• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.2
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• pp.655-666
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• 2013

A number of highway projects are in progress in Korea to accommodate increasing transportation demands. As the highway route becomes more complex, some projects include tunneling through unconsolidated sedimentary rock. Since an unconsolidated sedimentary rock mainly consists of rock and ground mass, the behavior and characteristics in unconsolidated sedimentary rock tunnel are quite different from typical rock tunnel. However, construction case histories and rock classifications method on unconsolidated sedimentary rock tunnel had not been developed or studied domestically. Consequently the case studies and rock classification system for unconsolidated sedimentary rock are required to better understand its behavior for tunneling. In this study, rock mass classification method is proposed to identify unconsolidated sedimentary rock based on point load and slake durability tests. Based on this, the proposed method of unconsolidated sedimentary rock can be applied well through comparisons with the results of convergence measurement.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.999-1008
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• 2009

A series of sedimentary rocks which are formed in the Tertiary are distributed around Samcheok(Samcheok-Pukpyoung basin), Younghae(Younghae basin), Pohang(Pohang basin), Gyeongju(Yangnam basin), Ulsan(Ulsan basin), Jeju(Seogyuipo formation) in the southern region of the Korean Peninsula. This study concerned with geological, geophysical, geotechnical properties of the unconsolidated rocks in the Pohang area. A consolidated rocks are classified as hard rock - soft rock - weathered rock - residual soil follows in degree of weathering. But unconsolidated rocks has soil properties as well as rock's at the same time. The results of field excursion, boring, borehole-logging, rock testing, geophysical survey, laboratory test are soft rock range, but the durability of the rock until the residual soil from the weathered rock. We accomplished the rock mass classification of the unconsolidated rocks.

• Tunnel and Underground Space
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• v.28 no.1
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• pp.25-37
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• 2018

Burger's model was used to analyze creep characteristics of unconsolidated rock. Burger's model should determine four physical parameters from two pairs of data. In this study, physical parameters of Burger's model were determined by applying mathematical concept solution. Creep was accelerated for three years using the determined physical parameters of the Burger's model for unconsolidated rocks. As a result, the creep behavior showed a continuous deformation behavior without convergence. Therefore, in this mine, it is analyzed that the application of U-Beam is more appropriate than roofbolt in terms of stability.

• Journal of the Korean Geotechnical Society
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• v.26 no.7
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• pp.25-36
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• 2010

Tertiary unconsolidated mudstones spread throughout the eastern coast area. The demand for high quality filling materials in these areas is increasing due to harbors and large-scale residential land development. Rock produced in-situ or near site has been used as road subbase construction or reclamation materials for economical reason, but it is hard to decide appropriateness of quality specification because of its characteristics. The test results showed that unconsolidated rocks are diversely considered according to a different method of the applied geotechnical investigation. Therefore, the site of tertiary unconsolidated mudstones, the classification of rock and evaluation of rock properties that must be evaluated by objective criteria and apply a different set of criteria are needed. In addition, the environmental impact must be considered due to acid mine drainage.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2007.10a
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• pp.188-209
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• 2007

• Tunnel and Underground Space
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• v.19 no.4
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• pp.339-347
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• 2009

Despite the recent improvement in tunnel excavation technique, Tunnel collapse accidents still happen. This paper suggest two typical cases in unconsolidated ground condition. Collapse causes of each case were analyzed by the measurement records and numerical simulation, and then mechanism of tunnel collapse was investigated about each case. From this study, the crucial indicators of tunnel collapse were the variation of shear strain and ground water level, also, tunnel collapse deeply related to how shear deformation around tunnel was developed according to the excavation step.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.107-112
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• 2005

