• Geomechanics and Engineering
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• v.11 no.1
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• pp.41-58
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• 2016

This paper focuses on the deformation behavior of tunnels crossing a weak zone in conventional tunneling. A three-dimensional finite element model was adopted that allows realistic modeling of the tunnel excavation and the support installation. Using the 3D FE model, a parametric study was conducted on a number of tunneling cases with emphasis on the spatial characteristics of the weak zone such as the strike and dip angle, and on the initial stress state. The results of the analyses were thoroughly examined so that the three-dimensional tunnel displacements at the tunnel crown and the sidewalls can be related to the spatial characteristic of the weak zone as well as the initial stress state. The results indicate that the effectiveness of the absolute displacement monitoring data as early warning indicators depends strongly on the spatial characteristics of the weak zone. It is also shown that proper interpretation of the absolute monitoring data can provide not only early warning for a weak zone outside the excavation area but also information on the orientation and the extent of the weak zone. Practical implications of the findings are discussed.

• The Journal of the Petrological Society of Korea
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• v.18 no.1
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• pp.19-30
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• 2009

The main fault of Yangsan Fault Zone (YFZ) and Quaternary fault were found in a trench section with NW-SE direction at an entrance of the Sinheung village in the northern Eonyang, Ulsan, Korea. We interpreted the movement history of the southern part of the YFZ from the geometric and kinematic characteristics of basement rock's fault of the YFZ (Sinheung Fault) and Quaternary fault (Quaternary Sinheung Fault) investigated at the trench section. The trench outcrop consists mainly of Cretaceous sedimentary rocks of Hayang Group and volcanic rocks of Yucheon Group which lie in fault contact and Quaternary deposits which unconformably overlie these basement rocks. This study suggests that the movement history of the southern part of the YFZ can be explained at least by two different strike-slip movements, named as D1 and D2 events, and then two different dip-slip movements, named as D3 and D4 events. (1) D1 event: a sinistral strike-slip movement which caused the bedding of sedimentary rocks to be high-angled toward the main fault of the YFZ. (2) D2 event: a dextral strike-slip movement slipped along the high-angled beddings as fault surfaces. The main characteristic structural elements are predominant sub-horizontal slickenlines and sub-vertical fault foliations which show a NNE trend. The event formed the main fault rocks of the YFZ. (3) D3 event: a conjugate reverse-slip movement slipped along fault surfaces which trend (E)NE and moderately dip (S)SE or (N)NW. The slickenlines, which plunge in the dip direction of fault surfaces, overprint the previous sub-horizontal slickenlines. The fault is characterized by S-C fabrics superimposed on the D2 fault gouges, fault surfaces showing ramp and flat geometry, asymmetric and drag folds and collapse structures accompanied with it. The event dispersed the orientation of the main fault surface of the YFZ. (4) D4 event: a Quaternary reverse-slip movement showing a displacement of several centimeters with S-C fabrics on the Quternary deposits. The D4 fault surfaces are developed along the extensions of the D3 fault surfaces of basement rocks, like the other Quaternary faults within the YFZ. This indicates that these faults were formed under the same compression of (N)NW-(S)SE direction.

• Economic and Environmental Geology
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• v.30 no.1
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• pp.67-77
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• 1997

Seismic data from Lake Tanganyika indicate a complex tectonic, structural, and stratigraphic history. The Lake Tanganyika rift consists of half grabens which tend to alternate dip-direction along the strike of the rift. Adjacent half-grabens are separated by distinct accommodation zones of strike-slip motion. These are areas of relatively high basement, and are classified into two distinct forms which depend on the map-view geometry of the border faults on either side of the accommodation zone. One type is the high-relief accommodation zone which is a fault bounded area of high basement with little subsidence or sediment accumulation. These high-relief areas probably formed very early in the rifting process. The second type is the low-relief accommodation zone which is a large, faulted anticlinal warp with considerable rift sediment accumulated over its axis. These low-relief features continue to develop as rifting processes. This structural configuration profoundly influences depositional processes in Lake Tanganyika. Not only does structures dictate where discrete basins and depocenters can exist, it also controls the distribution of sedimentary facies within basins, both in space and time. This is because rift shoulder topography controls regional drainage patterns and sediment access into the lake. Large fluvial and deltaic systems tend to enter the rift from the up-dip side of half-grabens or along the rift axis, while fans tend to enter from the border fault side.

