• Journal of Korean Society of Water and Wastewater
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• v.18 no.3
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• pp.307-311
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• 2004

The objective of this work is to evaluate the hypothesis that a good technique for supplying oxygen to the saturated zone in the presence of light nonaqueous phase liquid (LNAPL) pool contamination at the water table is to pass air through the unsaturated zone above the pool. This hypothesis was evaluated in experimental studies performed using a bench-scale, sand-tank reactor, Steady-state abiotic experiments in the sand-tank reactor with air flowing through the reactor headspace demonstrated that oxygen supply through the water table interface into the saturated zone was enhanced when an LNAPL (dodecane) pool was present at the water table. These experimental results confirmed the hypothesis that an LNAPL pool can serve as a high concentration oxygen source to the oxygen-limited area beneath the pool and, as a result, enhance the in situ biodegradation rate.

• The Journal of Engineering Geology
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• v.13 no.1
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• pp.51-65
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• 2003

A series of numerical simulations were carried out using STOMP( Subsurface Transport over Multiple Phase) simulator. The flow and distribution of LNAPL were analyzed in homogeneous fine and coarse sand. Vertical movement of LNAPL is faster in the coarser sand. But the total volume of LNAPL retained in the unsaturated zone is larger in the finer sand. A fine layer in the coarse sand domain is also simulated. The results showed that the retained LNAPL volume and shape are highly influenced by the Position of the fine layer. Flow and distributions of LNAPL were simulated when there were heterogeneous lenses in the sand domain. Water table fluctuation was also considered. In these cases, it was found that the heterogeneous lens was a barrier to LNAPL flow, and water table fluctuation stimulated the downward movement of retained LNAPL. The LNAPL flow and distribution observed in these numerical experiments show that in the subsurface environment, the behaviors of LNAPL highly depend on heterogeneities of unsaturated zone and the dynamic hydrogeologic condition such as water table fluctuation. These results can explain some of the complexity of LNAPL flow and distribution Patterns in LNAPL contaminated field sites.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.4C
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• pp.341-350
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• 2006

The sand table training is one of the most effective training method in military operations which can accomplish missions such as simulation and rehearsal without limitations related to time, space, money and so on. Previous sand table training has many problems like that the sand table cannot represent real field condition because of its physical properties. So, it is hard to be preserved and impossible to include much of information into them. In this paper, we make an approach based on Augmented Reality(AR) to solve these problems and propose an efficient military training briefing tool with virtual sand table environment described as actual battle field Virtual Tactical Map(VTM) can realize a virtual military training with simple action like moving marker or tangible interface by hand. Real-time state information of VTM gives us more organic intelligence for entire situation. Tangible AR interface provides users with a contents authoring tool that is natural, intuitive and easy to deal with as interaction between user in real world and system that augmented real world with virtual object. VTM is a newly designed military training briefing tools. A military training content can be reproduced and it is possible that user uses this content later. Thus, it shows us potential possibilities of AR applications on military leaning field.

• Advances in concrete construction
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• v.9 no.1
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• pp.93-102
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• 2020

In this study, we examined the relationship among the rheological properties, workability, and extrudability in the construction of concrete structures using additive manufacturing. We altered the component materials (binder type, water-binder (W/B) ratio, sand ratio) to assess their effect on the rheological properties experimentally. The results indicated that the W/B and sand ratios had the largest effect on the rheological properties. In particular, when the sand ratio increased, it indicated that adjusting the sand ratio would facilitate control over the rheological properties. Additionally, we compared the rheological properties with the results of a traditional workability evaluation, namely the table flow test. This indicated the possibility of inferring the rheological properties by using traditional methods. Finally, we evaluated extrusion quantity according to table flow. The extrusion rate was 350 g/s for a flow of 210 mm and 170 g/s for a flow of 130 mm, indicating that extrusion rate increased as flow increased; however, we concluded that a flow standard of approximately 140-160 mm is suitable for controlling the actual extrusion quantity and rate.

• Proceedings of the KSR Conference
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• 2002.05a
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• pp.289-294
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• 2002

Sand Compaction Pile (SCP) method, which uses sand material, is frequently used in Korea. However, the use of sand for SCP faces environmental and economical problems with the shortage of its resources. Therefore, it is necessary to substitute other materials for compaction piles. One of the alternatives is using gravel in lieu of sand. Granular Pile, constituted with sand and crushed-stone, is one of the methods to improve soft clay and loose sandy ground. In this study, modeled pile load tests are performed in test cell. The observations are made on the consolidation and the variation of water table of three different grounds, original, sand pile installed, and granular pile installed ground. In addition, engineering characteristics such as bearing capacity, settlement and drainage are investigated. The test results show that Gravel Compaction Pile (GCP) is more efficient for increasing bearing capacity and reducing settlement than SCP and had similar pore water pressure dissipation to sand. Therefore, the results show that GCP can be a good substitution for SCP.

• Earthquakes and Structures
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• v.15 no.6
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• pp.655-665
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• 2018

Shield tunnels are widely used throughout the world. However, their seismic performance has not been well studied. This paper focuses on the seismic response of a large scale model tunnel in compacted sand. A 9.3 m long, 3.7 m wide and 2.5 m high rigid box was filled with sand so as to simulate the sandy soil surrounding the tunnel. The setup was excited on a large-scale shake table. The model tunnel used was a 1:8 scaled model with a cross-sectional diameter of 900 mm. The effective shock absorbing layer (SAL) on the seismic response of the model tunnel was also investigated. The thickness of the tunnel lining is 60 mm. The earthquake motion recorded from the Kobe earthquake waves was used. The ground motions were scaled to have the same peak accelerations. A total of three peak accelerations were considered (i.e., 0.1 g, 0.2 g and 0.4 g). During the tests, the strain, acceleration and soil pressure on the surface of the tunnel were measured. In order to investigate the effect of shock absorbing layer on the dynamic response of the sand- tunnel system, two tunnel models were set up, one with and one without the shock absorbing layer of foam board were used. The results shows the longitudinal direction acceleration of the model tunnel with a shock absorbing layer were lower than those of model tunnel without the shock absorbing layer, Which indicates that the shock absorbing layer has a beneficial effect on the acceleration reduction. In addition, the shock absorbing layer has influence on the hoop strain and earth pressure of the model tunnel, this the effect of shock absorbing layer to the model tunnel will be discussed in the paper.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.188-197
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• 2010

