• Economic and Environmental Geology
• /
• v.46 no.4
• /
• pp.359-373
• /
• 2013

Shale is considered as a source rock for conventional oil and gas exploration and development because shale is fine-grained detrital sedimentary rock which can preserve the organic matter better. Shale has a good sealing capacity for the petroleum trap due to its low permeability. Commercial recoveries of gas from shale in the North America based on the development of technologies of horizontal drilling and hydraulic fracturing reveal that shale also function as a effective reservoir rock. Geochemical techniques to evaluate generation potential of the hydrocarbons from organic matter in the source rocks can be applied for the exploration of the shale gas resources. To evaluate shale gas resources, it is important to understand various geochemical processes and shale characteristics controlling generation, storage and estimation of shale gas reserves. In this paper, the generation mechanism of the oil and gas from organic matter is reviewed, and geochemical techniques which can be applied for the evaluation and characterization of shale gas are introduced.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.17 no.5
• /
• pp.533-551
• /
• 2015

The rock fracturing during waterjet cutting is very complicated because rock is inhomogeneous and anisotropic, compared with artificial materials (e.g., metal or glass). Thus, it is very important to verify the effects of rock properties on waterjet rock cutting performance. Properties affecting the rock cutting efficiency have been variously described in the literature, depending on the experimental conditions (e.g., water pressure, abrasive feed rate, or standoff distance) and rock-types studied. In this study, a rock-property-related literature review was performed to determine the key properties important for waterjet rock cutting. Porosity, uniaxial compressive strength, and hardness of the rock were determined to be the key properties affecting waterjet rock cutting. The results of this analysis can provide the basic knowledge to determine the cutting efficiency of waterjet rock cutting technology for rock excavation-related construction.

• Journal of Korea Water Resources Association
• /
• v.47 no.4
• /
• pp.307-319
• /
• 2014

Because of the rapid rising of water related disasters due to the global warming, the extreme design criteria of levee construction for severe flood has been applied in several developed countries such as USA and Netheland. In Korea, the national river restoration projects were carried out on 4 major rivers in recent several years. The projects consisted of riverbed dredge and levee reinforcement, and new construction have caused wide change of river environment. However, concrete countermeasures for levee safety and river management have not been suggested until now. Therefore, this study assesses the levee safety of Yulji levee located in Hoechon, Nakdong Basin, where the Levee Seepage Monitoring System installed. The stability of levee is assessed based on the simulation performed by SEEP/W(2D unsaturated seepage model) and the simulated results are compared with the observed data. The effects of the flood wave and levee shape on the levee safety are investigated through several simulations.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2017.05a
• /
• pp.242-242
• /
• 2017

산업혁명 이후 인간사회의 산업화 및 도시화의 가속으로 지구온난화는 기후변화를 야기해 왔으며, 이로 인한 각종 부정적인 영향과 심각성은 날로 커져가고 있는 현실이다. IPCC(Intergoverment Panel on Climate Change)는 기후변화의 주범인 온실가스를 감축할 지라도 기후의 탄성 때문에 앞으로 수세기 이상 계속 진행될 것으로 전망하였으며, 기후변화 영향의 근원적 방지는 불가능하기 때문에 결국 수자원 관리 측면에서도 기후변화에 적응하기 위한 각종 적응전략 개발의 필요성을 강조하였다(IPCC, 2007). 최근 제방의 안정성에 대한 문제로 기후변화에 따른 홍수위 또는 담수 등의 조건으로 제외지의 고수위를 유지하게 되어 제체 내 침투가 일어날 수 있고, 수위급강하로 제방사면의 활동등이 일어날 수도 있으며 기초지반의 지지력이 부족하여 침하가 과다하게 발생하므로 제방의 소요높이를 유지할 수 없게 되어 월류로 인한 피해가 발생할 수 있다. 본 연구는 제방의 간극수압자료와 2차원 지하수침투 모형인 SEEP/W를 이용하여 안양천과 오산천의 침투거동을 분석하여 침투안정성을 평가하고자 하였다. 또한, 4대강 살리기 마스터 플랜(국토해양부, 2009)에 수록된 제방보강의 방법 중 누수에 대하여 제방고, 제방폭 및 제내지반고의 변화를 통한 지하수 침투거동을 모의, 분석하여 침투안정성을 평가하였다. 또한 기후변화에 따른 도시하천의 수문특성 변화분석 결과를 바탕으로 향후 발생할 수 있는 극치 수문사상의 값을 반영한 설계기준 강화 수방시설 계획 등의 연구에 활용하며, 여러 가지 수문학적 불확실성에 의하여 가변 가능한 도시하천 유역의 취약성 평가 및 위험도 분석을 통한 기후변화 대응과 수공구조물 설계 및 수방전략 수립에 활용하고자 한다.

