• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1999년도 봄 학술발표회 논문집
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• pp.323-330
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• 1999

Daylight collapse have been occurred by about 5.0m deep at ground surface and collapse of the crown head part of the tunnel have connected to the ground surface during first step of shotcrete work after blasting of upper half section of the tunnel driving at two-way double track tunnel face section on highway construction. This study is for a successful illustration case for the earth improvement method through applying such strengthening methods as cement milk grouting, S.G.R grouting,, steel pipe reinforced multi-step grouting etc. for the purpose of earth strengthening of loosened earth block occurred by tunnel collapse.

• 한국지반신소재학회논문집
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• 제9권4호
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• pp.47-55
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• 2010

일반적으로 초연약지반에서는 건설장비의 주행성 확보 등을 위하여 토목섬유와 같은 표층 보강재를 적용하게 된다. 그러나 최근 토목섬유로 표층 처리된 초연약지반의 거동에 관한 많은 고찰이 수행되어 왔지만 대부분의 연구에서 토목섬유와 지반의 경계조건을 적절히 표현하지 못하고 있는 실정이다. 따라서 본 연구에서는 토목섬유와 지반의 경계조건이 토목섬유로 표층처리된 초연약지반의 거동에 미치는 영향에 대하여 수치해석적 고찰을 수행하였다. 수치해석에서는 토목섬유와 지반의 마찰에 대한 경계조건을 다양하게 표현하기 위하여 조인트 요소를 적용하였다. 수치해석의 결과는 기존의 실내모형실험 결과와의 비교를 통하여 그 신뢰성을 검증하였으며 파라메트릭 스터디를 통하여 토목섬유와 지반의 경계조건에 따른 초연약지반의 거동을 규명하였다.

• Geomechanics and Engineering
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• 제24권5호
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• pp.491-503
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• 2021

Shallow tunnels are vulnerable to earthquakes, and shallow ground is usually inhomogeneous. Based on the limit equilibrium method and variational principle, a solution for the seismic collapse mechanism of shallow tunnel in inhomogeneous ground is presented. And the finite difference method is employed to compare with the analytical solution. It shows that the analytical results are conservative when the horizontal and vertical stresses equal the static earth pressure and zero at vault section, respectively. The safety factor of shallow tunnel changes greatly during an earthquake. Hence, the cyclic loading characteristics should be considered to evaluate tunnel stability. And the curve sliding surface agrees with the numerical simulation and previous studies. To save time and ensure accuracy, the curve sliding surface with 2 undetermined constants is a good choice to analyze shallow tunnel stability. Parameter analysis demonstrates that the horizontal semiaxis, acceleration, ground cohesion and homogeneity affect tunnel stability greatly, and the horizontal semiaxis, vertical semiaxis, tunnel depth and ground homogeneity have obvious influence on tunnel sliding surface. It concludes that the most applicable approaches to enhance tunnel stability are reducing the horizontal semiaxis, strengthening cohesion and setting the tunnel into good ground.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1999년도 연약지반처리위원회 학술세미나
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• pp.14-22
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• 1999

Daylight collapse have been occurred by about 6.$^{0}$ m deep at ground surface which connected to the ground surface and excessive overbreak have been occurred by the space and height of 3.$^1$~6.$^2$m at crown head part of the tunnel during tunnelling of lower-half part after completing upper-half part on tunnelling of a phyllite mountain by NATM method at the construction work of two way-double track national road. This study is a successful illustration case of earth improvement by confirming structural safety of the tunnel in a whole through solving the cause of the tunnel collapse and the work have completed successfully through applying such earth strengthening method as cement mortarㆍcement milk injection, S.G.R, steel pipe reinforced multi-step grouting etc.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.1256-1263
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• 2010

Suction Drain Method is soft ground improvement technique, in which a vacuum pressure can be directly applied to the Vertical Drain Board to promote consolidation and strengthening the soft ground. This method does not require a surcharge load, different to embankment or Preloading Method. In this study, ground improvement efficiency of suction drain method was estimated when duplex loading pressure with vacuum and pressure. During suction drain method process, surface settlement and pore pressure were monitored, and cone resistance test as well as water content were also measured after the completion of Suction Drain Method treatment.

