• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.3
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• pp.275-283
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• 2010

Recently, the observational design and construction method in tunnels has been becoming important. Rock masses include various discontinuities such as joints, faults, fractures, bedding planes, and, cracks. The behavior of tunnels in hard rocks, therefore, is generally controlled by various discontinuities. In this study, a new key block analysis method for observational design and construction method in tunnels is proposed, and then applied to the actual tunnel with a super-large cross-section. The proposed analysis method considers finite persistence of discontinuities. The new analysis method can handle concave and convex shaped blocks. To demonstrate the applicability of this key block analysis method for observational design and construction method in tunnels, the analysis results are examined and compared with those of the conventional method.

• Journal of Korean Tunnelling and Underground Space Association
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• v.3 no.2
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• pp.3-12
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• 2001

This paper presents the proposed methods of DE (distinct element) modelling to estimate the stability of tunnels in jointed rock masses. First, the criterion to select the joint set(s) contributed to the discontinuous behaviour in a tunnel section is proposed. Selected joint set(s) is(are) considered to form the edges of distinct elements (rock blocks) and the others to modify the elastic properties of rock blocks. The complex DE model with the average and the deviation of joint orientation and joint length for each joint set was compared to the simple model with only the average of joint orientation and the assumption that joint length is infinite. As a result, the latter is suitable to the purpose of tunnel design because it can show the consistent behaviour of a jointed rock mass such as the locally discontinuous failure and the global anisotropic behaviour.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.1
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• pp.17-25
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• 2020

In this study, non-flammable mineral foam board using waste glass that can be produced to standardized specifications were developed and evaluated for the performance. In addition to the physical and mechanical performance, the environmental properties such as insulation, non-combustibility, gas hazard, sound absorption, etc. were tested to verify the use as interior and exterior building materials. Through the structural review, the validity was verified for the application of the office and restaurant building.

• Journal of IKEEE
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• v.21 no.2
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• pp.166-169
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• 2017

In this paper, maximum boost discrete PWM(DPWM) method of Z-Source Inverter(ZSI) is proposed. In general, a DPWM method is used to reduce the switching losses of the inverters and increase the efficiencies. The maximum boost PWM method of Z-Source Inverters is combined with the DPWM method. The proposed Maximum boost DPWM of ZSI is analyzed and it shows how to reduce the switching losses of ZSI. An experimental system has been built and tested to verify the effectiveness of the proposed method.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.6 s.46
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• pp.67-73
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• 2005

Precise analysis of soil-structure interaction requires a proper description of soil profile. However, such approach becomes generally nearly unpractical for soil exhibiting material discontinuity and complex geometry since meshes should match that material discontinuity line. To overcome these difficulties, a different numerical integration method is adopted in this paper, which enables to integrate easily over an element with material discontinuity without regenerating mesh fellowing the discontinuity line. As a result the mesh is highly structured, loading to very regular silliness matrix. The influence of the shape of soil profile on the response is examined and it is seen that the proposed soil-structure analysis method can be easily used on soil-structure interaction problems with complicated soil profile and produce reliable results regardless of material discontinuities.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.04b
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• pp.125-132
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• 2000

하중전달의 문제는 구조체가 하중을 지지할 때 하중을 받는 부재로부터 하중을 지지하지 않는 쪽의 구조로 얼마만큼의 하중이 전달되는가를 해석하는 것이라고 간단히 정의 할 수 있다. 효율적인 Load transfer mechanism 은 구조체의 설계와 해석의 중요한 인자와 직접적으로 관련이 되어 있기 때문에 구조체의 해석시에는 이러한 하중전달의 개념이 반드시 포함되어야 한다. 그러나 일반적인 구조체의 해석시에는 하중전달의 개념은 그 해석의 어려움과 이론적인 해석해의 부재 그리고 본질적으로 존재하는 복잡성 때문에 무시되어져 왔다. 또한 이러한 하중전달의 문제가 다른 역학적인 거동과 연관되어 해석되어 질때는 그 이론적인 해는 구할 수가 없게 된다. 따라서 본 연구에서는 다층구조체에 존재하는 하중전달의 문제를 구조체 내에 존재하는 불연속면의 영향을 고려하수 있는 수치해석적인 모델의 개발을 통하여 하중전달효율의 개념으로 분석하여 각각의 불연속면의 영향에 따른 구조체내에 존재하는 하중전달의 현상을 규명하고자 한다.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2001.03a
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• pp.97-108
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• 2001

