• Geomechanics and Engineering
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• 제35권4호
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• pp.385-393
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• 2023

To analyze the consolidation with horizontal sand drains, the plane strain consolidation model under multi-ramp loading is established, and its corresponding analytical solution is derived by using the separation of variables method. The proposed solution is verified by the field measurement data and finite element results. Then, the effects of the loading mode and stress distribution on consolidation and dissipation of pore pressure are investigated. At the same time, the influence of hydraulic conductivity and thickness of sand blankets on soil consolidation are also analyzed. The results show that the loading mode has a significant effect on both the soil consolidation rate and generation-dissipation process of pore water pressure. In contrast, the influence of stress distribution on pore pressure dissipation is obvious, while its influence on soil consolidation rate is negligible. To guarantee the fully drained condition of the sand blanket, the ratio of hydraulic conductivity of the sand blanket to that of clay layer k_d/k_v should range from 1.0×10⁴ to 1.0×10⁶ with soil width varying from 100 m to 1000 m. A larger soil width correspondingly needs a greater value of kd/kv to make sure that the pore water can flow through the sand blanket smoothly with little resistance. When the soil width is relatively small (e.g., less than 100 m), the effect of thickness of the sand blanket on soil consolidation is insignificant. And its influence appears obvious gradually with the increase of the soil width.

• 한국지반환경공학회 논문집
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• 제22권1호
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• pp.13-20
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• 2021

A suite of 3D large deformation finite element (FE) analyses was performed to investigate the load transfer mechanism and penetration resistance of spudcan foundations in heterogeneous soil profile consisting of sand and clay. The Elasto-Plastic models following Mohr-Coulomb and Tresca failure criteria were adopted for sand and clay, respectively. The accuracy of the numerical model was validated against centrifuge test measurements. The dense sand behavior with dilation is modeled using the non-associated flow rule. An investigation study consisting of key parameters, which includes variation in soil stratigraphy (sand-clay, sand-clay-sand), strength parameters of sand and clay (��' and su) and normalized height ratio of the sand layer (Hs/D) was conducted to assess the penetration behavior of spudcan. Based on calculated outputs, it was demonstrated that these parameters have a significant influence on the penetration resistance of spudcan. The calculated penetration resistance profiles are compared with the published (sand overlying clay) analytical model. It is confirmed that for the case of two-layer soil, the available theoretical model provides an accurate estimate of peak penetration resistance (qpeak). In the case of three-layer soil, the presence of a third stiff layer affects the penetration resistance profile due to the squeezing of the soil.

• 한국조경학회지
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• 제25권2호
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• pp.94-103
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• 1997

The purpose of this study is to find out the effects of brick paved under-surface soil physical properties which are changed by fixed trampling. Thus, a sandy loam which is known as a profitable soil for plants is used an experimental soil to study the changes of the soil physical properties. It is related to sand bed's thickness & particle size which are settled by experimental variable factors. According to the variation of sand bed's particle size, bulk density and soil hardness at natural dryed soilcondition result in 0.075~2.00mm>2.00~5.00mm>2.00~8.00mm>5.00~8.00mm, and water content at natural dryed soil condition are observed being insensible change rate from the point that sand thickness is 30~40mm and more sand bed's thickness constructed by the variation of sand bed's thickness.

• Geomechanics and Engineering
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• 제6권1호
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• pp.33-45
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• 2014

Use of geotextile as reinforcement material to improve the weak soil is a popular method these days. Tensile strength of geotextile and the soil-geotextile interaction are the major factors which influence the improvement of the soil. Change in fine content within the sand can change the interface behavior between soil and geotextile. In the present paper, the bearing capacity of unreinforced and geotextile-reinforced sand with different percentages of fines has been studied. A series of model tests have been carried out and the load settlement curves are obtained. The ultimate load carrying capacity of unreinforced and reinforced sand with different percentages of fines is compared. The interface behavior of sand and geotextile with various percentages of fines is also studied. It is observed that sand having around 5% of fine is suitable or permissible for bearing capacity improvement due to the application of geosynthetic reinforcement. The effectiveness of the reinforcement in load carrying capacity improvement decreases due to the addition of excessive amount of fines.

