• Geomechanics and Engineering
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• 제6권3호
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• pp.263-275
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• 2014

The development of transportation in large cities requires the construction of twin tunnels located at shallow depth. As far as twin tunnels excavated in parallel are concerned, most of the cases reported in literature focused on considering the effect of the ground condition, tunnel size, depth, surface loads, the relative position between two tunnels, and construction process on the structural lining forces. However, the effect of the segment joints was not taken into account. Numerical investigation performed in this study using the $FLAC^{3D}$ finite difference element program made it possible to include considerable influences of the segment joints and tunnel distance on the structural lining forces induced in twin tunnels. The structural lining forces induced in the first tunnel through various phases are considerably affected by the second tunnel construction process. Their values induced in a segmental lining are always lower than those obtained in a continuous lining. However, the influence of joint distribution in the second tunnel on the structural forces induced in the first tunnel is insignificant. The critical influence distance between two tunnels is about two tunnel diameters.

• 대한기계학회논문집
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• 제19권8호
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• pp.1972-1981
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• 1995

As a railway train enters a tunnel at high speed, a compression wave is formed in front of the train and propagates along the tunnel. The compression wave subsequently emerges from the exit of the tunnel, which causes an impulsive noise. The impulsive noise is closely related to the pressure gradient of the compression wave propagating the tunnel. In order to investigate the characteristics of the compression waves, in the present study an experiment was made using a shock tube. The results show that the strength of a compression wave decreases with the distance from the tunnel entrance and the nonlinear effect of compression wave appears to be significant if strength of the initial compression wave is greater than 7 kPa. Furthermore if the wave pattern is known, attenuation of the compression wave propagating in a tunnel can be reasonably predicted by a theoretical equation considering viscous action and heat transfer in boundary layer.

• 지질공학
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• 제13권4호
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• pp.445-456
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• 2003

배면그라우팅과 압밀그라우팅 보강기슬은 터널의 안정성 향상을 위해 터널현장에서 활발히 사용되고있다. 그러나 이에 대한 시공 및 관리 기술 연구는 상대적으로 대단히 미흡한 실정이다. 본 연구에서는 심부에 위치한 도수로 터널 시험 구간에 대하여 그라우팅 전후의 각종 현장 시험과 라이닝 계측을 실시하여 압밀그라우팅 및 배면그라우팅 보강이 콘크리트 라이닝의 응력 및 변형 특성에 미치는 영향을 분석하였다. 터널 그라우팅 보강 효과를 연구한 결과, 그라우팅 보강으로 인해 암반의 탄성계수는 최대 5배까지 증가하였으며 전체적으로 그라우팅의 고결효과는 주목할 만 하였다. 또한, 라이닝 배면에 작용하는 그라우팅 압력은 주입압의 약 10%에 불과하였다. 본 연구 결과는 콘크리트 라이닝 설계시 활용될 수 있을 것으로 기대된다.

• 한국터널지하공간학회 논문집
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• 제21권2호
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• pp.257-266
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• 2019

터널 굴착 중 발생하는 지하수는 터널 시공성 및 안정성에 중요한 영향을 끼친다. 따라서 터널의 굴착 중 발생하는 지하수의 유입을 감소시키기 위한 적절한 차수그라우팅이 필요하다. 대부분 터널 설계단계에서는 Pre Grouting을 적용하고 있으나 그라우팅 재료 및 차수효과의 적정성에 대한 분석은 미미하다. 본 연구에서는 현장의 차수 그라우팅 시공사례를 분석하고, 실측된 시공자료를 바탕으로 시공개선사항 및 그라우팅 영역의 투수계수 감소를 고려한 수치해석을 통해 차수효과를 분석하였다.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2002년도 동계연구발표회 논문개요집
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• pp.66-67
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• 2002