절리가 발달한 암반의 거동평가를 위한 해석적 방법은 연속체 모델과 불연속체 모델을 사용하는 방법으로 대별할 수 있으며, 연속체 모델을 사용할 경우에는 유한요소법이나 유한차분법을 이용하는 방법이 주종을 이루고 있다. 불연속체 모델은 개별 블록들의 움직임을 일일이 계산하므로 매우 매력적인 방법이지만 현재의 지반조사 기술수준으로는 지반내의 절리발달사항을 정확히 파악하기가 매우 어려우며, 컴퓨터의 계산용량이 너무 과다해지는 단점이 있다. 따라서, 불연속면을 포함한 암반을 연속체로 가정한 편재절리 모델(ubiquitous joint model)을 이용한 연구가 요구된다. 한편, 터널의 경우는 사면의 경우와는 달리 파괴면의 형상을 사전에 가정하기 어렵기 때문에 한계평형법에 기초한 해석법 등을 적용하여 안전율을 구하기가 곤란하다. 이러한 이유에서 터널을 대상으로 한 수치해석은 안전율을 구하기보다는 안정성을 평가하는 데만 제한적으로 사용되어 왔다. 본 논문에서는 편재절리모델을 이용한 절리암반터널의 거동 평가기법과 수치해석에 의해 터널의 안전율을 구하는 방법을 제시하는 데에 그 목적이 있다. 이를 위해 터널의 안전율 구하는 방법을 강도감소기법에 근거하여 제시하였다.

• Water for future
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• v.23 no.3
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• pp.363-371
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• 1990

Foundational experiments are conducted to examine the applicability of redox control in brak-point chlorination of ammonia on drinking water purification. Through the research, the behauial affects by ph and temperature to a chloromine forming reactions are evaluated. The possibility of redox control in breakpoint chlorination is recoguized by drawing up the titration curve in terms of redox potential and $C{\ell}_2$/N ratios.

• Journal of Korean Tunnelling and Underground Space Association
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• v.10 no.2
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• pp.119-128
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• 2008

In the case of a circular shaft, it is expected that asymmetric loads should apply on the surface rather than symmetric loads due to geographical factors and the non-homogeneity of the jointed rock masses. In this study, discontinuous numerical analysis was carried in order to analyze the characteristics of asymmetric load distribution on the wall of the circular shaft due to anisotropy caused by heterogeneity of rock masses affected by the discontinuities like as a Joint. And it was also analyzed that the effect of the mechanical properties varied with the rock mass rating and horizontal stress with depth had influence in the asymmetric load on the wall of the shaft. In the case of considering the effect of the joint as variable, asymmetric load ratio $(R_p)$, which was defined as the ratio of the load subtracted minimum from maximum to minimum, was below 25% in the hard rock. As regarding the variation of the rock mass rating with depth as variable, the value of $R_p$ was below than 25% in the hard rock, and the value between 30% and 40% in the soft rock. On the other hand, the $R_p$ of fractures rock was between $45{\sim}50%$ which value was much higher than that in better rock mass rating.

• Tunnel and Underground Space
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• v.32 no.6
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• pp.464-477
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• 2022

DFN (discrete fracture network) models that take account of spatial variability and correlation between rock fractures have been demanded for analysis of fractured rock mass behavior for wide areas with high reliability, such as that of underground nuclear waste repositories. In this regard, this report describes the spatial distribution characteristics of fracture networks, and the DFN modeling methodologies that aim to represent such characteristics. DFN modeling methods have been proposed to represent the spatial variability of rock fractures by defining fracture domains (Darcel et al., 2013) and the spatial correlation among fractures by genetic modeling techniques that imitate fracture growth processes (Davy et al., 2013, Libby et al., 2019, Lavoine et al., 2020).These methods, however, require further research for their application to field surveys and for modeling in-situ rock fracture networks.