• Economic and Environmental Geology
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• v.57 no.2
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• pp.243-251
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• 2024

In this study, a surface geological survey was first conducted to investigate aggregate resources in the Yeongam area of Jeollanam-do, and a drilling survey was conducted in the lower part of the surface, which was difficult to identify through a surface geological survey, to determine the spatial distribution of aggregates. Drilling sites were selected considering the topographical development and Quaternary alluvium characteristics of the study area, and river aggregate drilling surveys were conducted at a total of 5 points and land aggregate drilling surveys were conducted at a total of 28 points. Borehole core sediments were classified into seven sedimentary units to determine whether they could be used as aggregates, and optically stimulated luminescence dating was performed on representative boreholes to measure the depositional period for each sedimentary unit. As a result of the study, most of the Yeongam area had a very wide river basin, so it was estimated that there would be a large amount of aggregate, but the amount of aggregate was evaluated to be very small compared to other cities and counties. Most of the unconsolidated sedimentary layers in the Yeongam area are composed of blue-grey marine clay with a vertical thickness of more than 10 m. The sand-gravel layer corresponding to the aggregate section is distributed in the lower part of the marine clay, thinly covering the bedrock weathering zone. This is because the amount of aggregates themselves is small and most of the aggregates are distributed at a depth of 10 m below the surface, which is currently difficult to develop, so the possibility of developing aggregates is evaluated to be very low. As a result of dating, it can be seen that the blue-grey marine clay layer is an intertidal sedimentary layer formed as the sea level rose rapidly about 10,000 years ago. The deposition process continued from 10,000 years ago to the present, and as a result, a very thick clay layer was deposited. This clay layer was formed very dominantly for about 6,000 to 8,000 years, and the sand-gravel layer in the section where aggregates deposited in the Pleistocene period can exist was measured to have been deposited at about 13.0 to 19.0 ka, and about 50 ka, showing that it was deposited as paleo-fluvial deposits before the marine transgression process.

• Journal of the Korean Geotechnical Society
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• v.25 no.7
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• pp.5-10
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• 2009

The ground anchor is not usually used in soft clay and loose sand, because the pullout resistance of anchors can not be guaranteed. However, there is a method to increase the capacity of anchors using electric discharge geotechnical technologies, which are also known as pulse discharge and electric-spark technologies. The pulse-discharge anchor has a bulbed (or underreamed) bond length that is expanded by high voltage electrokinetic pulse energy. 24 anchors were installed in the weathered soil and sandy clay at the Geotechnical Experimentation Site at Sungkyunkwan University in Suwon, Korea. In this study, in order to define a relation between expansion rate of the anchor diameter and ultimate load, anchor load tests were carried out in accordance with testing procedures by AASHTO (AASHTO 1990) and FHWA (Weatheb 1998). And then several anchors were exhumed to measure the diameter of the pulse discharge anchors.

• Economic and Environmental Geology
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• v.54 no.5
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• pp.595-603
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• 2021

Sand layer distribution, which is the main target of river and land aggregate resources, mainly belongs to alluvial and river sedimentary environments among the Quaternary sedimentary environments. The distribution of aggregate resources in the area of Geumsan-gun, Chungcheongnam-do is characteristically developed around a sedimentation environment in which intrusive meandering river dominate. Although the area around Bonhwangcheon Stream and the area near the confluence of small streams are small, the river floodplain develops and corresponds to the aggregate distribution area. The sedimentary layer formed in the sedimentary environment such as colluvial deposits or alluvial fan deposits has a relatively low distribution rate of aggregate resources. The vertical distribution of the Quaternary sedimentary layers in the Geumsan-gun region ranges from about 5 to 12 m and has an average Quaternary sedimentary thickness of 8 m. The aggregate-bearing section has an average thickness of 3.6 m, and the average grain size is about 21% clay-silt, 67% sand, and 12% gravel. The main characteristics of the aggregate-bearing section are that coarse-grained sand predominates, and gravel is sub-angular or sub-rounded, and the sorting is generally poor and has a massive form of deposits, and the soil colour ranges from dark grey to yellowish-brown. In Geumsan-gun, the most likely distribution area for aggregate development is the alluvial sedimentary and river sedimentary layers distributed along the current and former riverbeds of the main Geumgang River, Bonhwangcheon and small River tributaries.

