• Magazine of the Korean Society of Agricultural Engineers
• /
• v.17 no.1
• /
• pp.3627-3641
• /
• 1975

The Government is trying to increase total food grain yield to meet national self sufficiency by means of increasing unit yield as well as extending crop land, and this year he set the target of 321,000 hectare of forest to clear for cropping. This study was carried to investigate the most efficient method of clearing hillock by bulldozer, and successful method to develope yielding potential of newly cleared land in short term. Since the conventional land clearing method is just earth leveling and root removing neglecting top soil treatment, the growth of crop was poor and farmer tends not to care the land. The top-soil-furrowing method is applied through out this study, that is advantageous especially for the land having shallow top soil and low fertility like Korean forest. In this study, various operating method were tried to find out most efficient method separately in connection with the land slope less than 25 percent and over, and several fertilizing methods to develop yielding potential. The results are as follows; 1) For the natural land slope utilization method, applicable to the land having less than 25 percent slope, reverse operating was more efficient than using forward gear of bulldozer. The operating time was 3 hour 32 minutes and 36 seconds using forward gear was 2 hour 32 minutes and 30 seconds for reverse gear operation per 1,000 square meter. 2) Bulldozer having angle blade adjustment needed 7hr 15min. for constructing of terrace per 10a compaire with the one having angle & tilt adjustment needed 6hr 4min for same operations. Specially there is significant difference for operation time of first period (earth cutting) such as bulldozer having angle blade adjustment needed 3hr 56min compaired with the one having angle & tilt adjustment 3hr 59min. In construction of terrace, the bull-dozer having tilting and angle blade adjustment was most suitable and performed efficiently. 3) For the fertilizer application treatment, the grass (Ladino clover) yield in first year was almost same as ordinary field's in the plot applied(N.P.K+lime+manure) while none fertilizer plot showed one tenth of it, and (N.P.K.+lime) applied plot yielded on third. 4) The effect of different land clearing method to yield showed significant difference between each treatment especially in the first year, and the conventional method was the lowest. In the second year, still conventional terracing plot yielded only half of ordinary field while the other plots showed as same as ordinary field's. 5) The downward top soil treatment plot showed most rapid improvement in soil structure during one year physio chemically, it showed increase in pH rate and organic composition, and the soil changed gradually from loam to sand-loam and the moisture content increased against the pF rate, and it gives good condition to grow hay due to the increase of field water capacity with higher available water content. 6) Since the soil of tested area was granite, the rate of soil errosion was increased about 2 to 5 percent influencing in soil structure more sand reducing clay content, and an optimum contour farming method should be prepared as a counter measure of errosion.

• International Journal of Highway Engineering
• /
• v.9 no.1 s.31
• /
• pp.47-56
• /
• 2007

Resilient characteristics on unbound pavement materials have been adopted for design and nonlinear analysis of pavement structure under traffic loadings. However, relatively few studies have been done on the nonlinear resilient behavior of unbound materials in Korea. In addition to that, only the limited information is available for estimating the resilient modulus values on subgrade soils. In this study, a laboratory resilient-deformation test under repeated loadings is performed in order to establish the nonlinear characteristics of unbound subgrade soils in test roads. Then, a constitutive model that correlates the resilient modulus with moisture and stress state from field condition is proposed respectively. The results from all procedures are presented in this paper. Finally, a comparative analysis is conducted to identify the proper models in the stress dependent modulus and seasonal moisture condition of subgrade soils in test roads respectively.

• Journal of The Korean Society of Grassland and Forage Science
• /
• v.25 no.1
• /
• pp.65-70
• /
• 2005

This study was conducted to investigate the effect of combine crawler attaching slurry spreader on soil and growth of rye. The performance test at actual field was conducted to test for possibility of practical use. Field test of the slurry spreader was operated in upland and paddy field. Experiments was conducted to compare the effects of the soil damage and crop productivity incorporating Pig slurry by two different types of slurry spreader. In this experiment a slurry spreader using crawler of combine have been designed and developed to enhance the operation in small field and reduce e damage of soil structure. but it was not suitable for transference in long distance. Conventional tractor mounted vacuum is not suitable for $71.6\%$ water condition in the small areas of paddy land. But the slurry spreader using crawler could be controlled the working point and moving by crawler in paddy land of small area. The wheels depths of soil in the supplementary application in the rye field was 4.9 m in tractor mounted spreader. but the wheels depth of crawler attaching spreader was 1.6cm. The dry matter yield of rye was reduced by $12\%$ in supplementary application of slurry due to mechanical damage from passage of the tires. This is particularly noticeable at high soil moisture condition in paddy land. It was concluded that the slurry spreader developed in this study could be successfully used for basal and supplementary application of slurry in rye paddy field.

