• Proceedings of the Korean Geotechical Society Conference
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• 2002.10a
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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.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.6
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• pp.495-501
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• 2013

Korean Utility Helicopter (KUH) has been designed to avoid the blade passing frequency and any instability due to a coupling of dynamic characteristics between the main rotor and the airframe in ground operation. For these design objectives, the vibration analysis and the ground resonance analysis were performed to analyze the dynamic characteristics of the airframe and the main rotor. Then, the whirl-tower test was conducted to identify the dynamic characteristics of the main rotor and the ground vibration test (GVT) was conducted to identify the dynamic characteristics of the airframe. The GVT for KUH was conducted with the test conditions and test articles established in consideration of each flight and ground condition. This paper shows the method and technique for performing the GVT for KUH and presents the correlation technique and the results for the correlated analysis model.

• Journal of the Korean Geotechnical Society
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• v.33 no.10
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• pp.59-69
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• 2017

The tension load of the ground anchor inserted in the ground gradually changes over time. In this regard the change of the initial tension load is primarily decreased by the fixation condition of the fixing head and the mechanical characteristics of the tensile material. The subsequent additional tension load is a time-dependent loss mostly due to the fixing conditions of the bonded length and the surrounding ground properties of the field. In this paper, therefore, a measurement system using a relative displacement detector that can relatively easily measure the change of tension load is discussed. As a result of the review, it was confirmed that the results using the relative displacement detector are similar to those of the real scale model test, and it was also confirmed that similar results were obtained with the result of the pull-out test conducted on the ground anchors fixed to weathered rocks condition. In addition, a pull-out test was conducted on the test anchors whose initial tension load loss was relatively large and through this test pull-out behavior of the tension type ground anchors was verified.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.1065-1070
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• 2004

Recenlty, there are many cases that structures are constructed on soft ground in domestic. Generally in those cases, appropriate geotechnical techniques for the ground are needed. In this study, an example for ground improvement of OO railroad station construction site is introduced and analyzed. The ground conditions of this site which is soft ground are that N value is under 6, average depth and ground water table is 24.4m, GL-1.7. So, as a countermeasure technique for bearing reinforcement, Compaction Grouting System (CGS) method was applied on construction site. To estimate the application of CGS method, piezo cone penetration test and static pile loading test were carried out during the construction. Results of analysis show that CGS method for improving the bearing capacity of soft ground is applicable for the ground well.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2008.05a
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• pp.313-316
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• 2008

This paper presents the error factors of Fall-of-potential test method used in measurements of the grounding-system impedance. This test methods inherently can introduce two possible errors in the measurements of grounding-system impedance: (1) ground mutual resistance due to current flow through ground from the ground electrode to the current probe, (2) ac mutual coupling between the current test lead and the potential test lead. The errors of ground mutual resistances and ac mutual coupling are expressed by the equation in calculating grounding impedance. These equations were calculated by Matlab that is commercial tool using mathematical calculation. The results of calculation were applied to correct grounding impedance.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.10 no.6
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• pp.139-151
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• 2007

