• Korean Journal of Environment and Ecology
• /
• v.26 no.2
• /
• pp.210-218
• /
• 2012

This study was carried out to analyze the vegetation properties, soil characteristics and ordination of Bletilla striata population in South Korea. The $Bletilla$ $striata$ population was classified into $Juniperus$ $rigida$ dominant population, $Rhododendron$ $yedoense$ var. $poukhanense$ dominant population, $Rhus$ $javanica$ dominant population, $Bletilla$ $striata$ typical population. $Bletilla$ $striata$ were mainly distributed along the coast of south-western regions of the Korean penninsula and it's population was located at an elevation of 4m to 40m. In the study sites, soil organic matter, total nitrogen, available phosphate, exchangeable potassium, exchangeable calcium, exchangeable magnesium, cation exchange capacity and soil pH were 2.38-6.70%, 0.09-0.27%, 1.81-6.85mg/kg, 1.08-1.72$cmol^+/kg$, 3.56-7.71$cmol^+/kg$, 1.52-3.21$cmol^+/kg$, 5.28-16.95$cmol^+/kg$ and 4.60-6.01 respectively. $Rhododendron$ $yedoense$ var. $poukhanense$ dominant population was found in the steep sloped area that has high percentage of organic matter, total nitrogen, cation exchange capacity and pH than other populations. $Rhus$ $javanica$ dominant population was found in the gentle sloped area that has less percentage of organic matter, total nitrogen, cation exchange capacity and pH. $Juniperus$ $rigida$ dominant population and $Bletilla$ $striata$ typical population were found in the medium sloped area that has medium percentage of organic matter, total nitrogen, cation exchange capacity and pH. Current status of $Bletilla$ $striata$ habitats is very vulnerable with local development constantly threatening the species' survival. Thus, concrete conservation plans to protect natural habitats should be set up as soon as possible.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.10 no.4 s.50
• /
• pp.15-24
• /
• 2006

This work reports the results of our study on the dynamic response of various buried pipelines depending on their boundary conditions. We have studied behavior of the buried pipelines both along the axial and the transverse direction. The buried pipelines are modeled as beams on elastic foundation while the seismic wave as a ground displacement in the form of a sinusoidal wave. The natural frequency, its mode, and the effect of parameters have been interpreted in terms of free vibration. In order to investigate the response on the ground wave, the resulting frequency and the mode shape obtained from the free vibration have been utilized to derive the mathematical formula for the forced vibration. The natural frequency varies most significantly by the soil stiffness and the length of the buried pipelines in the case of free vibration. The effects of the propagation direction and velocity and the frequency of ground wave on the dynamic responses of concrete, steel, and FRP pipes have been analyzed and then dynamic responses depending on the type of pipes have been compared. Through performing dynamic analyser for various boundary conditions and estimation of the location of maximum strain has been estimated for the type of pipes and boundary conditions.

• Korean Journal of Human Ecology
• /
• v.16 no.4
• /
• pp.855-875
• /
• 2007

The purpose of this study is to suggest a guideline for outdoor play settings in child care centers. From March to July, 2005, data were collected from 223 directors at child care centers through a structured questionnaire, field measurement survey and non-participatory observation in seventeen child care centers in Seoul and Daejeon. The statistical methods for analysing data were frequency, percentage, mean, $X^2$ and F-test. The results showed as follows: 1)the existing outdoor playground area in child care centers should be expanded more than $4\;m^2$ per child. 2) Outdoor play facilities should be equipped with two structured play sets, a play facility for unstructured play and an adventure facility to make child's various activities possible and to promote child development. 3)flooring materials for outdoor playground should be required to use more than three kinds such as solid coverings (cf. asphalt, standard concrete), wood, lawn, soil or sands. 4)to let children enjoy various activities, outdoor playground area should be composed of various play facilities like indoor play gyms and should be independent but have good connections between play facilities depending on characteristics of play activities. 5)Play spaces of outdoor playground should be composed of physical play space, unstructured and dramatized play space, rest space, space for nature and adventure space. In addition, appropriate play equipments should be provided in respective play space.

• Journal of the Korean Geosynthetics Society
• /
• v.8 no.3
• /
• pp.45-52
• /
• 2009

The use of geogrid-reinforced earth wall technologies has progressed rapidly over the past 10 years in Korea because these technologies have advantages such as economical efficiency, graceful appearance, and easy construction. The geogrid used in the reinforced earth wall with concrete block facing can be subjected to damage among the upper and lower blocks and at the interface between the block and the geogrid. Therefore, when design of the geogrid-reinforced soil walls the required connection strength of the geogrid to the wall facing is an issue. In this study, new connection system between facing block and geogrid is developed to improve the damages of geogrid in the existing connection systems. The new connection devices are made of steel and have I-shape. This paper describes the test method and results of the laboratory testing for determination of connection strength in connection system using the I-type connection device.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.28 no.3
• /
• pp.293-300
• /
• 2015

In this study, a series of forced vibration testing and ambient vibration measurement were performed at a lowrise masonry-infilled reinforced concrete frame structure before and after seismic retrofit and its dynamic properties were extracted using system identification techniques. Also, analytical models which show similar dynamic properties to the measures ones were constructed. The system identification results showed that damping ratios in x direction along which the dampers were installed has been increased. From the comparison between the analytical models, the effective stiffness of post-installed member and post-reinforced members(shear walls and damper frames) were only 50% of gross sectional stiffness of the members, which indicates that the these members were not fully integrated with the existing structure or members. In addition, support condition of post-installed footing has to be pinned in y direction to match the dynamic properties, which is seemingly caused by the change of fixity of the soil due to the installation of new footing.