Road is built continuously along with development of industry and cut slope is happened necessarily in road construction. Geoengineers are executing cut slope stability analysis considering various cut slope condition such as topography, geology, hydraulic condition and so on. The Tertiary Jungja Basin is located in the southeastern coastal area of the Korea Peninsula. Jungja Basin area is created by geotectonic movement of the plate after Early Miocene epoch. The northwestern and southwestern boundary of the basin is fault zone. The Basement rock is hornfels (Ulsan Formation). Basin-fills consist of extrusive volcanic rock(Tangsa Andesites), unconsolidated fluviatile conglomerate(Kangdong Formation) and shallow brackish-water sandstone(Sinhyun Formation). The characteristics of cut slopes in this area is different with cut slopes in the other site. Soil layers in this area is unconsolidated sediments and is not formed the weathering and erosion of the rock. So, the depth of soil layer is very thick. Faults of this area are northwest-southeast and northeast-southwest direction. Expandible clay mineral as smectite, chlorite et al. detected from fault gouge using XRD. Therefore, Jungja Basin area must consider the characteristics of the faults and soil layers thickness necessarily cut slopes stability analysis.

• Tunnel and Underground Space
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• v.24 no.2
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• pp.143-154
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• 2014

In this study, we simulated both dissociation of gas hydrate and mechanical deformation of hydrate-bearing sedimentary formation using geomechanical model. The geomechanical model analysis consists of two distinct codes of TOUGH+Hydrate and FLAC3D. The model is characterized by the fact that changes of temperature, pressure, saturation and their influence on the consequent evolution of effective stress, stiffness and strength of hydrate-bearing sediments during gas production could be well simulated. We compared the results of simulation for two different production methods, and showed that combination of depressurization and thermal stimulation results in the enhancement of production rate especially at early stage. We also presented that the hydrate dissociation-induced geomechanical deformation in unconsolidated clay is much larger than that in sandstone.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.674-677
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• 2005

The characteristics of geothermal resources in Korea was roughly estimated using hot springs, 580 geothermal gradients and 338 heat flow data. In the aspect of hot springs with geologic structure, location of hot springs coincide with fault zone, especially younger age of Cretaceous to Tertiary. In the aspect of geothermal gradients, Pohang area shows the highest geothermal gradient anomaly, which is covered with unconsol idated rock of low thermal conductivity preserving the residual heat from igneous activity or radioactivity elements decay. In the aspect of heat flow density, high anomaly can be found along the zone connecting Uljin-Pohang-Busan on the southeastern part of Korean peninsula at which big fault zone as Yangsan fault is well developed.

• Journal of the Korean Geophysical Society
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• v.2 no.1
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• pp.45-56
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• 1999

Seismic refracrion and reflection surveys were conducted along an E-W trending track of 482 m long in Ilwall-dong, Pohang. End-on spread was employed as source-receiver configuration with 2 m for both geophone interval and offset. Seismic data were acquired using 24 channels at every shot fired every 2 m along the track. Refraction data were interpreted using equations for multi-horizontal layers. Reflection data were processed in the sequence of trace edit, gain control, CMP sorting, NMO correction, mute, common offset gathering, and filtering to produce a single fold seismic section. There are two layers in shallow subsurface of the study area. Upper layer has the P-wave velocities ranging from 267 to 566 m/s and is interpreted as a layer of unconsolidated sediments. Lower layer has P-wave velocities of 1096-3108 m/s and is interpreted as weathered rock to hard rock. Most of the lower layer classified as soft rock. Upper layer has lateral variations in both P-wave velocity and thickness. The upper layer in the eastern part of the seismic line is 3-5 m thick and has P-wave velocity of 400 m/s in average. The upper layer in the western part is 8-10 m thick and has P-wave velocity of 340 m/s in average. The eastern part is interpreted as unconsolidated beach sand, while the western part is interpreted as infilled soil to develop a construction site. Three fault systems of high angle are imaged in seismic reflection section. It is interpreted that the area between these fault systems are relatively safe. Large buildings should be located in the safe ground condition of no fault and footings should be designed to be in the basement rock of 3-10 m deep below the surface.