• Korean Journal of Soil Science and Fertilizer
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• v.15 no.2
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• pp.128-140
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• 1982

The distribution and practical classification of sandy paddy soils, which have the most extensive acreage among low productive paddy soils in Korea and have distinctive improvement effects, were studied to propose a tentative new classification system of sandy textured paddy soils as a means of improving the "Paddy Soil Type Classification" scheme used. The results are summarized as follows; 1. The potential productivity of sandy textured paddy soils was about 86% of normal paddy and the coefficient of variation was relatively high indicating that the properties of soils included were not sufficiently homogeneous. 2. As the poorly drained and halomorphic (> 16 mmhos/cm of E.C. at $25^{\circ}C$) sandy soils are not included in the "Sandy Soil" type according to the criteria of "Soil Type Classification", the recommendation of "adding clay earth" become complicated, and the soil type have to change when the salts washed away or due to ground water table fluctuations. 3. Coarse textured soils were entirely included in the "Sandy Soils" in the tentative criteria of sandy soil classification proposed, and the sandy soils were subdivided into 4 subtypes that is "Oxidized leaching sandy paddy", Red-ox. intergrading sandy paddy", "Reduced accumulating sandy paddy" and "Reduced halomorphic sandy paddy". The system of sandy soil classification proposed were consisted of following categories; Type (Sandy paddy)-Sub-type (4)-Texture family (5)-Soil series (48). 4. The variation of productivities according to the proposed scheme was more homogenized than that of the present device. 5. The total extent of sandy paddy soils was 409, 902 ha (32.3% of total paddy) according to the present classification system, but the extent reached 492,983 ha (38.9%) by the proposed system. The provinces of Gyeong-gi (88.923ha), Jeon-bug (69.717 ha), Gyeong-bug (55.390 ha) have extensive acreage of sandy paddy soils, and the provinces that had high ratio of sandy paddy soils were Gang-weon (58.9%), Gyeong-gi (50.5%), Chung-bug (48.5%), Jeon-bug (41.0%) etc. The ratio was increased by the proposed scheme, e.g. 71.4% in the case of Gang-weon prov. 6. According to the suitability group of paddy soils, the sandy soils mostly belong to 3 class (69.1%) and 4 class (29.2%). Coarse loamy textural family (59.2%) and coarse silty (16.1 %) soils were dominantly distributed. 7. The "Red-ox. intergrading subtype" of sandy paddy pertinent to 49.6% (245,012 ha) while the "Oxidized leaching sub-type" reaches to 33.5% (64,890 ha) and the remained 16.9% (83,081ha) belong to "Reduced accumulating sub-type (14.0%) and "Reduced halomorphic sub-type (2.9%)" according to the proposed scheme.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.575-582
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• 2000

The flat Dilatometer test(flat DMT) has been known as an in-situ testing method which is simple and robust to use, and reliable for site stratification and evaluation of soil properties. It was designed and proposed by Marchetti in 1975 to characterize the properties of soils. There are many researches that have been done to evaluate the horizontal coefficient of consolidation from the dissipation test results of flat DMT on normally consolidated and slightly overconsolidated clays. The representative estimation methods of estimating the horizontal consolidation coefficient are DMT-C method which uses a C-reading dissipation curve and DMT-A method which uses a A-reading dissipation curve. This paper represents a comparison analysis of those two methods in obtaining the horizontal coefficients of consolidation. The reference values are also obtained by CPTU and other laboratory tests. The applicability of using flat DMT to characterize the consolidation behavior is also reviewed for two sites. According to the results, DMT-A method is not suitable for silty clays possibly because of the compressibility characteristics. As for the normally consolidated and slightly overconsolidated clays, the results obtained from the two methods are comparable with each other as well as with the laboratory test results.

• Magazine of the Korean Society of Agricultural Engineers
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• v.38 no.1
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• pp.79-89
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• 1996

It is expected that the soil hehaviours in the seahed subjected to cyclic wave loads are much different from that on the ground Cyclic shear stresses developed below the ocean bed as a result of a passing wave train may progressively build up pore pressure in certain soils. Such build-up pore pressure may be developed dynamic behaviour such as liquefaction and significant deformation of the seabed. Currently available analytical and testing methods for the seabed subjected to cyclic wave loads are not general. The purpose of the study are to provide a test method in laboratory and to analyse the mechanism of wave-induced stresses and liquefactions potentials of the unsaturated silty marine sand. It is showed that the test set-up made especially for this study delivers exactly oscillatory wave pressures of the form of sine function. Laboratory test results defining the cyclic shear strength of the unsaturated porous medium that is homogenously sedimented. It is understood that the pore water pressure due to induced-waves is not accumulated as the wave number increases but reveals periodical change on the still water surface. The magnitude of the pore water pressure tends to be attenuated radically with a certain time lag under the action of both high and low waves as depth increases.

• Magazine of the Korean Society of Agricultural Engineers
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• v.38 no.5
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• pp.85-94
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• 1996

For the geotechnical analysis in the construction and Deign of the coastal structures, one of the most important factors is the existence of waves. The dynamic behavior and deformation of the seabed subjected to wave load must be considered. It is expected that the soil behavior in the seabed subjected to cyclic wave load is much different from that on the ground subjected to dynamic forces such as earthquake. The purposes of this study are as follows ; Firstly, to provide a testing method to generate wave loads in the laboratory and measuring oscillatory pore water pressures in the unsaturated marine silty sand specimen, Secondly, to analyze the mechanism of wave induced pore water pressures and liquefaction potentials under the conditions in the testing. It is shown that the test set-up manufactured especially for the test is good to generate oscillatory wave pressures to the specimen with sine wave type. From the results of this study, it is understood that the pore water pressure due to induced waves is not accumulated as the wave number increases but is periodically varied with wave passage on still water surface. The magnitude of pore water pressures measured tends to be diminished radically with a certain time lag under the action of both high and low waves as depth increases.

