• Magazine of the Korean Society of Agricultural Engineers
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• v.25 no.4
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• pp.38-49
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• 1983

This study was intended to develop a curriculum for the agricultural engineering technology, and that on confidence with junior college characteristics. In order to per- formance with this study, job cluster was analyzed on 28 parts in respect to the agricultural engineering field and questionnaire was investigated to the field including in alumni 181, students 537, professional workers 174 and professors 54. The results from the above analysis and investigation can be summarized as follows. 1. According to the investigation on degree of important subjects from the questionnaire, it is presented at mathematics 43%, physics 36% in students and 32%, 12% in professional workers. Considering from this results, it is desirable that primary subjects should be forced. 2. In comparing with fundamental major subjects and applied it, it is presented at that 41%, this 34%, in the total investigations. It can be found that in the degree of requirement, this is lower than that among the major subjects. 3. In investigation to the degree of requirement in the experiment and practice, it is presented at surveying 63%. Soil mechanics 14%, materials 13%, hydraulics 9% in order, in total inspection. 4. From investigation to the degree of requirement on the subjects of established newly, it is presented at majoring and living English 64%, E.D.P.S 30%, in the total questionnaire. Judging from the results, it seems that the foreign language is necessary to technician more and more, for advance to abroad. Also, it is no wonder that make good use of the E.D.P.S. 5 The table 5 is represented the model curriculum from the above results in anaized data on the questionnaire and the job cluster of table 2.

• Journal of The Korean Society of Agricultural Engineers
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• v.60 no.4
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• pp.105-111
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• 2018

Institutional inertia anti-disaster standard was presented mainly on the upper surface, it is necessary to improve to the soil type standard and uplift the resistance standard greenhouse that are vulnerable to strong winds. In this study, we carried out a field test using the load control method in order to evaluate the uplift resistance of continuous foundation of greenhouse with different depths of the rafters. Institutional inertia anti-disaster standard of greenhouse foundation did not protect the greenhouse structure from the damages caused by strong winds and heavy snow. Therefore, field tests for behavior characteristics of continuous greenhouse foundation were carried out to ensure stable facility cultivation. The field test condition was evaluated using different embedded depth as follows: 30cm, 40cm, 50cm and spacing 50cm, 60cm, 70 cm. As a result of the uplift resistance field tests using the load control method, the minimum uplift resistance was found to be over 90kg and uplift resistance displacement was 9.4mm. Uplift resistance of the continuous greenhouse foundation was in the range of 90-180 kg according to embedded depth and spacing. Using the test condition, there was no constant trend in the uplift resistance.

• Structural Engineering and Mechanics
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• v.57 no.2
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• pp.327-355
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• 2016

A new analytical derivation of the elastodynamic point load solutions for an isotropic multi-layered half-space is presented by means of the precise integration method (PIM) and the approach of dual vector. The time-harmonic external load is prescribed either on the external boundary or in the interior of the solid medium. Starting with the axisymmetric governing motion equations in a cylindrical coordinate system, a second order ordinary differential matrix equation can be gained by making use of the Hankel integral transform. Employing the technique of dual vector, the second order ordinary differential matrix equation can be simplified into a first-order one. The approach of PIM is implemented to obtain the solutions of the ordinary differential matrix equation in the Hankel integral transform domain. The PIM is a highly accurate algorithm to solve sets of first-order ordinary differential equations and any desired accuracy of the dynamic point load solutions can be achieved. The numerical simulation is based on algebraic matrix operation. As a result, the computational effort is reduced to a great extent and the computation is unconditionally stable. Selected numerical trials are given to validate the accuracy and applicability of the proposed approach. More examples are discussed to portray the dependence of the load-displacement response on the isotropic parameters of the multi-layered media, the depth of external load and the frequency of excitation.

• Journal of Korea Water Resources Association
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• v.35 no.4 s.129
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• pp.425-442
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• 2002

The land reclamation area of Saemangeum(Kunsan) is located between $126^{\circ}10'\;E{\sim}126^{\circ}50'\;E\;and\;35^{\circ}35'\;N{\sim}36^{\circ}05'\;N$ at the western coast of the Korean peninsula. The reclamation area of Saemangeum has a range of 5.6m spring tide and the maximum tidal current speed is about $1.41m\;s^{-1}$. In ordinary spring tide. Most of the sediments deposited on the tidal flats are transported from the Geum river, the Mankyung river and the Dongjin river. The soil in this area consists of silty sand with the depth of 10m to 30m. The wind in winter is strong from the direction of northwest. Saemangeum coastal area is being constructed 33km the sea dike and 40,100ha reclamation area. The purpose of this study Is to find the residual circulations in four seasons before and after the dike construction by a robust diagnostic and prognostic numerical model.

