김은호 Kim Eun Ho , 이달원 Lee Dal Won

DOI: JKWST Vol.52(No.2) 1-9, 2010

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This study was carried out to comparison of coefficient of consolidation and the prediction of excess pore water pressure in agricultural reservoir on soft clay ground. For the purpose of verification of the proposed equation, laboratory model tests and field tests were performed and excess pore water pressure was compared to those predicted with the Terzaghi's method. The predicted excess pore water pressure according to ponding was very applicable to practice because it was close to the observed data. Also, for the comparison of coefficient of consolidation, the oedometer, constant rate of strain (CRS), and Rowe cell tests were performed. The coefficient of consolidation at the Rowe cell and CRS tests showed a greate increase than in the oedometer test. The ratio of the vertical and horizontal coefficient of consolidation showed a large difference according to various tests method and mixing ratio. Therefore, it is recommended that careful attention should be paid to predicting the required consolidation period in agricultural reservoir.

김두환 Kim Doo Hwan , 윤성수 Yoon Seong Soo , 박진선 Park Jin Seon

DOI: JKWST Vol.52(No.2) 11-17, 2010

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For the reasonable analysis of design problems for agricultural facilities, considered the reinforcing effect of thin-wall. The most of agricultural structure is constructed small scale and have many purposes. Thus it has been designed temporary rather than permanent structure, and has relatively large slenderness ratio, small section and semi-rigid condition. Therefore many agricultural facilities are consist of relatively strong frame with weak wall at the viewpoint of stiffness and have not been reflected in the design. But the tension field influences to collapse of structure have already known. Therefore, we need quantification the effect of tension field at structural analysis. In this study, present the method of quantification the effect of tension field that came out thin-plate surrounded by high stiffness frame. The numerical results show that the effect of tension field effect for thin-wall is about 5% of the sectional area of frame in study agricultural facilities.

손영환 Son Young Hwan

DOI: JKWST Vol.52(No.2) 19-25, 2010

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This study was conducted to determine the resilient modulus (Mr) and the unconfined compressive strength (UCS) of two recycled roadway materials such as recycled pavement material (RPM) and road surface gravel (RSG) with or without cement kiln dust (CKD). The recycled materials were blended with two CKD contents (5, 10 %) and 28 day curing time. Mr and UCS tests were also conducted after 10cycles of freezing and thawing to asses the impact of freeze-thaw cycling. Mr was determined conducting by the laboratory test method described by NCHRP 1-28A. Stabilized RPM and RSG had a modulus and a strength higher than unstabilized RPM and RSG. Mr and UCS of RPM and RSG mixed with CKD increased with increasing CKD content. The results indicated that the addition of CKD could be improved the strength and the stiffness of RPM and RSG. Therefore, RPM, RSG and CKD could be used as an effective materials in the reconstruction of roads.

윤득노 Youn Deuk No , 김태곤 Kim Tae Gon , 한이철 Han Yi Cheol , 이정재 Lee Jeong Jae

DOI: JKWST Vol.52(No.2) 27-34, 2010

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The PERT is one form of probabilistic network and can have many critical paths in the concept of each work has dispersed complete time. Here we propose two operators to estimate the probabilistic complete time about serial and parallel connections, and in each junction node, probability of critical path is estimated by new operator. Then we compare the estimated results with robability of critical path with deterministic CPM and Monte Carlo simulation (MCS). Our results show that all paths in PERT can be critical path, and proposed operators are efficient and accurate probabilistic calculators compare MCS result.

이용웅 Lee Yong Woong , 조종식 Cho Jong Sik , 주종길 Ju Jong Gil , 신창선 Shin Chang Sun , 여현 Yoe Hyun , 이종현 Lee Jong Hyun , 신한호 Sin Han Ho , 염창열 Yum Chang Yeol

DOI: JKWST Vol.52(No.2) 35-42, 2010

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In this paper, we propose a ubiquitous Farming Diary System which can support the easy and reliable recording of a farming diary for the certificate on environment-friendly agricultural products by using the USN(Ubiquitous Sensor Network) technologies. By using growth-related data, the system can also control farming facilities remotely and automatically. To achieve this goal, the UFDS(Ubiquitous Farming Diary System) is consisted with 3 layers. The first ‘physical layer’ can collect data from sensors, cameras and facilities then controls the growth environment based on the analyzed information. The second ‘Middle layer’ can process and store the data from ‘physical layer’ to sensor manager, image manager, control manager and diary manager separately. The third ‘application layer’ can provide growth-related services to users through various applications. The UFDS can recording grow history information automatically and Easily. Besides, the system can make an accurate and reliable farming diary with multimedia information such as motion and sound. Furthermore, environmental information such as temperature, humidity, luminance and soil conditions (soil temperature, soil humidity, soil EC) can be monitored in real-time and the facilities managed in remote sites.

