• Journal of the Korean Society for Railway
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• v.19 no.2
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• pp.204-212
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• 2016

The soils used as trackbed in Korea are selected using USCS utilizing basic soil properties such as Grain Size Distribution(GSD), % passing of #200 sieve ($P_{200}$), % passing of #4 sieve ($P_4$), Coefficient of uniformity ($C_u$), and Coefficient of curvature ($C_c$). Degree of compaction of the soils adapted in the code by KR should be evaluated by maximum dry density (${\gamma}_{d-max}$) and deformation modulus $E_{v2}$. The most important influencing factor that is critical to stability and deformation of the compacted soils used as trackbed is stiffness. Thus, it is necessary to construct a correlation between the modulus and the basic soil properties of trackbed soil in order to redefine a new soil classification system adaptable only to railway construction. To construct the relationship, basic soil test data is collected as a database, including GSD, maximum dry unit weight (${\gamma}_{d-max}$), OMC, $P_{200}$, $P_4$, $C_u$, $C_c$, etc.; deformation modulus $E_{v2}$ and $E_{vd}$ are obtained independently by performing a Repeated Plated Bearing Test (RPBT) and Light Weight Deflectometer Test (LWDT) for ten different railway construction sites. A linear regression analysis is performed using SPSS to obtain the relationship between the basic soil properties and the deformation modulus $E_{v2}$ and $E_v$. Based on the constructed relationship and the various obtained mechanical test data, a new soil classification system will be proposed later as a guideline for the design and construction of trackbed foundation in Korea.

• Magazine of the Korean Society of Agricultural Engineers
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• v.27 no.2
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• pp.57-71
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• 1985

The characteristics of compaction and unconfined compressive strength were investigated by mixing with lime to all soils adjusted by given percentages of two kinds of clays to sand to obtain the most effective distribution of grain size and the optimum lime content for soil stabilization. In addition, unconfined compressive strength and durability tested by adding of sodium metasilicate, sodium sulfate, sodium carbonate, sodium gydroxide and magnesium oxide to lime-soil mixture mixed with 8 percent lime to adjusted soil having the mixing percentage of 60 percent of cohesive black clay and 40 percent of sand by weight to get the effect and the optimum content of chemicals. The results obtained were as follows; 1.With the addition of more lime, the optimum moisture content was increased, and the maximum dry density was decreased, whereas the more the amount of clay and the less was the maximum drt density. 2. In the soil having more fine grain size the unconfined compressive strength was larger in the earlier stage of curing period, in accordance with the longer period, the mixing percentages of sand to clay showing the maximum unconfined compressive strength, on the basis of 28-day strength, were 60% : 40% (black clay) and 40% : 60% (brown clay) respectively. 3. The reason why the soil adjusted with black clay was remarkably bigger in the unconfined compressive strength than ones adjusted with brown clay for all specimen of lime-soil mixture was the difference in the kind of clay, the amount of chemical compositions the value of pH. Black clay was mainly composed of halloysite that reacted with lime satisfactorily, whereas the main composition of brown clay was kaolinite that was less effect in the enhance of unconfined compressive strength. Also the difference of unconfined compressive strength was because black clay was larger in the amount of composition of calcium oxide and magnesium oxide in the value of pH affecting directly on the unconfined compressive strength of lime-soil mixture than brown clay. 4. In the lime-soil mixture mixed with 8 percent of lime to soil that mixing percentage of sand to black clay was 60% : 40%, on the standard of 7-day strength, the effect of chemical was arranged in the order of magnesium oxide, sodium carbonate, sodium sulfate, sodium hydroxide and sodium metasilicate. 5. The optimum amount of chemical being applicable to the maximum unconfined compressive strength of lime-chemical-soil mixture was 1 percent by weight for air dry soil in the case of adding sodium carbonated and 0.75 percent on sodium hydroxide, the unconfined compressive strength was increased continuously with increase of the amount of chemical up to 2 percent of chemical content is the lime-chemical-soil mixture added sodium metasilicate, sodium sulfate and magnesium oxide. 6. It was considered that the chemical played and accelerant role of early revelation of strength because the rate of increase of unconfined compressive strength of all of lime-chemical-soil mixtures was largest on the 7-day cured specimen. 7. The effect of test on freezing and thawing after adding suitable amount of chemical on the lime-soil mixture mixed with 8 percent of lime to soil that mixing percentage of sand to black clay was 60% : 40% was arranged in the order of magnesium oxide, sodium carbonate, sodium sulfate, sodium metasilicate and sodium hydroxide.

