• Journal of the Korea Institute of Building Construction
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• 제9권1호
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• pp.49-55
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• 2009

In this study, reduction methods of surface air void were examined for high performance concrete having high viscosity. The effects of assumed influencing factors such as form types, form-coating materials, tamping equipments and methods were examined based on the tests on mock-up specimens made of high performance concrete. The test results can be summarized as follows: As for form types, the most favorable results were obtained when coated plywood form was used with panel-shape tamping equipments at the contact region with concrete, the second and the third being the water/air-permeable sheets and steel with coated plywood, respectively. As for tamping equipments, a vibrator with 6.5cm diameter was most effective. Finally, the shorter the tamping intervals, the better the reduction effect of surface air void. As a conclusion, an improved method was proposed to reduce surface air void and it was verified with the test result that only four air voids as large as $5{\sim}10mm$ are found in the are of $1m^2$.

• Geomechanics and Engineering
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• 제2권3호
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• pp.161-176
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• 2010

Discrete Element Method (DEM) simulations were developed to investigate the effectiveness of geosynthetic reinforcement and the effectiveness of maintenance techniques performed on a simulated ballast bed subjected to dynamic loading. The results from four samples subjected each one to a total of 425 load cycles are presented: one unreinforced and unmaintained sample, one unmaintained but reinforced sample, one unreinforced sample subjected to maintenance in the form of stoneblowing after 200 load cycles, and one unreinforced sample subjected to maintenance in the form of tamping after 200 load cycles. The obtained values of permanent deformation as a function of the applied number of load cycles for the four cases are presented together allowing a comparison of the effectiveness of each technique. Moreover, snapshots of the simulated track sections are presented at different moments of the simulations. The simulations indicated that the geosynthetic reinforcement may not be beneficial for the analyzed case while stoneblowing was the most effective maintenance technique.

• Proceedings of the Korea Concrete Institute Conference
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• 한국콘크리트학회 1996년도 봄 학술발표회 논문집
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• pp.198-201
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• 1996

The purpose of this study is to analyze the properties of high fluidity concrete using the viscosity agent of a cellulose system with W/C of 35~50% in hardened state. It is proven that properties of high fluidity concrete in hardened state is nearly the same with normal concrete in the same W/C and no strength difference by tamping method do not appeared. Therefore, no tamping method is thought to be reguired in high fluidity concrete.

• Journal of the Korean Society of Safety
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• 제25권2호
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• pp.55-64
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• 2010

Since various weathered soils are encountered in many domestic construction sites, it is necessary to estimate characteristics of natural weathered soils. However, the remolded sample of weathered soils are commonly used to estimate their characteristics because it is very difficult to sample weathered soils in undisturbed states. However, it is well known that the behavior of remolded sample is different from that of the undisturbed sample particularly in the dynamic response, because the particle structure of undisturbed sample maintains its original structure from the mother rock. Thus, to evaluate the influence of sampling method and preparation method on stress-strain behavior, the resonant column tests were performed on the block, tube samples, remolded samples with static compression and remolded samples with tamping of the weathered granite soils. The shear modulus of the remolded sample with tamping is larger than the other samples presumably due to the high tamping pressure enough to induce particle breakage. The tube samples show larger damping ratios than other samples. Furthermore, one-dimensional ground response analysis was performed to compare the results qualitatively.

• Journal of the Korean Geosynthetics Society
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• 제21권2호
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• pp.57-65
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• 2022

This study simulated the shock wave propagation through the tamping material between explosives and hole wall at blasting works and verified the effect of tamping materials. The Arbitrary Lagrangian-Eulerian(ALE) method was selected to model the mixture of solid (Lagrangian) and fluid (Eulerian). The time series analysis was carried out during blasting process time. Explosives and tamping materials (air or water) were modeled with finite element mesh and the hole wall was assumed as a rigid body that can determine the propagation velocity and shock force hitting the hole wall from starting point (explosives). The numerical simulation results show that the propagation velocity and shock force in case of water were larger than those in case of air. In addition, the real site at blasting work was modeled and simulated. The rock was treated as elasto-plastic material. The results demonstrate that the instantaneous shock force was larger and the demolished block size was smaller in water than in air. On the contrary, the impact in the back side of explosives hole was smaller in water, because considerable amount of shock energy was used to demolish the rock, but the propagation of compression through solid becomes smaller due to the damping effect by rock demolition. Therefore, It can be proven that the water as the tamping media was more profitable than air.