• Journal of the Korean Geotechnical Society
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• v.17 no.4
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• pp.93-105
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• 2001

해성토층(풍화토 및 모래질 충적토가 암반 위에 쌓인) 위에 준설매립된 수도권 해안매립지역에서 원형의 대심도 굴착공사로 인하여 발생하는 지중연속벽의 수평변위에 대한 현장계측을 중심으로 연구를 수행하였다. 현장측정으로는 지중연속벽의 8방향에서 벽체수평변위와 철근응력, 토압, 간극수압 등이 측정되었고, 정확한 측정결과를 얻기 위하여 합리적인 해석 및 보정방법이 연구되었다. 현장측정결과 굴착시공단계에 따라서 벽체수평변위가 증가하였으며, 일정깊이에 존재하는 점토층을 굴착함으로써 간극수압의 급격한 변화가 측정되었다. 한편, 굴착전후의 구속압감소에 따른 지반물성치의 변화를 정리하였다. 굴착전후의 탄성계수는 일정깊이까지 상당한 정도로 감소됨을 알 수 있었고 굴착전후 여러 가지 시험방법에 따른 탄성계수의 차이들을 비교하였다.

• The Journal of Engineering Geology
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• v.31 no.4
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• pp.589-601
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• 2021

Artificial recharge technology is a method for solving problems such as groundwater level drop and ground subsidence caused by groundwater withdrawal. This study investigated the applicability of using the hydraulic conductivity of an aquifer to predict injection test results for aquifer restoration. Pumping and injection tests were performed under the same conditions as those for the artificial injection facility located in Icheon, Gyeonggi-do. The hydraulic conductivity of the aquifer, which plays a decisive role in restoring the groundwater level, was derived from the pumping test. A numerical model of a simplified on-site aquifer was constructed, and a transient analysis was applied with the same conditions as the pumping test. The correlation between the measured and the resulting model values is strong (R² = 0.78). The injection test was performed in a sedimentary layer composed of silt sand and clay sand. From the results of the injection test, an empirical formula was derived using Theim's formula, which is a common well analysis solution to determine the parameters of the aquifer from time-level data. The model values from the empirical formula have a high degree of correlation (R² = 0.99) with measured values. Under specific conditions, for areas where it is difficult to conduct an injection test, the formula from this study, which relies on the hydraulic conductivity of the aquifer determined through the pumping test, may be used to predict reliable injection rates for groundwater restoration.

• Korean Journal of Soil Science and Fertilizer
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• v.42 no.2
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• pp.132-138
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• 2009

Soils originated from limestone, located at the southern part of Kangwon province and Jecheon, Danyang of Chungbuk province are mainly composed of fine texture, have different properties from soils originated from granite and granite gneiss, especially for water movement. This study was conducted for making PTF(Pedo-Transfer Function) for Kfs(field saturaton hydraulic conductivity) estimation, and for investigating the relation between soil particle distribution and the infiltration and percolation rate in soils originated from limestone. Soils used for the experiment were 6 soils of Gwarim, Mosan, Jangseong, Maji, Anmi and Pyongan series. Infiltration and percolation rate for the soil were measured by a disc tension infiltrometer and a Guelph permeameter, respectively. The particle size distribution and organic matter content of the soils were analyzed. Kfs was not related with sand, silt, clay, and organic mattrer (OM) content because of forest soils which contained high gravel, pebble, and cobble content, and O layer with high OM content. After Mosan soil series and O layer of Gwarim series were excluded for the data analysis, Kfs was explained as a linear function with sand and clay content and a exponential function with OM content. As a result, the PTF equation was obtained as Kfs=-4.20558+0.479706*(S)+0.023187*exp(1.829*OM) ($R^2=0.6558^{*}$).

• Journal of Korean Society of Forest Science
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• v.86 no.2
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• pp.186-199
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• 1997

The soils derived from granite gneiss occupy almost one third of the land area in Korea. The soils under forest vegetation, formed on granite gneiss, in Sun chon-shi, Chollanam-do in southern part of Korea, were studied to evaluate the weathering and the transformation of primary minerals into secondary minerals, clay minerals. The studied soils contained large amounts of ferromagnesian minerals, weathered biotites and were well weathered, strongly acid and low in organic matters and in ration exchange capacity. The clay contents in the Bt horizon were almost two times higher than those in the C horizon. The O horizon had a thin layer which consisted of a little decomposed plant components with a granic fabric and high porosity, and showed the micromorphological characteristics of moder humus. The related distribution pattern of the E horizon were enaulic and large amounts of silts and small amounts of sand grains were another characteristics of the E horizon. The most striking micromorphological features were multilaminated clay coating and infillings in the voids in the Bt and C horizons, and generally limpid ferriargillans ejected from the biotites and imparted red color to the soils in the Bt horizon. High clay contents in the Bt horizon was not only due to clay translocation, but also due to intensive in situ mineral weathering in this horizon. The most significant pedogenic process, revealed by the petrographic microscope and SEM, was the formation of iron oxides from biotites, the formation of tubular halloysites and the weathering models of biotites; wedge weathering and layer weathering. The thick coating on the weathering biotites showed the characteristics of the weathering process and the synthetic hematites were revealed in clays by TEM. Total chemical analysis of clays revealed extensive loss of Ca, and Na and the concentration of Fe and Al. Mineralogical studies of clays by XRD showed that micas were almost completely weathered to kaolinite, vermiculite-kaolinite intergrade, hematite, gibbsite, while halloysites from other primary minerals. Some dioctahedral mica appeared to be resistant in the soils. Parent rock of the soils contained a considerable amounts of biotites and this forest soils showed especially a dominant characteristics of biotite weathering.

