• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.1
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• pp.211-224
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• 2018

It is important to design tunnel support system considering the various loads acting on the tunnel because they have a direct impact on the stability of tunnels. In Korea, standardized support patterns are defined based on the rock mass classification system depending on the project, and it is stated that it should be modified appropriately considering the behavior of tunnel during construction. In this study, the tunnel support pattern optimization method is suggested based on the convergence-confinement method, earth pressure, axial force of rock bolt, and moment acting on the shotcrete. The length and spacing of the rock bolts and the thickness of the shotcrete were optimized by using the differential evolution algorithm (DEA) and the results were compared to the standard support pattern III for railway tunnel. Rock bolt length can be reduced and the installation interval can be widened for shallow tunnel. As the depth of tunnel increases, the thickness of shotcrete increases linearly. Therefore, the thickness of shotcrete should be thicker than the standard support pattern as the depth of tunnel increases to secure the stability of tunnel.

• The Korean Journal of Ecology
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• v.25 no.3 s.107
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• pp.145-152
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• 2002

Saussurea chabyoungsanica was recorded in new species by Lim Hyoung Tak in 1997. In order to understand the entity of new species, we investigated the new distribution sites, vegetation structure and soil environmental factors. Additionally discovered distribution sites of S. chabyoungsanica were Manduckbong, Mt. Sukbyoung, Mt. Duckhang, and Sukgaejae, which were located on ridge of the Taebaek Mountains. Those sites are typical limestone zones of Korea and among them Sukgaejae belongs to lower great limestone area and Manduckbong, Mt. Sukbyoung and Mt. Duckhang belong to upper great limestone area. According to the result of phytosociological study, plant communities of S. chabyoungsanica were classified by 1 Community group, 4 Communities and 2 Subcommunities; Carex humilis var. nana-Saussurea chabyoungsanica Community group in wide sense Quercus mongolica Community group, Lespedeza maximowiczii-Saussurea chabyounsanica Community, Galium kinuta-Saussurea chabyoungsanica Community, Salvia chanryonica-Saussurea chabyoungsanica Community, Zabelia coreana-Saussurea chabyoungsanica Community. Environmental factor analysis of habitat showed that the distribution site of S. chabyoungsanica was ridge of North aspect and displayed pH $7{\sim}8$ typical of limestone. Soil moisture content was high, whereas organic matter content was low. Considering its high occurrence in sites of $1{\sim}10cm$ in soil depth, and of $30{\sim}45%$ in relative light intensity, major distribution sites were outcrops and boundaries between shrubland and forest. After community division by vegetation structure in habitat of S. chabyoungsanica, we investigated characters of soil environment by community. As a result of PCA analysis of soil sample by community, it was possible to divide community by characters of soil environmental factor. The cumulative value of contribution rate represented in second dimension space was 73% and the major factors for that value were soil texture, organic matter content and field capacity.

• The Journal of Engineering Geology
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• v.14 no.4 s.41
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• pp.487-498
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• 2004

There is an increasing trend of construction works in mountainous areas by the urban development in Busan that is mainly composed of mountains. The study area, Hwangryeong Mt., is one of developing sites in the urban area, too. Landslides and cut-slope failures that occur large damages of human beings and the properties are influenced by soil characteristics as well as rock properties. This study analyzed geotechnical characteristics of soil dependent on geology at Hwangryeong Mt. where a large slope failure had been occurred in 1999. Geology of the study area is composed of the Cretaceous sedimentary rocks and volcanic rocks. Soil layer of the slopes can be grouped into sand mixed with clay and silt. The cohesion is plotted between $0.001\;and\;0.066kg/cm^2$. The friction angles are distributed in the ranges between $32^{\circ}\;and\;39^{\circ}$, meaning soil bearing a high friction angle. The permeability coefficients are plotted between $2.34\times10^{-4}cm/sec\;and\;2.58\times10^{-2}cm/sec$, indicating fine sand and loose silt with a medium grade of permeability. The sedimentary rocks area shows relatively higher permeability coefficients than those volcanic rocks area.

