Optimum Reinforcement Conditions of Large Diameter Reinforcement for Steep Slope of Conventional Railway Embankment under Train Loading

Chang-Won Kwak; Dae-Sang Kim

doi:10.7843/kgs.2016.32.11.43

All Issue

2016 Vol.32, Issue 11 Preview Page Next Page

Optimum Reinforcement Conditions of Large Diameter Reinforcement for Steep Slope of Conventional Railway Embankment under Train Loading 기존선 성토사면 급구배화를 위한 열차 하중 하 대구경 봉상보강재의 최적 보강조건

30 November 2016. pp. 43-50

PDF XML

Abstract

A reinforcement is required to ensure the structural safety in case of railway embankment excavation under railway load. A large diameter soil nailing with concrete wall is applied as the reinforcement method instead of the conventional soil nailing system. In this study, a series of 3 dimensional numerical analyses are performed to investigate the optimum reinforcement considering 15 different conditions based on the length, lateral spacing, diameter, and inclination of the reinforcement. The interface between soil nail and perimetric grout is considered by means of cohesion, stiffness and perimeter of the grout. 0.3 m of reinforcement diameter is assessed as the most appropriate based on the economical viewpoint though ground displacement decreases with the increase of diameter, however the difference of displacement is negligible between 0.4 m and 0.3 m of diameter. Surface settlement, lateral displacement of wall, and stress of reinforcement are calculated and economic viewpoint to reinforce embankment considered. Consequently, the optimum reinforcement conditions considering those factors are evaluated as 3 m in length, 0.3 m in diameter, 1.5 m in lateral spacing, and 10 degree of inclination angle in the case of 3 m of excavation depth. Additionally, inclined potential failure surface occurs with approximately 60 degrees from the end of nails and the surface settlement and wall lateral displacement are restrained successfully by the large diameter soil nailing, based on the result of shear strain rate.

Keywords

Railway embankment

Large diameter soil Nailing

3 Dimensional Numerical Analysis

Optimum Reinforcement

철도하중을 지지하고 있는 성토사면을 연직으로 굴착할 경우 철도노반의 안정성 확보를 위하여 보강이 필요하다. 본 연구에서는 사면굴착 후 전면 벽체를 형성하고, 통상적으로 사용되고 있는 쏘일네일링 시스템보다 짧으면서도 대구경인 봉상보강재를 적용하여 보강재의 길이, 수평 간격, 직경 및 설치 각도를 기준으로 총 15개 Case로 구분하여 각각에 대하여 조건별 안정성을 3차원 수치해석을 이용하여 검토하였다. 수치해석시 보강재와 주변 그라우팅과의 접촉면을 고려하기 위하여 그라우트재의 점착력과 강성 및 주면장을 고려하였다. 굴착심도 3m인 경우, 그라우트 직경 변화에 따른 변위해석 결과 보강재 직경이 커질수록 변위가 감소하나 직경 0.3m일 경우와 0.4m일 경우의 변위 차이가 미소하므로 경제성을 고려한다면 직경 0.3m가 가장 적합한 것으로 검토되었다. 보강재 조건별로 굴착 시 지표면 침하량과 벽체의 수평변위 및 보강재의 응력 및 경제성을 수치해석적으로 검토한 결과, 보강재 길이 3m, 직경 0.3m, 수평간격 1.5m, 경사각도 10도로 보강재를 배치하는 것이 최적의 조건으로 검토되었다. 또한 보강노반의 잠재적인 파괴면은 보강재 끝단에서 약 60도의 경사면으로 나타났으며, 철도하중 재하 시 보강재가 지표침하 및 벽체 수평변위를 안정적으로 억제하고 있는 것으로 판단되었다.

References

1.Fan, C.C. and Luo, J.H. (2008), “Numerical Study on the Optimum Layout of Soil-nailed Slopes”, Computers and Geotechnics, Vol. 35, pp.585-599.

2.FLAC3D User’s Guide. (2005), Itasca Consulting Group, Minneapolis, Minnesota.

3.Hang, M., Song, E., and Chen, Z. (1999), “Ground Movement Analysis of Soil Nailing Construction by Three-dimensional (3-D) Finite Element Modeling (FEM)”, Computers and Geotechnics, Vol.25, pp.191-204.

4.Juran, I., Baudrand, G., Farrag, K., and Elias, V. (1990), “Kinematical Limit Analysis for Design of Soil-nailed Structures”, Journal of geotechnical engineering, Vol.116, No.1, pp.54-72.

5.Manual for Design & Construction Monitoring of Soil Nail Walls, Federal Highway Administration, 1996, US Department of Trans-portation, pp.11-51.

6.Michalowski, R. L. (1998), “Limit Analysis in Stability Calculations of Reinforced Soil Structures”, Geotextiles and Geomembranes, Vol.16, No.6, pp.311-331.

7.Ministry of Land, Transport and Maritime Affairs. (2011), “Railway design standards”, pp.8-31-43.

8.Rabie, M. (2016), “Performance of Hybrid MSD/Soil Nail Walls Using Numerical Analysis and Limit Equilibrium Approaches”, HBRC Journal, Vol.12, pp.63-70.

9.Smith, I.M. and Su, N. (1997), “Three-dimensional FE Analysis of a Nailed Soil Wall Curved in Plan”, International Journal for Numerical and Analytical Methods in Geomechanics, Vol.21, No.9, pp.583-597.

10.Unterreiner, P., Benhamida, B., and Schlosser, F. (1997), “Finite Element Modelling of the Construction of a Full-scale Experimental Soil-nailed Wall”, French National Research Project CLOUTERRE. Proceedings of the Institution of Civil Engineers-Ground Improvement, Vol.1, No.1, pp.1-8.

11.Wei, W.B. and Cheng, Y.M. (2010), “Soil Nailed Slope by Strength Reduction and Lmit Equilibrium Methods”, Computers and Geotechnics, Vol.37, No.5, pp.602-618.

12.Yang, M.Z. and Drumm, E.C. (2000), “Numerical Analysis of the Load Transfer and Deformation in a Soil Nailed Slope”, Numerical Methods in Geotechnical Engineering, pp.102-115.

13.Yuan, J.X., Yang, Y., Tham, L.G., Lee, P.K.K., and Tsui, Y. (2003), “New Approach to Limit Equilibrium and Reliability Analysis of Soil Nailed Walls”, International Journal of Geomechanics, Vol. 3, No.2, pp.145-151.

Information

Publisher :The Korean Geotechnical Society
Publisher(Ko) :한국지반공학회
Journal Title :Journal of the Korean Geotechnical Society
Journal Title(Ko) :한국지반공학회 논문집
Volume : 32
No :11
Pages :43-50
Received Date : 2016-08-11
Revised Date : 2016-10-17
Accepted Date : 2016-11-01
DOI :https://doi.org/10.7843/kgs.2016.32.11.43

Journal of the Korean Geotechnical Society ISSN:1229-2427(Print) 2288-646X(Online) 한국지반공학회 논문집

All Issue