• Journal of the Korean Geotechnical Society
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• v.31 no.2
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• pp.47-63
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• 2015

A fundamental study of drilled shafts subjected to lateral cyclic loading in weathered soil was carried out based on field tests and numerical analysis. The emphasis was given on quantifying the cyclic p-y curve function from lateral cyclic loading tests and three-dimensional finite element analysis. Lateral cyclic loading tests and three-dimensional finite element analysis were carried out to investigate the behavior of drilled shafts according to the direction of cyclic loading. Based on the field tests and numerical analysis, a modified lateral load transfer relationship and design chart with degradation factors were proposed by considering the characteristics of cyclic loading. It was found that the prediction by the proposed p-y curve function is in good agreement with the general trends observed by in-situ measurements, and it represents a practical improvement in the prediction of lateral displacement and bending moment distribution of drilled shafts subjected to cyclic loading.

• Korean Journal of Agricultural Science
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• v.12 no.1
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• pp.86-100
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• 1985

In order to investigate the strength characteristics of weathered granite soils in unsaturated state, the five physically different weathered granite soils and the common soil (sandy loam) were examined. The disturbed and the undisturbed material were prepared for triaxial compression test. The following conclusions were drawn from the study; 1. Dry density of the undisturbed soil samples was lower than maximum dry density determined from the compaction test and it showed the higher value at the well graded soil. 2. The failure strength of the samples decreased with the increase of moisture content of the soil and these results were highly pronounced at the common soil sample having a good cohesive property. 3. On weathered granite soils, the cohesion was lower measured and the internal friction angle highly, the decrease rate at internal friction angle with increase of moisture content of the soil was more significant than that of cohesion 4. The modulus of deformation of the samples decreased with increase of moisture content of the soil and these phenomena were highly pronounced at the weathered granite soils than common soil. 5. The failure strength of the samples increased with in crease of confining pressure and effect of confining pressure on failure strength was highly significant at the lower moisture content of the soil.

• Water for future
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• v.24 no.3
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• pp.49-60
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• 1991

As a second part of the study entitled "Field Measurement and Analysis of Fluvial Sediment in the Cheongmi-Strea", this study concerns mineralogical and contaminative characteristics of sediment particles collected at Wonbu-Gyo and Hanpyeong-Gyo in the Cheongmi-Stream. The mineralogical analysis of the bed sediment collected reveals that, in general , quarz is the most abundant mineral found in sands with feldspars and rock fragments in the next, which confirms what is known in the literature. The shape factor of sand particles is about 0.7, which also agrees to what is known in the foreign literature. The analysis also reveals that the clay particles collected are composed mainly of illite, kaolinate, and chlorite. The analysis of contamination reveals that there is no substantial difference between the contents of organic material and heavy metals in the surface water and those in the pore water beneath the river bed. It is because the sampling for this analysis was conducted right after the September flood during which the fresh top soil from the upstream watershed replaced the old bed sediment and pore water that would probably be more contaminated. The contents of geavy metals in the bed sediment of sand particles do not exceed those in the soils adjacent to the river. For fine sediment such as clays, however, the contents of heavy metals, especially of mercury and zinc, far exceed those in the soils adjacent to the river. These fine sediments are transported downstream in the form of wash load and deposited in part on flood plains, which could be a new source of contaminants.taminants.

• Journal of the Korean Geotechnical Society
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• v.29 no.4
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• pp.57-65
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• 2013

Assessment of uncertainties of loads and resistances is prerequisite for the development of load and resistance factor design (LRFD). Many previous studies related to resistance factor calculations of piles were conducted for short or medium span bridges (span lengths less than 200m) reflecting the live load uncertainty for ordinary span bridges. In this study, by using a revised live load model and its uncertainty for long span bridges (span lengths longer than 200m and shorter than 1500m), resistance factors are recalibrated. For the estimation of nominal pile capacity (both base and shaft capacities), the Imperial College Pile (ICP) design method is used. For clayey and sandy foundation, uncertainty of resistance is assessed based on the ICP database. As long span bridges are typically considered as more important structures than short or medium span bridges, higher target reliability indices are assigned in the reliability analysis. Finally, resistance factors are calculated and proposed for the use of LRFD of driven piles for ordinary span and long span bridges.

• Journal of the Korean GEO-environmental Society
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• v.8 no.3
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• pp.67-75
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• 2007

This study was undertaken in order to investigate the load bearing capacity of raft in a piled raft through the laboratory model tests, the numerical and analytical analyses. The model tests were conducted about a piled raft, the free-standing pile group, a single pile, as well as a shallow foundation under equal conditions. The pile spacing and length, group type and soil conditions were varied in the laboratory model tests. The experimental results were compared with those by the commercial program, DEFPIG, conventional methods and Phung's method. According to this study, the behavior of piled raft was affected by pile spacing, length and soil conditions. Phung's method proved to be reliable for estimating the experimental results.