• Geomechanics and Engineering
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• 제9권5호
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• pp.601-618
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• 2015

Soil-reinforcement interaction mechanism is an important issue in the design of geosynthetic reinforced soil structures. This mechanism depends on the soil properties, reinforcement characteristics and interaction between these two elements (soil and reinforcement). In this work the shear strength of sand/geotextile interfaces were characterized through direct and simple shear tests. The direct shear tests were performed on a conventional direct shear device and on a large scale direct shear apparatus. Unreinforced sand and one layer reinforced sand specimens were characterized trough simple shear tests. The interfaces shear strength achieved with the large scale direct shear device were slightly larger than those obtained with the conventional direct shear apparatus. Notwithstanding the differences between the shear strength characterization through simple shear and direct shear tests, it was concluded that the shear strength of one layer reinforced sand is similar to the sand/geotextile interface direct shear strength.

• 한국토양비료학회지
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• 제43권6호
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• pp.776-781
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• 2010

본 실험은 토양의 염류도 평가를 위한 전기전도도 측정시 기준으로 적용되는 포화 전기전도도가 이상적인 측정방법인 포장용수량의 전기전도도를 대표할 수 있는지 평가하기 위하여 수행되었다. 염류집적 시설재배지 22점과 간척지 토양 18점을 채취하여 포화반죽과 포장용수량의 토양용액을 추출하고, 주요 구성 양이온, 음이온과 전기전도도를 비교하였다. 시설재배지 토양의 양이온, 음이온과 간척지 토양에서 ${NO_3}^-$와 ${PO_4}^{3-}$를 제외한 나머지 양이온, 음이온 모두 높은 상관을 나타내었고, 포장용수량과 포화 전기전도도 또한 높은 상관관계를 보였다. 포화 전기전도도와 불포화 조건인 포장용수량 전기전도도를 비교하였을 때 시설재배지 토양에서는 기울기가 0.923, 간척지 토양에서는 1.009로 거의 차이가 없었으며, 통계 결과 유의성이 인정되지 않아 포화반죽으로 전기전도도를 평가하는 것이 합리적인 것으로 판단되었다. 시설재배지와 간척지 토양을 sand, silt, clay 각각을 기준으로 비교한 결과 sand 함량과 포장용수량, 포화 전기전도도 비율이 비례하는 것으로 나타났다. 시설재배지 토양에서 sand 50% 이하에서는 0.811, Sand 50% 이상에서는 1.179, 간척지 토양은 sand 50% 이하에서 0.848, Sand 50% 이상에서 1.087배 차이나는 것으로 나타났으며, sand 함량이 많을수록 포장용수량과 포화 수분퍼센트의 차이가 크게 나타나 토성에 의한 수분 보유력이 관련된 것으로 판단되었다.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2003년도 추계학술발표회
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• pp.11-24
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• 2003

This paper presents the results of laboratory investigation performed to study the role of different air sparging system parameters on the removal of benzene from saturated soils and groundwater. A series of one-dimensional experiments was conducted with predetermined contaminant concentrations and predetermined injected airflow rates and pressures to investigate the effect of soil type and the use of pulsed air injection on air sparging removal efficiency. On the basis of these studies, two-dimensional air sparging remediation systems were investigated to determine the effect of soil heterogeneity on the removal of benzene from three different homogeneous and heterogeneous soil profiles. This study demonstrated that the grain size of the soils affects the air sparging removal efficiency. Additionally, it was observed that pulsed air injection did not offer any appreciable enhancement to contaminant removal for the coarse sand; however, substantial reduction in system operating time was observed for fine sand. The 2-D experiments showed that air injected in coarse sand profiles traveled in channels within a parabolic zone. In well-graded sand the zone of influence was found to be wider due to high permeability and increased tortuosity of this soil type. The influence zone of heterogeneous soil (well-graded sand between coarse sand) showed the hybrid airflow patterns of the individual soil test. Overall, the mechanism of contaminant removal using air sparging from different soil conditions have been determined and discussed.

