• 자원환경지질
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• 제54권4호
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• pp.483-494
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• 2021

본 연구에서는 폐금속광산과는 달리 우려기준 전후의 낮은 비소 오염농도 분포특성을 가지는 폐석탄광산 농경지 토양을 대상으로 광해방지사업(토양개량·복원사업) 시 복토층의 두께 감소 가능여부를 벼를 식재한 담수형 컬럼실험을 통해 검토하였다. 담수 후 4개월 동안 토양용액의 pH, EC, ORP 및 무기원소(Fe, Mn, Ca, As) 농도를 모니터링한 결과 컬럼하층에서 상층으로 미치는 영향은 높지 않은 것으로 나타났다. 복토 두께에 따른 비교에서도 하층의 영향보다는 복토층 두께 변화에 따른 ORP 변화가 복토재 무기원소의 거동에 영향을 미치는 결과를 보였다. 이러한 결과는 토양용액의 거동이 상하층간 반응의 영향보다는 각 층별 나타나는 토양의 이질성에 우선하여 나타난 것으로 판단되었다. 모니터링 종료시점에서 채취한 벼 뿌리의 비소 농도는 현행 사업 조건과 같은 40 cm 두께의 복토층을 조성한 경우 컬럼하층의 안정화 처리여부에 상관없이 대조구 대비 98%가 감소되었다. 20 cm 두께의 복토층에서는 오염토의 안정화가 없을 경우 58%, 안정화처리 시 80%의 전이감소 효율을 나타내었다. 따라서 오염 농경지 토양에 대한 적정 안정화 처리를 수행할 경우 복토재의 사용량을 감소시킬 수 있으며, 경제적인 사업수행효과도 이룰 수 있을 것으로 판단된다.

• Coupled systems mechanics
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• 제2권3호
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• pp.289-302
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• 2013

The piled raft is a geotechnical construction, consisting of the three elements-piles, raft and the soil, that is applied for the foundation of a tall buildings in an increasing number. The piled rafts nowadays are preferred as the foundation to reduce the overall and differential settlements; and also, provides an economical foundation option for circumstances where the performance of the raft alone does not satisfy the design requirements. The finite element analysis of the piled raft foundation is presented in this paper. The numerical procedure is programmed into finite element based software SAFE in order to conduct the parametric study wherein soil modulus and raft thickness is varied for constant pile diameter. The problems of piled raft for three different load patterns as considered in the available literature (Sawant et al. 2012) are analyzed here using SAFE. The results obtained for load pattern-I using SAFE are compared with those obtained by Sawant et al. (2012). The fair agreement is observed in the results which demonstrate the accuracy of the procedure employed in the present investigation. Further, substantial reduction in maximum deflections and moments are found in piled raft as compared to that in raft. The reduction in deflections is observed with increase in raft thickness and soil modulus. The decrease in maximum moments with increase in soil modulus is seen in raft whereas increase in maximum moments is seen in piled raft. The raft thickness and soil modulus affects the response of the type of the foundation considered in the present investigation.

• 환경영향평가
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• 제32권3호
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• pp.157-165
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• 2023

폐석탄광산 주변 농경지의 주요 토양오염물질은 비소이며, 폐금속광산과는 달리 그 오염수준이 관련 환경기준을 경미하게 초과하는 특성을 가진다. 이에 선행연구에서는 폐석탄광산 농경지의 토양개량·복원사업(안정화 처리 및 복토층 조성) 시 복토층 두께를 기존 40 cm에서 20 cm 두께로 낮추는 방안의 적용성을 실내 포트실험으로 확인한 바 있다. 금번 후속연구에서는 본 방안을 실제 농경지에서 벼 재배를 통해 실증하였다. 4개월이 넘는 벼 재배기간 중 쌀알로 전이된 비소의 농도는 20 cm 두께의 복토 시 44% 이상의 전이감소율을 보였다. 특히 오염된 원지반을 안정화 처리한 후 복토한 경우엔 이의 감소율이 56%까지 증가하였다. 따라서 본 실증연구를 통해 복토층 두께 20 cm의 적용성을 확인하였고, 이는 곧 복토재 사용량 감소로 인한 사업비 절감도 가능함을 시사한다.

