• Journal of the Korean GEO-environmental Society
• /
• v.11 no.4
• /
• pp.51-59
• /
• 2010

This article is a case study for the example of the foundation design, in the project area of the silty sand layer that is spread shallowly with loose status, to make the site for a structure and build it up. The site is located on the dredged and reclaimed land in Gun-San and In-Cheon that is formed the silty sand layer with loose status range around 10 meters underground level, the solid ground for the lower pile is shown around 20 meters underground level. Therefore, this area has to be done by ground improvement when applying for the shallow method of foundation. Dynamic compaction method considering the conditions of the design loads in each zone has to be decided through comparative review on the method of foundations and pilot field test was conducted, and drilling investigation and plate bearing test were achieved as well. The analysis results of the tests prove that stability against bearing capacity was acquired by ground improvement effect.

• The Journal of the Convergence on Culture Technology
• /
• v.7 no.3
• /
• pp.517-522
• /
• 2021

In this study, the causes of damage to the concrete sleepers in a ballast track with under sleeper pads attached to the base of the sleepers installed in the sharp curved track(R=180m) of the urban railway bridge were analyzed. The damage types of concrete sleepers were investigated, and the correlation with track irregularity was reviewed. Also, stress generated in the concrete sleeper was reviewed through structural analysis. As a result, most of the cracks of the sleepers occurred in the section with severe track irregularity. In addition, as a result of the analysis, the stress generated in the track components and the sleepers was found to be reduce in the fastening system using the 4-anchor.

• The Journal of Engineering Geology
• /
• v.33 no.4
• /
• pp.599-609
• /
• 2023

In the seismic retrofitting of harbor breakwaters in Korea, the recovery rate is often uncertain due to site conditions and site conditions, and problems continue to arise. Therefore, in this study, we analyzed the recovery rate and compressive strength of the improved material through drilling survey by grouting confirmation method after applying low-fluidity mortar injection method, and furthermore, we checked the elastic modulus by downhole test and tomography to confirm the reinforcement effect of soft ground after ground improvement. The experimental results showed that the average shear wave velocity of the ground increased from 229 m/s to 288 m/s in BH-1 and BH-3 boreholes to a depth of 28.0 m, and the average shear wave velocity of the ground to a depth of 30.0 m tended to increase from 224 m/s to 282 m/s in the downhole test. This is believed to be a result of the increased stiffness of the ground after reinforcement. The results of the tomographic survey showed that the Vs of the soft ground of the sample at Site 1 increased from 113 m/s to 214 m/s, and the Vs of the sample at Site 2 increased from 120 m/s to 224 m/s. This shows that the stiffness of the ground after seismic reinforcement is reinforced with hard soil, as the Vs value satisfies 180 m/s to 360 m/s in the classification of rock quality according to shear wave velocity.

• Korean Journal of Soil Science and Fertilizer
• /
• v.17 no.1
• /
• pp.12-17
• /
• 1984

In order to find out the effects of soil conditioner treatment on the water movement in sandy loam and silt loam soils were treated with two different kinds of soil conditioners, hydrophobic Bitumen 0.4% or hydrophillic Uresol 0.6%, and the changes of wetting angle (soil-water contact angle), penetrability and diffusivity were measured. The results were summarized as follows: 1. Uresol 0.6% treatment decreased the wetting angle of sandy loam more than $10^{\circ}$, but there was no big difference in silt loam. 2. Sandy loam soil was changed to almost hydrophobic and the wetting angle of silt loam soil was increased to $84.9^{\circ}$ as compared to $76.0^{\circ}$ of untreated soil by Bitumen 0.4% treatment. 3. By Uresol treatment, penetrability of sandy loam was doubled but there was not difference in silt loam, and it was decreased to half in two soils by Bitumen treatment. 4. A significant positive correlation between penetrability and the cosine of wetting angle was recognized. 5. Soil water diffusivity was greatly changed by soil conditioner treatment, and the big differences were appeared at lower soil moisture content.

• The korean journal of orthodontics
• /
• v.27 no.6 s.65
• /
• pp.871-880
• /
• 1997

Multiple features of occlusion have been combined by epidemiologists in attempts to objectively to determine malocclusion severity and treatment priority. Jenny et al were developed DAI(Dental Aesthetic Index), which is an orthodontic index based on socially defined aesthetic standards. This study aimed to evaluate association between 10 occlusal components of DAI and individual measures of skeletal morphology by use of univariate and multivariate analysis. In addition the relationship between a Dental Aesthetic Index score and skeletal morphology was evaluated. The data for this study were obtained from cephalometric radiographs and dental casts of 182 Korean patients(79 men, 103 women) with permanent dentition who had been accepted for the orthodontic treatment at Department of Orthodontics, Chonbuk National University. The results are as follows: 1. Several occlusal components of DAI(missing, crowding and spacing in the incisal segment, diastema, largest anterior irregularity on upper and lower arch) were not associated with individual measures of craniofacial morphology. 2. Sagittal occlusal components of DAI were associated with anteroposterior skeletal measures. 3. The relation between vertical occlusal components of DAI and vertical skeletal measures was low magnitude. 4. A Dental Aesthetic Index, which is based on several aspects of occlusion, did not identify craniofacial morphology. We can conclude that combination of certain occlusal components of the DAI may be related with specific skeletal morphology; but, this concept could not be accepted generally.

