• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.4C
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• pp.163-174
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• 2009

Mechanical device using the load cell or strain gage sensor can be influenced by tempearute changes because temperature change can cause a shift in the load cell or straing gage output at zero loading. In this paper, micro cone penetrometers with 1~7mm in diameter, are developed by using an optical fiber sensor (FBG: Fiber Bragg Grating) to compensate the continous temperature change during cone penetration test. Note the temperature compensated method using optical fiber sensor which has hair-size in diameter, and is not affected by environmental conditions because the measured data is the wavelength shifting of the light instead of the intensity of the electric voltage. Temperature effect test shows that the output voltage of strain gage changes and increases with an increase in the temperature. A developed FBG cone penetrometer, however, achieves excellent temperature compensation during penetration, and produces continuous change of underground temperature. In addition, the temperature compensated FBG cone shows the excellent sensitivity and detects the interface of the layered soils with higher resolution. This study demonstrates that the fiber optic sensor renders the possibility of the ultra small size cone and the new fiber optic cone may produce more reliable temperature compensated tip resistance.

• Proceedings of the Mineralogical Society of Korea Conference
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• 2003.05a
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• pp.55-55
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• 2003

호남전단대는 옥천대 남서부지역에 북동 내지 북북동 방향으로 발달하는 일련의 우수향 연성전단대로 한반도를 포함하는 동북아 지역의 중생대 부가작용과 관련하여 매우 중요한 조구조적 요소이며, 특히 북중국 대륙과 남중국 대륙이 유라시아 대륙에 부가되는 과정과 관련하여 동북아 지역의 중생대 지체구조 발달사를 설정하는데 매우 중요하게 생각되고 있다. 그러나 이러한 조구조적 중요성에도 불구하고 호남전단대의 정확한 운동 시기는 아직 밝혀지지 않고 있다. 이번 연구는 전주전단대가 지나가는 김제 금산사 지역과 무안 지역에 분포하는 화강암류를 대상으로 SHRIMP U-Pb 저어콘 연대 측정을 실시하여 전단운동시기를 밝혔다. 금산사 지역은 엽리상 각섬석-흑운모 화강섬록암이 흑운모 화강암에 포획된 명확한 지질학적 증거를 보이고 있는 곳으로 화강섬록암의 U-Pb 저어콘 연대는 172.7 $\pm$ 1.4 Ma이며 화강암의 연대는 169.6 $\pm$ 1.8 Ma과 167.5 $\pm$ 2.4 Ma로 구해졌다. 따라서 전주전단대의 전단운동은 약 173 - 170 Ma 기간에 일어났다. 특히 화강암 내에 포획된 화강섬록암 내에는 전반적인 우수향 전단운동 후기에 관입한 다수의 석영질 맥이 좌수향의 전단운동을 받은 증거가 관찰되는데 이러한 사실은 우수향의 전단운동 이후 화강암의 관입 이전에 좌수향의 전단 운동이 있었음을 지시한다. 무안 지역은 전주전단대의 끝 부분에 해당하는 곳으로 각섬석화강섬록암과 이를 관입한 각섬석화강암이 모두 우수향의 전단운동을 받았다. 화강섬록암의 U-Pb 저어콘 연대는 176.3 $\pm$ 1.7 Ma이며 화강암의 연대는 165.8 $\pm$ 2.0 Ma로 구해졌으며, 따라서 최종 우수향 전단운동의 시기는 166 Ma 이후로 생각된다. 무안 지역에 분포하는 화강섬록암과 화강암의 관입시기는 금산사 지역의 화강섬록암과 화강암과 각각 조화적이다. 호남전단대의 운동 시기를 밝히기 위해 전주전단대에 해당하는 금산사 지역과 무안 지역에 분포하는 화강암류에 대한 U-Pb 저어콘 연대 측정을 실시한 결과 호남전단대의 특징적인 우수향 전단운동은 적어도 2회에 걸쳐 일어났음을 알 수 있다. 즉 첫 번째 광역적인 전단운동은 약 173 - 170 Ma 시기에 일어났으며, 두 번째 전단운동은 166 Ma 이후에 일어났음을 알 수 있다. 한편 전기의 우수향 전단운동은 후기 화강암 관입 이전에 좌수향 전단 운동에 의해 부분적으로 재활성 되었으며, 후기 화강암의 관입 이후에 재차 우수향 전단운동으로 활성화 되었음을 알 수 있다. 이상의 결과를 종합하면 호남전단대는 쥬라기 중기에 발생한 광역적인 우수향의 연성전단운동이나, 운동 특성은 연속적이기 보다는 단속적으로 일어난 것으로 생각된다.