• The Journal of Engineering Geology
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• v.17 no.3
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• pp.393-404
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• 2007

The purpose of this study is to capture the essentials in survey and evaluation scheme which are able to assess the hazard of a rock slope systematically. Statistical analysis are performed on slope instability parameters related to failure of the rock slope. As the slope instability parameters, twelve survey items are considered such as tension crack, surface deformation, deformation of retaining structures, volume of existing failures, angles between strike of discontinuity and strike of cut slope face, angles between dip of discontinuity and dip of cut slope face, discontinuity condition, cut slope angle, rainfall or ground water level, excavation condition, drainage condition, reinforcement. A total of 233 road cut slopes located in Gyeongnam were considered. The stability of the road cut slopes were evaluated by estimating the slope instability index(SII) and corresponding stability rank. 126 rock slopes were selected to analyze statistical relation between SII and slope instability parameters. The multiple regression analysis was applied to derive statistical models which are able to predict the SII and corresponding slope stability rank. Also, its applicability was explored to predict the slope failures using the variables of slope instability parameters. The results obtained in this study clearly show that the methodology given in this paper have strong capabilities to evaluate the failures of the road cut slope effectively.

• The Journal of Engineering Geology
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• v.10 no.3
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• pp.237-245
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• 2000

This study was for characterizing the engineering geological properties of Moryang Fault, and providing the basic data for tunnel design. Land-sat image analysis, geologic surveys, resistivity prospecting and 3-dimensional analysis for results of resistivity prospecting, core boring, mineralogical identification and chemical analysis for the bedrock, and K-Ar age dating for fault clay were carried out for the study of Moryang Fault which is located at Duckhyunri Sangbukmyun Uljinkun Ulsan metropolis. As a result of the study, it was shown that strike/dip was N20-3$0^{\circ}C$E/70-9$0^{\circ}C$NW, width of fault ranged from 20 to 60m(maximum 80m), and depth was more than 50m. K-Ar age dating results of fault clay were 5,700$\pm$1.129Ma and 1,900$\pm$0.380Ma. Hydraulic fracturing test results showed the principal stress direction similar to the strike of Moryang Fault.

• Economic and Environmental Geology
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• v.26 no.2
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• pp.227-237
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• 1993

Lineaments in the Kyungsang basin most intensely develop in the East coast domain including the Yangsan fault, which dominantly run in NNE direction. The geometry of small fault population near or along the Yangsan fault represents the dominant strikes of N35E, high angle dips and shallowly plunging rakes with dextral movement sense. Stereographic solution on the Yangsan fault geometry gives the dip of 88SE, the slip direction of 17,024 and the slip rake of 18, which were determined from the strike (N23E) of the fault measured on map, and the average attitude (N35E, 84SE) and fault striation (16, 037) of small fault population considered as Riedel shears. It is judged from the geometry of small fault population to the main Yangsan fault and dragging features of bedding attitude near the fault that the Yangsan fault was produced from dextrally strike-slip movement. The movement of the Yangsan and the adjacent parallel faults is thought to be taken place much later than the other fault sets in the Kyungsang basin. It might occur during the geologic age from Eocence to early Miocene according to the consideration of K-Ar ages of the igneous rocks near the fault. The estimated paleostress state indicates ENE shortening and NNW extension. The displacement of the Yangsan fault in the study area is not constant along the fault but decreases from the south to the north. Taking the northern end of the study area as a separating point the whole extension of the Yangsan fault may be divided into southern and northern segments.

