쏘일네일링 공법을 도심지 지하굴착 공사에 있어, 지중매설물이 인접하여 존재하거나 대지경계선 등의 준수 등 시공조건에 따라서 설치네일의 길이가 제한되는 경우 및 연약한 지반을 보강할 경우 등과 같은 벽체변위 및 지표침하 억제와 안정성 증대 등을 위하여, 지반앵커공법과 유사한 프리텐션 방식의 도입이 필요한 실정이다. 지반앵커공법과 유사한 프리텐션 방식의 쏘일네일링 공법을 도입하게 될 경우, 단계별 굴착시 발생하는 변위를 최소화할 수 있을 것으로 예상되며 국부적인 안정성도 증대할 것으로 사료된다. 따라서, 본 연구에서는 단계별 굴착시 유발되는 벽체변위 및 침하량 등을 억제하기 위한 노력의 일환으로, 프리텐션 쏘일네일링 시스템을 개발하였다. 또한 최대 프리텐션하중 및 프리텐션 시스템의 안정성을 평가하기 위해, 영향원 반경, 다이레이턴시 각, 정착길이 등을 반영한 설계기법을 제안하였으며, 펀칭전단파괴에 저항할 수 있는 숏크리트의 요구두께를 결정하는 신뢰도 평가기법을 제안하였다. 아울러 설계예제와 $FLAC^{2D}$ 프로그램 수치해석을 통해 프리텐션에 의한 변위 감소효과를 살펴봤으며, 전단강도감소기법을 도입한 안정해석이 $FLAC^{2D}$ 프로그램을 토대로 수행되었다.
쏘일네일링 공법을 도심지 지하굴착 공사에 있어, 지중매설물이 인접하여 존재하거나 대지경계선 등의 준수 등 시공조건에 따라서 설치네일의 길이가 제한되는 경우 및 연약한 지반을 보강할 경우 등과 같은 벽체변위 및 지표침하 억제와 안정성 증대 등을 위하여, 지반앵커공법과 유사한 프리텐션 방식의 도입이 필요한 실정이다. 지반앵커공법과 유사한 프리텐션 방식의 쏘일네일링 공법을 도입하게 될 경우, 단계별 굴착시 발생하는 변위를 최소화할 수 있을 것으로 예상되며 국부적인 안정성도 증대할 것으로 사료된다. 따라서, 본 연구에서는 단계별 굴착시 유발되는 벽체변위 및 침하량 등을 억제하기 위한 노력의 일환으로, 프리텐션 쏘일네일링 시스템을 개발하였다. 또한 최대 프리텐션하중 및 프리텐션 시스템의 안정성을 평가하기 위해, 영향원 반경, 다이레이턴시 각, 정착길이 등을 반영한 설계기법을 제안하였으며, 펀칭전단파괴에 저항할 수 있는 숏크리트의 요구두께를 결정하는 신뢰도 평가기법을 제안하였다. 아울러 설계예제와 $FLAC^{2D}$ 프로그램 수치해석을 통해 프리텐션에 의한 변위 감소효과를 살펴봤으며, 전단강도감소기법을 도입한 안정해석이 $FLAC^{2D}$ 프로그램을 토대로 수행되었다.
The ground anchor support system may not be occasionally used because of space limitations in urban excavation sites nearby the existing structures. In this case, soil nailing system with relatively short length of nails could be efficiently adopted as an alternative method. The general soil nailing...
The ground anchor support system may not be occasionally used because of space limitations in urban excavation sites nearby the existing structures. In this case, soil nailing system with relatively short length of nails could be efficiently adopted as an alternative method. The general soil nailing support system, however, may result in excessive deformations particularly in an excavation zone of the existing weak subsoils. Pretensioning the soil nails then could play important roles to reduce deformations mainly in the upper part of the nailed-soil excavation system as well as to improve local stability. In this study, a newly modified soil nailing technology named as the PSN (Pretension Soil Nailing), is developed to reduce both facing displacements and ground surface settlements in top-down excavation process as well as to increase the global stability. Up to now, the analytical procedure and design technique are proposed to evaluate maximum pretension force and stability of the PSN system. Also, proposed are techniques to determine the required thickness of a shotcrete facing and to estimate probability of a failure against the punching shear, Based on the proposed procedure and technique, effects of the radius of a influence circle and dilatancy angle on the thickness of a shotcrete facing, bonded length and safety factors are analyzed. In addition, effects of the reduction of deformations expected by pretension of the soil nails are examined in detail throughout an illustrative example and the $FLAC^{2D}$ program analysis. And a numerical approach is proposed PSN system using the shear strength reduction technique with the $FLAC^{2D}$ program.
The ground anchor support system may not be occasionally used because of space limitations in urban excavation sites nearby the existing structures. In this case, soil nailing system with relatively short length of nails could be efficiently adopted as an alternative method. The general soil nailing support system, however, may result in excessive deformations particularly in an excavation zone of the existing weak subsoils. Pretensioning the soil nails then could play important roles to reduce deformations mainly in the upper part of the nailed-soil excavation system as well as to improve local stability. In this study, a newly modified soil nailing technology named as the PSN (Pretension Soil Nailing), is developed to reduce both facing displacements and ground surface settlements in top-down excavation process as well as to increase the global stability. Up to now, the analytical procedure and design technique are proposed to evaluate maximum pretension force and stability of the PSN system. Also, proposed are techniques to determine the required thickness of a shotcrete facing and to estimate probability of a failure against the punching shear, Based on the proposed procedure and technique, effects of the radius of a influence circle and dilatancy angle on the thickness of a shotcrete facing, bonded length and safety factors are analyzed. In addition, effects of the reduction of deformations expected by pretension of the soil nails are examined in detail throughout an illustrative example and the $FLAC^{2D}$ program analysis. And a numerical approach is proposed PSN system using the shear strength reduction technique with the $FLAC^{2D}$ program.
