Hydraulic Fracturing In Situ Stress Estimations in a Potential Geothermal Site,Seokmo Island,South Korea   总被引：1，自引：0，他引：1  

Chandong Chang  Yeonguk Jo  Yangkyun Oh  Tae Jong Lee  Kwang-Yeom Kim 《Rock Mechanics and Rock Engineering》2014,47(5):1793-1808

We conducted hydraulic fracturing (HF) in situ stress measurements in Seokmo Island, South Korea, to understand the stress state necessary to characterize a potential geothermal reservoir. The minimum horizontal principal stress was determined from shut-in pressures. In order to calculate the maximum horizontal principal stress (S _Hmax) using the classical Hubbert–Willis equation, we carried out hollow cylinder tensile strength tests and Brazilian tests in recovered cores at depths of HF tests. Both tests show a strong pressure rate dependency in tensile strengths, from which we derived a general empirical equation that can be used to convert laboratory determined tensile strength to that suitable for in situ. The determined stress regime (reverse-faulting) and S _Hmax direction (ENE–WSW) at depths below ~300 m agrees with the first order tectonic stress. However the stress direction above ~300 m (NE–SW) appears to be interfered by topography effect due to a nearby ridge. The state of stress in Seokmo Island is in frictional equilibrium constrained by optimally oriented natural fractures and faults. However, a severe fluctuation in determined S _Hmax values suggests that natural fractures with different frictional coefficients seem to control stress condition quite locally, such that S _Hmax is relatively low at depths where natural fractures with low frictional coefficients are abundant, while S _Hmax is relatively high at depths where natural fractures with low frictional coefficients are scarce.  相似文献   

Influence of rain infiltration on the stability of compacted soil slopes   总被引：1，自引：0，他引：1  

Won Taek Oh  Sai K. Vanapalli 《Computers and Geotechnics》2010

Stability analyses for a homogeneous compacted embankment were undertaken considering infiltration of water into the embankment. The analyses include several different practical scenarios: (i) saturated condition, (ii) ponding (or runoff) along with saturated condition, (iii) short term analysis for unsaturated conditions, and (iv) long term analysis for unsaturated conditions. The appropriate shear strength parameters of the compacted soil required for analyzing different practical scenarios were determined using conventional and modified triaxial shear apparatus. The results of the study show that typically shallow circular failures above water front occur due to infiltration rather than the conventional infinite slope type failures.  相似文献   

Application of nonylphenol and coprostanol to identification of industrial and fecal pollution in Korea     

Li D  Shim WJ  Dong M  Oh SH 《Marine pollution bulletin》2007,54(1):101-107

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Modulation Cycles of Galactic Cosmic Ray Diurnal Anisotropy Variation     

S. Y. Oh  Y. Yi  J. W. Bieber 《Solar physics》2010,262(1):199-212

The diurnal variation of the galactic cosmic ray (GCR) count rates measured by a ground-based neutron monitor (NM) station represents an anisotropic flow of GCR at 1 AU. The variation of the local time of GCR maximum intensity (we call the phase) is thought in general to have a period of two sunspot cycles (22 years). However, other interpretations are also possible. In order to determine the cyclic behavior of GCR anisotropic variation more precisely, we have carried out a statistical study on the diurnal variation of the phase. We examined 54-year data of Huancayo (Haleakala), 40-year data from Rome, and 43-year data from Oulu NM stations using the ‘pile-up’ method and the F-test. We found that the phase variation has two components: of 22-year and 11-year cycles. All NM stations show mainly the 22-year phase variation controlled by the drift effect due to solar polar magnetic field reversal, regardless of their latitudinal location (cut-off rigidity). However, the lower the NM station latitude is (the higher the cut-off rigidity is), the higher is the contribution from the 11-year phase variation controlled by the diffusion effect due to the change in strength of the interplanetary magnetic fields associated with the sunspot cycle.  相似文献   

Landslide susceptibility maps comparing frequency ratio and artificial neural networks: a case study from the Nepal Himalaya   总被引：11，自引：5，他引：6  

Chandra Prakash Poudyal  Chandong Chang  Hyun-Joo Oh  Saro Lee 《Environmental Earth Sciences》2010,61(5):1049-1064