• Journal of the Korean Geotechnical Society
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• v.28 no.9
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• pp.97-106
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• 2012

In order to investigate mechanics of mixtures composed of sand and non-plastic silt, various specimens, with sand dominating the soil structure, and with varying fines content, fines content varying were produced. Isotropic consolidation tests were performed using high pressure triaxial test apparatus within high pressure levels where sand grain crushing happened. Experimental results showed that compressive curve of sand after yielding contracts to the NCL due to breakage of sand grains. Moreover, with the increase of fines content, coarse grains are surrounded by fines to form cushion effect, which made the breakage of coarse grains become difficult. Therefore, the maximum inclination of compressive curve became flatter and yield stress increased.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.11 no.2
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• pp.12-18
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• 2015

The energy pile, used for both structural foundations and heat exchangers, brings about heat exchange with the ground formation by circulating a working fluid for heating and cooling buildings. As heat exchange occurs in the energy pile, thermal stress and strain is generated in the pile body and surrounding ground formation. In order to investigate the thermo-mechanical behavior of an energy pile, a comprehensive experimental program was conducted, monitoring the thermal stress of a cast-in place energy pile equipped with five pairs of U-type heat exchanger pipes. The heating and cooling simulation both continued for 30 days. The thermal strain in the longitudinal direction of the energy pile was monitored for a 15 operation days and another 15 days monitoring followed, without the application of heat exchange. In addition, a finite element model was developed to simulate the thermo-mechanical behavior of the energy pile. A non-linear contact model was adopted to interpret the interaction at the pile-soil interface, and thermal-induced structure mechanics was considered to handle the thermo-mechanical coupled multi-field problem.

• Structural Engineering and Mechanics
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• v.48 no.3
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• pp.367-382
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• 2013

Different types of long slender pile shall buckle with weak soil and liquefied stratum surrounded. Different from considering single side earth pressure, it was suggested that the lateral earth pressure can be divided into two categories while buckling: the earth pressure that prevent and promotes the lateral movement. Active and passive earth pressure calculation model was proposed supposing earth pressure changed linearly with displacement considering overlying load, shaft resistance, earth pressure at both sides of the pile. Critical buckling load calculation method was proposed based on the principle of minimum potential energy quoting the earth pressure calculation model. The calculation result was contrasted with the field test result of small diameter TC pile (Plastic Tube Cast-in-place pile). The fix form could be fixed-hinged in the actual calculation assuring the accuracy and certain safety factor. The contributions of pile fix form depend on the pile length for the same geological conditions. There exists critical friction value in specific geological conditions that the side friction has larger impact on the critical buckling load while it is less than the value and has less impact with larger value. The buckling load was not simply changed linearly with friction. The buckling load decreases with increased limit active displacement and the load tend to be constant with larger active displacement value; the critical buckling load will be the same for different fix form for the small values.

• Tunnel and Underground Space
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• v.17 no.3 s.68
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• pp.175-185
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• 2007

When filling material such as clay is included along the discontinuity, it may cause instability on a slope even if the direction of discontinuity works in a positive way. In the study area, slope sliding occurred at the boundary between a clay filling material and weathered soil because the physical properties differ across the boundary; and this is very similar to the situation where foliation in a rock works as a weak zone during a structural behavior, causing an inter-layer slip. In most analysis, if there exists a clay filling material, a single discontinuity is assumed to perform analysis. In those cases, the discontinuity is modeled as a slip surface within clay. Therefore, the characteristics of the boundary are not considered in the analysis, so that ultimately the physical property of clay usually prevails. The result of evaluating the slope stability affected by clay filling material shows the significant difference in the safety level due to the strength parameter depending on the failure type of the discontinuity by a filling material.

• Tunnel and Underground Space
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• v.21 no.5
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• pp.341-348
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• 2011

As a result of the detailed site investigation performed for the design of a 4.3 km long tunnel, geological anomalies of four fault zones and a rock boundary were discovered on the tunnel route. Most of all, it was confirmed that pyrite, which may corrode steel material, is contained inside the geological anomalies, and pressured ground water flows out of the fault fractured zone. To overcome these geological conditions, antisulfur concrete for the concrete lining and anticorrosive swelling rock bolts are designed in the pyrite-containing sections. For the sections where a great amount of groundwater outflows, water blocking methods including grouting are applied according to the result of numerical analyses on the seepage. In addition, since the past earthquakes occurred around Korea have take place mainly near fault zones, seismic analyses were performed based on the Soil-Structure Interaction (SSI) concept and the strength of concrete tunnel lining is designed to be 27 MPa from 24 MPa in order to reinforce the tunnel structure.

• Geomechanics and Engineering
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• v.14 no.2
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• pp.151-159
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• 2018

Annually, the global production of construction aggregates reaches over 40 billion tons, making aggregates the largest mining sector by volume and value. Currently, the aggregate industry is shifting from sand to hard rock as a result of legislation limiting the extraction of natural sands and gravels. A major implication of this change in the aggregate industry is the need for understanding rock fragmentation and energy absorption to produce more cost-effective aggregates. In this paper, we focused on incorporating dynamic rock and soil mechanics to understand the effects of loading rate and water saturation on the rock fragmentation and energy absorption of three different sandstones (Red, Berea and Buff) with different pore sizes. Rock core samples were prepared in accordance to the ASTM standards for compressive strength testing. Saturated and dry samples were subsequently prepared and fragmented via fast and dynamic compressive strength tests. The particle size distributions of the resulting fragments were subsequently analyzed using mechanical gradation tests. Our results indicate that the rock fragment size generally decreased with increasing loading rate and water content. In addition, the fragment sizes in the larger pore size sample (Buff sandstone) were relatively smaller those in the smaller pore size sample (Red sandstone). Notably, energy absorption decreased with increased loading rate, water content and rock pore size. These results support the conclusion that rock fragment size is positively correlated with the energy absorption of rocks. In addition, the rock fragment size increases as the energy absorption increases. Thus, our data provide insightful information for improving cost-effective aggregate production methods.