• 한국지반공학회논문집
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• 제30권8호
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• pp.13-24
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• 2014

지반아칭을 규명하기 위해 일련의 트랩도어 모형실험을 실시하였다. 이 모형실험에서 지반아칭현상은 모형토조바닥에 작용하는 연직토압의 변화를 관찰함으로서 확인할 수 있었다. 트랩도어 재하판의 하강으로 지반변형을 발생시킴으로서 트랩도어 상부지반에 이완영역이 발생하였다. 이때 이완영역내의 응력은 지반아칭현상에 의해 트랩도어 주변의 정지영역으로 전이됨을 알 수 있었다. 즉 연직토압은 이완영역 내에서는 급격히 감소하였고 정지영역에서는 크게 증가하였다. 이완영역 내 연직토압의 최대감소율과 정지영역에서의 연직토압의 최대증가율은 지반밀도에는 영향을 받지 않았으나 트랩도어 재하폭의 크기에는 영향을 크게 받았다. 이완영역은 타원형상으로 정의할 수 있었으며 이타원의 장축은 트랩도어 중앙에서의 이완영역높이의 두 배 크기에 해당하였고 단축은 트랩도어 폭 크기에 해당하였다. 여기서 트랩도어 중앙에서의 이완영역높이는 트랩도어 폭의 1.5배 크기로 나타났다.

• Geomechanics and Engineering
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• 제8권6호
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• pp.829-844
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• 2015

In the current paper the results of a numerical simulation that were verified by a well instrumented experimental procedure for studying the arching effect over a trapdoor in sand is presented. To simulate this phenomenon with continuum mechanics, the experimental procedure is modeled in ABAQUS code using stress dependent hardening in elastic state and plastic strain dependent frictional hardening-softening with Mohr Coulomb failure criterion applying user sub-routine. The apparatus comprises rectangular trapdoors with different width that can yield downward while stresses and deformations are recorded simultaneously. As the trapdoor starts to yield, the whole soil mass deforms elastically. However, after an immediate specified displacement, depending on the width of the trapdoor, the soil mass behaves plastically. This behavior of sand occurs due to the flow phenomenon and continues until the stress on trapdoor is minimized. Then the failure process develops in sand and the measured stress on the trapdoor shows an ascending trend. This indicates gradual separation of the yielding mass from the whole soil body. Finally, the flow process leads to establish a stable vault of sand called arching mechanism or progressive collapse of the soil body.

• Geomechanics and Engineering
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• 제38권6호
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• pp.571-581
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• 2024

Concrete linings in tunnels constructed by drilling and blasting such as NATM serve as a secondary support structure. However, these linings can face unexpected earth pressures if the primary support deteriorates or if ground conditions become unfavorable. It is crucial to determine the loosening earth pressure that allows the lining to maintain its structural integrity and prevent damage caused by this pressure. This study proposes a numerical model for simulating the trapdoor test and developing a method for calculating the loosening earth pressure. The discrete element method (DEM) was employed to describe the soil characteristics around the tunnel. Using this numerical model, a sequence of experimental trapdoor steps was simulated, and the loosening earth pressure was analyzed. Contact parameters were calibrated based on an analysis of a triaxial compression test. The reliability of the developed model was confirmed through a comparison between simulation results and laboratory test findings. The model was used to calculate the contact force applied to the trapdoor plate and to assess the settlement of soil particles. Furthermore, the model accounted for the soil-arching effect, which effectively redistributes the load to the surrounding areas. The proposed model can be applied to analyze the tunnel's cross-sectional dimensions and design stability under various ground conditions.

