• Ecology and Resilient Infrastructure
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• v.5 no.3
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• pp.180-188
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• 2018

Biopolymer based on microbial ${\beta}$-glucan and xanthan gum is a rising geotechnical material that can enhance the cohesion between soil particles and consequently reduce soil erosion. Recently, biopolymer is proposed to utilize for the riverbank strengthening. As an effort of the ecological assessment of biopolymer application in civil engineering, this study examined the effects of biopolymer on seed germination and growth of nine plant species inhabiting in the Korean riverside. Responses of above-ground growth to the biopolymer differed among plant species. One species grew less but others maintained their growth when plants were grown in the soil with biopolymer. In contrast, root grew more vigorously and root/shoot ratio decreased in the biopolymer across testing plant species. These results indicate that biopolymer application on the river bank likely stimulate root growth of native plant species, which, in turn, possibly reinforces riverbank. Species specific responses of above-ground growth implies that ecological effects of biopolymer application would depend on the species composition of the ecosystem.

• Magazine of the Korean Society of Agricultural Engineers
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• v.13 no.4
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• pp.2456-2470
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• 1971

Compaction of soil is very important for construction of soil structures such as highway fills, embankment of reservoir and seadike. With increasing compaction effort, the strength of soil, interor friction and Cohesion increas greatly while the reduction of permerbilityis evident. Factors which may influence compaction effort are moisture content, grain size, grain distribution and other physical properties as well as the variable method of compaction. The moisture content among these parameter is the most important thing. For making the maximum density to a given soil, the comparable optimum water content is required. If there is a slight change in water content when compared with optimum water content, the compaction ratio will decrease and the corresponding mechanical properties will change evidently. The results in this study of soil compaction with different water content are summarized as follows. 1) The maximum dry density increased and corresponding optimum moisture content decreased with increasing of coarse grain size and the compaction curve is steeper than increasing of fine grain size. 2) The maximum dry density is decreased with increasing of the optimum water content and a relationship both parameter becomes rdam-max=2.232-0.02785 $W_0$ But this relstionship will be change to $r_d=ae^{-bw}$ when comparable water content changes. 3) In case of most soils, a dry condition is better than wet condition to give a compactive effort, but the latter condition is only preferable when the liquid limit of soil exceeds 50 percent. 4) The compaction ratio of cohesive soil is greeter than cohesionless soil even the amount of coarse grain sizes are same. 5) The relationship between the maximum dry density and porosity is as rdmax=2,186-0.872e, but it changes to $r_d=ae^{be}$ when water content vary from optimum water content. 6) The void ratio is increased with increasing of optimum water content as n=15.85+1.075 w, but therelation becames $n=ae^{bw}$ if there is a variation in water content. 7) The increament of permeabilty is high when the soil is a high plasticity or coarse. 8) The coefficient of permeability of soil compacted in wet condition is lower than the soil compacted in dry condition. 9) Cohesive soil has higher permeability than cohesionless soil even the amount of coarse particles are same. 10) In generall, the soil which has high optimum water content has lower coefficient of permeability than low optimum water content. 11) The coefficient of permeability has a certain relations with density, gradation and void ratio and it increase with increasing of saturation degree.

• Korean Journal of Agricultural Science
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• v.13 no.2
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• pp.227-242
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• 1986

This paper describes the observed behavior in the direct shear test on decomposed granite soil having the complicate engineering properties at various different levels of factors. The objectives of this study were to investigate the characteristics of the decomposed granite soil under controlled various moisture content, dry density, strain rate and soaking which give influence to the shear strength. The results were summarized as follows; 1. The shear strength was decreased remarkably with the increasing of moisture contents of A and B soil were 5-10% and 15-20% respectively. 2. Cohesion and angle of internal friction were decreased with the increasing of moisture content and increased with the increasing of dry density. 3. The shear strength was increased with the increasing of normal stress and volume change was decreased on the whole. The shear strength was generally increased with the increasing of the strain rate. 4. As dry density increases, A-soil shows the progressive failure and the decrease of volume change while B-soil shows the initial failure and the increase of volume change. 5. The relationships between the soaked and unsoaked specimens were as follows ; ${\tau}_f=0.1009+1.026{{\tau}_f}^*$ (A-soil), ${\tau}_f=0.1586+0.8005{{\tau}_f}^*$ (B-soil) 6. Angle of internal friction of the direct shear test shows larger value than that of the triaxial compression test. All effective stress path was nearly similar.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.1
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• pp.115-123
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• 1990

