performance for gravel beaches.