• Structural Engineering and Mechanics
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• 제56권1호
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• pp.49-56
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• 2015

Dynamic compaction (DC) is a useful method for improvement of granular soils. The method is based on falling a tamper (weighting 5 to 40 ton) from the height of 15 to 30 meters on loose soil that results in stress distribution, vibration of soil particles and desirable compaction of the soil. Propagation of the waves during tamping affects adjacent structures and causes structural damage or loss of performance. Therefore, determination of the safe or critical distance from tamping point to prevent structural hazards is necessary. According to FHWA, the critical distance is defined as the limit of a particle velocity of 76 mm/s. In present study, the ABAQUS software was used for numerical modeling of DC process and determination of the safe distance based on particle velocity criterion. Different variables like alluvium depth, relative density, and impact energy were considered in finite element modeling. It was concluded that for alluvium depths less than 10 m, reflection of the body waves from lower boundaries back to the soil and resonance phenomenon increases the critical distance. However, the critical distance decreases for alluvium depths more than 10 m. Moreover, it was observed that relative density of the alluvium does not significantly influence the critical distance value.

• Proceedings of the Korean Geotechical Society Conference
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• 한국지반공학회 2002년도 가을 학술발표회 논문집
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• pp.404-410
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• 2002

Dynamic compaction is an efficient ground improvement technique for loose soils and waste landfill. The improvement is obtained by controlled high energy tamping and its effects vary with the soil properties and energy input. This study demonstrated the application of dynamic compaction method for the improvement of waste landfill in construction site. Various tests and measurements such as standard penetration test, bore hole loading test, crater settlement, ground settlement, pore water pressure were peformed during dynamic compaction field test. From the field test results, the efficiency of dynamic compaction method for the improvement of waste landfill was proved.

• Geomechanics and Engineering
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• 제1권3호
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• pp.241-257
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• 2009

The one-dimensional compressibility of sand is an important property for the estimation of settlement or deformation of sand deposits. The $K_0$ value of sand is also an important design parameter. Experimental results are presented in this paper to study the compressibility of sand in $K_0$ consolidation tests. The $K_0$ consolidation tests were carried out using a triaxial cell and a plane-strain apparatus. Specimens prepared using both the moist tamping and the water sedimentation methods were tested. The testing data demonstrate that the type of testing apparatus does not affect the $K_0$ measurement if proper boundary conditions are imposed in the tests. The data also show that the compressibility and the $K_0$ value of loose sand specimens prepared using the moist tamping method are very sensitive to the variation of void ratio. The $K_0$ values measured from these tests do not agree with the $K_0$ values calculated from Jaky's equation. The compressibility and $K_0$ values of sand obtained from tests on specimens prepared using different preparation methods are different which may reflect the influence of soil fabrics or structures on the one dimensional compression behavior of sand.

• Proceedings of the Korea Concrete Institute Conference
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• 한국콘크리트학회 1995년도 봄 학술발표회 논문집
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• pp.48-53
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• 1995

Recently, work of construction industry is not enough to do in tamping because of a lack of expert, advanced-age of worker, increase of structure of high-dengity arrangment and machanization of concrete pumping method Accordingly it is required for high-qualuily concrete with excellent flowability, Self-placeability and regregation registance. In this point of view, this study is investigated for requiremend properties of ultar-flow concrete using dimestic material as for development of Ultra-Flow concrete in the side of material

• Proceedings of the Korea Concrete Institute Conference
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(II)
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• pp.153-156
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• 2005

Surface dry condition examination method on the KS F 2504(Testing method for specific gravity and absorption of fine aggregate) has dim detail prescriptions which can cause different ways of understanding based on one's convinence, not on correct means of rule. So we investigate the problems about the inconsistency on decisioing surface dry condition at management examination in the lab and scene. In conclusion, free-falling method is easier and faster than self-weight method. And we also found that the most important face on decisioning surface dry is compacting factor of tamping rod.