남효석 Nam Hyo Seok , 이상호 Lee Sang Ho

DOI: JKWST Vol.52(No.2) 43-50, 2010

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This study was carried out to evaluate the vertical stress properties in sandy soil according to changes of foundation condition in soil bin compacted three layers. The following conclusions and comparisons have been made based on careful analysis from theoretical and experimental methods. : When sandy soil subjected to circular uniform load, the vertical stress increments (Δσz) was increased as load increasing, the maximum values of Δσz was achieved at the point loading axis, and Δσz was not shown over at a distance of three times of loading plate width (B). The vertical stress increments were achieved largely at 80 % relative compaction (Rc) compared to 95 % relative compaction due to stress concentration in sandy soil. When sandy soil subjected to circular uniform load, the Δσz differences between theoretical and experimental values as load increased were more increased and its maximum differences were achieved at stress axis. When gravel surface macadamized over sandy soil subjected to load, the Δσz was concentrated to load axis as load increasing, so that macadamization will be decreased load transmission.

손영환 Son Young Hwan

DOI: JKWST Vol.52(No.2) 51-57, 2010

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Many models have been used to represent the effects of confining stress, bulk stress, and shear stress on the value of the resilient modulus (Mr). This study was conducted to estimate Mr of the recycled materials such as recycled concrete aggregate (RCA) and recycled asphalt pavement (RAP) through the repeated load cyclic test. Also, two models were applied to estimation of Mr for comparing between measured Mr values and predicted Mr values. The first model (A-model) can provide a quick and easy estimation of the Mr based on the bulk stress, while the second model (N-model) includes not only the bulk stress but also the shear stress. Statistical analysis indicated that all results using the both of models are significant at a 95 % confidence level. Therefore, the both of models could be used as an effective prediction model of Mr for RCA and RAP. Especially, the Model 2 including the parameters of the bulk stress and the shear stress could give more reliable estimation at the high range of Mr values.

김영익 Kim Young Ik , 이익상 Lee Ik Sang , 최돈환 Choi Don Hwan , 임은상 Im Eun Sang , 김용성 Kim Yong Seong

DOI: JKWST Vol.52(No.2) 59-66, 2010

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This study was performed to develop the embankment protection method that can reduce demage by prevention of embankment loss and collapse from overflow due to heavy rain and flood. For overflow test, model dam was prepared and embankment behaviors were monitored with the established piezometer and strain meter during overflow. As a result of overflow test for model dam, in case of embankment without waterproof mat, the lower end of embankment was collapsed within 40 seconds after beginning of overflow. On the other hand, in case of embankment with waterproof mat, embankment collapse didn't occurred during overflow. Accordingly, establishment of waterproof mat for embankment showed that be absolutely effective for the embankment protection during overflow in reservoir. Also, it showed that the minimum establishment range of waterproof mat to prevent embankment collapse in reservoir is from maximum storage level to the lower end of embankment.

문종필 Moon Jong Pil , 윤남규 Yun Nam Kyu , 이성현 Lee Sung Hyoun , 김학주 Kim Hak Joo , 이수장 Lee Su Jang , 김영화 Kim Young-hwa

DOI: JKWST Vol.52(No.2) 67-73, 2010

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Unlike Urban building, horticultural facilities has a lot of heat loss through plastic or glass covering material which could be much influential to growing plant and consuming energy for heating greenhouse. In many cases, heat loss from a break of cover, a gap of joint sealing, the entrance to greenhouse and windows for ventilation are the main factors considered in calculating the heating load for horticultural facilities. however the normal observation through human eye and digital camera could not recognize where the heat loss occurred. but the infrared thermal image camera with detecting thermal difference could be very effective for noticing heat loss by analyzing infrared thermal image. In this study, greenhouse structure, covering material, internal and external provisions for Horticultural facilities were surveyed in different sites and Infrared thermal camera shooting and image analysis were performed for auditing heat loss from cultivation facilities The results from this study were that unexpected heat loss had been noticed in 7 representative cases of greenhouse such as side wall covered with single or double plastic, and the joint of horizontal thermal curtain, roof without horizontal thermal curtain, entrance to greenhouse, windows for ventilation. the most important factors for keeping heat energy were whether the horizontal thermal curtain with multifold thermal material was installed or not. The internal or external covering using multifold thermal curtain proved to be the most effective ways to keep heat energy from losing through heat transmission, heat radiation. from inside to outside the horticultural facilities.