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문제 정의
In the present study, analytical design procedures are proposed to evaluate the maximum pretension forces and to estimate local or overall stability of the PSN system. Also this study dealt with a determination of the required thickness of the shotcrete facing. In addition, modified facing wall system (Hand Lay Up (HLU) board + shotcrete / Sheet M이d Compound (SMC) board + shotcrete) is proposed focusing on a failure against the punching shear.
제안 방법
Since full-scale experimental data are not presently available, restricted analysis data obtained from the numerical analysis are performed in the present study. Based on the proposed procedure and technique, effects of the thickness of a shotcrete facing, bonded length and safety factors on pretension force are analyzed. In addition, effects of the reduction of deformations expected by pretension of the soil nails are examined in detail throughout an illustrative example and FLAC2。program analysis.
In addition, effects of the reduction of deformations expected by pretension of the soil nails are examined in detail throughout an illustrative example and FLAC2。program analysis. And a numerical approach is further made to determine a postulated failure surface as well as a minimum safety factor of the proposed PSN system using the shear strength reduction technique and the FLAC20 program. Global minimum safety factors and local safety factors at various excavation stages computed in case of the PSN system are analyzed through comparisons with the results expected in the case of the general soil nailing system.
And a numerical approach is further made to determine a postulated failure surface as well as a minimum safety factor of the proposed PSN system using the shear strength reduction technique and the FLAC20 program. Global minimum safety factors and local safety factors at various excavation stages computed in case of the PSN system are analyzed through comparisons with the results expected in the case of the general soil nailing system. Based on the soil properties and geometric conditions described in Table 1 and Fig.
Since full-scale experimental data are not presently available, restricted analysis data obtained from the numerical analysis are performed in the present study. Applying the maximum pretension forces and the required thickness of the shotcrete facing evaluated on the basis of the proposed procedures, the FLACfD program analyses are performed at every excavation stages to estimate accumulated deformations. As clearly observed in Fig.
In the present study, analytic시 design procedures are proposed to evaluate the maximum pretension forces that can be applied to the corresponding nails, and to estimate local or global stability of the PSN system, includiii응 a determination of the required thickness of the shotcrete facing. Validity of the proposed procedures is examined comparing with data obtained from the shear strength reduction technique with the FLACeD program. As an efficient resolution of the excessive facing thickness due to the additionally applied pretension force, modified facing wall system is also proposed.
이론/모형
2%. Also, it agrees with the results analyzed by shear strength reduction technique which is proposed in this study. While, in the case of prestressed nail which is installed 1st to 5 th step, it is estimated that the shotcreted facing of the PSN system may require more thickness about 1.
성능/효과
40 which is not applied pretension force. But, in each step of the excavation, the effective range of local increment of safety factor was estimated by fair value of 28.6% to 49.2%. Also, it agrees with the results analyzed by shear strength reduction technique which is proposed in this study.
참고문헌 (10)
FHWA, Manual for Design and Construction Monitoring of Soil Nail Walls, Publication No. FHWA-SA-96-069, pp.63-136
Hanna, A. and Ghaly, A. (1994), 'Ultimate Pullout Resistance of Groups of Vertical Anchors', Canadian Geotechnical Journal, Vol.31, pp.673-682
Juran, I., Elias, V. (1990), Behavior and Working Stress Design of Soil Nailed Retaining Structure, Performance of Reinforced Soil Structures, British Geotechnical Society, Thomas Telford, pp. 207-212.
Kim, H. T. et al. (1995), 'A Prediction of the Mobilized Tensile Forces of Nailed-soil Excavated Wall', Journal of the Korean Geotechnical Society, Vol.11, No.2, pp.79-97
Kim, H. T. and Park, S. S. (2004), 'Stability Analysis and Application Evaluation of the Pretension Soil Nailing System', proc. of the Korean Geotechnical Society Spring Conference, Seoul, pp.783-790
Liang, Y. R. and Feng, Y. X. (1997), 'Development and Application of Anchor-Soil Interface Models', A Short Course on Soil Nailing, Ground Anchoring, and Anchored Excavation, The Graduate School of Industrial Technology and Environment, Dongguk University
Park, Si-Sarn (2003), Stability Analysis and Application of the Pretension Soil Nailing Systems, Ph.D Thesis, Department of Civil Engineering, Hongik University, Seoul, Korea.
Schlosser, F. (1991), Recommendations CLOUTEREE ; Soil Nailing Recommendations, French National Research Project Report, No. FHWA-SA-93-026
Schlosser, F. and Unterreiner, P. (1991), 'Soil Nailing in France ; Research and Practice', Transportation Research Record, No.1330, pp.72-79
Vermeer, P. A. and Borst, R. (1998), 'Non-Associated Plasticity for Soils, Concrete and Rock', NATO ASI series. Series E, Applied sciences, Vol.350, pp.163-196
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