• The Korean Journal of Ecology
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• v.25 no.2
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• pp.75-82
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• 2002

Saussurea chabyoungsanica was recorded in new species by Lim Hyoung Tak in 1997. In order to understand the entity of new species, we investigated the new distribution sites, vegetation structure and soil environmental factors. Additionally discovered distribution sites of S. chabyoungsanica were Manduckbong, Mt. Sukbyoung, Mt. Duckhang, and Sukgaejae, which were located on ridge of the Taebaek mountains. Those sites are typical limestone zones of Korea and among them Sukgaejae belongs to lower great limestone area and Manduckbong, Mt. Sukbyoung and Mt. Duckhang belong to uper great limestone area. According to the result of phytosociological study, plant communities of S. chabyoungsanica were classified by 1 Community group, 4 Communities and 2 Subcommunities; Carex humilis var. nana - Saussurea chabyoungsanica Community group in wide sense Quercus mongolica Community group, Lespedeza maximowiczii- Saussurea chabyoungsanica Community, Galium kinuta - Saussurea chabyongsanica Community, Saliva chanryonica - Saussurea chabyoungsanica Community, Zabelia coreana - Saussurea chabyoungsanica Community. Environmental factor analysis of habitat showed that the distribution site of S. chabyoungsanica was ridge of North aspect and displayed pH 7∼8 typical of limestone. Soil moisture content was high, whereas organic matter content was low. Considering its high occurrence in sites of 1∼10cm in soil depth, and of 30∼45% in relative light intensity, major distribution sites were outcrops and boundaries between shrubland and forest. After community division by vegetation structure in habitat of S. chabyoungsanica, we investigated characters of soil environment by community. As a result of PCA analysis of soil sample by community, it was possible to divide community by characters of soil environmental factor. The cumulative value of contribution rate represented in second dimension space was 73% and the major factors for that value were soil texture, organic matter content and field capacity.

• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.6
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• pp.623-641
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• 2020

About 5 km length of tunnels were constructed by mechanized tunnelling method using closed type shield TBM. In order to avoid construction delay problems for ensuring timely electricity transmission, it is necessary to increase the prediction accuracy of the excavation process involving machines according to rock mass types. This is important to corroborate the project duration and optimum operation for various considerations involved in the machine. So, full-scale tunnelling tests were performed for developing the advance rate model to be appropriately used for 3.6 m diameter shield TBM. About 100 test cases were established and performed using various operational parameters such as thrust force and rotational speed of cuttterhead in representative uniaxial compressive strengths. Accordingly, relationships between normal force and penetration depth and, between UCS and torque were suggested which consider UCS and thrust force conditions according to weathered, soft, hard rocks. Capacity analysis of cutterhead was performed and optimum operational conditions were also suggested based on the developed model. Based on this study, it can be expected that the project construction duration can be reduced and users can benefit from the provision of earlier service.

• Tunnel and Underground Space
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• v.22 no.6
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• pp.383-392
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• 2012

This study introduces $M_{(i,j,k)}BCP$ (Mining Business Continuity Planning) which is the smart management system of mine disasters to achieve the safe and eco-friendly mining. Where, 'i' is mine kinds, 'j' is mining processes, and 'k' is risks at process respectively. By specifically setting 'i=1=limestone mine', this study also suggests that $M_{(i,j,k)}BCP$ is the smart management system of limestone mine. Mining risks used in this study were obtained from professional survey and literature review. This study classified these risks by five different mining processes and reduced risk numbers approximately 60 to 26. And they were all allocated into $M_{(i,j,k)}BCP$ and assessed. To do assess risks, this study used four risk indexes which are probability, casualty, facility loss, and discontinuity respectively. By the results of the assessment of risks, results could be four specific groups based on their causes and impacts. In addition, one of the results showed that the most possible risks at limestone mine was the roof-fall and rock-fall in digging process. This result means that $M_{(1,2,1)}BCP$ should be established as a first priority at limestone mine.