• Journal of the Korean GEO-environmental Society
• /
• v.20 no.3
• /
• pp.39-46
• /
• 2019

The liquefaction is a phenomenon that the effective stress becomes zero due to the rapidly accumulated excess pore water pressure when a strong load acts on the ground for a short period of time, such as an earthquake or pile driving, resulting in the loss of the shear strength of the ground. Since the Geongju and Pohang earthquake, liquefaction brought increasing domestic attention. This liquefaction can be assessed mainly through the semi-empirical procedures proposed by Seed and Idriss (1982) and the liquefaction risk based on the penetration resistance obtained from borehole DB and SPT. However, the geotechnical information data obtained by the in-situ tests or boring information fundamentally have an issue of the representative of the target area. Therefore, this study sought to construct a ground information database by classifying and reviewing the ground information required for liquefaction assessment, and tried to solve the representative problem of the soil layer that is subject to liquefaction evaluation by performing spatial interpolation using GIS.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2015.05a
• /
• pp.252-252
• /
• 2015

우리나라에서는 대하천정비사업을 통해 주요 국가하천마다 보와 제방을 신설 및 보축하여 홍수의 방어 및 예방에 힘을 기울이고 있으며, 근래에는 이러한 정비사업이 완료되어 가고 있는 상황이다. 제방에 대한 정비사업의 내용은 보축 및 신설이 주를 이루나, 제내지의 성토와 제외지의 보강 및 저수로의 준설 등도 함께 수행되었다. 이러한 정비사업의 영향으로 지하수 및 하천의 흐름양상은 정비사업 전과는 다르게 변화 될 것으로 추정되며, 이는 제방 안정성에 영향을 줄 수 있는 중요한 문제로 판단된다. 따라서, 이와 같은 지하수 및 하천흐름의 변화양상이 제방의 안정성에 얼마나 영향을 미칠 수 있는지 정량적으로 분석할 필요가 있을 것으로 보인다. 특히, 대하천정비사업으로 지반누수를 방지하기 위한 제내지 성토나 퇴사제거를 위한 하천준설 등이 수행되면서 제방의 외적인 환경들이 많이 변하게 되었으나 이에 대한 정량적인 연구들이 거의 수행되지 않은 것으로 판단된다. 따라서, 본 연구에서는 낙동강과 회천 합류부에 위치한 율지제를 대상으로 이곳에 설치된 간극수압계의 데이터와 2차원 침투해석 프로그램인 SEEP/W를 이용하여 제내지와 제외지 표고변화에 따른 파이핑 안정성을 분석하였다. 그 결과 제내지 표고가 상승하면 파이핑 안전율이 증가하고 표고가 하강하면 안전율은 감소하는 것으로 나타났다. 한편, 제외지의 표고변화는 제방안정성에 거의 영향을 주지 않으며 오히려 하천수위의 영향을 지배적으로 받는 것으로 판단된다. 따라서, 제방안정성을 확보하기 위해서는 기초지반의 경우, 제내지측을 상승시키고 하천수위를 하강하는 것이 효과적일 것으로 판단된다.

• Journal of the Korean GEO-environmental Society
• /
• v.12 no.8
• /
• pp.5-12
• /
• 2011

This study was performed to analyze the degree of rainfalls, the duration time of rainfalls, the inclination of slopes and other damage causes depending on the ground condition, when the landslide occurs by the rainfall. Based on that, a big and a small model soil box were compared to examine the features of landslides, which is ultimately for forecasting landslides. An artificial rainfall device was installed in the model box, and the large model box has a real-size slope in it. Also, various measures were fulfilled such as collapse forms, a pore pressure, an earth pressure and moisture contents in order to analyze the effect of the model box size on the landslide mechanism and to test the usability of a small model box as a material for landslide experiments.

• Journal of the Korean Geotechnical Society
• /
• v.25 no.11
• /
• pp.75-86
• /
• 2009

This paper presents the results of a numerical investigation on load carrying capacity of geogrid-encased stone columns to use as load carrying column(s) supporting a foundation load. A validated 3D stress-pore pressure coupled model that can effectively show rapid drainage capability of stone columns and encasement effect of geogrid was adopted and a parametric study was carried out on a number of influencing factors. It is shown that the geogrid encased stone columns can be effectively used as foundation load supporting columns in soft ground. The results of numerical investigation were presented so that the relationship between the load carrying capacity of geogrid-encased stone columns and the influencing factors can be identified. Practical implications of the findings are also discussed.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.11 no.3
• /
• pp.243-254
• /
• 2009

Tunnel problems relate to pore water pressure generally occur due to the restriction of groundwater flow into the tunnel which is generally caused by the deterioration of drainage systems. Previous studies have identified the problem as combined mechanical and hydraulic interaction occasions. In this study, detrimental effects of pore water pressure on the lining were investigated using the finite element method considering deterioration of the drainage system. Particularly, double-lined linings with drain-holes are considered. Deterioration of drainage system is represented as blockages of drain-holes. It is identified that the secondary lining ran be influenced by the deterioration of drainage system. It is shown that a tunnel with all drain-holes blocked moved upward, and unbalanced drain-hole blocking may result in torsional behavior of the tunnel which causes significant damages to the secondary linings.

• The Journal of the Acoustical Society of Korea
• /
• v.25 no.1
• /
• pp.7-13
• /
• 2006

Fisheries policy change from catching to farming requires more intensive consideration for aquaculture industry. The oceanic farm is a desirable cost effective aquaculture method. However. in odor to gather fish in the oceanic farm, eating sound or any attracting sound should be radiated through underwater loudspeaker. In this Paper, it has been found in literature that the frequency range responding to fish is about 16Hz to 13kHz but sensitive frequency range is about 150Hz to 2kHz and sound pressure level is about 100dB to 150dB reference $1{\mu}Pa$. Therefore, frequency range and output sound level of designed underwater loudspeaker has been specified as 150Hz to 3kHz and 100dB to 145dB reference $1{\mu}bar$. respectively To verify the stability and the endurance to the pressure of 40m water depth, manufactured underwater loudspeaker was examined before sea trial in manufactured water pressure tank which gives a maximum of 10 atmospheric Pressure. We experimented on acoustic characteristic with manufactured underwater loudspeaker under water depth of 10m.