• The Journal of Engineering Geology
• /
• v.29 no.1
• /
• pp.1-12
• /
• 2019

Earthquake can change underground stress condition around the hypocenter and affect the fracture systems of the rocks. In Korea, the M5.8 Gyeongju earthquake on September 12, 2016 and M5.4 Pohang earthquake on November 15, 2017 occurred inside the Yangsan fault zone and possibly affected the fracture systems in the Yangsan fault zone and nearby rock masses. In this study, the characteristics of the fracture system (fracture orientation, number of the fractures, fracture spacing and aperture, dip angle, fracture density along depth, and relative rock strength) of the rocks in the low/intermediate level radioactive waste repository site located in the coastal area of the East Sea are analyzed by the impact of the Gyeongju and Pohang earthquakes using acoustic televiewer data taken from the boreholes at the radioactive waste repository site in 2005 and 2018. As a result of acoustic televiewer logging analysis, the fracture numbers, fracture aperture, and fracture density along depth overall increased in 2018 comparing to those in 2005. This increase tendency may be due to changes in the fracture system due to the impact of the earthquakes, or due to weathering of the wall of the boreholes for a long period longer than 10 years after the installation of the boreholes in 2005. In the borehole KB-14, on the whole, the orientation of the fractures and the average fracture spacing are slightly different between 2005 and 2018, while dip angle and relative rock strength in 2005 and 2018 are similar each other.

• Economic and Environmental Geology
• /
• v.56 no.3
• /
• pp.277-291
• /
• 2023

To analyze the crustal velocity structures beneath 21 broadband seismic stations in Gangwon Province, South Korea, we first applied the H-κ stacking method to 139 teleseismic event data (Mw ≥ 5.8 and the epicentral distance of 30° - 90°) occurring between March 18, 2019 and December 31, 2022 to estimate the Moho depths and V_p/V_s ratios beneath each station. The Moho depths and V_p/V_s ratios from the H-κ stacking method range from 24.9 to 33.2 km depth and 1.695 - 1.760, respectively, and the estimated V_p/V_s ratios were applied to the joint inversion of receiver functions and surface wave dispersion to obtain 1-D crustal velocity models beneath each station. The resulting Moho depths range from 25.9 to 33.7 km depth, similar to the results from the H-κ stacking method. Moho depth results from the both methods are generally consistent with Airy's isostasy. The 1-D crustal velocity models confirm that the existence of 2 km thick low-velocity layers with P-wave velocities of 5 km/s or less at some stations in the Taebaeksan basin, and at the stations CHNB and GAPB in northern Gangwon Province, which are located above the Cenozoic sedimentary layer. The station SH2B, although not overlying a sedimentary layer, has a low P-wave velocity near the surface, which is probably due to various factors such as weathering of the bedrock. We also observe a velocity inversion with decreasing velocity with depth at all stations within 4 - 12 km depths, and mid-crustal discontinuities possibly due to density differences in the rocks at around 10 km depth below some stations.

• Journal of the Korean Geotechnical Society
• /
• v.29 no.9
• /
• pp.5-15
• /
• 2013

In this paper, the unsaturated slope stability analysis considering suction stress (Lu and Godt, 2008) was introduced and the results applied for a certain sand slope were analyzed. The unsaturated slope stability analysis considering suction stress can analyze both conditions of steady infiltration and no infiltration, and it can estimate the safety factor of slope as a function of soil depth. Also, the influence of weathering phenomenon at a certain depth from the ground surface can be considered. The stability analysis considering suction stress was applied to the unsaturated infinite slope composed of sand with the relative density of 60%. The suction stress under no infiltration condition was affected by ground water table until a certain influencing depth. However, the suction stress under steady infiltration condition was affected by seepage throughout the soils. Especially, the maximum suction stress was displayed around ground surface. The factor of safety in the infinite slope under no infiltration condition rapidly increased and decreased within the influence zone of ground water table. As a result of slope stability analysis, the factor of safety is less than 1 at the depth of 2.4 m below the ground surface. It means that the probability of slope failure is too high within the range of depths. The factor of safety under steady infiltration condition is greater than that under no infiltration condition due to the change of suction stress induced by seepage. As the steady infiltration rate of precipitation was getting closer to the saturated hydraulic conductivity, the factor of safety decreased. In case of the steady infiltration rate of precipitation with $-1.8{\times}10^{-3}cm/s$, the factor of safety is less than 1 at the depths between 0.2 m and 3 m below the ground surface. It means that the probability of slope failure is too high within the range of depths, and type of slope failure is likely to be shallow landslides.