• 한국지반공학회논문집
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• 제30권4호
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• pp.65-80
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• 2014

본 연구에서는 실제 터널 단면의 형상을 갖는 Trapdoor시험과 수치 해석을 수행하여 주변지반의 거동, 이완하중의 분포 및 점진적인 파괴 현상에 대하여 분석하였다. 지반하중은 Trapdoor의 하강에 따라 급격히 감소 후에 다시 크게 증가하여 일정한 이완하중에 도달하여 아칭효과를 확인 할 수 있었으며, 느슨 모래의 경우가 조밀 모래 보다 상대적으로 큰 값을 나타내었다. 전단대의 형성은 터널 어깨부에서 발생하여 터널 측벽에서 $63^{\circ}$(느슨) 및 $69^{\circ}$(조밀) 방향으로 시작하여 완만한 곡선을 이루며 지표를 향하여 진행하는 형상을 나타내었다. 터널 상부에서의 전단대의 폭원은 1.83b~1.92b(b는 터널폭)로서 기존 제안식으로 구한 값과 유사한 범위를 보였으나, 전단대의 높이는 대심도의 경우 터널고의 1.5~2.0배 정도로서 기존의 제안 값(약 3.0배) 보다 상대적으로 낮은 것으로 나타났다.

• 한국지반공학회논문집
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• 제32권10호
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• pp.31-40
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• 2016

트랩도어 하강이 일어나는 토체 내부에서 발생하는 흙 아치 구조의 변화를 관찰하기 위해서 광탄성 측정 기법을 이용하여 입상체의 다양한 거동을 관찰하였다. 광탄성 반응 재료로 코팅된 원주형 모형 입자를 적층하여 입상체를 구성하였다. 광탄성 기법을 이용하여 입상체 내부에서 발생하는 입자 간 접촉력 전달 구조의 변화를 촬영하여 관찰하였으며 이를 입상체 하부 로드셀에서 측정된 압력 변화 및 내부 활동면의 변화 양상과 비교 분석하였다. 트랩도어 하강 초기에 형성된 흙 아치 구조는 하강이 지속되면 붕괴되지만 다시 확장된 아치 구조가 새롭게 형성되었다. 트랩도어 하강 초기에 일치하였던 흙 아치 구조의 경계면과 활동면은 트랩도어 하강이 진행되면서 활동면이 포함된 영역이 접촉력을 잃은 영역 내부에 포함되었다.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제33권6호
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• pp.520-524
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• 2011

A 27-year-old female presented to our hospital with a slow growing, hard and soft palate mass on the right that had been present for the several months. Physical examination showed a 2 cm, firm, well-circumscribed, painless mass on the right side of the palate. PNS computer tomographic imaging showed a $1.5{\times}1.3{\times}2$ cm well-defined cystic mass on the right side of both the hard and soft palate without any underlying bone change. The lesion was completely excised under general anesthesia. In order to preserve the palatal mucosa, trapdoor approach for removal of the pleomorphic adenoma was done. This technique provided more comfortable healing of the operative site. Three years after surgery, there was no evidence of recurrence. If pleomorphic adenoma without bony and mucosal destruction exists, we suggest consideration of the trapdoor approach to protect the palatal mucosa. In view of the potential for tumour recurrence, long-term follow-up and careful examination are necessary.

• Archives of Plastic Surgery
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• 제37권5호
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• pp.619-625
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• 2010

Purpose: Trapdoor orbital blowout fracture is most common in orbital blowout fracture. Various materials have been used to reconstruct orbital floor blowout fracture. Absorbable alloplastic implants are needed because of disadvantages of nonabsorbable alloplastic materials and donor morbidity of autogenous tissue. The aim of the study is to evaluate usefulness of absorbable mesh plate as a reconstructive material for orbital blowout fractures. Methods: From December 2008 to October 2009, 18 trapdoor orbital floor blowout fracture patients were treated using elevator fixation, depressor fixation, or elevatordepressor fixation techniques with absorbable mesh plates and screw, depending on degree of orbital floor reduction, because absorbable mesh plates are less rigid than titanium plates and other artificial substitutes. Results: Among 18 patients, 5 elevator fixation, 4 depressor fixation, and 9 elevator and depressor fixation technique were performed. In all patients, postoperative computed tomographic (CT) scan showed complete reduction of orbital contents and orbital floor, and no displacement of bony fragment and mesh plate. Mean follow-up was 10 months. There were no significant intraoperative or postoperative complications. Conclusion: Three different techniques depending on the degree of orbital floor reduction are useful for open reduction and internal fixation of trapdoor orbital floor blowout fracture with absorbable mesh plates.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제46권6호
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• pp.428-434
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• 2020