• Structural Engineering and Mechanics
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• 제23권1호
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• pp.43-61
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• 2006

An investigation of the effectiveness of the interface treatment when column concrete jacketing is performed is presented. Alternative methods of interface connection were used in order to investigate the performance of strengthened concrete columns. These connecting techniques involved roughening the surface of the original column, embedding steel dowels into the original column and a combination of these two techniques. The experimental program included three strengthened specimens, one original specimen (unstrengthened) and one as-built specimen (monolithic). The specimens represented half height full-scale old Greek Code (1950's) designed ground floor columns of a typical concrete frame building. The jackets of the strengthened specimens were constructed with shotcrete. All specimens were subjected to displacement controlled earthquake simulation loading. The seismic performance of the strengthened specimens is compared to both the original and the monolithic specimens. The comparison was performed in terms of strength, stiffness and hysteretic response. The results demonstrate the effectiveness of the strengthening methods and indicate that the proper construction of a jacket can improve the behaviour of the specimens up to a level comparable to monolithic behaviour. It was found that different methods of interface treatment could influence the failure mechanism and the crack patterns of the specimens. It was also found that the specimen that combined roughening with dowel placement performed the best and all strengthened columns were better at dissipating energy than the monolithic specimen.

• 한국지반신소재학회논문집
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• 제8권3호
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• pp.9-16
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• 2009

최근 우리나라에서 활발히 진행되고 있는 준설매립 공사에서는 일반적으로 시공 장비의 주행성을 확보하기 위한 표층처리공법으로써 지오텍스타일을 부설하는 경우가 많다. 지오텍스타일이 부설된 초연약점토지반의 지지력의 계산은 기존에 몇 가지 제안되어 있지만 아직 명확히 확립되어있지 않기 때문에 시공실적에 기초한 경험적인 방법이 사용되고 있는 실정이다. 본 논문에서는 지오텍스타일이 부설된 초연약지반의 합리적인 지지력 산정방법 확립의 일환으로 일련의 수치해석을 실시하였다. 수치해석결과 초연약지반의 표층을 지오텍스타일로 보강함으로써 초연약지반의 항복 후에도 개량된 지반의 지반응력은 증가함을 알 수 있었으며 지요텍스타일에서 발생되는 최대인장응력은 하중이 증가함에 따라 재하 끝단부에서 크게 발생됨을 알 수 있었다.

• The Journal of Korean Physical Therapy
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• 제27권4호
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• pp.228-233
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• 2015

Purpose: Gait is the most basic element when evaluating the quality of life with activities of daily living under ordinary life circumstances. Symmetrical use of the lower extremities requires complicated coordination of all limbs. Thus, this study examined asymmetry of muscle activity quadriceps femoris and tibialis anterior as a baseline for training during over-ground walking and stair walking of stroke patients. Methods: Subjects were 14 stroke patients included as one experimental group. Gait speed used in this study was determined by the subject. Low extremity paretic and non-paretic EMG was compared using the surface EMG system. Results: The low extremity EMG difference was statistically significant during over-ground walking and stair walking (p<0.05). The result of low extremity EMG substituted symmetry ratio formula was compared to EMG symmetry ratio in both legs during over-ground walking and stair walking. The average symmetry ratio of quadriceps femoris during over-ground walking was 0.65, and average symmetry ratio of quadriceps femoris during stair walking was 0.47, with significant difference (p<0.05). Conclusion: EMG data was higher in stair walking than over-ground walking. However, in the comparison of symmetry ratio, asymmetric EMG of quadriceps femoris was significantly increased during stair walking. These findings suggested that application of stair walking for strengthening of both legs can be positive, but the key factor is maintaining asymmetrical posture of both legs. Therefore, physical therapists should make an effort to reduce asymmetry of quadriceps femoris power during stair walking by stroke patients.