• Tunnel and Underground Space
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• v.21 no.1
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• pp.20-32
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• 2011

Failure aspects of cut-slope, which induce the sequential collapses during the excavation stage, have been analyzed. Slope rock structures are investigated by examining the orientations and positions of discontinuity planes calculated based on the BIPS image inside the boreholes. Drilled core log has been also used to identify the structural defects. Clay minerals of swelling potentials are detected through XRD analysis. Numerical analysis for slope stability has been performed by utilizing the joint shear strength acquired from the direct joint shear test. Cut-slope collapse characteristics have been studied by investigating the posture of failure-prawn joint planes and the stability of tetrahedral blocks of different sizes. Cross-section analysis has been also performed to analyze the cut-slope behavior and to estimate the amount of reinforcement required to secure the stability of cut-slope. Behavior of reinforced cut-slope is also investigated by analyzing the slope monitoring data.

• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.6
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• pp.451-468
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• 2021

Predicting hazardous ground conditions ahead of a TBM (Tunnel Boring Machine) tunnel face is essential for efficient and stable TBM advance. Although there have been several studies on the electrical resistivity survey method for TBM tunnelling, sufficient experimental data considering TBM advance were not established yet. Therefore, in this study, the laboratory-scale model experiments for simulating TBM excavation were carried out to analyze the applicability of an electrical resistivity survey for predicting hazardous ground conditions ahead of a TBM tunnel face. The trend of electrical resistivity during TBM advance was experimentally evaluated under various hazardous ground conditions (fault zone, seawater intruded zone, soil to rock transition zone, and rock to soil transition zone) ahead of a tunnel face. In the course of the experiments, a scale-down rock ground was provided using granite blocks to simulate the rock TBM tunnelling. Based on the experimental data, the electrical resistivity tends to decrease as the tunnel approaches the fault zone. While the seawater intruded zone follows a similar trend with the fault zone, the resistivity value of the seawater intrude zone decreased significantly compared to that of the fault zone. In case of the soil-to-rock transition zone, the electrical resistivity increases as the TBM approaches the rock with relatively high electrical resistivity. Conversely, in case of the rock-to-soil transition zone, the opposite trend was observed. That is, electrical resistivity decreases as the tunnel face approaches the rock with relatively low electrical resistivity. The experiment results represent that hazardous ground conditions (fault zone, seawater intruded zone, soil-to-rock transition zone, rock-to-soil transition zone) can be efficiently predicted by utilizing an electrical resistivity survey during TBM tunnelling.

• 한국석유지질학회:학술대회논문집
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• autumn
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• pp.6-22
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• 2001

A study of the fracture systems in outcrops of southern onshore Vietnam revealed two kinds of fracture groups according to their origin: cooling fractures and deformation related fractures. Cooling of magma introduced extensive fractures in the batholiths with wide spacing and narrow aperture. They are found widespread in all magmatic bodies, but result in poor reservoir quality due to low bulk porosity and narrow aperture. Cooling fractures are often reactivated during later stress regimes. Deformation related fractures, especially 'fault damage zones' and 'hanging wall deformation' is thought to form the most important reservoir type in the fractured basement rock. The porosity formed by intense fracturing and fault breccia along minor fault zones is thought to be the producing zones in the producing fields of Cuu Long basin. They are found along major faults and widespread in hanging wall blocks.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.05a
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• pp.162-163
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• 2016

This paper presents a mathematical model for optimizing earthwork allocation plan that minimizes earthwork cost. The model takes into account operational constraints in the real-world earthwork such as material-type (i.e., quality level of material) and quantities excavated from cut-sections, required quality of material and quantities for each embankment layer, top-down cutting and bottom-up filling constraints, and allocation orders. These constraints are successfully handled by assuming the rock-earth material as the three dimensional (3D) blocks. The study is of value to project scheduler because the model identifies the optimal earth allocation plan (i.e., haul direction (cut and fill pairs), quantities of soil, type of material, and order of allocations) expeditiously and is developed as an automated system for usability. It is also relevant to estimator in that it computes more realistic earthworks costs estimation. The economic impact and validity of the mathematical model was confirmed by performing test cases.