• Structural Engineering and Mechanics
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• 제20권4호
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• pp.421-434
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• 2005

In this paper, the finite element method is applied to investigate the effect of the lateral boundary in homogenous soil on the seismic response of a superstructure. Some influencing factors are presented and discussed, and several parameters are identified to be important for conducting soil-structure interaction experiments on shaking tables. Numerical results show that the cross-section width L, thickness H, wave propagation velocity and lateral boundaries of soil layer have certain influences on the computational accuracy. The dimensionless parameter L/H is the most significant one among the influencing factors. In other words, a greater depth of soil layer near the foundation should be considered in shaking table tests as the thickness of the soil layer increases, which can be regarded as a linear relationship approximately. It is also found that the wave propagation velocity in soil layer affects the numerical accuracy and it is suggested to consider a greater depth of the soil layer as the wave propagation velocity increases. A numerical study on a soil-structure experimental model with a rubber ring surrounding the soil on a shaking table is also conducted. It is found the rubber ring has great effect on the soil-structure interaction experiments on shaking table. The experimental precision can be improved by reasonably choosing the elastic parameter and width of the rubber ring.

• Structural Engineering and Mechanics
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• 제15권2호
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• pp.249-267
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• 2003

In this study, circular plates subjected to general type of loads and supported on a two-parameter elastic foundation are analysed. The stiffness, elastic bedding and soil shear effect matrices of a fully compatible ring sector plate element, developed by Saygun (1974), are obtained numerically assuming variable thickness of the element. Ring sector soil finite element is also defined to determine the deflection of the soil surface outside the domain of the plate in order to establish the interaction between the plate and the soil. According to Vallabhan and Das (1991) the elastic bedding (C) and shear parameters ($C_T$) of the foundation are expressed depending on the elastic constants ($E_s$, $V_s$) and the thickness of compressible soil layer ($H_s$) and they are calculated with a suitable iterative procedure. Using ring sector elements presented in this paper, permits the generalization of the loading and the boundary conditions of the soil outside the plate.

• Advances in Computational Design
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• 제3권2호
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• pp.201-212
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• 2018

Decrease in availability of suitable subbase and base course materials for highway construction leads to a search for economic method of converting locally available troublesome soil to suitable one for highway construction. Present study insights on evaluation of benefits of stabilization of subgrade soils in term of extension in service life (TBR) and layer thickness reduction (LTR). Laboratory investigation consisting of Atterberg limit, Compaction, California Bearing Ratio, unconfined compressive strength and triaxial shear strength tests were carried out on two types of soil for varying percentages of stabilizers. Vertical compressive strains at the top of unstabilized and stabilized subgrade soils were found out by elastoplastic finite element analysis using commercial software ANSYS. The values of vertical compressive strains at the top of unstabilized and stabilized subgrade, were further used to estimate layer thickness reduction or extension in service life of the pavement due to stabilization. Finite element modeling of the flexible pavement layered structure provides modern technology and sophisticated characterization of materials that can be accommodated in the analysis and enhances the reliability for the prediction of pavement response for improved design methodology. If the pavement section is kept same for unstabilized and stabilized subgrade soils, pavement resting on lime, fly ash and fiber stabilized subgrade soil B will have service life 2.84, 1.84 and 1.67 times than that of unstabilized pavement respectively. The flexible pavement resting on stabilized subgrade is beneficial in reducing the construction material. Actual savings would depend on the option exercised by the designer for reducing the thickness of an individual layer.

• 한국환경복원기술학회지
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• 제14권5호
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• pp.127-136
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• 2011

This study was conducted on the field application for a method which is currently used. Although the method was performed with experimental knowledge, this study attempted to approach scientific ways through thirty sets of test-bed and three times monitoring limited by control variations for three months. The factors on previous studies are slope location, slope degree, type (roadfill vs. roadcut), aspect, vegetation cover, species, thickness, vertical length, horizontal length, soil type, elevation, erosion, soil-moisture, soil-hardness, pH, and so on. However, the factors of a suitable and significant level are slope degree, type, aspect, thickness, soil-moisture, vertical length and horizontal length in slope revegetation. the results were as follows : As a result of survey on soil types based on the status before construction, the rate of vegetation cover with non-mesh construction in soil areas was better than the rate of vegetation cover with fiber meshes and wire meshes. The rate of vegetation cover with fiber meshes in weathered rocks was better than using wire meshes. The rate of vegetation cover with the wire meshes in blasted rocks was better than using fiber meshes. Also, the factors affecting the rate of vegetation cover presented the number of appearance species, soil-moisture, thickness. this result presented the more appearance species as a positive role, and the lower soil-moisture and the thicker soil as a negative role.