The purpose of this study was to examine the uses of coal ash as a type of construction material. The methods of examination were chemical anlysis, soil laboratory test and the soil vibration test. Materials used were coal ash obtained as a by-product from 5 thermal power plants in Yongdong, Yongwol, Sochon(anthracite coal) and in Samchonpo and Honam (bituminous coal). Over 70% of the coal ash consisted of silica and alumina. The fly ash grain size showed a uniform distribution from fine-sand to silt, and that of the bottom ash showed from sand to gravel. The specific gravity and density of the coal ash were low. The long term strength increased gradually due to the self-setting property resulting from pozzolanic activity. The shear strength was higher than that of general soil. Cohesion and optimum moisture content of anthracite coal ash were higher than bituminous coal ash, whereas the maximum dry density was higher in bituminous coal ash. The coal ash dynamic Young's modulous curve range was similar to that of general soil. Of the results from the soil vibration test by car-running, the size relative acceleration level in the ash pond was higher than that of natural ground, but the damping ratio was lower than that of natural ground near the ash pond. The coal ash has more advantageous engineering properties than general soil with particles of the same size. For example, the California Bearing Ratio of the bottom ash at both Yongdong and Yongwol was 77~137%. Therefore we expect that if further study is done, coal ash can be used as a construction material when reclaiming seashore, construction embankments, road construction, making right-weight aggregate, or as a general construction material.

• Journal of the Korean GEO-environmental Society
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• v.7 no.5
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• pp.31-39
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• 2006

In this study, modified triaxial compression tests were carried out to investigate the characteristics of shear strength of unsaturated dredged soils. The variation of shear strength generally depends on more matric suction than drained conditions, and then is gradually converged in matric suction 100kPa. It indicates that the effective angle of internal friction and effective cohesion in unsaturated conditions increase due to degree of saturation, namely, matric suction than those of saturated conditions. Therefore, it shows that apparent friction angle, ${\phi}^b$ due to the variation of matric suction to evaluate reasonable shear strength parameters in unsaturated soils should be considered.

• Journal of the Korean Geosynthetics Society
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• v.8 no.4
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• pp.27-34
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• 2009

In this paper, characteristics of shear strength and deformation of geosynthetics-reinforced slag materials are described. In order to investigate the effect of geosynthetics on shear strength and deformation behavior of slags, when they are reinforced with geosynthetics or geomat such as PET mat, large triaxial tests were performed under consolidated-drained condition. The materials used in the study are real ones as they are in the field, so that the scale effect of samples disappeared. From the large triaxial tests, it was observed that the stress-strain relationship of geosynthetics-reinforced slags shows relatively small dilatancy and weak tendency of strain hardening, compared with that of slags without reinforcement. The shear strength parameters such as apparent cohesion and internal friction angle increase with PET mat reinforcement, consequently result in about 1.2 (for low confining pressure) to 1.4 (for high confining pressure) times of shear strength of un-reinforced sample. Therefore, the adoption of geomat-reinforced slag layers leads to an increase in the factor of safety for embankment design on soft soil formations.

• The Journal of Engineering Geology
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• v.30 no.2
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• pp.131-145
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• 2020

The construction on these flimsy ground, activation of unsymmetrical surcharges, can often cause of the embankment road lateral flow or the destruction of the activities. In this study, the stability of the abutment pile foundation installed on soft ground and its behavior has been evaluated. The behavior of the abutment pile foundation under lateral flow was studied by verifying the behavior and reinforcement effects of the abutment pile foundation of previous studies about horizontal loads acting on the pile due to the lateral flow of the ground by performing finite element analysis. As a result of the consolidation analyses, the undrained cohesion or the strength of the soft ground, was increased by about 1.1 to 1.8 times by the increase in the strength of the soft ground according to the degree of consolidation. It is deemed reasonable to use 3.8 cm of the allowable displacement both economically and constructively, but considering the importance of the structure and the uncertainty of the ground, measurement shall be carried out during construction and thorough safety management of the lateral flow should be done.