• Journal of the Korean earth science society
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• v.25 no.4
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• pp.270-276
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• 2004

Multi-channel Analysis of Surface Waves (MASW) and Seismic Cone Penetration Test (SCPT) have been recently developed to obtain S-wave velocity profiles which were conventionally investigated by a down-hole seismic survey. For unconsolidated sedimentary sites, we studied these three methods, and compared the results with a drilling log. All the methods showed that the changes in the S-wave velocities were consistent with the changes in the sedimentary facies. In addition, the SCPT was most sensitive to changes in sedimentary facies among the three profiles. The results of the SCPT showed that there exists a low velocity zone, which is mainly composed of clayey sand, at the depth of 8${\sim}$12m in the sediments.

• The Journal of the Acoustical Society of Korea
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• v.23 no.1
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• pp.8-16
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• 2004

An inversion method is presented for the determination of the compressional wave speed, compressional wave attenuation, thickness of the sediment layer and density as a function of depth for a horizontally stratified ocean bottom. An experiment for estimating those properties was conducted in the shallow water of South Sea in Korea. In the experiment, a light bulb implosion and the propagating sound were measured using a VLA (vertical line array). As a method for estimating the geoacoustic properties, a coherent broadband matched field processing combined with Genetic Algorithm was employed. When a time-dependent signal is very short, the Fourier transform results are not accurate, since the frequency components are not locatable in time and the windowed Fourier transform is limited by the length of the window. However, it is possible to do this using the wavelet transform a transform that yields a time-frequency representation of a signal. In this study, this transform is used to identify and extract the acoustic components from multipath time series. The inversion is formulated as an optimization problem which maximizes the cost function defined as a normalized correlation between the measured and modeled signals in the wavelet transform coefficient vector. The experiments and procedures for deploying the light bulbs and the coherent broadband inversion method are described, and the estimated geoacoustic profile in the vicinity of the VLA site is presented.

• Journal of the Geological Society of Korea
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• v.54 no.5
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• pp.477-488
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• 2018

Fluid muds commonly occur in estuarine environments, but their ancient examples have rarely been studied in terms of depositional characteristics and processes. Cores of estuarine channel deposits of the Early Cretaceous McMurray Formation, Alberta, Canada show various mudstone layers that possess depositional characteristics of high clay-concentration flows. These mudstone layers are examined in detail through microscopic observation of thin sections and classified into three microfacies (<1 to 25 mm thick) on the basis of sedimentary texture and structures. Structureless mudstone (Microfacies 1) consists mainly of clay particles and contains randomly dispersed coarser grains (coarse silt to fine sand). This microfacies is interpreted as being deposited by cohesive mud flows, i.e., fluid muds, which possessed sufficient strength to support suspended coarser grains (quasi-laminar plug flow). Silt-streaked mudstone (Microfacies 2) mainly comprises mudstone with dispersed coarse grains and includes very thin, discontinuous silt streaks of coarse-silt to very-fine-sand grains. The texture similar to Microfacies 1 indicates that Microfacies 2 was also deposited by cohesive fluid muds. The silt streaks are, however, suggestive of the presence of intermittent weak turbulence under the plug (upper transitional plug flow). Heterolithic laminated mudstone (Microfacies 3) is characterized by alternation of relatively thick silt laminae and much thinner clay laminae. It is either parallel-laminated or low-angle cross-laminated, occasionally showing low-amplitude ripple forms. The heterolithic laminae are interpreted as the results of shear sorting in the basal turbulent zone under a cohesive plug. They may represent low-amplitude bed-waves formed under lower transitional plug flows. These three microfacies reflect a range of flow phases of fluid muds, which change with flow velocities and suspended mud concentrations. The results of this study provide important knowledge to recognize fluid-mud deposits in ancient sequences and to better understand depositional processes of mudstones.