• Journal of the Korean Geotechnical Society
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• v.29 no.10
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• pp.67-74
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• 2013

The objective of this study was to identify the effect of engineering properties on the resilient modulus ($M_r$) of cohesive soils as subgrade. Eight representative cohesive soils representing A-6, and A-7-6 soil types collected from road construction sites, were tested in the laboratory to determine their basic engineering properties. The laboratory tests for the engineering properties were Atterberg limits test, sieve analysis, hydrometer test, Standard Proctor compaction test, and unconfined compressive strength test. Resilient modulus test and unconfined compressive strength test were conducted on unsaturated cohesive soils at three different moisture contents (dry of optimum moisture content, optimum moisture content, and wet of optimum moisture content). The increase in moisture content considerably affected the decrease in the resilient modulus. The resilient modulus increased with an increase in maximum unconfined compressive strength, percent of clay, percent of silt and clay, liquid limit and plasticity index. The resilient modulus decreased with an increase in percent of sand.

• The Journal of Engineering Geology
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• v.20 no.3
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• pp.297-310
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• 2010

This study represents basic research into the utilization of mixed ash (fly ash and bottom ash) from the ash pond of the Taean Thermal Power Plant as a construction material. We conducted physical and mechanical experiments on the mixed ash and examined its engineering characteristics in terms of its use as a material for road landfill and structure backfill. We evaluated the physical and chemical characteristics of the ash by performing tests to determine specific gravity, maximum and minimum density, liquid limit and plastic limit, grain size distribution, composition (by X-ray diffraction), and loss on ignition. We also evaluated the mechanical characteristics by testing for permeability, compaction, CBR, and tri-axial compression. The experiments on the mixed ash yielded a specific gravity of 2.18-2.20, dry density of $9.38-13.32\;kN/m^3$, modified CBR of 16.5%-21%, permeability coefficient of 1.32 to $1.89-10^{-4}cm/sec$, and drained friction angle of $36.43^{\circ}-41.39^{\circ}$. The physical and mechanical properties of the mixed ash do not meet the quality standards stipulated for road landfill and structure backfill materials. Mixed ash with a high content of fly ash failed to meet some of the quality standards. Therefore, in order to utilize the mixed ash as a material for road landfill and structure backfill, it is necessary to improve its properties by mixing with bottom ash.

• International Journal of Highway Engineering
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• v.17 no.3
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• pp.49-58
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• 2015

PURPOSES : The use of environmentally friendly construction methods has been recently encouraged to reduce fuel consumption and the effects of global warming. For this purpose, the roller compacted concrete pavement (RCCP) construction method has been developed. RCCP is more environmentally friendly and economically efficient than general concrete by reducing the amount of CO2 generated through the application of a smaller amount of cement. RCCP has a number of advantages such as an easy construction method, low cost, high structural hydration performance, and aggregate interlocking. However, mix design standards and construction guidelines of RCCP are required for domestic application. In addition, a study on aggregate selection, which has an effect on the characteristics of RCCP, is necessary owing to a limited number of researches. Thus, the aggregate effect on the performance of RCCP in securing the required strength and workability was evaluated in consideration of domestic construction. METHODS : Sand and coarse aggregates of both 19mm and 13mm in maximum size were used in this study. Four types of aggregate gradations (s/a = 30%, 58%, and 70% for the sand and coarse aggregate of 19mm in maximum size, and s/a = 50% for a combination of the three types of aggregates) were set up to investigate the effects of the PCA band on the RCC characteristics. The conditions of s/a = 30% and 70% were evaluated to check the gradation effect outside of the recommended band. The conditions of s/a = 58% and 50% were used because they are the optimum combination of the two and three types of aggregates, respectively. RCCP gradation band was suggested gradation with a proper construction method of RCCP by synthetically comparing and analyzing the correlation of optimum water content, maximum dry density, and strength of requirements through its consistency and compaction test. RESULTS : The lower and upper limit lines are insufficient to secure a relatively strong development and workability compared to an aggregate gradation in the RCCP gradation band region. On the other hand, the line in the RCCP gradation band and the 0.45 power curve in the RCCP gradation band region were satisfactory, ensuring the required strength and workability. CONCLUSIONS : The suitable aggregate gradation on RCCP process should meet the RCCP gradation band area; however, fine particles passing through a #60 sieve do not need to be within the recommended gradation band because the influence of this region on such fine particles is small.

• The Journal of Engineering Geology
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• v.27 no.2
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• pp.153-164
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• 2017

The geological factors for causing ground subsidence are very diverse. It can be affected by any geological or extrinsic influences, and even within the same geological factor, the soil depression impact factor can be determined by different physical properties. As a result of reviewing a large number of papers and case histories, it can be seen that there are seven categories of ground subsidence factors. The depth and thickness of the overburden can affect the subsidence depending on the existence of the cavity, whereas the depth and orientation of the boundary between soil and rock are dominant factors in the ground composed of soil and rock. In case of soil layers, more various influencing factors exist such as type of soil, shear strength, relative density and degree of compaction, dry unit weight, water content, and liquid limit. The type of rock, distance from the main fracture and RQD can be influential factors in the bedrock. When approaching from the hydrogeological point of view, the rainfall intensity, the distance and the depth from the main channel, the coefficient of permeability and fluctuation of ground water level can influence to ground subsidence. It is also possible that the ground subsidence can be affected by external factors such as the depth of excavation and distance from the earth retaining wall, groundwater treatment methods at excavation work, and existence of artificial facilities such as sewer pipes. It is estimated that to evaluate the ground subsidence factor during the construction of underground structures in urban areas will be essential. It is expected that ground subsidence factors examined in this study will contribute for the reliable evaluation of the ground subsidence risk.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.8 no.3
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• pp.207-213
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• 2010