• Journal of Korean Society of Forest Science
• /
• v.90 no.5
• /
• pp.608-618
• /
• 2001

To understand the weathering processes of the soil by submicroscopic method is very important to realize the properties of the soils. In this study soil formation processes show every steps to the changes in chemical and mechanical properties and the submicroscopic characteristics of soil weathering on the profiles of forest soils derived from granite in southern part of Korea. Fecal pellets(SEM) are given a full detail of the positive activities of the forest soil animals; mainly invertebrates in the O horizon and the E horizon. External shapes of fecal pellets have been divided into five groups : spherical, ellipsoidal, cylindrical, platy and threadlike. But doughnutlike form of fecal pellets is observed in this study. The soluble and suspended materials in the soils move downwards by percolation from the A horizon to the B or the BC horizons, and result in the illuviation cutans(SEM) on the ped surface of the lower horizon and deposited stack of kaolinite. Illuviated cutans are deposited on the ped surface even in the depth of 312cm in the BC horizon as well as the Bt horizon and comprise of fine silt, coarse clay and fine clay. A lot of halloysites are observed on the cutan surface. Halloysite formation from feldspars has been well known but a lot of hallyosite formation are observed in this study. The formation were predicted by Jackson(1962), inferred by Wada and Kakuto(1983a, b) and proved evidently by Cho and Mermut(1992a, b). This also suggests that halloysites in the soils derived from granite are formed a lot from ferruginous chlorites. The release of Fe from the chlorite structure are significant pedogenic processes and newly formed Fe oxides imparted a red color to the soils. The iron oxides particles, which are ejected and recrystalized, aggregate thickly on the edge of the ferruginous chlorites, and this indicates the release of structural Fe from weathered chlorites. Hematites and goethites are frequent in the fine clay in this soils.

• Journal of the Korean GEO-environmental Society
• /
• v.15 no.1
• /
• pp.53-62
• /
• 2014

In Korea, in general, separation distance between existing parallel tunnels was set at two to five times as distant as the diameter of the tunnels according to ground conditions. Recently, however, actual applicability of closely spaced parallel tunnels whose distance between tunnel centers was shorter than the diameter has increased due to environmental damages resulting from massive cutting, restriction in purchase of required land, and maintenance of linear continuity. In particular, when the pillar width of tunnel decreases, the safety of pillars affects behaviors of the tunnel and therefore the need for diverse relevant studies has emerged. However, research so far has been largely confined to analysis of behavior characteristics of pillars, or parameters affecting design, and actually applicable and quantitative data have not been presented. Accordingly, in order to present a stability evaluation method which may maximally reflect construction conditions of spots, this study reflected topographical and stratigraphic characteristics of the portal part with the highest closeness between the tunnels, simulated multi-layer conditions with rock mass and complete weathering, and assessed the degree of effect the stability of pillars had on the entire tunnels through numerical analysis according to changes in pillar width by ground strength. This study also presented composite analysis result on ground surface settlement rates, interference volume rates, and average strength to stress and a formula, which may be applicable to actual work, to evaluate safety rates of closely spaced parallel tunnel pillars and minimum pillar width by ground strength based on failure criteria by Hoek-Brown (1980).

• Journal of Life Science
• /
• v.15 no.5 s.72
• /
• pp.826-833
• /
• 2005

This study was conducted to inform basic data for management of abandoned mine that was based on soil heavy metal concentration of the non-rearing and the rearing sites in Guundong Mine which had been completed of improve contamination soils, and examined into standard plant which had tolerances about pollution that analyzed into its accumulated heavy metals contents in the wild plant of naked soil. Consider form the result of contents by depth of soils heavy metals in the non-rearing sites, S1 point judged by contaminated to heavy metals of tailing leach after weathering caused by rainfall and permeate in S1 point soils when restored rest of tailing in 1996 restoration project. Lead of S2 point was not contaminated seriously by restoration and S3 point considered that heavy metals which leach by rainfall in the contaminated soils in mine vicinity accumulated in the abandoned paddy through river When heavy metals of rearing sites soils were examined from the view point of upside of mine point (SP1, SP2, and SP3) of same above the sea level, zinc (537.5 mg/kg) content of SP1 point was highest, and copper (535 mg/kg) and lead (141.5 mg/kg) in the SP3 point were high. To considered as orderly plenty of heavy metals in the plant were respectively in order, Perilla frutescens var. cauta KUDO (SP1 and SP4) >Artemisia princeps PAMPAN (SP2) > Miscanthus sinensis ANDERSSON(SP5) > Vicia angustifolia var. segetilis (THUILL.) K. KOCH. (SP2). Especially, there were plenty of heavy metals in P. frutescens var. acuta, so it judged as a standard plant which have tolerances about heavy metals pollution sites. Therefore, we need more study about the heavy metals accumulate ability of P frutescens var. acuta in future.