• Geotechnical Engineering
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• v.9 no.3
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• pp.35-48
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• 1993

This paper was focused on the design and construction of stone columns as a method of reinforcements in slightly soft clay or loose silty sand overlying the firm strata. It was intended to find out the effects of soil improvement by field tests in Kwangmyoung Haan Site by comparing the test results performed before and after the installation of stone columns . The results of this experimental study are as follows : the hearing capacity was increased by 3.33 times and the SPT N -valued was increased by 3.9 times by installing the stone columns : the stone column method can cut down the construction cost almost 35% compared to the precast concrete pile method in economic viewpoints.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.529-536
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• 2005

Based on an estimating method for post-cyclic strength and stiffness with cyclic triaxial tests, Direct Simple Shear (DSS) tests were carried out to confirm whether the method can be adapted to DSS test on fine-grained soils: silty clay, plastic silt, and non-plastic silt. Results from post-cyclic DSS tests were interpreted by a modified method as adopted for post-cyclic triaxial tests. In particular, influence of plasticity index for fine-grained soils was emphasised. Findings obtained from the present study are: (i) the higher the plasticity index of fine-grained soils is, the less not stiffness ratio but strength ratio decreases with increment of a normalised excess pore water pressure; and (ii) post-cyclic strength and stiffness results from DSS tests agree well with those predicted by the method modified from a procedure used for triaxial test results.

• Journal of the Korean Geotechnical Society
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• v.27 no.9
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• pp.55-66
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• 2011

The compulsory replacement method for soft ground treatment is simple but excellent in economic feasibility. However, the accurate replacement depth is not easy to properly predicted since an theoretical algorithm has not presently been established so far. In this research a prediction equation is proposed in a new form based on the liquid limit and natural moisture content rather than on the bearing capacity of the soft soil layer. The equation is based on the monitoring as well as the confirmatory boring at the site. In addition, the equation has been derived from the data obtained from the analysis of the characteristics of silt/clay of Sihwa region. The final prediction equation has been drawn by applying the regression analysis method.

• The Korean Journal of Quaternary Research
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• v.9 no.1
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• pp.43-60
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• 1995

The Kanweoldo Deposit in the Cheonsoo Bay western coast of Korean Peninsula is considered to be influenced by severe freezing condition under cold humid environment of the last glacial age. The evidence of severe freezing in the some upper part of the fine-grained Kanweoldo Deposit is characteristically irregular wavy la-mellar structure with the interval of 2∼8mm. In particular lamina show very compacted fabrics composed of rounded or spheroidal discrete aggregates covered by silt caps. Such laminar structure and associated micro-fabrics might owe to soil freezing such as ice segregation in lens form cryophoresis pressure from growing ice and disturbance by frost-creep. Furthermore pedogenesis of cold-humid type such as gleyzation or peseudo-gleyzation also might af-fect the kanweoldo Deposit in the priod of severe cold-humid cli-mate of the Wrm. The Kanweoldo sediment and organic remnant(16,708 B.P. with error limit of 250 years) affected by severe cryogenic activities sug-gest that the paleoclimate of Late Wrm in Korea might be so cold and humid as to engender the cryogenic structure in subaerial silty and sandy silt deposits.

• Journal of the Society of Disaster Information
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• v.8 no.3
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• pp.204-212
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• 2012

Lightweight soils are very economical and environment friendly materials that are valuable in field without wasting construction materials, dredged soils and clay/ silty soils during construction. Recently, the research of lightweight soils mixed with recycled material (recycled tire powder, rice husks) have been investigated. In this study the mix design factors (i.e., weight of soil, water content, foaming agent and added water) were analyzed and optimized mix design was suggested using cement content for revealing strength. For the analysis the stress-strain behavior, strength with respect to time, and experimental strength for the component of recycled material were analyzed. Finally, target strength was determined to calculate reasonable and economical mix ratio and the optimized cement content was suggested.

• Journal of the Korean GEO-environmental Society
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• v.12 no.7
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• pp.31-37
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• 2011

Only a few studies have been conducted using reduced slag as recycled material. The reduced slag in electric furnace is produced as a by-product in making a steel and a few applications of the reduced slag as expensive additives and bonding materials or as the stabilized soils was reported. The purpose of this study is to present the feasibility of the reduced slag as recycled material, especially, in a field of civil engineering. In order to achieve the purpose experiments such as SEM and XRF analysis was conducted for the reduced slag in electric furnace. Based on the results various geotechnical experiments were conducted to know engineering properties of slag-soil mixtures. Weathered soils and clay are mixed with reduced slag for various ratios. As the ratio of reduced slag to weathered soil increases, the maximum dry unit weight of the mixture decreased with increasing optimum moisture content. The results indicates that there is no effect on a reduced slag by compaction efforts. The shear strengths of the weathered soil-slag mixtures are slightly higher or similar to those of weathered soils. The permeability of the weathered soil-slag mixtures is similar to that of silty or sandy soils. Therefore, it is possible to use the mixtures as embankment or backfill materials in the fields. The unconfined strength of the mixtures of reduced slag and clay is higher than that of clay and it tends to increase with the curing time. Therefore it can be used to improve the soft ground.