Mechanism of steel pipe reinforcement grouting based on tunnel field measurement results

Hyunkang Shin; Hyuksang Jung; Yong-joo Lee; Nag-young Kim; Sungil Ko

doi:10.9711/KTAJ.2021.23.3.133

All Issue

2021 Vol.23, Issue 3 Next Page

Research Paper

Mechanism of steel pipe reinforcement grouting based on tunnel field measurement results 터널 현장 계측결과를 통한 강관보강 그라우팅의 거동 메커니즘

31 May 2021. pp. 133-149

PDF XML

Abstract

This study aims to report the behavioral mechanism of steel pipe reinforcement grouting, which is being actively used to ensure the stability of the excavation surface during tunnel excavation, based on measurements taken at the actual site. After using a 12 m steel pipe attached with a shape displacement meter and a strain gauge to reinforce the actual tunnel surface, behavioral characteristics were identified by analyzing the measured deformation and stress of the steel pipe. Taking into account that the steel pipes were overlapped every 6 m, the measured data up to 7 m of excavation were used. In addition, the behavioral characteristics of the steel pipe reinforcement according to the difference in strength were also examined by applying steel pipes with different allowable stresses (SGT275 and SGT550). As a result of analyzing the behavior of steel pipes for 7 hours after the first excavation for 1 m and before proceeding with the next excavation, the stress redistribution due to the arching effect caused by the excavation relaxation load was observed. As excavation proceeded by 1 m, the excavated section exhibited the greatest deformation during excavation of 4 to 6 m due to the stress distribution of the three-dimensional relaxation load, and deformation and stress were generated in the steel pipe installed in the ground ahead of the tunnel face. As a result of comparing the behavior of SGT275 steel pipe (yield strength 275 MPa) and SGT550 steel pipe (yield strength 550 MPa), the difference in the amount of deformation was up to 18 times and the stress was up to 12 times; the stronger the steel pipe, the better it was at responding to the relaxation load. In this study, the behavior mechanism of steel pipe reinforcement grouting in response to the arching effect due to the relaxation load was identified based on the measured data during the actual tunnel excavation, and the results were reported.

Keywords

Tunnel

Arching effect

Steel pipe

The reinforcement grouting of steel pipe

The mechanism of reinforcement grouting of steel pipe

본 논문은 터널 굴착 시 굴착면의 안정성 확보를 위해 매우 활발히 적용되고 있는 강관보강 그라우팅의 거동 메커니즘을 실제 현장의 계측결과를 이용하여 연구한 결과를 수록하였다. 계측방법은 12 m의 강관에 형상변위계와 변형률계를 부착하여 실제 터널면에 보강을 시행한 다음 강관의 변형과 응력의 계측값을 분석하여 거동 특성을 파악하였으며, 6 m마다 강관이 중첩되는 것을 고려하여 7 m 굴착 시까지의 계측결과를 활용하였다. 또한, 허용응력이 다른 강관(SGT275와 SGT550)을 적용하여 강도차이에 따른 강관 보강재의 거동 특성도 확인하였다. 굴착면에 강관을 설치하고 최초 1 m 굴착 후 다음 굴착이 진행되기 전까지 7시간 동안의 강관 거동을 분석한 결과 굴착 이완하중에 따른 아칭효과로 응력이 재분배되는 거동 특성을 확인할 수 있었다. 1 m씩 굴착됨에 따라 3차원적인 이완하중의 응력분배로 인해 굴착된 구간은 4~6 m 굴착 시 가장 큰 변형을 나타내었다. 이러한 계측을 통해 굴착 전방지반의 설치된 강관에도 변형과 응력이 발생되는 것을 확인할 수 있었다. 또한, SGT275강관(항복강도 275 MPa)과 SGT550강관(항복강도 550 MPa)의 거동을 비교한 결과 변형량의 차이는 최대 18배, 응력은 최대 12배 정도 차이가 발생되어 강도가 큰 강관일수록 이완하중에 대응이 유리한 것으로 나타났다. 본 논문에서는 실제 터널 굴착에 따른 강관의 계측결과를 이용하여 이완하중의 아칭효과에 대응하는 강관 보강 그라우팅의 거동 메커니즘을 확인할 수 있었고, 그 결과를 본 논문에 수록하였다.

키워드

터널

아칭효과

강관 보강재

강관보강 그라우팅

터널 강관보강 메커니즘

References

Bae, G.J., Kim, C.Y., Moon, H.D., Hong, S.W. (1997), “A study on the ground movement around tunnel reinforced by umbrella arch method”, Tunnel and Underground Space, Vol. 7, No. 4, pp. 299-309.

Barisone, G., Pelizza, S., Pigorini, B. (1982), “Umbrella arch method for tunnelling in difficult conditions-analysis of Italian cases”, Proceedings of the 4th Congress of International Association for Engineering Geology, Vol. 4, New Delhi, pp. 15-27.

Choi, Y.K., Kim, C.Y., Han, M.H., Hwang, C.H. (1997), “Application of umbrella arch method for tunneling in the soft ground”, Journal of the Korean Geotechnical Society, Vol. 1997, No. 3, pp. 133-139.

Geo-Fronte Research Association (1994), Technical report on the Rodin Jet Fore-Poling (RJFP) method.

Kim, H.T. (1995), Application of nonlinear 3-D tunnel analysis program for the improved effects of steel pipe reinforced multi step grouting method, Master Thesis, Graduate School of Dankook University, pp. 5-52.

Kim, S.H., Moon, H.K. (2002), “A study on the reinforcement effect of umbrella arch method and prediction of tunnel crown settlement”, Journal of the Korean Society of Mineral and Energy Resources Engineers, Vol. 39, No. 3, pp. 197-205.

Muraki, Y. (1997), The umbrella method in tunnelling, Doctoral Thesis, Massachusetts Institute of Technology, pp. 34-52.

Pelizza, S., Peila, D. (1993), “Soil and rock reinforcements in tunnelling”, Tunnelling and Underground Space Technology, Vol. 8, No. 3, pp. 357-372. 10.1016/0886-7798(93)90020-V

Song, K.I., Cho, G.C. (2006), “Equivalent design parameter determination for effective numerical modeling of pre-reinforced zones in tunnel”, Journal of Korean Tunnelling and Underground Space Association, Vol. 8, No. 2, pp. 151-163.

Terzaghi, K. (1936), Stress distribution in dry and in saturated sand above a yielding trap-door, Proceedings of the First International Conference on Soil Mechanics and Foundation Engineering, Cambridge, Massachusetts, pp. 307-311.

Yoo, C.S., Shin, S.W., Kim, Y.J., Kim, Y.J. (1995), “Three-dimensional finite element analysis on tunnel behavior reinforced by umbrella arch method”, Proceedings of the Korean Geotechnical Society Conference, Seoul, pp. 97-102.

Information

Publisher :Korean Tunneling and Underground Space Association
Publisher(Ko) :한국터널지하공간학회
Journal Title :Journal of Korean Tunnelling and Underground Space Association
Journal Title(Ko) :한국터널지하공간학회 논문집
Volume : 23
No :3
Pages :133-149
Received Date : 2021-03-12
Revised Date : 2021-04-23
Accepted Date : 2021-04-23
DOI :https://doi.org/10.9711/KTAJ.2021.23.3.133

Journal of Korean Tunnelling and Underground Space Association ISSN:2233-8292(Print) 2287-4747(Online) 한국터널지하공간학회 논문집

All Issue