The effect of temperature on swelling pressure was observed with a Korean domestic Ca-bentonite which has been considered as a potential buffer material in the engineering barrier of a high level radioactive waste (HLW) disposal system. The Ca-bentonite was compacted to a dry density of 1.6 g/$cm^3$, and then de-ionized water was supplied into it with a constant pressure of 0.69 MPa. The equilibrium swelling pressures were measured with different temperatures of $25^{\circ}C$, $30^{\circ}C$, $40^{\circ}C$, $50^{\circ}C$, $60^{\circ}C$, $70^{\circ}C$, respectively. The Ca-bentonite showed a sufficiently high swelling pressure of 5.3 MPa at room temperatures. Then it was clearly showed that the equilibrium swelling pressure was decreased with an increase of temperature. Interestingly, there were some differences in temperature effect on the equilibrium swelling pressure when the environmental temperature is increasing or decreasing. For further clarifying the swelling behaviour of a Korea domestic Ca-bentonite, the change of a compaction level, and the composition variation of a supplied water would be needed to use in conceptual design of HLW disposal system.

• Journal of the Korean Society of Marine Environment & Safety
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• v.12 no.2 s.25
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• pp.107-113
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• 2006

Water treatment plant sludge occurred in sedimentation and inverse wash process is generally disposed by ocean dumping or reclamation after dehydration processing using mechanical or natural dry method. Recently, ocean dumping of sludge is limited actually by London Convention. Physical, chemical, and geotechnical characteristics of water treatment plant sludge were analyzed by experiments. The possibilities for recycling of the dehydration sludges as materials for covering sanitary landfill were examined. Experiments performed with sludges mixed with general soil to improved the sludge properties are the hydrometer analysis, the liquid and plastic limit test, the specific gravity test, the compaction test, and the unconfined compression test. The value of ${\gamma}_{dmax}$ is increased and OMC(Optimum Moisture Content) is lessened with mixed sludge. The value of maximum compressive strength and friction angle are increased and the cohesion is decreased with mixed sludge. The ratio between sludge and soil in mixed sludge was 3:7 and the strength of mixed sludge showed $3.6kg/cm^2$. These results satisfy the regulation of U.S. E.P.A regarding materials for covering sanitary landfill.

• Journal of Korea Water Resources Association
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• v.52 no.2
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• pp.133-139
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• 2019

In this study, the degree of scouring according to the bed material according to the flow rate and the relationship between the flow velocity and the bed scouring were investigated in order to examine the operability of the revetment and embankment. The materials used in the experiment were sand and loess as materials used in the embankment. We measured the scouring of the material according to the change of the flow velocity by using the indoor high flow velocity experiment device and verified the flow rate. In this way, The purpose of this study was to compare and analyze changes in material before and after scouring, and compare basal scouring evaluation by bed material with high flow velocity. In case of sand, the cohesive force is very weak, so more than 40% of the material is lost even at less than 1.0 m/s. In the case of loess, less than 6% of the bed material is lost at more than 2 m/s. The reason why the material was lost was that the cohesion was so strong that the material was dried after the compaction and cracked. As a result, the material was lost from the part where the dry crack occurred. In this study, the composition and loss of bed materials were evaluated.

• Journal of the Korean GEO-environmental Society
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• v.12 no.7
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• pp.31-37
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• 2011

Only a few studies have been conducted using reduced slag as recycled material. The reduced slag in electric furnace is produced as a by-product in making a steel and a few applications of the reduced slag as expensive additives and bonding materials or as the stabilized soils was reported. The purpose of this study is to present the feasibility of the reduced slag as recycled material, especially, in a field of civil engineering. In order to achieve the purpose experiments such as SEM and XRF analysis was conducted for the reduced slag in electric furnace. Based on the results various geotechnical experiments were conducted to know engineering properties of slag-soil mixtures. Weathered soils and clay are mixed with reduced slag for various ratios. As the ratio of reduced slag to weathered soil increases, the maximum dry unit weight of the mixture decreased with increasing optimum moisture content. The results indicates that there is no effect on a reduced slag by compaction efforts. The shear strengths of the weathered soil-slag mixtures are slightly higher or similar to those of weathered soils. The permeability of the weathered soil-slag mixtures is similar to that of silty or sandy soils. Therefore, it is possible to use the mixtures as embankment or backfill materials in the fields. The unconfined strength of the mixtures of reduced slag and clay is higher than that of clay and it tends to increase with the curing time. Therefore it can be used to improve the soft ground.