• Tunnel and Underground Space
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• v.25 no.3
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• pp.244-254
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• 2015

The tunnel is excavated through the alluvial layer composed of sand and gravel with groundwater deposited on rock. A portion of upper part of the tunnel is located in the alluvial layer and there are several buildings just above the curved section of the tunnel. It is necessary to prevent from sand-flowing into the tunnel due to low strength of the alluvial, high groundwater level and shallow depth of the tunnel from the ground surface. For this, the alluvial around the tunnel is pre-reinforced by umbrella arch method with multi-stage grouting through large diameter steel pipes or jet grouting before excavating the tunnel. The effect of the pre-reinforcement of the tunnel and the safety of the buildings are monitored by measurement of ground deformation occurred during tunnelling.

• Journal of the Korean earth science society
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• v.33 no.4
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• pp.320-328
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• 2012

To investigate geomorphic development of alluvial plains and climatic environment change during the late Holocene carbon dating, soil organic carbon analysis and humus analysis of sediments from alluvial plain of Hampyeongcheon basin were performed. The lowest peat layer was formed under warm and humid climates, which is considered to correspond to the Atlantic period in the Holocene. Yellowish brown sandy clay layer was deposited in the natural levee, which we think were deposited in the generally warm and dry climates. The carbon dating age is 1,879-1,532 BC, and this period correspond to the Sub-boreal period in the Holocene. Light brown clay layer is assumed to have been deposited in transitional environment from the natural levee to the back marsh. The climatic environment was warm and humid, which is considered as transitional period from the Sub-boreal to the Sub-Atlantic in the Holocene. Light yellowish brown and light brown clay layer of the upper part are regarded as sediments of the back marsh. Light yellowish brown clay layer was deposited in the cold and dry climates, which is considered to correspond to the Sub-Atlantic period in the Holocene. Light brown clay layer was deposited in the warm and dry climates. The carbon dating age is 211-427 AD, this period corresponds to the Post Roman Warm Period in the Holocene.

• Korean Journal of Hydrosciences
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• v.1
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• pp.61-71
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• 1990

The characteristics of radial thickness of ice jam at the center part of channel bends were analyzed briefly in this paper. Jam thickness in channel bends increases both toward the inner bank, and dowmstream. For this study, slope at the jam's underside was assumed to be liner with similarity of radial slope of bed in alluvial bends. Radial slope at the jam's underside in floating ice elements was estimated using the force equilibrium theory in the radial direction. The eqution which can be estimated the radial slope of ice jam was suggested using Falcon and Kennedy's bed layer theory. Experimental data, which were measured at the center part of cross-section in a single 180-degree bend, were compared to the calculated values using the suggested equtions. The result shows that the calcultated values were smaller than the measured ones. Ot is considered that the estimated value of shear stress in the radial direction may be smaller than the actual and two-layer model may be not suibable for alluvial bend flow.

• Water for future
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• v.12 no.2
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• pp.36-42
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• 1979

This study has been conducted to find out the location and amount of the subterrain water body developed in the alluvial stratum in Paho-Dong, Sungsee-Myo-n, Dalsung-Kun are. An earlier test drilling was done in this area by R.O.K. Agricultural Promotion Corporation. The area consists of a small river basin and surrounding low hills developed around the junction of the Nakdong and Kumho Rivers. The strata of this area are made of Paldal gravel, Bokhyundong and Banyawol layers which were formed in the cretaceous period of the Meso-saicera or acid dikes and covered with-irregular alluvial layers. The alluvial layer in this area is composed of rather minute particles and proportional electric resistance tests on this layer show $10^2\;-\;10^3\;\Omega/cm$. The drillings up to 12meters deep showed only the sand layer (Form 3 to 26meters in thickness) contains water. The sand layers can not be considered a good water trapping one. Applying the data from the drillings to A.Hazen's equation, $K\;=\;{cd_e}^2\;(0.7\;+0.03t)$ to get the theoretical value of the water infilterated, I calculated it as K=13.92m/day. And again the value was set to Dupuit equation, (equation omitted) to acquire the pumping water amount the result was $Q_1\;=\;77.20\;\textrm{m}^3/day$. When the data-applied to the equation for pumping water amount, (equation omitted), the results were $Q_2\;=\;122.39\;\textrm{m}^3/day$ and K = 38m/day $Q_1\;and;Q_2$ (tow types of pumping water amount) represent proper value decrease and maximum value decrease respectively. Therefore, $Q_2$ is the least amount of water we can pump. The area covers about $1,555,000\;\textrm{m}^2$ and the maximum water needed in this area amounts to $155,000\textrm{m}^3$. That means we have to drill 1,406 pumping wells. It is concluded that undertaking the project in this area is irrational or even desperate and surface water should be developed more favorably.