• Geotechnical Engineering
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• v.10 no.4
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• pp.153-166
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• 1994

In this paper, the experimental study on the behavior of the dredged clay was performed by introducing the consolidation teat method using continuous loading. Also a new testing method was examined and the strength of the dredged clay using thin plate was evaluated. The rheological characteristics of the dredged clay are described by the gingham model. The static and rheologic thin plate penetration test is proposed for the shear strength testing method. It is found that both of testing methods are reasonable and have a practicability. Especially, the strength increases for a water content which is less than two times of liquid limit in case of silty soil and clayey soil. About plasticity index, the strength increases rapidly for a value less than 10 for silt, 5 for clay which a water content is normalized by plasticity index of silty soil rather than clayey soil.

• Journal of the Korean Geotechnical Society
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• v.24 no.10
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• pp.57-70
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• 2008

The advantage of piezocone penetration test is a guarantee of continuous data, which is a source of reliable interpretation of target soil layer. Many researches have been carried out f3r several decades and several classification charts have been developed to classify in-situ soil from the cone penetration test result. Since most present classification charts or methods were developed based on the data which were compiled over the world except Korea, they should be verified to be feasible for Korean soil. Furthermore, sometimes their charts provide different soil classification results according to the different input parameters. However, unfortunately, revision of those charts is quite difficult or almost impossible. In this research a new soil classification model is proposed by using fuzzy C-mean clustering and neuro-fuzzy theory based on the 5371 CPT results and soil logging results compiled from 17 local sites around Korea. Proposed neuro-fuzzy soil classification model was verified by comparing the classification results f3r new data, which were not used during learning process of neuro-fuzzy model, with real soil log. Efficiency of proposed neuro-fuzzy model was compared with other soft computing classification models and Robertson method for new data.

• The Journal of the Petrological Society of Korea
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• v.11 no.2
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• pp.74-89
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• 2002

Rock units, relating with the Guamsan caldera, are composed of Guamsan Tuff and rhyolitic intrusions. The Guamsan Tuff consists almost entirely of ash-flow tuffs with some volcanic breccias and fallout tuffs. The volcanic breccia comprises block and ash-flow breccias of near-vent facies and caldera-collapse breccia near the ring fracture. The lower ash-flow tuffs are of an expanded pyroclastic flow phase from the pyroclastic flow-forming eruption with an ash-cloud fall phase of the fallout tuffs on the flow units, but the upper ones are of a non-expanded ash-flow phase from the boiling-over eruption. The rhyolitic intrusions are divided into intracaldera intrusions and ring dikes that are subdivided into inner, intermediate and outer dikes. We compile the volcanic processes along a single cycle of cadela development from the eruptive phases in the Guamsan area. The explosive eruptions began with block and ash-flow phases from collapse of glowing lava dome caused by Pelean eruption, progressed through expanded pyroclastic flow phases and ash-cloud fallout phases during high column collapse of pyroclastic flow-forming eruption from a single central vent. This was followed by non-expanded ash-flow phases due to boiling-over eruption from multiple ring fissure vents. The caldera collapse induced the translation into ring-fissure vents from a single central vent in the earlier eruption. After the boiling-over eruption, there followed an effusive phase in which rhyolitic magma was injected and erupted to be progressively emplaced as small plugs/dikes and ring dikes with many lava domes on the surface. Finally rhyodacitic magma was on emplaced as a series of dikes along the junction of both outer and intermediate dikes on the southwestern side of the caldela.

• Journal of the Korea Concrete Institute
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• v.14 no.6
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• pp.973-981
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• 2002

Recently, the use of high strength concrete (HSC) has increased dramatically md however, few studies have been conducted on the early-age properties of HSC such as setting. The penetration resistance test (specified by KS F 2436) that is the standard test method for determining initial and final setting times of concrete, may not be appropriate for HSC because of the high viscosity of the mortar mixture. To address this issue, an ultrasonic pulse velocity (UPV) monitoring system was used to investigate the setting behavior of mortar and concrete. The experimental study was carried out to measure the UPV's of mortars and concretes having various water/binder ratios (W/B) and various fly ash replacement levels, during the first 24 hours of testing. Test results showed that the UPV in concrete was developed faster than that of mortar with the same W/B, and that of ordinary concrete was greater than that of fly ash concrete. Typical values of UPV were suggested that correspond to the initial and final setting times, based on following criteria: (1) the penetration resistance method; (2) the instant when the UPV begins to develop; and (3) the instant when the UPV development rate is maximum. The method and UPV monitoring device used in this study is promising for the setting assessment of concrete, particularly for HSC.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.2C
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• pp.83-94
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• 2008

In this study an effective stress analysis was performed to evaluate liquefaction potential and ground settlement for reclaimed sites. The effective stress model can simulate the stiffness degradation due to excess pore pressure and resulting ground deformation. It is applicable to a wide range of strain. An equivalent linear analysis suitable for low strain levels was also carried out to compare the effective stress analysis. Shear stress ratio calculated from an equivalent linear analysis was used to determine SPT blow count to prevent liquefaction. Depending on the magnitude of potential earthquake and fine contents, the SPT blow count was converted into an equivalent cone tip resistance. It was compared with the measured cone tip resistance. The measured elastic shear wave velocity and cone tip resistance from two reclaimed sites in Incheon were used to perform liquefaction analyses. Two liquefaction evaluation methods showed similar liquefaction potential which was evaluated continuously. The predicted excess pore pressure ratio of upper 20 m was between 40% and 70%. The calculated post-shaking settlement caused by excess pore pressure dissipation was less than 10 cm.