• Tunnel and Underground Space
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• v.30 no.4
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• pp.359-381
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• 2020

Within the framework of DECOVALEX-2019 Task D, full-scale engineered barriers experiment (FEBEX) at Grimsel Test Site was numerically simulated to investigate an applicability of implemented Barcelona basic model (BBM) into TOUGH2-MP/FLAC3D simulator, which was developed for the prediction of the coupled thermo-hydro-mechanical behavior of bentonite buffer. And the calculated heater power, temperature, relative humidity, total stress, saturation, water content and dry density were compared with in situ data monitored in the various sections. In general, the calculated heater power and temperature provided a fairly good agreement with experimental observations, however, the difference between power of heater #1 and that of heater #2 could not captured in the numerical analysis. It is necessary to consider lamprophyre with low thermal conductivity around heater #1 and non-simplified installation progresses of bentonite blocks in the tunnel for better modeling results. The evolutions and distributions of relative humidity were well reproduced, but hydraulic model needs to be modified because the re-saturation process was relatively fast near the heaters. In case of stress evolutions due to the thermal and hydraulic expansions, the computed stress was in good agreement with the data. But, the stress is slightly higher than the measured in situ data at the early stage of the operation, because gap between rock mass and bentonite blocks have not been considered in the numerical simulations. The calculated distribution of saturation, water content, and dry density along the radial distance showed good agreement with the observations after the first and final dismantling. The calculated dry density near the center of the FEBEX tunnel and heaters were overestimated compared with the observations. As a result, the saturation and water content were underestimated with the measurements. Therefore, numerical model of permeability is needed to modify for the production of better numerical results. It will be possible to produce the better analysis results and more realistically predict the coupled THM behavior in the bentonite blocks by performing the additional studies and modifying the numerical model based on the results of this study.

• Geomechanics and Engineering
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• v.21 no.1
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• pp.23-33
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• 2020

An advancing cutting roof for gob-side entry retaining with no-pillar mining under specific geological conditions is more conducive to the safe and efficient production in a coalmine. This method is being promoted for use in a large number of coalmines because it has many advantages compared to the retaining method with an artificial filling wall as the gateway side filling body. In order to observe the inner structure of the gateway cutting roof and understand its stability mechanism, an equivalent material simulation experiment for a coalmine with complex geological conditions was carried out in this study. The results show that a "self-stabilization bearing structure" equilibrium model was found after the cutting roof caving when the cut line deviation angle was unequal to zero and the cut height was greater than the mining height, and the caving roof rock was hard without damage. The model showed that its stability was mainly controlled by two key blocks. Furthermore, in order to determine the optimal parameters of the cut height and the cut line deviation angle for the cutting roof of the retaining gateway, an in-depth analysis with theoretical mechanics and mine rock mechanics of the model was performed, and the relationship between the roof balance control force and the cut height and cut line deviation angle was solved. It was found that the selection of the values of the cut height and the cut line deviation angle had to conform to a certain principle that it should not only utilize the support force provided by the coal wall and the contact surface of the two key blocks but also prevent the failure of the coal wall and the contact surface.

• The Journal of Engineering Geology
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• v.15 no.3
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• pp.349-363
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• 2005