• 한국조경학회지
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• 제35권5호
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• pp.46-55
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• 2007

This study was carried out to analyze both the root structure and the fine root phytomass of the vertical and horizontal distribution of Zelkova serrata Makino. which was transplanted in the reclaimed land from the sea in Gwangyang, Jeonnam, South Korea. The base ground was reclaimed land from the sea. $Z_1$ of the planting ground was filled to a $100{\sim}150cm$ thickness with the improved soil instead of the reclaimed soil from the sea, $Z_2$ of the planting ground was covered to a $20{\sim}30cm$ thickness with the improved soil and $Z_3$ of the planting ground was mounded to 120cm thickness with the improved soil on the reclaimed land from the sea. In addition, $Z_4,\;Z_5\;and\;Z_6$ of the planting grounds were at the large-sized mound on the reclaimed land from the sea. $Z_4$ of the planting ground was located at the lowest level, $Z_5$ planting ground was located at the slope and $Z_6$ planting ground was located at the top of the large-sized mound. The large-sized mounds contain 3 layers, the base layer was reclaimed land from the sea and the second layer was mounded to a $200{\sim}300cm$ thickness with the desalinized soil from the sea on the base layers and the finally layers were mounded to a $80{\sim}120cm$ thickness with improved soil on the second layer. The planting grounds $Z_3,\;Z_4,\;Z_5\;and\;Z_6$ developed roots such as tap roots, lateral roots and heart roots. However, in $Z_1\;and\;Z_2$ roots development were inhibited. The fine-root phytomass of the 6 planting ground types was as follows: $113.5g\;DM/m^2$ for $Z_5$, $105.5g\;DM/m^2$ for $Z_4$, $88.3g\;DM/m^2$ for $Z_3$, $81.0g\;DM/m^2$ for $Z_6$, $73.0g\;DM/m^2$ for $Z_2$, $43.3g\;DM/m^2$ for $Z_1$. The vertical distribution of the fine root phytomass decreased from the upper to the deeper soil profiles in the 6 mound types. The fine root phytomass was $43.3{\sim}71.8%$ in a $0{\sim}20cm$ thickness of soil layer and it decreased according to the distance from the nearest trees. The root growth in the improved soil was better than in the reclaimed soil from the sea. However, root growth decreased more in the disturbed soils even though the planting grounds contained the improved soils. The retarded development of roots and the spatial distribution patterns of the fine root phytomass were closely connected to the reclaimed soil from the sea. In the disturbed soil, the soil hardness and alkalic cation($Na^+,\;K^+,\;Ca^{2+},\;Mg^{2+}$). were high and the soil water was lacking. We suggest that the construction of planting grounds and the improvement of bad soil are necessary for the proper and effective growth of landscaping plants.

• 산업기술연구
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• 제34권
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• pp.45-52
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• 2014

In this paper the settlement characteristic of shallow foundation on sandy soil overlained by rigid ground was investigated by analyzing results of model tests. For model experiments, model tests were performed with sandy soils sampled from the field, changing the relative density of sandy soil and the ratio of thickness of sandy layer(H) to the width of model strip footing(B). As result of tests, settlement of sandy soils increases as the value of H/B increases, whereas it increases with relative density of soil. Bearing capacity decreases as the thickness of the sand layer relative to the footing width increases. In order to analyze the settlement characteristics of sandy ground, the results of model tests were compared with the predicted values using the empirical formulas proposed by Terzaghi, De Beer and Schmertmann. The method by De Beer was found to be in good agreements with test results.

• Coupled systems mechanics
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• 제5권1호
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• pp.41-58
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• 2016

The study deals with physical modeling of a typical building frame resting on pile raft foundation and embedded in cohesive soil mass using finite element based software ETABS. Both- the elements of superstructure and substructure (i.e., foundation) including soil is assumed to remain in elastic state at all the time. The raft is modelled as a thin plate and the pile and soils are treated as interactive springs. Both- the resistance of the piles as well as that of raft base - are incorporated into the model. Interactions between raft-soil-pile are computed. The proposed method makes it possible to solve the problems of uniformly and large non-uniformly arranged piled rafts in a time saving way using finite element based software ETABS. The effect of the various parameters of the pile raft foundation such as thickness of raft and pile diameter is evaluated on the response of superstructure. The response included the displacement at the top of the frame and bending moment in columns. The soil-structure interaction effect is found to increase displacement and increase the absolute maximum positive and negative moments. The effect of the soil- structure interaction is observed to be significant for the type of foundation and soil considered in the present study.