• Weed & Turfgrass Science
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• 제3권3호
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• pp.240-245
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• 2014

This study was carried out to determine the possible use of volcano eruption sand at Merapi mountain area compared with clayey soil, alfisol as turfgrass growing media. Indonesia has abundant source of eruption sand and clayey soil. Native zoysiagrass (Z. matrella) was collected from Sleman district and seashore paspalum (P. vaginatum) from Solo region. The experimental plots were treated with both organic and inorganic fertilizers. Zoysiagrass and seashore paspalum can grow on the mixture of eruption volcano sand and alfisol soil. Fertilizers application increased turf color, surface coverage rate and recovery rate of turfgrass. While fertilizer treated alfisol have no effect on the length and dry weight of zoysiagrass root. Mixing of volcano eruption sand on growing media resulted in longer root length, higher shoot dry weight of zoysiagrass than in alfisol soil. Type of fertilizer affected the pH, soil organic matter, total N, available P, available K and electrical conductivity of sand and alfisol after cultivation. Similarly to zoysiagrass, the recovery of seashore paspalum was increased by application of fertilizer, even the inorganic fertilizer showed faster recovery than organic fertilizer. Surface coverage of seashore paspalum was faster than that of zoysiagrass with or without fertilizer.

• Geomechanics and Engineering
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• 제15권1호
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• pp.695-710
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• 2018

Formation of a soil plug in an open-ended pile is a very important factor in determining the pile behavior both during driving and during static loading. The degree of soil plugging can be represented by the incremental filling ratio (IFR) which is defined as the change in the plug length to the change of the pile embedment length. The experimental tests carried out in this research contain 138 tests that are divided as follows: 36 tests for single pile, 36 tests for pile group ($2{\times}1$), 36 tests for pile group ($2{\times}2$) and 30 pile group ($2{\times}3$). All tubular piles were tested using the poorly graded sand from the city of Karbala in Iraq. The sand was prepared at three different densities using a raining technique. Different parameters are considered such as method of installation, relative density, removal of soil plug with respect to length of plug and pile length to diameter ratio. The soil plug is removed using a new device which is manufactured to remove the soil column inside open pipe piles group installed using driving and pressing device. The principle of soil plug removal depends on suction of sand inside the pile. It was concluded that the incremental filling ratio (IFR) is changed with the changing of soil state and method of installation. For driven pipe pile group, the average IFR for piles in loose is 18% and 19.5% for L/D=12 and 15, respectively, while the average of IFR for driven piles in dense sand is 30% and 20% for L/D=12 and L/D=15 respectively. For pressed method of pile installation, the average IFR for group is zero for loose and medium sand and about 5% for dense sand. The group capacity increases with the increase of IFR. For driven pile with length of 450 mm, the average IFR % is about 30.3% in dense sand, 14% in medium and 18.3% for loose sand while when the length of pile is 300 mm, the percentage equals to 20%, 17% and 19.5%, respectively.

• Weed & Turfgrass Science
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• 제5권2호
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• pp.88-94
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• 2016

Vehicular traffic on turf results in loss of green cover due to direct tearing of shoots and indirect long-term soil compaction. Protection of turfgrass crowns from wear could increase the ability of turf to recover from heavy traffic. Plastic turfpavers have been installed in trafficked areas to reduce soil compaction and to protect turfgrass crowns from wear. The objectives of this study were to evaluate traffic performance of turfgrasses (Zoysia matrella and Axonopus compressus) and soil mixture (high, medium and low sand mix) combinations on turf-paver complex. The traffic performance of turf and recovery was evaluated based on percent green cover determined by digital image analysis and spectral reflectance responses by NDVI-meter. Bulk density cores indicated significant increase in soil compaction from medium and low sand mixtures compared to high sand mixture. Higher reduction of percent green cover was observed from A. compressus (30-40%) than Z. matrella (10-20%) across soil mixtures. Both turf species displayed higher wear tolerance when established on higher sand (>50% sand) than low sand mixture. Positive turf recovery was also supported by complementary spectral responses. Establishment of Zoysia matrella turf on turfpaver complex using high sand mixture will result in improved wear tolerance.