Orbital floor blowout fractures can result in a variety of signs and symptoms depending on the severity of the bone defect. Large defects often result in enophthalmos and restriction of ocular movement; yet the timing of surgery can be delayed up to two weeks with good functional outcomes. In contrast, an orbital trapdoor defect with entrapment of the inferior rectus muscle usually elicits pain with marked restriction of the upward gaze and activation of the oculocardiac reflex without significant dystopia or enophthalmos. When autonomic cardiac derangement is diagnosed along with an orbital floor fracture, it has been suggested that the fracture should be treated immediately. Otherwise, it will result in continued hemodynamic instability and muscular injury and may require a second surgery. This article reports the management of an unusual presentation of a trapdoor blowout orbital floor fracture surgery with oculocardiac response in an adult, with emphasis on its pathophysiology, management, and differential diagnosis.

• 한국인터넷방송통신학회논문지
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• 제15권5호
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• pp.9-17
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• 2015

무선 통신 기술의 발전과 ICT 시장의 변화에 따라 M2M 서비스 활성화 및 기술은 지속적인 발전을 거듭하고 있다. 사람의 제어나 직접적인 개입 없이 사물과 사물간의 통신환경을 구축하는 M2M 환경이 주목받고 있다. 무선 통신 환경의 특성으로 데이터 노출, 위조, 변조, 삭제, 프라이버시 등의 문제에서 다양한 보안 위협에 노출 될 가능성과 안전한 통신 보안 기술이 중요 요구사항으로 이슈화되고 있다. 본 논문은 트랩도어 충돌 해쉬의 요구사항을 분석하고, 트랩도어의 특수성을 이용하여 M2M 환경에서 그룹간의 키를 생성하고, 이를 세션키로 교환하는 기법을 제안한다. 그리고 그룹키 생성에 이은 디바이스와 게이트웨이의 인증을 확인하는 기법을 제안한다. 제안하는 기법은 충돌 메시지와 충돌 해쉬의 특수성을 이용하여 그룹 통신 구간의 위장 공격, 중간자 공격, 재전송 공격 등의 공격 저항성을 가지는 안전한 기법임을 확인하였다.

• Geomechanics and Engineering
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• 제37권4호
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• pp.341-358
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• 2024

This paper reports several plane-strain trapdoor tests conducted to investigate the effects of reinforcement on soil arching development under localized surface loading with a loading plate width three times the trapdoor width. An analogical soil composed of aluminum rods with three different diameters was used as the backfill and Kraft paper with two different stiffness values was used as the reinforcement material. Four reinforcement arrangements were investigated: (1) no reinforcement, (2) one low stiffness reinforcement R1, (3) one high stiffness reinforcement R2, and (4) two low stiffness reinforcements R1 with a backfill layer in between. The stiffness of R2 was approximately twice that of R1; therefore, two R1 had approximately the same total stiffness as one R2. Test results indicate that the use of reinforcement minimized soil arching degradation under localized surface loading. Soil arching with reinforcement degraded more at unloading stages as compared to that at loading stages. The use of stiffer reinforcement had the advantages of more effectively minimizing soil arching degradation. As compared to one high stiffness reinforcement layer, two low stiffness reinforcement layers with a backfill layer of certain thickness in between promoted soil arching under localized surface loading. Due to different states of soil arching development with and without reinforcement, an analytical multi-stage soil arching model available in the literature was selected in this study to calculate the average vertical pressures acting on the trapdoor or on the deflected reinforcement section under both the backfill self-weight and localized surface loading.