• Proceedings of the Mineralogical Society of Korea Conference
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• 2003.05a
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• pp.52-52
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• 2003

경기육괴 서남부에 위치한 홍성지역의 기반암은 선캠브리아 화강암질 편마암으로 이루어진 것으로 알려져 왔으나, 적어도 일부는 신원생대(약820 Ma) 시기에 관입한 토날라이트질 심성암체로 구성된다. 토날라이트의 주 구성광물은 석영, 사장석, 흑운모, 각섬석이며, 저어콘, 스핀, 녹니석, 인회석 등이 소량으로 산출한다. 이 연구에서는 야외 및 미세구조 관찰을 통해, 홍성 화강암질암에서 나타나는 구조적 요소들이 화성기원임을 보고한다. 홍성 토날라이트에서 관찰되는 구조들이 화성기원인 증거는: (1) 엽리가 연속성이 부족하고 주향과 경사가 불규칙하며, 드물게는 사층리처럼 보이기도 한다. (2) 자형 내지 반자형의 장석과 각섬석이 엽리면에 평행 또는 준평행하게 배열되어 있으며, 반정 주변에는 음영대(pressure shadow)가 발달하지 않는다 (3) 고철질 포획체(mafic enclave)는 주변암의 엽리에 평행하게 신장되어 있고, 완전히 고화 되지 않은 상태에서 형성되는 불꽃 구조(flame structure)가 드물게 관찰된다. (4) 고철질 포획체의 주 구성광물인 흑운모와 각섬석은 주변암의 엽리와 평행하게 배열되어 있으나, 소성변형의 증거를 보이지 않는다. 홍성 토날라이트에서 관찰되는 모든 조직들이 화성기원이라고 주장하기는 어렵지만, 모두 고체상태에서의 변형작용으로 설명하기는 더욱 힘들다. 후자가 화성기원의 조직에 어느 정도 영향을 주었는지는 추후의 연구를 통해 밝혀져야 할 것이다.

• Geotechnical Engineering
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• v.13 no.4
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• pp.95-108
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• 1997

For normally consolidated clay, several researchers have developed a number of theoretical time factors to determine the coefficient of consolidation However, depending on the assumptions and analytical techniques, it could considerably vary even for a specific degree of consolidation. In this paper, a method is proposed to determine a consistent coefficient of consolidation over all ranges of degree of consolidation by applying the concept of the Optimum Design Technique. The initial excess pore pressure distribution is assumed to be obtainable by the successive spherical cavity expansion theory. The dissipation of pore pressure is simulated by means of two dimensional linear-uncoupled axisymmetric consolidation analysis. The minimization of the differences between the measured and the predicted excess pore pressures was carried by BFGS unconstrained optimum design algorithm with one dimensional golden section search technique. By analyzing numerical and real field examples, it can be found that the adopted optimum technique gives a consistent and convergent results.

• Economic and Environmental Geology
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• v.24 no.4
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• pp.421-434
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• 1991

Ground magnetic surveys were conducted at four areas where the Yangsan fault, the most prominent lineament in the Kyeongsang basin, appears to be passed through. For data processing, IGRF correction, upward continuation and reduction-to-the-pole were performed. The automatic inversion by using a matrix computation method, which takes the depth to bottom layer of the horizontal two layer structure as the model parameter, has been attempted to delineate the subsurface structure. Upward continuation of the surface magnetic map to the same level of the aeromagnetic survey (KIER, 1989) resulted in very similiar patterns to those of aeromagnetic data. Subsurface modeling of eight profile data show that the strike and dip of the Yangsan fault in study areas are $N6^{\circ}-15^{\circ}E$, and near vertical to somewhat eastward, repectively, despite of the local lithological contrast of each study area. It seems that the magnetic effect of faulting in the study area 1, which locates in the most northern part of the survey areas, is disturbed by that of igneous intrusion. At study area 2, the possibility of volcanic or igneous intrusion, which is 200-300 meters wide along the fault plane was presented. At study area 3, unlike other study areas, distinct fracture zone of 500-700 meters in width was revealed along the surface fault line. The andesitic rocks of the study area 4 have very high susceptibilities and the fault line on surface of this area was shifted about 500 meter eastward, as compared with the inferred fault line by the previous study.