• Journal of the Korean Geotechnical Society
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• v.20 no.5
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• pp.5-16
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• 2004

This paper presents the modeling of geosynthetic-reinforced compacted soils and discusses the reinforcement effect arising from confining the dilatancy deformation of the soil by geosynthetics. A series of compressive shear tests for compacted sandy soil specimens wrapped by geosynthetics are carried out by quantitatively examining the geosynthetic-reinforcement effect, occurring from a confinement of the dilative deformation in compacted soils during shearing. In the test, the initial degree of compaction is changed for each series of sandy soil specimens so that each series has different degree of dilatancy characteristics. Herein, the axial forces working on the geosynthetics so as to prevent dilative deformation of compacted soils during shearing are measured. Furthermore, the elasto-plastic modeling of compacted soils and a rational determination procedure for input parameters needed in the elasto-plastic modeling are presented. And to describe the irreversible deformation characteristics of compacted soils during shearing, the subloading yielding surface (Hashiguchi (1989)) to the elasto-plastic modeling is introduced. Finally, the elasto-plastic finite element simulation is carried out and the geosynthetic-reinforcement effect is discussed.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.6 no.1
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• pp.23-33
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• 1994

Liquefaction characteristics of the reclaimed marine sand deposits is studied by means of the dynamic response analysis and the cyclic triaxial compression test. 1) From the result of the dynamic response analysis. it was found that the amplification of ground surface maximum acceleration varied with input earthquake motions and soil data, and earthquake coefficients were proposed to be applicable in evaluating liquefaction potential by simplified prediction methods. 2) For upper and soft sand deposits with small N-value, liquefaction strengths estimated by Seed and Idriss's simplified method were lower than those by the cyclic triaxial test while those by Iwasaki & Tatsuoka's or Vs-method were not lower. 3) Simplified methods were inclined to overestimate liquefaction potential in comparison with the dynamic response analysis and the cyclic triaxial compression test Allowable depths of liquefaction(safety factor 1) were estimated to be 7-14m for 0.1 -0.2g of input maximum acceleration.

• Journal of the Korean Geotechnical Society
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• v.17 no.6
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• pp.193-205
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• 2001

In this study the behavior of pile groups is investigated experimentally. Special attention is given to the load transfer characteristics of pile groups and to the evaluation of the group effects under vertical and horizontal loadings. In the laboratory experiments, vertical and lateral loadings were imposed on model piles in sand. Model piles made of PVC embedded in Joomoonjin sand were used in this study. Pile arrangements($2\times2,\; 3\times3$) and pile spacings(2.5D, 5.OD, 7.5D) were considered. Load-transfer curves(t-z, q-z and p-y curves), load-deflection curves and group interaction factors were obtained from the experimental results. The group interaction factors under both vertical and horizontal loadings were proposed for the cases of $2\times2\; and\; 3\times3$ pile groups with varying ratios of pile spacings. p-multipliers in this study were found for the individual piles in $2\times2\; and\; 3\times3$ pile groups.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.3
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• pp.273-282
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• 2016

This study estimates tunnel face pressure through existing 8 analytical equations and 3D numerical analysis, and compares and examines it. In general, the estimating tunnel face pressure of domestic shield TBM has been examined by a method according to analytical equation and empirical method, but numerical analysis is combined in a section passing complicated stratigraphic condition and special soil condition. Therefore, the researcher is to find a reliable method to examine of tunnel face pressure by confirming a correlation between tunnel face pressure estimated by equation and tunnel face pressure estimated by numerical analysis program. When tunnel face pressure is estimated, both analytical equation and numerical analysis were identically examined in soil conditions such as sandy soil and cohesive soil. In addition, existing analytical equation is used as equation, and 3D analysis copying construction process and shield tunnel as numerical analysis.

• Journal of the Korean Geotechnical Society
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• v.15 no.5
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• pp.291-300
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• 1999

Surfactant flushing for enhancing the removal of BTEX from contaminated sand/clay mixtures was investigated. Eight soil columns packed with relatively undisturbed BTEX contaminated soils, were leached with water, methyl alcohol and then flushed with surfactant with or without several additives. Initial concentrations of BTEX mixture range from 278mg/kg to 1975mg/kg. Initial BTEX removal efficiency was 98% when the contaminated soil was flushed with water of 850 pore volumes. Because of tailing effect, water flushing could not remove below 8mg/kg concentrations during the experimental period. Eventually, the most effective surfactant for flushing was turned out to be 4% SOFTANOL(equation omitted)-90 with 3% ethyl alcohol and 3% SXS. In interrupted flow conditions, the removal efficiency was 99.5% with the flushed water of 95 pore volumes. The BTEX mixture removed from the soil columns during the surfactant flushing ranges from 84.5% to 99.5% of the initial amount for both water leaching(850 pore volumes) and surfactant flushing(95-165 pore volumes), respectively. Test results indicated that surfactant flushing could enhance the removal of BTEX mixture from contaminated soils and could reduce the aqueous phase BTEX mixture concentration in leachate.