This study considers landslide susceptibility mapping by means of frequency ratio and artificial neural network approaches using geographic information system (GIS) techniques as a basic analysis tool. The selected study area was that of the Panchthar district, Nepal. GIS was used for the management and manipulation of spatial data. Landslide locations were identified from field survey and aerial photographic interpretation was used for location of lineaments. Ten factors in total are related to the occurrence of landslides. Based on the same set of factors, landslide susceptibility maps were produced from frequency ratio and neural network models, and were then compared and evaluated. The weights of each factor were determined using the back-propagation training method. Landslide susceptibility maps were produced from frequency ratio and neural network models, and they were then compared by means of their checking. The landslide location data were used for checking the results with the landslide susceptibility maps. The accuracy of the landslide susceptibility maps produced by the frequency ratio and neural networks is 82.21 and 78.25%, respectively.  相似文献   

Quantitative landslide susceptibility mapping at Pemalang area,Indonesia   总被引：3，自引：0，他引：3  

Hyun-Joo?Oh  Saro?LeeEmail author  Gatot?Moch?Soedradjat 《Environmental Earth Sciences》2010,60(6):1317-1328

For quantitative landslide susceptibility mapping, this study applied and verified a frequency ratio, logistic regression, and artificial neural network models to Pemalang area, Indonesia, using a Geographic Information System (GIS). Landslide locations were identified in the study area from interpretation of aerial photographs, satellite imagery, and field surveys; a spatial database was constructed from topographic and geological maps. The factors that influence landslide occurrence, such as slope gradient, slope aspect, curvature of topography, and distance from stream, were calculated from the topographic database. Lithology was extracted and calculated from geologic database. Using these factors, landslide susceptibility indexes were calculated by frequency ratio, logistic regression, and artificial neural network models. Then the landslide susceptibility maps were verified and compared with known landslide locations. The logistic regression model (accuracy 87.36%) had higher prediction accuracy than the frequency ratio (85.60%) and artificial neural network (81.70%) models. The models can be used to reduce hazards associated with landslides and to land-use planning.  相似文献   

Taxing the rich: recombinations and bubble growth during reionization     

Steven R. Furlanetto  S. Peng Oh 《Monthly notices of the Royal Astronomical Society》2005,363(3):1031-1048

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Probing the dark ages with metal absorption lines     

S. Peng Oh 《Monthly notices of the Royal Astronomical Society》2002,336(3):1021-1029

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The abundance of dark galaxies     

Licia Verde  S. Peng Oh  Raul Jimenez 《Monthly notices of the Royal Astronomical Society》2002,336(2):541-549

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Tidal variability in benthic silicic acid fluxes and microphytobenthos uptake in intertidal sediment     

Aude Leynaert  Sorcha Ní Longphuirt  Soonmo An  Jae-Hyun Lim  Pascal Claquin  Jacques Grall  Bong Oh Kwon  Chul Hwan Koh 《Estuarine, Coastal and Shelf Science》2011

Silicic acid (DSi) benthic fluxes play a major role in the benthic–pelagic coupling of coastal ecosystems. They can sustain microphytobenthos (MPB) development at the water–sediment interface and support pelagic diatoms when river DSi inputs decrease. DSi benthic fluxes have been studied at the seasonal scale but little is known about their dial variations. This study measured the amplitude of such variations in an intertidal area over an entire tidal cycle by following the alteration of DSi pore water concentrations at regular intervals over the flood/ebb period. Furthermore we independently estimated the potential DSi uptake by benthic diatoms and compared it to the variations of DSi pore water concentrations and fluxes. The microphytobenthos DSi demand was estimated from primary production measurements on cells extracted from the sediment. There were large changes in DSi pore water concentration and a prominent effect of tidal pumping: the DSi flushed out from the sediment at rising tide, occurs in a very short period of time, but plays a far more important role in fueling the ecosystem (800 μmol-Si m⁻² d⁻¹), than diffusive fluxes occurring throughout the rest of the tidal cycle (2 μmol-Si m⁻² d⁻¹). This process is not, to our knowledge, currently considered when describing the DSi cycling of intertidal sediments. Moreover, there was a large potential MPB requirement for DSi (812 μmol-Si m⁻² d⁻¹), similar to the advective flow periodically pumped by the incoming tide, and largely exceeded benthic diffusive fluxes. However, this DSi uptake by benthic diatoms is almost undetectable given the variation of DSi concentration profiles within the sediment.  相似文献