• The Journal of Engineering Geology
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• v.30 no.2
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• pp.185-198
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• 2020

High-density rapid expansion material is a method that increases the solid volume of injection materials due to hydration and foam reactions at the same time as spraying. It is an effective method for securing ground stability, restoring subsidence, and loading during construction of structures. In this regard, through the mechanical experiments of injection materials, the stability of the foundation ground of the structure and the effect of increasing the endurance using site construction were analyzed. The results of the experiment showed that the unit weight of soil decreased by 10.5% after injection of the filling material, and the allowable support for the structure was deemed safe, and the subsidence by each section after ground improvement was determined to be safe at 2.28, 1.55 and 0.46 cm, respectively, with an acceptable subsidence of less than 5 cm. After the field test, five inclinometers were installed on the top floor of the target building to measure the displacement of the X and Y axes. As a result of the measurement, no displacement related to the phenomenon of inequality or subsidence cracks of the structure was measured for about 16 months (509 days) after construction. This can be judged to be a sufficient increase in the stability of the ground after the injection of rapid expansion.

• Journal of Korean Society of Forest Science
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• v.85 no.4
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• pp.571-576
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• 1996

The geological and hydrological survey was carried out in Hyuseok-dong landslide area(10 ha), Youngchoon-myeon, Danyang-gun, Choongcheongbuk-do. The results showed that the bed rocks in this area consisted of shale, sandstone and limestone, and the piles of stones debris were also scattered around the hill above the study area. Soil texture was sandy loam, and bulk density of the soil in the lower part of the area was higher than that of the upper part, but void ratio of the soil in the lower part was lower than that of the upper part. Subsurface water was springing out to the surface in many places in this area. In this area, the storms over 70mm/day were frequent during the summer period from June through September. It was concluded that the occurrence of landslide had a close relationship with the geological characteristics, hydrological conditions and the rainfall distribution.

• Asian Journal of Turfgrass Science
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• v.17 no.1
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• pp.19-33
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• 2003

The objective of this study was to evaluate the effects of crumb rubber recycled from used tires as a soil incorporation and topdressing materials on a trafficked Korean lawngrass‘Zenith’(Zoysia japonica). In Exp 1, incorporation treatments included three particle sizes (PS: coarse =4∼6.35 mm, medium =2∼4 mm, and One : less than 2 mm in diameter) and two incorporation rate (IR: 10 and 20%). Wear treatments were applied 30 passes per day by compactor weights being 60 kg with soccer shoes. Topdressing treatments included three PS and two topdressing depth (TD: 5 and 10 mm). Wear treatments were the same as described in Exp 1. In Exp 1, the treatment with medium PS+IR 20 resulted in the tendency to have high total clipping yield. There was no significant difference in clipping yield, turfgrass visual color, coverage, and root length among the treatments. Compared to control, tissue Zn levels increased about 6.5-fold by the treatments. The treatment with fine PS +IR 20 caused a less peak deceleration than coarse PS +IR 10. Total porosity, air-filled porosity, and capillary porosity increased with fine PS +IR 20. In Exp 2, compared to controls, however, there was a difference in turfgrass visual color after the termination of traffic treatment. There was no difference in root length. The treatment with fine PS + TD 10 resulted in the highest total clipping yield. As a result of soil physical analysis, soil penetration resistance was reduced by the treatments. The treatment with coarse PS resulted in a less peak deceleration than fine PS. In conclusion, turfgrass growth was increased by crumb rubber incorporation which enhanced soil physical properties. The crumb rubber topdressing was able to cushion the crown tissue area while still providing a smooth and uniform surface, improve overall turfgrass quality, and reduce compaction.

• Journal of the Geological Society of Korea
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• v.54 no.5
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• pp.557-566
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• 2018

Pohang earthquake (Main shock magnitude = 5.4) occurred in Southeastern region of South Korea in November 15, 2017. Groundwater levels of 6 monitoring wells with 5 minutes interval measurements located in that region and stream water levels of 4 stations located along the Hyeongsan-gang stream are used for the analysis of earthquake induced effects. Four groundwater monitoring wells show a short-term decrease of groundwater level after a main shock and one well does an increase and the maximum change is about 42.0 cm. Especially, groundwater levels at two monitoring wells near the epicenter are consistently maintained after a decrease. There is little relationship between earthquake magnitude or a distance to epicenter and changing amount of groundwater level and it may be due to the inhomogeneity of geologic material and unconsolidated sediments distribution. The changes in permeability of fractured zone and groundwater levels occasionally cause changes in stream flow rate, and water level of the Hyeongsan-gang stream in the study area decreases just after the earthquake and increases again up to the normal level and next shows an more gentle decreasing slope. Total increasing flow rates at S1 (upstream site) and S4 (downstream site) stations are about $12,096m^3$ and $116,640m^3$, respectively, during the increasing period.