• Journal of the Korean Geographical Society
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• v.34 no.3
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• pp.231-246
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• 1999

The geomorphic deformation of the alluvial fans by tectonic movement was investigated along the lineaments of the northern part of the Bulguksa fault system. Based on the aerial photographs interpretation and field surveys Bulguksa fault system was identified as an active reverse fault which has displaced the Quaternary fan deposits. Bulguksa fault system strikes for the direction of NW-SE and N-S. These two lineaments of active fault are crossing at Jinty village in Kyungju city and the fault plane forms here almost vertical dip. Thelateral pressures from the two directions have possibly influenced on the formation of the vertical dip at Jinty village. It should be resulted from that the two pressures responsible for the active reverse fault at which the one with the NW-SE strike thrusts the hanging wall of Tohamsan block southwestward and the other pressure with the N-S jstrike thrusts it westwrd over the foot wall of the fan deposits. The marine oxygen isotope stage 8(0.30-0.25 Ma. BP) and stage 6(0.20-0.14 Ma. BP) are presumed to be the ages of high and middle surfaces of the alluvial fan, repectively. The vertical dispiacements on the high surface along the Bulguksa fault system are about 10.5m at Ha-dong, 9.5-10.5m at Jinhyun-dong, and about 10m at Jinty village. And the vertical displacement on the middle surface was measured about 6m high at Ha-dong. The average slip rate of vertical displacements is calculated about 0.03-0.043mm/y.

• The Journal of the Petrological Society of Korea
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• v.21 no.4
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• pp.397-403
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• 2012

Fe-REE deposits occurred in Jaeunri, Hongcheon formed by carbonatitic melts consist of 3 parts such as northern, middle and southern ore bodies showing discontinuous distribution, and extension shape of ore bodies can be figured through field survey and geometric analysis. Foliations in gneiss around northern and middle ore bodies represent NNE, whereas toward south its direction changes gradually from NE to ENE and finally N-S direction appears in southern ore body. From Jaeungyo to Saemaeulgyo geometric analysis from field work gives that fold shape in this area is open synclinal fold concavely and gently to NW with $45^{\circ}$ northwestward plunging axis, in contrast small scale anticline with $45^{\circ}$ northwestward plunging axis in Yagsooteo area near western part of Saemaeulgyo. Dragging effect could be occurred on these folds by WNW trending dextral strike-slip fault from Yagsooteo to Saemaeulgyo. New ore body can be confirmed from folding structure estimated by trend of foliation, and thus unidentified ore body may be exist under alluvial surface from middle to southern ore body and its distribution could show reversed "ㄱ", one of Korean consonants, considering with estimated strike and dip of foliations. This estimated extension of ore body figured out by structural analysis in the studied area works an important role for measuring of ore reserve and selecting of drilling site to find new ore body.

• Economic and Environmental Geology
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• v.17 no.1
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• pp.57-78
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• 1984

The object of this study is to offer the standarized data for the design and calculating engineering cost of the rock excavation an the construction of the 3rd and 4th Seoul Subway lines From Jnauary to March in 1983, this study was carried out by the both methods of the field and laboratary studies. In the field, the geological survey in the entire area of Seoul City and sites on the subway lines were carried out and also a site measure of uniaxial compressional strength of rock masses by using Schmidt hammer was done. The labartory studies were carsied out by a study of preuions surveyes, microscopic studies of the mineral composition and degree of weathering of rocks, and measure of uniaxial compressional strengths Finally an engineering classification of each rock masses of South Africa council for Scientific and Industrial Research, CSIR, after Bieniawski, 1974. was done. In this method of classification 6 parameters such as strength of intact rock material, rock quality designation, spacing of fractures, condition of fractures, groundwater conditions, and the effect of fracture strike and dip orientation in tunnelling were used to evaluate rating of each rock mass.

• Economic and Environmental Geology
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• v.42 no.6
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• pp.627-634
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• 2009

Redefining the difference among the Yamaguchi's 'so-called Yeoncheon system,' north Korean's 'Rimjin System' and Yeoncheon Group of national geological map, authors tried to avoid a possible misunderstanding of concept between Yeoncheon Group and Imjingang fold Belt. As a tool of preliminary geological mapping and or N-S reconnaissance of the whole Yeoncheon Group, an interpretation technique of satellite image from various angles has been applied to understand the geometrical attitude of strike and dip of random spot, and a further concept like as cross section.