• Proceedings of the KSRS Conference
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• v.2
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• pp.728-731
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• 2006

Ground subsidence near abandoned underground coal mines has become a serious social problem in Korea. The purpose of this study is to perform a comparative analysis between the ground subsidence area and the electrical resistivity measured by field survey at Samcheok City. A raster database composed of ground subsidence areas and electrical resistivity data was constructed for GIS. To analyze correlation between the two constructed raster datasets, we used a frequency ratio model. The results show that low and high electrical resistivity anomaly zones coincide with the existing subsidence areas. We infer that the high anomaly zone means saturated and low anomaly zone means vacant. It suggests that electrical resistivity might be a useful factor for analyzing ground subsidence hazard zone.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.3
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• pp.383-392
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• 2015

In subsea tunnelling, prediction of the fractured zone (or water bearing zone) ahead of tunnel face saturated by seawater with high water pressure has been a key factor for safe construction. This study verified the feasibility of utilizing induced polarization (IP) survey at tunnel face for predicting the ground condition ahead of the subsea tunnel face. A pore model was proposed to compute chargeability in granular material, and the relationship correlating chargeability with the variables affecting the chargeability was derived from the model. Parametric study has been performed on the variables to figure out the most influential factors affecting the chargeability. The results of the parametric study show that the size of narrow pores ($r_1$) and the salinity of pore water are the most influential factors on chargeability. Laboratory tests were conducted on various types of ground condition by changing the salinity of pore water, the thickness of the fracture zone and the existence of gouge (weathered granite) within the joints of the fractured zone to figure out the effect of the ground characteristics on the IP phenomenon. Test results show that the chargeability of the fractured zone saturated by seawater increases if the joints in the fractured zone are filled with gouge since the infilled gouge will decrease the size of narrow pores ($r_1$).

• The Journal of Engineering Geology
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• v.19 no.4
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• pp.501-508
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• 2009

This study aims to clarify the characteristics of the physical and mechanical properties of soil-slope failure of Okcheon metamorphic zone. Soil samples were collected from 35 collapsed and uncollapsed artificial slopes along national roads. A series of laboratory experiments was carried out to examine physical and mechanical properties of soils and rocks. The results show that failure slopes have weakness of failure at 0.75 of AMI or higher, 32% of liquid limit or higher, and 31% of saturated moisture content or higher. The plastic index of failure slopes is correlated to wet density and saturated density. It turned out that failure could easily happen according to a high plastic index even if the void ratio was low. The greater the contents of bigger-sized soil, i.e. contents of sands and gravels rather than of clays, is the greater the chance to fail at the slope.

• Geomechanics and Engineering
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• v.28 no.1
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• pp.77-87
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• 2022

Many geotechnical analyses require the investigation of water flow within partially saturated soil zone to incorporate the effect of climatic conditions. It is widely understood that the hydraulic properties of the partially saturated soil should be included in the transient seepage analyses. However, the characteristics of dual porosity soils with dual-mode water retention curve are normally modelled using single-mode mathematical equation for simplification of the analysis. In reality, the rainwater flow can be affected significantly by the dual-mode hydraulic properties of the soil. This paper presents the variations of safety factor for dual porosity soil slope with dual-mode water retention curve and dual-mode unsaturated permeability. This paper includes the development of the new dual-mode unsaturated permeability to represent the characteristics of soil with the dual-mode water retention curve. The finite element analyses were conducted to examine the role of dual-mode water retention curve and dual-mode unsaturated permeability on the variations of safety factor under rainfall loading. The results indicate that the safety factor variations of dual porosity soil slope modelled using the dual-mode water retention curve and the unsaturated permeability equation are lower than those of dual porosity slope modelled using single-mode water retention curve and unsaturated permeability equations.

• Proceedings of the Korea Water Resources Association Conference
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• 1988.07a
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• pp.85-92
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• 1988

A model for the transient one-dimensional moisture movement in the saturated-unsaturated zone using a finite difference method is developed. Hysteresis in the soil water retention is incorporated. The model considers layered geologic formations. Monte Carlo simulation, together with the nearest neighbor model is used. Outputs of the model include pressure head, water content, and the water table elevation. Two Monte Carlo simulations of 100 realizations each are made for a 12-day simulation period with different input values. The simulation results show that the S.D. of the outputs increases with an increase in the input, the S.D. of the log K$$. The model is applied to predict a long term water table fluctuation, and the predicted water table agress well with the observed one.