• Geophysics and Geophysical Exploration
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• v.11 no.3
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• pp.242-249
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• 2008

Recently, AVO analysis has been widely used in oil exploration with seismic subsurface section as a direct indicator of the existence of the gas. In the case of the deep reservoirs like the gas reservoirs in the East-sea, it is often difficult to observe AVO responses in CMP gathers even though the bright spots are shown in the stacked section. Because the reservoir becomes more consolidated as its depth deepens, P-wave velocity does not decrease significantly when the pore fluid is replaced by the gas. Thus the difference in Poisson's ratio, which is a key factor for AVO response, between the reservoir and the layer above it does not increase significantly. In this study, we analyzed the effects of Poisson's ratio difference on AVO response with a variety of Poisson's ratios for the upper and lower layers. The results show that, as the difference in Poisson's ratio between the upper and lower layers decreases, the change in the reflection amplitude with incidence angle decreases and AVO responses become insignificant. To consider the limitation of AVO responses shown in the gas reservoir in East-sea, the velocity model was made by simulation Gorae V structure with seismic data and well logs. The results of comparing AVO responses observed from the synthetic data with theoretical AVO responses calculated by using material properties show that the amount of the change in reflection amplitude with increasing incident angle is very small when the difference in Poisson's ratio between the upper and lower layers is small. In addition, the characteristics of AVO responses were concealed by noise or amplitude distortion arisen during preprocessing. To overcome such limitations of AVO analysis of the data from deep reservoirs, we need to acquire precisely reflection amplltudes In data acquisition stage and use processing tools which preserve reflection amplitude in data processing stage.

• Journal of the Korean Geotechnical Society
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• v.28 no.7
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• pp.41-53
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• 2012

During rainfall period, to identify the characteristics of the infiltration of moisture, electrical resistivity monitering survey was carried out to weathered zone. Four regions of geophysical exploration areas with different rock types, four regions were selected. An area consists of mafic granite and three areas are composed of sedimentary rocks (Sandstone, Shale, Unconsolidated Mudstone). Survey was conducted from June (rainy season) to November (dry season), and during the period the change in resistivity was observed. According to the result of monitoring exploration on Geumjeong and Jinju areas, for the estimation of the standard rainfall, it is necessary to estimate the effects of the antecedent rainfall during the rainy season based on the overall rainfall from June till October and also necessary to consider this for the estimation of the half period. Also, the vertical distribution of the low resistivity anomaly zone does not show that the infiltration of moisture does not occur uniformly from the surface of the ground to the lower ground but shows that it occurs along the relaxed gap of the crack or soil stratum of the weathering zone. In Pohang area, the type of moisture infiltration is different from that of the granite or sedimentary rock. Since, after the rainfall, the rate of infiltration to the lower ground is high and the period of cultivation to the lower bedrock aquifer is short, it has similar effect to that of the antecedent rainfall applied for the estimation of the standard rainfall being presently used. In Danyang, due to the degree of water content of the ground, the duration period of the low resistivity anomaly zone observed in the lower ground of the place where clastic sedimentary rock is distributed is similar to that in Pohang area. The degree of lateral water diffusion at the time of localized heavy rain is the same as that of the sedimentary rock in Jinju. According to the above analysis results, in Danyang area, the period when the antecedent rainfall has its influence is estimated as three weeks or so.