• Journal of the Korean Applied Science and Technology
• /
• v.27 no.4
• /
• pp.427-436
• /
• 2010

Much oyster shell is breeding by character and conduct of oyster-industry for a long time among them. An experimental study was carried out to investigate the recycling possibility of waste oyster shells, which induce environmental pollutions by piling up out at the open or the temporary reclamation. The purpose of this study is to develope eco-friendly binder using waste oyster shells, and to reinforce soils fur soft soil improvement. In this paper, a series of laboratory tests including compressive pot tests were performed to evaluate characteristics of soils treated by developed waste oyster shells with different water content of soils. Based on test results, eco-friendly Supporter manufactured from waste oyster shells were estimated as good resource materials for soft soil improvements. We got the conclusion by a series of experiment, It is verified that change of pH of soil is improved by mixing with oyster shells. The homogenization method for deducing apparent of oyster shells, which can consider micro-structure of mixed soil, is introduced. The improvement treatment leaded to enlarge fluctuation of soil moisture content. The effect of calcium concentration was good though improvement treatment of physical property. In addition, the crop yield in amelioration plots increased. It means that the increase of crop yield was caused by improvement of soil physical properties rather than improvement of calcium concentration.

• Journal of the Korean Society for Railway
• /
• v.12 no.2
• /
• pp.183-189
• /
• 2009

The track structure of Gyungbu High Speed Railway line from Daegu to Busan is concrete track. It has a very strict specification for residual settlement because of its rigid type structural characteristics. The residual settlement of it comes from the residual settlement of the subgrade and the ground. The residual settlement of railway subgrade composed of crushed rock and soil might be major parts of total residual settlement depending on the field compaction qualities. Therefore, it is a key to minimize the residual settlement of the subgrade for a successful concrete track construction. In this paper, total 31 large scale compaction tests were performed to understand the compaction behaviors of the crushed rock-soil mixture. The test specimens were constituted with soil, crushed shale and mudstone taken from two sites under construction. The compaction tests were performed with the variations of rock types, #4 sieve passing contents, maximum particle size, and moisture contents. The influence of those factors on maximum dry unit weights of crushed rock-soil mixture was evaluated.

• The Journal of Engineering Geology
• /
• v.31 no.3
• /
• pp.257-267
• /
• 2021

Constraints on the structure and composition of the active layer are important for understanding permafrost evolution. Soil convection owing to repeated moisture-induced freeze-thaw cycles within the active layer promotes the formation of self-organized patterned ground. Here we present the results of ground penetrating radar (GPR) surveys across a selected sorted circle near King Sejong Station, Antarctica, to better delineate the active layer and its relation to the observed patterned ground structure. We acquire GPR data in both bistatic mode (common mid-points) for precise velocity constraints and monostatic mode (common-offset) for subsurface imaging. Reflections are derived from the active layer-permafrost boundary, organic layer-weathered soil boundary within the active layer, and frozen rock-fracture-filled ice boundary within the permafrost. The base of the imaged sorted circle possesses a convex-down shape in the central silty zone, which is typical for the pattern associated with convection-like soil motion within the active layer. The boundary between the central fine-silty domain and coarse-grained stone border is effectively identified in a radar amplitude contour at the assumed active layer depth, and is further examined in the frequency spectra of the near- and far-offset traces. The far-offset traces and the traces from the lower frequency components dominant on the far-offset traces would be associated with rapid absorption of higher frequency radiowave due to the voids in gravel-rich zone. The presented correlation strategies for analyzing very shallow, thin-layered GPR reflection data can potentially be applied to the various types of patterned ground, particularly for acquiring time-lapse imaging, when electric resistivity tomography is incorporated into the analysis.

• The Korean Journal of Ecology
• /
• v.25 no.3 s.107
• /
• pp.145-152
• /
• 2002

Saussurea chabyoungsanica was recorded in new species by Lim Hyoung Tak in 1997. In order to understand the entity of new species, we investigated the new distribution sites, vegetation structure and soil environmental factors. Additionally discovered distribution sites of S. chabyoungsanica were Manduckbong, Mt. Sukbyoung, Mt. Duckhang, and Sukgaejae, which were located on ridge of the Taebaek Mountains. Those sites are typical limestone zones of Korea and among them Sukgaejae belongs to lower great limestone area and Manduckbong, Mt. Sukbyoung and Mt. Duckhang belong to upper great limestone area. According to the result of phytosociological study, plant communities of S. chabyoungsanica were classified by 1 Community group, 4 Communities and 2 Subcommunities; Carex humilis var. nana-Saussurea chabyoungsanica Community group in wide sense Quercus mongolica Community group, Lespedeza maximowiczii-Saussurea chabyounsanica Community, Galium kinuta-Saussurea chabyoungsanica Community, Salvia chanryonica-Saussurea chabyoungsanica Community, Zabelia coreana-Saussurea chabyoungsanica Community. Environmental factor analysis of habitat showed that the distribution site of S. chabyoungsanica was ridge of North aspect and displayed pH $7{\sim}8$ typical of limestone. Soil moisture content was high, whereas organic matter content was low. Considering its high occurrence in sites of $1{\sim}10cm$ in soil depth, and of $30{\sim}45%$ in relative light intensity, major distribution sites were outcrops and boundaries between shrubland and forest. After community division by vegetation structure in habitat of S. chabyoungsanica, we investigated characters of soil environment by community. As a result of PCA analysis of soil sample by community, it was possible to divide community by characters of soil environmental factor. The cumulative value of contribution rate represented in second dimension space was 73% and the major factors for that value were soil texture, organic matter content and field capacity.

