• Geomechanics and Engineering
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• 제18권4호
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• pp.449-457
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• 2019

Physical model tests were first performed to investigate the failure pattern of multiple pillar-roof support system. It was observed in the physical model tests, pillars were design with the same mechanical parameters in model #1, cracking occurred simultaneously in panel pillars and the roof above barrier pillars. When pillars 2 to 5 lost bearing capacity, collapse of the roof supported by those pillars occurred. Physical model #2 was design with a relatively weaker pillar (pillar 3) among six pillars. It was found that the whole pillar-roof system was divided into two independent systems by a roof crack, and two pillars collapse and roof subsidence events occurred during the loading process, the first failure event was induced by the pillars failure, and the second was caused by the roof crack. Then, for a multiple pillar-roof support system, three types of failure patterns were analysed based on the condition of pillar and roof. It can be concluded that any failure of a bearing component would cause a subsidence event. However, the barrier pillar could bear the transferred load during the stress redistribution process, mitigating the propagation of collapse or cutting the roof to insulate the collapse area. Importantly, some effective methods were suggested to decrease the risk of catastrophic collapse, and the deep-hole-blasting was employed to improve the stability of the pillar and roof support system in a room and pillar mine.

• Geomechanics and Engineering
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• 제30권2호
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• pp.107-121
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• 2022

Coal pillar assessment is of broad importance to underground engineering structure, as the pillar failure can lead to enormous disasters. Because of the highly non-linear correlation between the pillar failure and its influential attributes, conventional forecasting techniques cannot generate accurate outcomes. To approximate the complex behavior of coal pillar, this paper elucidates a new idea to forecast the underground coal pillar stability using combined unsupervised-supervised learning. In order to build a database of the study, a total of 90 patterns of pillar cases were collected from authentic engineering structures. A state-of-the art feature depletion method, t-distribution symmetric neighbor embedding (t-SNE) has been employed to reduce significance of actual data features. Consequently, an unsupervised machine learning technique K-mean clustering was followed to reassign the t-SNE dimensionality reduced data in order to compute the relative class of coal pillar cases. Following that, the reassign dataset was divided into two parts: 70 percent for training dataset and 30 percent for testing dataset, respectively. The accuracy of the predicted data was then examined using support vector classifier (SVC) model performance measures such as precision, recall, and f₁-score. As a result, the proposed model can be employed for properly predicting the pillar failure class in a variety of underground rock engineering projects.

• Geomechanics and Engineering
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• 제29권6호
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• pp.697-706
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• 2022

In order to explore the stable anchoring conditions of coal side under the mining disturbance of soft section coal pillar in Wangcun Coal Mine of Chenghe Mining Area, the distribution model of the anchoring support pressure at the coal pillar side was established, using the strain-softening characteristics of the coal to study the distribution law of anchoring coal side support pressure. The analytical solution for the reinforcement anchorage stress in the coal pillar side was derived with the inelastic state mechanical model. The results show that the deformation angle of the roadway side and roof increases with the roof subsidence due to the mining influence at the adjacent working face, the plastic deformation zone extends to the depth of the coal side, and the increase of anchorage stress can effectively control the roof subsidence and further deterioration of plastic zone. The roadway height and the peak support pressure have a certain influence on the anchorage stress, the required anchorage stress of the coal side rises with the roadway height and the peak support pressure. The required anchorage stress of the coal pillar side decreases as the cohesion between the coal seam and the roof and floor and the anchor length increases. Then, applied the research result to Wangcun coal mine in Chenghe mining area, the design of anchor cable reinforcement support was proposed for the section of coal pillars side that has been anchored and deformed, which achieved great results and effectively controlled the convergence and deformation of the side, providing a safety guarantee for the roadway excavation and mining.

• 터널과지하공간
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• 제11권2호
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• pp.109-119
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• 2001

우리나라의 양수발전소는 지금까지 단일공동을 굴착하였다. 그러나 양양 양수발전소는 두 개의 대공동 즉, 발전소와 주 변전소로 구성된다. 이 경우 공동 구조물의 안정성, 특히 두 공동사이에 형성되는 암주를 영구적으로 안전하게 유지할 수 있도록 보장되어야 한다. 본 연구에서는 개별요소법을 이용하여 두 공동과 암주의 구조적 안정성을 평가하였으며, 구성모델로 Barton-Bandis의 절리모델을 이용하였다. 현지 암반의 초기응력, 자연절리면의 거칠기계수, 불연속면의 공간적 분포 특성과 같은 중요한 요인들은 현지 조사를 통하여 구하였다. 이외에 두가지 경우 즉, 무보강과 보강의 경우 지보시스템의 최적화를 분석하였으며, 또한 보강효과를 검토하였다. 연구결과 보강의 경우 수평변위와 절리의 전단변위가 감소되었으며 암주내 이완영역 역시 감소됨을 확인하였다. 두 공동사이에 있는 약 36 m 두께의 암주에 적절한 보강조치를 취하여 안정성을 확보할 수 있었다.