• 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)

• Geophysics and Geophysical Exploration
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• v.16 no.3
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• pp.154-162
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• 2013

Vertical electrical sounding and 2D electrical resistivity survey were applied for evaluating the characteristics of alluvial layers at a groundwater artificial recharge site. The fine particles in alluvial layer, main target layer of groundwater artificial recharge, may cause clogging phenomena. In this case, electrical resistivity method is an effective technique to verify the spatial distribution of low-resistivity layers, such as saturated silts and clays. On the other hand, much attention should be paid to interpret the resistivity data in unconsolidated layers, because thick clayey overburden sometimes produces a masking effect on underlying interbedded resistive sands and gravels. Considering these points, we designed 35 points arranged in a grid form for vertical electrical sounding and 10 lines for 2D electrical resistivity survey, and concentrated our effort on enhancing the vertical and horizontal resolution of resistivity images. According to the results, 15 meters thick layers consisting of sands and gravels are located in 30 meters below ground. And the spatial distribution of silts and clays are mapped, which may cause clogging. Consequently, this approach can contribute to design and determine the location and depth of injection and observation wells for groundwater artificial recharge.

• Journal of Soil and Groundwater Environment
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• v.25 no.1
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• pp.12-24
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• 2020

This study was conducted to examine an artificial recharge system, which was considered to be an alternative for securing additional groundwater resources in a high-density greenhouse region. An injection well with a depth of 14.0 m was placed in an alluvial plain of the zone. Eight monitoring wells were placed in a shape of dual circles around the injection well. Aquifer tests showed that the aquifer was comprised with high-permeable layer with hydraulic conductivities of 1.5×10^-3~2.4×10^-2 cm/sec and storage coefficients of 0.07~0.10. A step injection test resulted in a specific groundwater-level rising (Sr/Q) values of 0.013~0.018 day/㎡ with 64~92% injection efficiencies. Results of the constant-rate injection test with an optimal injection rate of 100 ㎥/day demonstrated an enormous storage capacity of the alluvial aquifer during ten experimental days. To design an optimal recharge system for an artificial recharge, the high-permeable layer should be isolated by dual packers and suitable pressure should be applied to the injection well in order to store water. An anisotropy ratio of the alluvial aquifer was evaluated to be approximately 1.25 : 1 with an anisotropy angle of 71 degrees, indicating intervals among injection wells are almost the same.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.03a
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• pp.283-290
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• 2001

In this study, static Pile load tests and PDA for open-ended steel pipe pile($\phi$ = 609.6 mm, t = 14 mm) penetrated into the gravel layer(GP - GM) was accomplished and axial load distribution was measured. Based on the tests results, the ultimate bearing capacity and axial load bearing mode were examined. Also, the ultimate pile capacity was calculated by APIL $E^{PLUS}$./.

• Journal of the Korean Geographical Society
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• v.33 no.2
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• pp.127-142
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• 1998

Unsan alluvial plain is the backmarsh of Seomseokcheon which is a river originated from Chilseongdae(954m) on Mts Taeback, flowing into Donghae in southern Kangreung City, Kangwon Province. The vegetation change, geomorphic develoopment and depositional environment during the late Holocene have been investigated, using the methods such as boring, pollen analysis and radiocarbon dating. Because the deposits fo the study area are mainly consisted of peat and paety sand, they contained many pollen fossils. The peat layer has been sedimented since the high sea-level periods, 3,200 y. BP, and the records of vegetation change until now has well preserved here. According to archeological researches and the results of pollen analysis in east coast of Korea, it is supposed that the prehistoric rice farming in this area has begun since ca. 1,800 y. BP.

• The Journal of Engineering Geology
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• v.12 no.4
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• pp.471-484
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• 2002

Alluviums in the Keum River watershed cover an areal extent of $3,029{\;}\textrm{km}^2$ and contain about 8.1 billion tons of groundwater. However, the waters are severely polluted by nitrate, possibly due to the application of nitrogen fertilizer (>250 N kg/ha) on agricultural land. This paper aims to elucidate the pollution status and behaviors of nitrate in alluvial groundwaters in the Keum River watershed area, based on regional hydrogeochemical study. Most of the collected samples (n = 186) are polluted by nitrate (average = 42.2 mg/L, maximum = 295 mg/L). About 29% of the samples have the nitrate concentrations exceeding Korean Drinking Water Standard (44 mg/L $NO_3$). The distribution of nitrate concentrations in the study area is largely dependant on geochemical environments of alluvial aquifers. In particular, the decrease of redox potential of alluvial groundwaters showed a good correlation with the decreases of nitrate, iron, and manganese concentrations. Thus, the change of redox state in alluvial aquifers, likely reflecting their sedimentary environments, controls both the behavior and fate of nitrogen compounds and their natural attenuation (denitrification) in aquifers. A carbon-rich, silty layer within alluvium strata forms a reducing condition and possesses a buffering capacity on nitrate pollution.