To protect the surface of ground-cutting slopes and ground-raised slopes and to recover environment-friendly slopes at the national road expansion construction between Gamchon and Yaechon, test-construction work was done using several modes of hydro-seeding measures to select a suitable construction method through the field survey; the results were as follows : As a result of survey on physio-chemical characteristics of soil, the average soil inclination on ground-raised slopes was from 4.73 mm to 5.37 mm; the average soil acidity was from pH 6.47 to 6.73; the average soil humidity was within the scope of 0.57~1.70 %,; the average soil inclination on ground-cutting slopes was 9.17~10.43mm; the average soil acidity was pH 6.67~6.77 and the average soil humidity was within the scope of 0.53~1.27 %; considered overall, they showed generally satisfactory base materials for plant breeding. As a result of the number of sprouting individuals, the average sprouting number of individuals on test spots executed by Coir net with Seed spray construction methods and the average number of sprouting individuals on other test spots executed by furrow-digging with Seed spray and Straw mat-mulching measures were 1,172 number of per square meter and 970 number of per square meter respectively; thus they showed higher numerical value comparing with other test spots. Likewise, the average number of sprouting individuals on test spots of the ground-cutting slopes executed by Coir net with Seed spray method and the average number of sprouting individuals on other test spot executed by furrow-digger with Seed spray and Straw mat-mulching measures were found to be 1,107 number of per square meter and 1,105 number of per square meter respectively, whose numerical value showed rather higher other test spots. As a result of a survey on living plants' breeding index [dried weight], the weight in dried state on test spots executed by Coir net with Seed spray method and other test spots executed by furrow-digger with Seed spray and Straw mat-mulching measures on both ground-raised and ground-cutting slopes was found to be higher and showed similar characteristics statistically. As a result of survey on the surface-covering degree of ground-raised slopes, nine weeks after test construction, test spots executed by Coir net with Seed spray method and other test spots executed by furrow-digger with Seed spray and Straw mat-mulching measures showed commonly more than 70% of surface-covering degree, but other test spots showed only below 35% of surface covering degree; especially in case of test spots by Verdvol seed spray measures, they showed 10% of the lowest surface-covering. Surface-covering degree on the test spot of ground-cutting slopes nine weeks after test construction showed more than 75% both executed by Coir net with Seed spray construction method and executed by furrow-digger with Seed spray and Straw mat-mulching measures. As a result of survey on appearing plants on the test spots, there dominates Eragrostis curvula both on ground-raised slopes and on ground-cutting slopes with other seeding plant life's lower breeding and there appear intruders, such as Setaria viridis Beauv, Digitaria sanguinalis Scop, and Chenopodium album var.centrorubrum Makino. As for water-borne excavation and soil's washing-away on the slopes, there happened less washing-away and water-borne excavation with good breeding of plant life on test spots executed both by Coir net with Seed spray construction method and by furrow-digger with Seed spray and Straw mat-mulching measures, but there happened much more soil's washing-away along with water-home excavation at the test spot executed by Seed spray with measures. After the research results of test construction sites are examined overall, it's presumed that furrow-digger with Seed spray and Straw mat-mulching measures [interval between lines is 40cm, 5cm in depth] will be preferred to prevent erosion and water-home excavation of slopes located within the construction sites.

• Proceedings of the Korean Geotechical Society Conference
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• 1998.03a
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• pp.365-372
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• 1998

• Journal of The Korean Society of Agricultural Engineers
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• v.59 no.5
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• pp.83-91
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• 2017

Recently, ground subsidence frequently occurs in downtown area. The major causes of the subsidence on the subsurface were the damages of the water supply and sewer pipelines and excavation works in adjacent areas, etc. Because of these various factors, it is not easy to analyze the tendency of occurrence of ground subsidence. The purpose of this study is to clarify the effect of ground subsidence by the change of the fine particle content and ground water level and to establish the ground subsidence mechanism. In this study, a model soil-box was manufactured to simulate the failure of the old sewer pipe which is one of the causes on ground subsidence. And a model test was conducted to investigate the effects of fine contents and ground water level on the cavity occurrence. From the test results, firstly the higher the ground water level, the faster the primary cavity is formed as the seepage stress increases. As a result, the secondary cavity and the ground subsidence rapidly progress due to the relaxation of the surrounding ground. The total amount of discharged soil was decreased as the fine content increased.

• Aerospace Engineering and Technology
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• v.13 no.2
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• pp.73-79
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• 2014

During developing cubesat flight software, Communication test between cubesat and ground station is needed. For this, we have constructed indoor ground station without outdoor antenna for decreasing total cost and time. In this time, if output power of ground station is high, it will affect for cubesat transceiver to be fail. For solving this problem, ground station must be designed for output power of it to be lower than input power of cubesat satellite, and it must be verified. In this paper, first, we describe cubesat indoor ground station using UHF and VHF. Second, we describe output power decreasing test for indoor operation of ground station by attaching attenuators in the end of the output connector.

• Journal of Positioning, Navigation, and Timing
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• v.2 no.1
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• pp.41-48
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• 2013

When the ground subsystem of Ground Based Augmentation System(GBAS) is installed at the airport, the functions and performance of subsystem should be evaluated through ground and flight testing at the pre-commissioning phase. In the case of GBAS flight testing, it can be conducted by the existing flight check aircraft, but the GBAS ground testing requires the development of specially customized equipment to perform the ground testing. Therefore, this paper describes the preliminary design of GBAS onboard test equipment which can be independently used for the GBAS ground testing and flight testing on a car and an aircraft.