• The Journal of the Petrological Society of Korea
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• v.25 no.4
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• pp.373-388
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• 2016

To understand human activity in the past, the information about past environmental change including geomorphological and climatic conditions is essential and this can be traced by using age dating and geochemical analysis of sediments from the prehistoric sites. The sedimentary sequence of Seokgwan-dong Paleolithic Site located in Seoul was 5m long unconsolidated sediments and consists of lower part bedrock weathering sediments, slope deposits and upper-part fluvial deposits. In this study, upper part sediments were used to reconstruct past environmental change through age dating and various physical and chemical analyses including grain size, magnetic susceptibility and mineral and elements. The fluvial sediments can be divided into 4 units including three organic layers. Grain size analysis results showed that the sediments were very poorly sorted with fining upward features. Magnetic susceptibility was relatively high in the organic layers, indicating environmental changes causing mineral composition change at that times. The mineral and major element composition are similar to Jurassic biotite granite which mainly consists of quartz, K-feldspar, biotite and muscovite. The radiocarbon age of $14,240{\pm}80yr$ BP was obtained from the lower most organic layer of Unit III(O), suggesting that the fluvial sediments formed at least from the early stage of deglacial period after the end of Last Glacial Maximum. Subsequent wet and warm climates and resultant fluvial process including slope sedimentation during the Holocene may have been responsible for the sedimentary sequence in Seokgwan-dong paleolithic site and surrounding area. The observed organic layers suggests frequent wetland occurrence combined with natural levee changes in this area.

• Journal of the Korea Institute of Building Construction
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• v.9 no.5
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• pp.127-133
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• 2009

It is important to increase the strength of binders in order to enhance the strength of concrete. However, when the mineral admixture used for high strength concrete is incorporated individually, its dispersibility decreases due to the phenomenon of compaction, which reduces its fluidity and results in insufficient strength being created. To solve this problem, we can pre-mix each binder in advance to disperse a mineral admixture among binders, which will strengthen the fluidity and strength of concrete. Therefore, this study analyzed the properties of high strength concrete depending on the mix method used, to determine the effect of pre-mix cements ranging from W/B 15 to 35%. It was found that the fluidity of pre-mix increased to a level higher than that of individual mix due to its dispersion and ball bearing effect. The air content was slightly decreased from the result of individual mix due to the micro filler effect, which causes fine particles of silica-fume to fill the voids among cement particles, while the setting time of pre-mix was shorter than that of individual mix, because enhanced dispersion of pre-mix affects hydration heat time. The compressive strength of pre-mix increased due to the phenomenon of compaction of gap structure, and the variation of coefficient decreased by 1.69% on average in strength variation.

• Journal of the Korean GEO-environmental Society
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• v.17 no.10
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• pp.73-81
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• 2016

In the construction on low strength and high compressible soft ground, the many problems have been occurred in recent construction project. therefore, the soil improvement have been developed to obtain high strength in relatively short period of curing time. Based on the laboratory tests using undisturbed marine clay, the effect of improvement on soft ground was estimated. Deep mixing method by cement have been virtually used for decades to improve the mechanical properties of soft ground. However, previous researches set the focus on the short term strength the about 10% of cement treated clay. In this paper, cement and Natural Soil Stabilizer (NSS) were used as the stabilizing agent to obtain trafficability and mechanical strength of the soft clay. Based on the several laboratory tests, optimum condition was proposed to ensure the mechanical strength and compressibility as the foundation soil using cement and NSS mixed soil. Finally, research data was proposed about the applicability of NSS as the stabilizing agent to soft clay to increase the mechanical strength of soil.

• Economic and Environmental Geology
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• v.42 no.6
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• pp.635-643
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• 2009

In this paper, a Quaternary fault is described, which is developed in the mid-eastern part of Ulsan Fault Zone, near the southern Gaegok-ri, Oedong-eub, Gyeongju, Korea. The Gaegok 6 fault is developed along the contact between Early Tertiary granite and Quaternary gravel deposit overlying unconformably the granite. The fault strikes $N02^{\circ}{\sim}22^{\circ}E$ and dips $45^{\circ}{\sim}80^{\circ}$ to the west. This fault has a 30~50 cm wide cataclastic shear zone with gouge zone, mixed with Quaternary sediments and fault breccia of granite. In the main Quaternary fault plane, the orientation of striation is $17^{\circ}$, $356^{\circ}$, indicating a dextral strike-slip faulting with some normal component. There is another striation ($78^{\circ}$, $278^{\circ}$ and $43^{\circ}$, $270^{\circ}$) with reverse-slip sense, developed on the subsidiary plane which cuts the main Quaternary fault plane. In brief, the fault has been developed between the granite in the western part and the Quaternary gravel deposit in the eastern part. The western block of fault is uplifted. The striations and movement senses of faults indicate multiple compressional stages in this region. The fault has a similar orientation, westward dipping geometric pattern, and reverse sensed kinematic pattern with Gaegok 1 fault developed in the north. Thus, the Gaegok 6 fault is probably a southern extension of Gaegok 1 fault.