• Tunnel and Underground Space
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• v.27 no.6
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• pp.343-350
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• 2017

Amid increasingly saturated ground space, development of underground space has been booming throughout the world and excavation has been underway near the structure above or under the ground level. But the ground subsidence caused by improper or poor construction technologies, underground water leakage, sudden changes of stratum and the problem with earth retaining system component has been emerged as hot social issue. To deal with such problems nationwide, establishment of preventive and proactive disaster management and rapid restoration system has been pushed now. In this study, collection of the data on technology development trend to secure the underground safety was made, taking into account of internal change elements (changing groundwater level, damage to underground utilities, etc) and external change elements (vehicle load, earthquake and ground excavation, etc) during excavation. Amid the growing need of ground behavior analysis, ground subsidence evaluation technology, safe excavation to prevent ground subsidence and reinforcement technology, improvement of rapid restoration technology in preparation for ground subsidence and development of independent capability, this study is intended to introduce the technology development in a bid to prevent the ground subsidence during excavation. It's categorized into prediction/evaluation technology, complex detect technology, waterproof reinforcement technology, rapid restoration technology and excavation technology which, in part, has been in process now.

• Tunnel and Underground Space
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• v.28 no.1
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• pp.111-124
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• 2018

The purpose of this study is to analyze ventilation design factor for network-type double-deck road tunnel that have been developed actively around the world. A numerical analysis was carried out through computational fluid dynamics (CFD) to derive shock loss coefficient that occurs due to the change in cross sectional area at both merging section and diverging section. The model used for the numerical analysis is real-scale model and the reliability of the result is secured by comparing with the coefficient of the previous studies. As a result of this study, shock loss coefficient was calculated depending on the change in cross-sectional area ratio and was higher than the result of previous studies in case of both merging section and diverging section. It is considered that the characteristics of the geometrical structure of network-type double-deck road tunnel have a great impact on shock loss coefficient. Therefore, the result of this study is expected to be helpful for more accurate ventilation design of network-type double-deck road tunnel.

• The Journal of Engineering Geology
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• v.15 no.1
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• pp.41-55
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• 2005

This research is aimed at investigating the ground characterization of the Cheongju granite area using the geophysical methods. Test site was chosen from the building site in Chungbuk University, Chongju, Chungbuk province. Furthermore, geophysical methods are employed on the outcrops in the east to map the distribution of fault and intrusion and reveal the degree of weathering. The subsurface structure mapped from seismic re-fraction survey mainly consists of two units of weathered soil and rock. Threshold of the units were determined on the basis of seismic velocity of 800 m/s, supported from the standard classification table. From the results of standard penetrating test(SPT), these units are found to show medium-high and high density, respectively. Weathering soil is subdivided in unsaturated layer and saturated layer with thresholds of seismic velocity (500 m/s) and resistivity (200 ohm-m). In particular, unsaturated layer is again classified into dry and wet portions using the GPR section. The boundary between unsaturated and saturated weathering soils corresponds to the groundwater table at depth of approximately 5～6.2 m, which is well correlated with the one from drill-core data. However, bedrock is not delineated by geophysical methods. In the GPR section, fault and intrusion observed on the outcrop are revealed not to extend to the building site. With respect to weathering degree, the outcrop characterized by low resistivity and velocity corresponds to the grade of 'completely weathered' from the geotechnical investigations.

• The Journal of Engineering Geology
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• v.17 no.3
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• pp.471-481
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• 2007

The Landslide in natural slope is occurred mostly by a heavy rain of the summer. This landslide is influenced in soil property of the surface than the rock mass. Soils in natural slope are created by weathering phenomena of the bedrock. These soils differed to the geological conditions such as sedimentary rock, metamorphic rock and volcanic rock. Therefore, estimation of landslide in natural slope is the most important analysis of the bedrock distributions and soil characteristics. This study analyzed the soil property to the natural slopes of Busan area where is distributed to volcanic rock, granite and sedimentary rock. Soil sample conducted various soil tests for estimate the soil physical property and soil engineering characteristics, and analysis of the correlation of geological conditions. In the experiment result, soils were mainly classified by a clayey sand. It is also established that $1.07{\sim}1.99kg/cm^3$ for wet density, $28.2{\sim}39.6^{\circ}$ for angle of shearing resistance, and $8.10{\times}10^{-5}{\sim}8.38{\times}10^{-2}cm/sec$ for coefficient of permeability. From the physical parameter, the soils are estimated to the permeable ground with good shear strength, and soil properties are showed a differential tendency for each geological condition.