• Magazine of the Korean Society of Agricultural Engineers
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• v.26 no.1
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• pp.29-37
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• 1984

This study was made to find several significant relations among various physical and mechanical properties including cone penetration resistance. The alluvial clay samples were taken at the Daebul Reclaimed Tideland in Samhomyeon, Yeongamgun, Jeonranamdo. The results of the study are summarized as follows; 1.Most samples belong to medium or high plastic, inorganic, silty clay(clay contents;32-64%, silt contents; 36-68%, sand contents; 0-3%). The specific gravities range from 2.70 to 2.73, the unit weights from 1.45 to 1. 75g/cm$^3$, the natural moisture contents from 45 to 77%, the liquid limits from 32 to 56%. It is certain that the foundation is weak because the natural moisture contents are much higher than the liquid limits. 2.It is known from the shear tests that the unconfined compression strenghs vary from 0.09 to 0. 38kg/cm2, the cohesions from 0.05 to 0. 21kg/cm2, the internal friction angles from 0 to 3˚. 3.The consolidation tests show that the initial void ratios range from 1.25 to 2.28, the compression indeices from 0.43 to 0.84, the preconsolidation loads from 0.21 to 0.74kg/cm$^2$. 4.Cone penetration resistances are usually less than 5kg/cm$^2$ from ground surface to the depth of about 8m, and from S to l0kg/cm$^2$ in the layer below about 8m to hard layer. 5.The cohesion and cone penetration resistance are in proportion to the depth of soil layer. 6.The correlations between various physical and mechanical properties including cone penetration resistance for the alluvial clay samples are as follows; a) Wn=0.944C+ l2.733 (r=0.829) b) LL=0. 728Cy+6. 991 (r=0. 873) c) PI=0.659Cy-8.168 (r=0.860) d) rt=0. 0077(272-Wn) =2.092-0. 0077Wn (r=0. 859) e) 60=0. 035wn-0 447 (r=0. 893) f) C=0.380qw+0.031 (r=0.816) g) qu=0.0707qc+0.029 (r=0.810) h) C=0.018Z+0.055 (r=O.802) I) qc=0. 415Z+1, 438 (r=0. 943)

• Proceedings of the KSR Conference
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• 2001.05a
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• pp.451-458
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• 2001

The purpose of this study was to evaluate shear parameters on cutting slope of weathered granite soils by using small dynamic cone penetration test on the very moment of its cutting. The results were : On the relations among N$\_$c/, Li, and CEC, the condition of Li＞6%, CEC＞14(meq/100g) corresponds to that of N$\_$c/ values of 2∼30, and 3＜CEC＜14(meq/100g) to N$\_$c/=30∼50. Comparing the smallest penetration depth from two small dynamic cone penetration tests done at 5m below from the top of the slope on April 15th, October 31t. there was a l0cm difference. So we could find out the degree of weathering on the slope. And dividing the difference by 190 days (the whole testing time), we could know it's being weathered 0.052mm each day. The more N. value increases, the more shear parameters(internal friction angle ; $\phi$, cohesion : c) increase at a standard pressure($\sigma$＞32㎪). So the condition of N$\_$c/=2∼50 corresponds to that of $\phi$=27∼50, c=12∼49㎪. From the above testing results, the N$\_$c/ values more correspond to $\phi$ values than c values. In conclusion, this study suggests that on small dynamic cone penetration test a penetration boundary line of 5 centimeters is decided at around Li=4%, CEC=3(meq/100g) which is classified as a strong weathering soil. It also shows that as Li increases CEC increases as well, while N$\_$c/ decreases.

• Earthquakes and Structures
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• v.15 no.6
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• pp.687-699
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• 2018

This paper investigates the pseudo-static analysis of reinforced slopes with geosynthetics under the influence of the uniform surcharge to evaluate the maximum tensile force of reinforcements. The analytical approach has basically been used to develop the new practical procedure to estimate both tensile force and its distribution in the height of the slope. The base of developed relationships has been adapted from the conventional horizontal slice method. The limit equilibrium framework and the assumptions of log-spiral failure surface have directly been used for proposed analytical approach. A new analytical approach considering a single layer of non-cohesion soil and the influence of uniform surcharge has been extracted from the 5n equation and 5n unknown parameters. Results of the proposed method illustrated that the location of the surcharge, amount of internal friction and the seismic coefficient have the remarkable effect on the tensile force of reinforcement and might be 2 times increasing on it. Furthermore, outcomes show that the amount of tensile force has directly until 2 times related to the amount of slope angle and its height range. Likewise, it is observed that the highest value of the tensile force in case of slope degree more than 60-degree is observed on the lower layers. While in case of less degree the highest amount of tensile force has been reported on the middle layers and extremely depended to the seismic coefficient. Hence, it has been shown that the tensile force has increased more than 6 times compared with the static condition. The obtained results of the developed procedure were compared with the outcomes of the previous research. A good agreement has been illustrated between the amount results of developed relationships and outcomes of previous research. Maximum 20 and 25 percent difference have been reported in cases of static and seismic condition respectively.