Many Quaternary faults are recognized as thin gouge and narrow cataclastic zone juxtaposing the Bulguksa granite and Quaternary deposit bed in the eastern block of the Using Fault, Korea: Gaegok 1, Caegok 2, Singye, Madong Wonwonsa and Jinhyeon faults. This study was performed to calculate chemical change, volume change, silica loss and fluid-rock ratio taken place in gouge zones of these Quaternary faults using XRF, XRD, EPMA. The chemical compositions of fault rocks reveal that the fault gouges are depleted in $SiO_2,\;Na_2\;O,and\;K_2O$ and enriched in $Al_2O_3,\;Fe_2O_3,\;P_2O_5,\;MgO,\;MnO,\;CaO,\;and\;LOI(H_2O+CO_2)$ relative to protoliths. The fact that there is enrichment of relatively immobile elements and depletion of the more soluble elements in the fault gouges relative to protoliths can be explained by fluid-assisted volume loss of $56\%$ for Caegok 1 fault, $22\%$ for Caegok 2 fault,$34\%$, for Singye fault, $8\%$ for Madong fault, $2\%$ for the Wonwonsa fault and $53\%$ for the linhyeon fault. Madong fault and Wonwonsa fault where ratios of the volume change, silica loss and fluid-rock are low might have acted as a closed system for fluid activity, whereas Caegok 1 fault and Jinhyeon fault with high ratios in those factors be an open system. The volumetric fluid-rock ratios range $10^2\sim10^4$ for all faults, being highest in Caegok 1 fault and Jinhyeon fault whose fluid activity was most significant.

• The Journal of Engineering Geology
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• v.20 no.1
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• pp.101-109
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• 2010

There are many slopes generally developed by excavation and cut slope with small steps on massive slopes of roads. Especially these cut slopes which excavating around fault fracture zone need a reinforcement technology in order to ensure safety. In the case of slope excavation, it is difficult to use the existing slope support at fracture zone because of geological characteristics. Especially the factor of safety decreases significantly due to the movement of blocks in bed rocks and the expansion of interspace of discontinuous planes in fractured zones caused by excavation. Thus an efficient reinforcement technique in accordance with geological properties of fracture zones needs to be developed because the existing slope support has a restricted application. Therefore it is necessary to develop the specialized rock bolt technique in order to ensure an efficient factor of safety for anomalous fracture zones in slopes and tunnels. The purpose of this study is to develop newly improved rock bolt to increase a supporting effect of the swellex bolt method used recently as a friction type in fracture zones.

• Journal of Conservation Science
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• v.25 no.3
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• pp.323-333
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• 2009

The Jincheonsagongnimaaeyeoraeipsang is a great stone relief Buddha in Goryeo Dynasty, transmitting sculptural styles of the Silla Kingdom. The Buddha was carved on the biotite granite basement, and was undergone cleaning treatment in 2007. The basement rock was opened in plenty cracks bringing out structural instability. And the top of the basement rock was colonized by trees obstructing sunshine and raising humidity. As a result of failure analysis, the basement rock of the Buddha had a major possibility of wedge failure in the parts of the face, hands and cloths. Therefore, the cracks were filled up with epoxy resin L-50, and titanium bars and wire ropes were applied to bind cracked rock blocks. The surface of the crack filler was colored by granite and talc powder with inorganic pigment and L-30. The crack meters were installed on the stone relief Buddha to monitor further behavior, lastly.

• Tunnel and Underground Space
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• v.20 no.5
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• pp.352-359
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• 2010

Stability of twin tunnels depends on the pillar width and the ground condition. In this study, large scale model tests were conducted for investigating the influence of the pillar width of twin tunnels on their behavior in the regular horizontal jointed rock mass. Jointed rocks was composed of concrete blocks. Pillar width of twin tunnels varied in 0.29D, 0.59D, 0.88D and 1.18D, where D is the tunnel width. During the test, pillar stress, lining stress, tunnel distortion, and ground displacement were measured. Lateral earth pressure coefficient was kept in a constant value 1.0. As a result, it was found that the pillar stress and the displacement of the ground and tunnel were increased by decreasing pillar width. The maximum displacement rate was measured just after the upper excavation in each construction sequence. And the maximum influence position was the right shoulder of the preceeding tunnel at the pillar side. It was also found that for the stability assessment the inner displacement was more critical than the crown displacement. The influence zone was formed at the pillar width 0.59D~0.88D that was smaller than 0.8D~2.0D, which was proposed by experience for a good ground condition. And it would be concluded that horizontal joints could also influence on the stability of the twin tunnels.