• The Journal of Engineering Geology
• /
• v.8 no.2
• /
• pp.115-130
• /
• 1998

An analysis on landslide types and susceptibilities associated with geomorphic characteristics has been conducted with 916 landslide inventories in Yeonchon-Chulwon District, where two day's heavy rainfall was concentrated on July, 1996. The precipitation during the 2 days, which is equivalent to 0.372 of event cofficient, can cause large landslides based on Olivier's equation. Sliding materials are dominantly composed of debris mixed with rock fragments and soil derived from colluvium and residual soils. 66% of the landslides are belong to debris flow md 23% are due to sediments flow, in accordance with the classification of sliding materials. Most of landslides(> 90%) are small and shallow, less than l00m in length and about 1m in depth, and classified as transitional type. Granite is more susceptible as much as 4.7 times than metamorphic rocks and 2.7 times than volcanic rocks, probably due to higher weathering grade of granite. The highest landslide frequency is concentrated on the areas between 200 and 300m in height and on the slopes between $10-20^{\circ}$ in dgree. More than 50% of landslides occurred under these geomorphic conditions. Consequently, colluviums and residual soils distributed on the gentle slopes are most susceptible to the landslides of the area.

• The Journal of Engineering Geology
• /
• v.23 no.3
• /
• pp.293-304
• /
• 2013

Because the present groundwater law broadly regulates a simple and impractical guideline ignoring aquifer characters and geology, general purpose facilities for protection of groundwater contamination is still considered unsatisfactory to ensure groundwater resources. In recent, there have been growing attempts in the packer development as crucial techniques and devices for groundwater protection. This study investigated the application of packer grouting techniques to contaminated groundwaters of two well sites in the Andong and Yeongi areas, both of which revealed a satisfactory effect with improved water quality: 94% decrease in turbidity at the Andong area and 60% decrease in $NO_3$-N, respectively. Based on aquifer characters including geology, weathering depth, fracture pattern, hydraulic gradient, and the flow path of contaminants, the integrated properties of groundwater contamination should be evaluated and treated with the help of accurate analyses such as bore hole imaging and monitoring data. Packer grouting and casing on well to ensure the useful aquifer free of contaminant are expected to play important role in inhibiting the inflow of contaminants when adequately applied. Therefore it is concluded that these can serve as reliable tools in remediation and protection of contaminated groundwater as well as efficient utilization of groundwater.

• Journal of the Korean association of regional geographers
• /
• v.2 no.1
• /
• pp.39-49
• /
• 1996

There is a limestone basin surrounded by the mountains consisted of Paleozoic sedimentary and metamorphic rocks in the Masung, Munkyung city, Kyungsangpook do. The purpose of this paper is to elucidate the geomorphic processes of the gentle hillslopes in the marginal piedmont of Masung basin. To do so, I analyzed deposits over hillslopes and the relation ship between the distance from the divide and the height(above sea level) at the longitudinal profile of the hillslope, and considered interrelation between the distributions of the gentle hillslopes(less than 230m) and lithology. Geomorphic processes of Masung basin are as follow: (1) The depth of deposits over hillslope increases toward downstream of the hillslope. Most gravels within deposits, whose lithology is limestone, are those eroded at the boundary(overthrust fault zone) between the back-mountain and the hillslope. Deposits at the outward margin of hillslope is well sorted. and moderately imbricated. (2) Hillslope at the margin of the basin(160-230m asl) is formed by the action of 'the flow with channel'. At the boundary between the soft rock(limestone; basin floor) and hard rock(sedimentary and metamorphic rock; back-mountain), the relatively weak limestone is eroded to fresh bedrock by the subsequent action of the overland flow, and therefore discontinuity in slope appeared. (3) After hills lopes were formed, sediments(boulders and fine material) produced during dissection in back-mountain buried deposits over hillslope. In conclusion, geomorphic processes of Masung basin is 'differential erosion due to differentiation of lithological hardness' having suggested as geomorphic processes of granitic basin. However it is not 'removal of weathering material due to sheetflow' but 'erosion due to the overland flow with channel'.

• Journal of the Korean Geophysical Society
• /
• v.6 no.1
• /
• pp.39-46
• /
• 2003

Twin stone pagodas of the ruins of Kamunsa temple at Kyongju city, Kyungsangbukdo were believed to be built in 682 during the Unified Shilla Kingdom. The 13.4-m-high granodiolite pagodas with the base of 6.78 m x 4.4 m are the largest three-story stone pagoda in Korea. The western pagoda which was re-organized in 1959 is observed to be on the process of severe weathering. Also, some stone contacts are represented by the shape of sharp chevron, which is probably caused by the uneven loading due to the structural unbalance. For the structure-safety diagnosis of the western pagoda, it is necessary to understand its site characteristics and surrounding subsurface environment. Combined geophysical survey such as seismic and resistivity methods was carried out around the western pagoda. The range of 55∼350 Ωm is shown around the pagoda from the electrical resistivity mapping by the Wenner method. The higher resistivities occur the southwestern area, while the lower (<100 Ωm) values indicating the weaker subsurface appear to be on the northeastern area. This result coincides with the measurement of a leaning angle of the pagoda. Along 6 seismic lines, about 3-m-thick uppermost section around the pagoda shows the P-wave velocity of 200∼700 m/s from the refraction survey. Based on the integrated geophysical survey, the foundation of the pagoda is estimated to be in the form of 11-m-side square down to the depth of 3 m.