• The Korean Journal of Ecology
• /
• v.25 no.2
• /
• pp.75-82
• /
• 2002

Saussurea chabyoungsanica was recorded in new species by Lim Hyoung Tak in 1997. In order to understand the entity of new species, we investigated the new distribution sites, vegetation structure and soil environmental factors. Additionally discovered distribution sites of S. chabyoungsanica were Manduckbong, Mt. Sukbyoung, Mt. Duckhang, and Sukgaejae, which were located on ridge of the Taebaek mountains. Those sites are typical limestone zones of Korea and among them Sukgaejae belongs to lower great limestone area and Manduckbong, Mt. Sukbyoung and Mt. Duckhang belong to uper great limestone area. According to the result of phytosociological study, plant communities of S. chabyoungsanica were classified by 1 Community group, 4 Communities and 2 Subcommunities; Carex humilis var. nana - Saussurea chabyoungsanica Community group in wide sense Quercus mongolica Community group, Lespedeza maximowiczii- Saussurea chabyoungsanica Community, Galium kinuta - Saussurea chabyongsanica Community, Saliva chanryonica - Saussurea chabyoungsanica Community, Zabelia coreana - Saussurea chabyoungsanica Community. Environmental factor analysis of habitat showed that the distribution site of S. chabyoungsanica was ridge of North aspect and displayed pH 7∼8 typical of limestone. Soil moisture content was high, whereas organic matter content was low. Considering its high occurrence in sites of 1∼10cm in soil depth, and of 30∼45% in relative light intensity, major distribution sites were outcrops and boundaries between shrubland and forest. After community division by vegetation structure in habitat of S. chabyoungsanica, we investigated characters of soil environment by community. As a result of PCA analysis of soil sample by community, it was possible to divide community by characters of soil environmental factor. The cumulative value of contribution rate represented in second dimension space was 73% and the major factors for that value were soil texture, organic matter content and field capacity.

• Korean Journal of Ecology and Environment
• /
• v.46 no.1
• /
• pp.53-59
• /
• 2013

The purpose of this study was to analyze the topographic effect of the LAI (Leaf Area Index), which has been widely used as an index that quantifies the structure of forest vegetation in Deogyusan National Park. With this aim, the study was conducted through a regression analysis which took as explanation the following variables: the elevation, slope, aspect, and soil moisture conditions. The LAI was taken as the response variable. Overall, the correlation between the Field-LAI and topographic factors was less than 0.5, which was relatively low. Except for topographic altitude, there was no statistical significance regarding the correlation with other factors. Meanwhile, regarding the orientation of the correlation, the higher the attitude, the steeper slope, the lower the soil moist, the lower the LAI value. The topographic altitude was found as a statistically significant explanation variable. The TWI (Topographic Wetness Index), which was used in this study to explain the soil moisture conditions, was not significantly related to the LAI distribution. The results of this study are expected to be utilized as basic data in more accurate forecasting the LAI distribution using remote sensing data.

• Journal of Ecology and Environment
• /
• v.30 no.4
• /
• pp.347-356
• /
• 2007

The structure and dynamics of Korean red pine stands established in the riparian zone were studied in the Tsang stream in Mt. Seorak National Park, in east-central Korea. Pine stands were classified into four successional stages, the initial, establishing, competitive, and stabilizing stages, based on the age distribution of a dominant tree, Pinus densiflora, the vegetation stratification, and the microtopography of the riverine environment. The stages usually corresponded to disturbance frequencies, depending on the horizontal and vertical distances from the watercourse. Stands of the initial and establishing stages lacked tree or subtree layers, or both. As stands progressed through the developmental stages, soil particle size became finer and moisture retention capacity was improved. The stand ordination reflected the developmental stage, and the species ordination differentiated species specializing in relatively dry and wet habitats. The results of the analysis of vegetation dynamics provided ecological information which will be useful for understanding the developmental processes of vegetation established in riparian zones. Species diversity indices usually increased across developmental stages, following the typical pattern for successional processes. We discuss the importance and necessity of riparian vegetation in Korea, where most riparian forests have disappeared due to excessive human land use.