• Journal of the Korean Society for Railway
• /
• v.16 no.5
• /
• pp.379-385
• /
• 2013

In this study, partial drilled shafts (Bottom Cast-in-place Concrete pile) were applied to the pilot test site to ensure the bearing capacity; we used the skin friction force in the IGM to analyze the feasibility of the application of IGM theory. The soil characteristics were analyzed in cohesive, non-smear, and smooth conditions for the application of the IGM theory via geotechnical investigation and measurement of the disturbance and surface roughness. Static load and load transfer tests were conducted to calculate the allowable bearing capacity and the skin friction force by depth. The skin friction force increased with increase in the depth and standard settlement, showing a very high correlation. In addition, because the unconfined strength ($q_u$), which is the most important parameter in the cohesive IGM, cannot be measured in a weathered granite area, the static load and load transfer test results and the N value were used to obtain $q_u$.

• Journal of the Korean Geosynthetics Society
• /
• v.18 no.4
• /
• pp.193-204
• /
• 2019

Reliability analyses of sixteen domestic design cases of open cell caisson breakwaters against circular sliding failure were conducted in this study. For the reliability analyses, uncertainties of parameters of soils, mound, and concrete cap were assessed. Bishop simplified method was used to obtain load and resistance of open cell caisson breakwater for randomly generated open cell caisson breakwater. Sufficient number of Monte Carlo simulations were conducted for randomly generated open cell caisson breakwaters, and statistical analysis was conducted on loads and resistances collected from the large number of Monte Carlo simulations. Probability of failure produced from Monte Carlo simulation has a nonconvergence issue for very low probability of failure; therefore, First-Order Reliability Method (FORM) was conducted using the statistical characteristics of loads and resistances of open cell caisson breakwaters. In addition, effects of safety factor, uncertainties of load and resistance, and correlation between load and resistance on reliability of open cell caisson breakwaters against circular sliding failure were examined.

• Journal of the Korean Geosynthetics Society
• /
• v.16 no.4
• /
• pp.139-149
• /
• 2017

The maintenance, repair, and reinforcement projects and structural stability assessments of Seokguram have primarily focused on examining the condition of stone members of Seokguram and the concrete dome structure for Seokguram. However, a 12 m-high rock slope located behind Seokguram raises a concern of slope failure and rockfall, which may reduce stability of Seokguram. It is also unclear whether the soil slopes and masonry wall at the side and the front of Seokguram have sufficient long-term stability against localized heavy rains and earthquakes, which have been frequent in recent years. The present study investigates the ground and the slopes around Seokguram using detailed field survey to identify geographical and geological risk factors, and assess structural stability of the exposed rock mass behind and the slope in front of Seokguram and the masonry wall using stability analysis.

• Journal of the Korean Geosynthetics Society
• /
• v.4 no.2
• /
• pp.47-56
• /
• 2005

Recently, geosynthetic reinforced earth walls are gradually replacing conventional concrete retaining walls for reasons of economy, expediency of construction, and aesthetics. A number of reinforced soil walls having more than 10m heights have been constructed to make more effective development in the country. However, mistakes in design and construction of reinforced earth walls have resulted in many troubles such as failure of reinforced earth walls, horizontal deformationor breakdown of facings, and so forth during or after construction. In this paper, a case study on global sliding failure of a geogrid-reinforced tiered wall is carried out to investigate the causes of the failure and suggest the proper countermeasures. From the subsurface investigation and field instrumentation, It is found that the cause of the global sliding failure was occurred by decreasing of bearing capacity of foundation ground induced by infiltration of rainwater.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.11 no.4
• /
• pp.1827-1831
• /
• 1969

Resulties of research on the capacity of ground water of 994 concrete-pipe-wells and 97 infiltration-gallerys in ground-water-developement-works region executed from March to Julyin 1969, in Choong Chung Nam Do, and research on the quality of ground water for 88 wells for home-use around of River Geum Area, are as fellows: (1) Thickness of aquifer is no more than 2.85m averagely even at river-overflowed plain, alluvial plain and valley plain area that are estimated to contain ground water mostly. And so, it is guessed that ground water capacity is not much especially. (2) Soil of aquifer of the above area is sand or gravel and it is estimated to be good for ground water developement and its mean permeability coefficient is bout $2.5{\times}10^{-3}$(m/sec), and its porosity is about 33.9%. (3) The quality of ground water is good for irrigation water exception of delta plain area. Warm water plan is to need for irrigation water when water temperature is less than 19 degrees below zero. (4) Prospect of ground water developement, judging from quality and quantity, expects to lay infiltration gallery under the ground at river bed in order to utilize under-flow-water of river bed, river-overflowed plain, alluvial plain and valley plain that ground level is less than 50m. (5) Collectable water volume of under-flow-water of river bed is about 450 to $750m^3/day$ to be able to irrigate 3ha to 5ha of the cultivated land in case that infiltration gallery length is 50m and its depth is about 5m. (6) Collectable water volume at river-overflowed plain, alluvial plain and valley plain area, is estimated $150m^3/day$ to be able to irrigated 1ha of the cultivated land.