This paper presents experimental results of a series of 1-g shaking table model tests performed on end-bearing single piles and pile groups to investigate the effect of particle size on the dynamic behavior of soil-pile systems. Two soil-pile models consisting of a single-pile and a $4{\times}2$-pile group were tested twice; first using Jumoonjin sand, and second using Australian Fine sand, which has a smaller particle size. In the case of single-pile models, the lateral displacement was almost within 1% of pile diameter which corresponds to the elastic range of the pile. The back-calculated p-y curves show that the subgrade reaction of the Jumoonjin-sand-model ground was larger than that of the Australian Fine-sand-model ground at the same displacement. This phenomenon means that the stress-strain behavior of Jumoonjin sand was initially stiffer than that of Australian Fine sand. This difference was also confirmed by resonant column tests and compression triaxial tests. And the single pile p-y backbone curves of the Australian fine sand were constructed and compared with those of the Jumoonjin sand. As a result, the stiffness of the p-y backbone curves of Jumunjin sand was larger than those of Australian fine sand. Therefore, using the same p-y curves regardless of particle size can lead to inaccurate results when evaluating dynamic behavior of soil-pile system. In the case of the group-pile models, the lateral displacement was much larger than the elastic range of pile movement at the same test conditions in the single-pile models. The back-calculated p-y curves in the case of group pile models were very similar in both sands because the stiffness difference between the Jumoonjin-sand-model ground and the Australian Fine-sand-model ground was not significantly large at a large strain level, where both sands showed non-linear behavior. According to a series of single pile and group pile test results, the evaluation group pile effect using the p-multiplier can lead to inaccurate results on dynamic behavior of soil-pile system.

• Economic and Environmental Geology
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• v.15 no.3
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• pp.113-122
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• 1982

The surveyed Boseong river, flows from south to north crossing Boseong gun Mirukg myon, Nodong myon, Yuleo myon, Bocgnae myon, Mundeog myon, and Seungju gun Nam myon, Jeonranam do. The geology of the surveyed area consists of age-unknown composite gneiss and schist, crystaline chlorite gneiss, porphyroblastic gneiss and granite gneiss, and metasediments of Myon Bong formation and Seologri formation. These metamorphic rocks are intruded by cretaceous biotite granite, granodiorite, and quartz diorite. The heavy sands occur in Quarternary alluvium and colluvium. The composition of the river bed is sand 60%, gravel 30%, and clay 10%. The gravel content of the river bed decreases as the increases. The average depth of auger boring is 0.87 m. The average heavy mineral composition of the heavy sand is monazite 6.83%, zircon 4.88%, ilmenite 11.36%, magnetite 8.36% and garnet 4.84%. The best heavy minerals separation procedure would be primary treatment of the sand by humphrey spiral and table, and retreatment of the table concentrate by magnetic separator. The minimum economically feasible capacity of gravity and magnetic separation plant would be 500 ton/hr when only the heavy minerals are recovered but it may be reduced to 100 ton/hr. capacity, if gravels and sands are added to the valuable products.

• Geomechanics and Engineering
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• v.19 no.3
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• pp.229-240
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• 2019

The physical models are useful to understand the soil behaviour. Hence, these tools allow validating analytical theories and numerical data. This paper addresses the design, construction and implementation of a physical model able to simulate the soil liquefaction under different cyclic actions. The model was instrumented with a piezoelectric actuator and a set of transducers to measure the porewater pressures, displacements and accelerations of the system. The soil liquefaction was assessed in three different grain size particles of a natural sand by applying a sinusoidal signal, which incorporated three amplitudes and the fundamental frequencies of three different earthquakes occurred in Colombia. In addition, such frequencies were scaled in a micro shaking table device for 1, 50 and 80 g. Tests allowed identifying the liquefaction susceptibility at various frequency and displacement amplitude combinations. Experimental evidence validated that the liquefaction susceptibility is higher in the fine-grained sands than coarse-grained sands, and showed that the acceleration of the actuator controls the phenomena trigging in the model instead of the displacement amplitude.

• Economic and Environmental Geology
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• v.34 no.4
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• pp.417-422
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• 2001

Sutfactants may be used in remediation of subsoil and aquifer contaminated with hydrophobic compounds. The objectives of this study were to select potentially suitable sUlfactants that solubilize toluene present as a contaminant and to determine the effectiveness of toluene removal from Ottawa sand by the selected surfactants. Material used as the model soil was Ottawa sand and the organic used as model contaminant was toluene. Used experimental methods were separatory funnel experiment and shaker table agitation/centrifugation experiments. Based on the experimental results, the following conclusions were drawn; t) In the surfactant selection, six different surfactants were chosen based on surfactant types, toxicity, and water solubility. These six were focused into two on the basis of HLB and surface tension study, separatory funnel experiment, shaker table and centrifugation experiments. The two most suitable surfactants were Sandopan JA36 (an anionic surfactant), and Pluronic L44 (a non-ionic surfactant). 2) In the shaker table agitation and centrifugation experiments, the highest recovery of the toluene was 96% which was obtained with one surfactant wash plus two water rinses using an anionic surfactant (Sandopan JA36).