• Journal of the Korean Geotechnical Society
• /
• v.19 no.6
• /
• pp.307-323
• /
• 2003

In this study the pilot test of C.G.S (Compaction Grouting System) as injection method by low slump mortar was performed and the results were analyzed in order to find out the application of this method to the soft ground and the effect of settlement restraint. The site for pilot test is adjacent to apartments supported by pile foundations. Sand drain method was performed previously as countermeasures against settlement, but settlement occurs continuously because this ground is very soft. Site investigations such as SPT, CPT and vane shear test were performed to determine the characteristics of ground improvement after the installation of C.G.S. Field measurements were performed on purpose to find out the displacement of ground during the installation of C.G.S. From the results of this study, C.G.S method can be optimized by the control of radius, space, depth, injection material and injection pressure. C.G.S improves soft ground with radial consolidation of adjacent soft ground. Considering that increase of N value to about 3, C.G.S can be considered as an effective method to increase the bearing capacity as well as constrain the settlement of soft ground. It is also expected to be economic and effective in the improvement of ground when it is used in applicable sites.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.29 no.6C
• /
• pp.251-258
• /
• 2009

In this study, the optimum design conditions for embankment construction on soft clay layer improved by soil compaction pile (SCP) are discussed by comparing the practical design method to the reliability design which is based on the loss function and advanced first order second moment (AFOSM) method. The results are summarized as follows; 1) the relationship between safety factor and failure probability becomes heavy exponentially, failure probability decreases rapidly till 1% approximately until safety factor is smaller than 1.2 and after then, failure probability decrease gradually along the increase of the safety factor. The design safety factor of 1.2 may be the critical value that has been established on considering both relationships appropriately, 2) the safety factor of 1.15 at the minimum expected total cost is a little smaller than the design safety factor of 1.2 and the failure probability is about 1%, 3) the sensitivities of the ratio of stress share and the internal friction angle of sand is larger than the variables related the undrained shear strength of soft layer. This result means that the distribution characteristic of n and ${\phi}$ influences on the stability analysis considerably and they should be considered necessarily on stability analysis of embankment on soft layer improved by SCP, 4) new failure points of the input variables at the design safety factor of 1.2(below failure probability of 0.1~0.3%) is far 1~2 times of standard deviation from the initial design values of themselves.

• Research in Plant Disease
• /
• v.10 no.4
• /
• pp.268-271
• /
• 2004

Occurrence and soil fumigation effect on black root rot of peony was investigated. Peony was severely infected to black root rot caused by Cylindrocarpon destructans in continuous cropping field, but in first cropping field was less infected. To control black root rot, soil improvement, soil fumigation and the root dipping in chemicals were trialed in peony continuous cropping field. Black root rot was not decreased by soil improvement, but incidence of black root rot of peony cultivated in continuous croping field of peony was decreased by soil fumigation with Dazomet GR. and dipping of peony root in chemicals.

• Journal of Sericultural and Entomological Science
• /
• v.10
• /
• pp.41-43
• /
• 1969

The experimental studies were intended to clarify the effects leaf yield calculations, and also aimed at estimating the heritabilities on some characters for the selection of desirable stocks of mulberry trees. The method of estimating heritabilities for the eight characters-branch length, node number, branch diameter, branch number per stock, total branch weight, old branch weight, new shoot and leaf weight, and leaf weight, was the variance components procedures in a replicated trial for the varietal lines. The results are summarized as follows: Means, variances and standard errors for the characters are shown in table 1, and the results of variance analyses are also shown in table 2. Heritability values of node number was the highest, and these of branch number per stock was the lowest, and these of other six characters were intermediate values. These all calculated heritability values were higher than anticipated. This was expected since these values, which were the broad sense heritability, contain the variance due to dominance and epistasis in addition to the additive variance.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.27 no.2
• /
• pp.163-168
• /
• 1982

Tobacco seedling which were sown 20 days earlier than conventional, both at 4-5 and 7-8 leaf stages, were once sprayed with ethrel (0, 500, and 1,000 ppm concentrations) and transplanted simultaneously to investigate the subsequent effects. The number of leaves and days to flower were tend to decrease when seedlings were treated at an early developmental stage than at later stage. The highest yield was obtained from seedlings treated with 500 ppm of ethrel at the 4-5 leaf stage, showing 40% increment above conventional seedlings, partly due to more number and bigger size of the leaves. Finally possible mechanisms for the result were discussed.