• Geomechanics and Engineering
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• 제11권2호
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• pp.177-195
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• 2016

To secure the stability of geotechnical infrastructures and minimize failures during the construction process, a number of support systems have been introduced in the last several decades. In particular, stabilization methods using steel bars have been widely used in the field of geotechnical engineering. Rock bolt system is representative support system using steel bars. Pre-stressing has been applied to enhance reinforcement performance but can be released because of the failure of head or anchor sections. To overcome this deficiency, this paper proposes an innovative support system that can actively reinforce the weak ground along the whole structural element by introducing an active tension bolt containing a spring unit to the middle of the steel bar to increase its reinforcement capacity. In addition, the paper presents the support mechanism of the active tension bolt based on a theoretical study and employs an experimental study to validate the performance of the proposed active tension bolt based on a down-scaled model. To examine the feasibility of the active tension unit in a pillar, the paper considers a pullout test and a small-scale experimental model. The experimental results suggest the active tension bolt to be an effective support system for pillar reinforcement.

• 터널과지하공간
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• 제23권2호
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• pp.130-140
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• 2013

본 연구에서는 $30^{\circ}$ 경사진 층리면을 가진 풍화암 물성의 이방성 암반에서 필러 폭이 0.5D와 0.25D로 매우 작은 근접병설터널을 시공할 경우에 대한 터널 안정성을 조사하였다. 이를 위해 터널간 이격거리와 지보조건이 서로 다른 6가지 모형을 제작하고 측압계수 1의 하중조건으로 축소모형실험을 실시하였다. 모형별 균열개시압력, 최대압력, 필러 및 터널의 변형거동을 조사하였으며, 복공지보와 필러보강 여부가 터널의 안정성에 미치는 영향을 알아보았다. 필러 폭이 큰 모형일수록 균열개시압력이 더 크게 나타나 터널 안정성은 증가하였으며, 복공지보를 설치한 모형은 무지보 모형에 비해 균열개시압력와 최대압력이 더 크고 내공단면의 변형량은 적어 풍화암 근접병설터널에서 복공지보의 필요성을 확인하였다. 복공지보와 더불어 필러보강을 실시한 모형은 다른 모형에 비해 터널 안정성이 더 크게 나타났으며, 특히 필러 폭 0.25D인 근접병설터널은 복공지보뿐 아니라 필러보강도 실시해야 터널 안정성이 확보됨을 알 수 있었다.

• 한국터널지하공간학회 논문집
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• 제16권5호
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• pp.487-495
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• 2014

본 연구에서는 주방식 지하구조물에서 지보재 설계를 위한 매개변수 연구를 수행하였다. 지보재 설계에 앞서 설계에 필요한 암주와 공간의 형상별 천단변위, 최대 주응력, 소성영역에 대한 해석을 수행하였다. 해석에 사용할 매개변수를 최적화 하기위해 주방식 지하구조물의 대상 심도와 지반 조건은 기존 지하철 정거장 건설 사례를 분석하여 결정하였으며 지하공간의 활용 목적에 따라 암주의 형상과 공간의 형상을 설정하여 총 180가지의 경우를 선택하였다. 매개변수 해석을 통해 획득한 결과는 향후 지하구조의 안정성과 공간 활용성, 시공장비의 적용성을 고려하여 지보재 설계와 설치 여부를 판단할 수 있는 근거자료로 활용될 수 있을 것으로 판단된다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2003년도 봄 학술발표회 논문집
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• pp.225-232
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• 2003

The behaviour of ground induced by tunneling of 2arch tunnels may differ from the one caused by usual type tunnels. This paper describe the behaviour created by the size of pilot tunnel and the condition on the construction method of center piller Also, loads acting on the supports of the first tunnel and the center pillar during the excavation of second tunnel is investigated by numerical analyses. The results of numerical analyses are compared to the data records of measurement results, i.e. force on the support system and ground displacement.

• 반도체디스플레이기술학회지
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• 제9권1호
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• pp.49-54
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• 2010

Windows are still the thermally weakest part in considering energy efficiency. The vacuum glazing is considered as a new alternative in terms of energy efficiency. Vacuum glazing are consisting of two separated glass, pillars are support the under and upper glass. Therefore in this paper suggested the pillar shapes and array arrangements method using Finite Element Method and validity were proved by comparing and analyzing with the research that it is announced through the existing experiment. It is considered to solve pillar shapes and arrangement method problem of the vacuum glazing using proposed FEM analysis.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2004년도 춘계 학술발표대회 개요집
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• pp.237-239
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• 2004

This paper presents the analysis results of deformation induced by welding of stiffeners which will be attached for structural reinforcements of deck pillar support in LNG carrier. (omitted)