• Magazine of the Korean Society of Agricultural Engineers
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• v.44 no.4
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• pp.51-61
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• 2002

The objective of this study is to develop GLEANS-PADDY model to predict nutrients loading from paddy-field areas. This model is developed by modifying the GLEANS model which is used for uplands, and composed of hydrology and nutrient submodels. The optimal field size for CLEANS-PADDY model application is about up to 50 ha with mild slope, relatively homogeneous Soils and spatially rainfall, and a single crop farming. The CLEAMS model is modified to handle ponded soil surface condition and saturated soil profile in paddy field. In the hydrology submodel of the CLEAMS-PADDY model. the ponded depth routing method is used to handle the ponded water condition of paddy field. To compute potential evapotranspiration the FAO-24 Corrected Blaney-Criddle method is used for paddy field instead of Penman-Monteith method in the CLEAMS model. In the nutrients submodel of the CLEAMS-PADDY model, the soil was assumed saturated and soil profile in the root zone was divided into oxidized and reduced zones.

• The Journal of Engineering Geology
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• v.26 no.1
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• pp.87-99
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• 2016

We present the results of two-dimensional numerical simulations predicting the flow of groundwater in a fractured unsaturated zone. We applied the k-field distribution of permeability derived from discrete fracture network (DFN) modeling as the hydraulic properties of a model domain. To model an unsaturated zone, we set the depth from the ground surface to the underground aquifer. The rate of water infiltration into the unsaturated zone was divided into two parts, an artificial structure surface and unsaturated soil zone. The movement of groundwater through the unsaturated zone was simulated with particular emphasis on contaminant transport. It was clearly observed that the contaminants dissolved in groundwater transported vertically from the ground surface to the saturated zone.

• Journal of Soil and Groundwater Environment
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• v.11 no.6
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• pp.18-27
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• 2006

Air Sparging (IAS, AS) is a ground-water remediation technique, in which organic contaminants are volatilized into air as they rise from saturated to vadose soil zone. This study was conducted to investigate the variation characteristics of TPH, VOCs and $CO_2$ for air sparging of diesel contaminated saturated soil. Initial TPH concentration was 10,000 mg/kg for saturated soil phase and 1,001 mg/L for soil aquifer phase. After 36 days of air sparging, the equilibrium temperature of 2-Dimension experiment system was $24.9{\pm}1.5^{\circ}C$. The saturated soil TPH concentration (in the C10 port close to air diffuser) was reduced to 66.0% of the initial value. The mass amount of $CO_2$ was 3,800 mg and 3,200 mg in air space (C70 port) and in unsaturated soil zone (C50 port), respectively. The VOCs production kinetic parameter was 0.164/day in the air space (C70 port) and 0.182/day in the unsaturated soils (C50 port).

• Structural Engineering and Mechanics
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• v.6 no.3
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• pp.245-257
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• 1998

This paper present an analysis which may be used to obtain a rational design of a system of inclined piles used in preventing downhill creep of unsaturated clay formations. It uses two simple and relatively easy to measure parameters (an estimate of the maximum downhill creep together with a knowledge of the depth of the so called active zone) to calculate the required section size and the optimal spacing (pitch) of the piles for a desired efficiency of the system as a whole. Design charts are provided to facilitate the process.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.4
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• pp.137-139
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• 2008

Floating zone, neutron transmutation-doped and magnetic Czochralski silicon crystals are being widely used for fabrication power devices. To improve the quality of these devices and to decrease their production cost, it is necessary to use large-diameter wafers with high and uniform resistivity. Recent developments in the crystal growth technology of Czochralski silicon have enable to produce Czochralski silicon wafers with sufficient resistivity and with well-controlled, suitable concentration of oxygen. In addition, using Czoehralski silicon for substrate materials may offer economical benefits, First, Czoehralski silicon wafers might be cheaper than standard floating zone silicon wafers, Second, Czoehralski wafers are available up to diameter of 300 mm. Thus, very large area devices could be manufactured, which would entail significant saving in the costs, In this work, the conventional Czochralski silicon crystals were grown with higher oxygen concentrations using high pure polysilicon crystals. The silicon wafers were annealed by several steps in order to obtain saturated oxygen precipitation. In those wafers high resistivity over $5,000{\Omega}$ cm is kept even after thermal donor formation annealing.