Magnetic tunnel junction에서는 spin의 tunneling이 가장 기본적인 현상이기 때문에 tunnel junction의 특성은 tunnel barrier의 성질에 크게 의존한다. Tunnel barrier로는 지금까지 $Al_2$O$_3$가 주로 사용되고 있다. 하지만 $Al_2$O$_3$의 경우는 barrier height가 2-3 eV로 높기 때문에 저 저항의 tunnel junction을 형성하기 위해서는 Al의 두께가 1nm 이하로 낮아져야 한다. 따라서 이를 극복하기 위해서 $Al_2$O$_3$ 보다 낮은 barrier height를 갖는 절연막을 tunnel barrier로 사용하고자 하는 연구가 많이 진행되고 있다 (예를 들면 TaOx [1], ZrOx [2], GaOx [3], and HfOx [4]). (중략)

• 한국환경보건학회지
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• 제19권4호
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• pp.9-13
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• 1993

This paper describes the impact of reflected sound in tunnel. The impact of reflected sound is obtained from making a comparision between measurements of tunnel and bridge. Sound level of tunnel is higher than that of bridge because reflected sound is generated in tunnel. Road traffic noise cannot be freely propagated because there are many buildings in urban. Therefore, a tunnel effect is generated in urban road. The impact of reflected sound is generated not only in tunnel, but also in urban road. This study provides the basic data for tunneling work and noise control strategy in urban road.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2008년도 정기총회 및 학술발표대회
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• pp.541-544
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• 2008

Generally numerical analysis of tunnel lining, under dynamic loading condition, performed not considering pore pressure. But if tunnel excavated under the surface of water, such as bottom of the sea, the river bed, tunnel lining can take pore water pressure. It may be different from evaluated numerical analysis not considering pore pressure. Therefore tunnel design should consider effect of water pressure acting on tunnel lining.

• Ocean Systems Engineering
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• 제1권4호
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• pp.297-315
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• 2011

New applications of streamlined Autonomous Underwater Vehicles require an AUV capable of completing missions with both high-speed straight-line runs and slow maneuvers or station keeping tasks. At low, or zero, forward speeds, the AUV's control surfaces become ineffective. To improve an AUV's low speed maneuverability, while maintaining a low drag profile, through-body tunnel thrusters have become a popular addition to modern AUV systems. The effect of forward vehicle motion and sideslip on these types of thrusters is not well understood. In order to characterize these effects and to adapt existing tunnel thruster models to include them, an experimental system was constructed. This system includes a transverse tunnel thruster mounted in a streamlined AUV. A 6-axis load cell mounted internally was used to measure the thrust directly. The AUV was mounted in Memorial University of Newfoundland's tow tank, and several tests were run to characterize the effect of vehicle motion on the transient and steady state thruster performance. Finally, a thruster model was modified to include these effects.

• 한국전산유체공학회지
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• 제15권4호
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• pp.53-59
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• 2010

Preliminary design of a ground plate, a device installed close to the aircraft model for wind tunnel test to simulate the ground effect, was performed by a numerical simulation. A two-dimensional numerical study was performed initially to decide the optimal leading edge and flap configurations. Then, three-dimensional studies were conducted to decide the optimal flap deflection angle for pressure distribution reduction since the plate and the plate supporting system generate static pressure difference between the upper and lower flow regions. Three-dimensional simulation additionally studied the effect of the clearance between the plate and the wind tunnel side wall. For the efficiency of computation, half model was simulated and a symmetric boundary condition was applied on the center plane. Based on the preliminary design, a ground plate was designed, manufactured and tested at the Korea Aerospace Research Institute(KARI) wind tunnel. The measured pressure differences versus flap deflection angle agreed well with the predicted results.

• Wind and Structures
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• 제1권4호
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• pp.351-364
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• 1998

In wind tunnel experiments, the blockage effect is a very important factor which affects the test results significantly. A number of investigations into this problem, especially on the blockage correction of drag coefficient, have been carried out in the past. However, only a limited number of works have been reported on the wind tunnel blockage effect on wind-induced vibration although it is considered to be fairly important. This paper discusses the aerodynamic characteristics of the square model and square model with corner cut based on a series of the wind tunnel tests with various blockage ratios and angles of attack. From the test results, the aerodynamic behavior of square models with up to 10% blockage ratio are almost the same and square models with up to 10% blockage ratio can be tested as a group which behaves similarly.