Stability Analysis of Tunnel Face Reinforced with Longitudinal Fiberglass Dowels Together with Steel Pipe Umbrella
Abstract
:1. Introduction
2. Stability Analysis of the Tunnel Face Reinforced with Longitudinal Fiberglass Dowels Together with Steel Pipe Umbrella
2.1. The New Analytical Prediction Model
2.2. Power of the External Loads Pe
2.2.1. Power of the Soil Unit Weight
2.2.2. Power Induced by the Friction on Both Sides
2.2.3. Power Induced by the Vertical Stress on the Sliding Wedge Body
- (1)
- Both the beam theory and the theory of beam on Winkler elastic foundation are adopted to investigate the mechanical behavior and characteristics of advanced small pipes in tunnel construction. Beam theory is used to analyze the advanced small pipes that are embedded in soil in the front of the tunnel face, whereas the theory of beam on Winkler elastic foundation is used to analyze the advanced small pipes behind the tunnel face, as rendered in Figure 3.
- (2)
- It is assumed that the fixed end A has certain vertical displacement y0, which is a known value and is considered as the measured vault subsidence value.
- (3)
- The length of the advanced small pipes consists of two parts, which includes unsupported span (length in 1.5a, includes excavation footage 1.0a and the length 0.5a due to support delay effect) and the length of the wedge (length in l), as depicted in Figure 3. The symbol a denotes the excavation footage—that is, the length of the tunnel for each excavation.
- (4)
- In order to simplify the analysis, the horizontal projection length of advanced small pipes is considered.
- (1)
- The remaining length le of the pipe in soil is longer than the length l of the wedge (Type I). The stability analysis model I is shown in Figure 3a. The subgrade reaction force that acts on the wedge is p (triangular distribution).
- (2)
- The remaining length le of the pipe in soil is shorter than the length l of the wedge (Type II). The stability analysis model II is shown in Figure 3b. The load that acts on the wedge can be divided into two parts, one is the subgrade reaction force p (trapezium distribution) along the pipe and the other is the uniform load q that acts on the wedge.
- (1)
- For Type I, the control differential equations of the reinforced foundation beam for different segments are obtained as follows:
- (2)
- For Type II, the control differential equations of the reinforced foundation beam for different segments are obtained as follows:
2.2.4. Power Induced by the Longitudinal Fiberglass Dowels
2.3. Dissipation Power on Discontinuity Surface Pv
2.4. Critical Reinforcement Density of Longitudinal Fiberglass Dowels
3. Sensitivity Analysis
3.1. Longitudinal Fiberglass Dowels in the Excavation Face Alone
3.1.1. The Influence Rules of the Cover Depth on Limit Reinforcement Density
3.1.2. The Influence Rules of the Tunnel Shape on Limit Reinforcement Density
3.1.3. The Influence Rules of the Reinforcement Installation Interval on Limit Reinforcement Density
3.2. Longitudinal Fiberglass Dowels in the Excavation Face Together with Pre-Supports
4. Conclusions
- (1)
- The advanced pre-reinforcement structure of the steel pipe umbrella is considered as the beam on the Winkler elastic foundation, which shows that the existence of the steel pipe umbrella effectively reduces the vertical pressure exerted by overlaying ground. Under general conditions, with the increase in the length of the pre-reinforcement, its promoting effect on tunnel face stability is obvious. However, when the surplus length of the pre-reinforcement structure reaches the critical fracture length, the length of the pre-reinforcement structure on the stability of the tunnel face is no longer a key factor.
- (2)
- The strengthening effect of the longitudinal fiberglass dowels depends primarily on the tensile bearing capacity of the bolt or the bond strength of the ground–bolt interface. The ground extrusion in the front of the tunnel face is effectively reduced for the installation of longitudinal fiberglass dowels. Moreover, the limit reinforcement density of longitudinal fiberglass dowels is assessed under specific lengths with or without the consideration of the steel pipe umbrella.
- (3)
- The results indicate that the required reinforcement density does not increase significantly when the cover depth is greater than the width of the face. The C-D tunneling method is more stable than the full-face tunneling method and benching tunneling method. Moreover, the results show that large installation intervals of bolts require greater reinforcement density.
Author Contributions
Funding
Acknowledgments
Conflicts of Interest
References
- Wang, L.; Han, K.; Xie, T.; Luo, J. Calculation of Limit Support Pressure for EPB Shield Tunnel Face in Water-Rich Sand. Symmetry 2019, 11, 1102. [Google Scholar] [CrossRef] [Green Version]
- Mi, B.; Xiang, Y. Analysis of the Limit Support Pressure of a Shallow Shield Tunnel in Sandy Soil Considering the Influence of Seepage. Symmetry 2020, 12, 1023. [Google Scholar] [CrossRef]
- Al Hallak, R.; Garnier, J.; Leca, E. Experimental study of the stability of a tunnel face reinforced by bolts. Geotechnical aspects of underground construction in soft ground. Balkema Rotterdam 2000, 12, 65–68. [Google Scholar]
- Yoo, C. Finite-element analysis of tunnel face reinforced by longitudinal pipes. Comput. Geotech. 2002, 29, 73–94. [Google Scholar] [CrossRef]
- Yoo, C.; Shin, H.K. Deformation behaviour of tunnel face reinforced with longitudinal pipes-laboratory and numerical investigation. Tunn. Undergr. Space Technol. 2003, 18, 303–319. [Google Scholar] [CrossRef]
- Kamata, H.; Mashimo, H. Centrifuge model test of tunnel face reinforcement by bolting. Tunn. Undergr. Space Technol. 2003, 18, 205–212. [Google Scholar] [CrossRef]
- Oreste, P.P.; Peila, D.; Pelizza, S. Face reinforcement in deep tunnels. Felsbau 2004, 22, 20–25. [Google Scholar]
- Lee, I.M.; Lee, J.S.; Nam, S.W. Effect of seepage force on tunnel face stability reinforced with multi-step pipe grouting. Tunn. Undergr. Space Technol. 2004, 19, 551–565. [Google Scholar] [CrossRef]
- Hisatake, M.; Ohno, S. Effects of pipe roof supports and the excavation method on the displacements above a tunnel face. Tunn. Undergr. Space Technol. 2008, 23, 120–127. [Google Scholar] [CrossRef]
- Shin, J.H.; Choi, Y.K.; Kwon, O.Y.; Lee, S.D. Model testing for pipe-reinforced tunnel heading in a granular soil. Tunn. Undergr. Space Technol. 2008, 23, 241–250. [Google Scholar] [CrossRef]
- Song, K.I.; Cho, G.C.; Chang, S.B.; Lee, I.M. Beam-spring structural analysis for the design of a tunnel pre-reinforcement support system. Int. J. Rock Mech. Min. Sci. 2013, 59, 139–150. [Google Scholar] [CrossRef]
- Grasso, P.; Mahtab, A.; Ferrero, A.M.; Pelizza, S. The role of cable bolting in ground reinforcement. Soil Rock Improv. Undergr. Works 1991, 1, 127–138. [Google Scholar]
- Dias, D.; Kastner, R.; Jassionnesse, C. Sols renforcés par Boulonnage-Etude numérique et application au front de taille d’un tunnel profond. Géotechnique 2002, 52, 15–27. [Google Scholar] [CrossRef]
- Dias, D.; Kastner, R. Modélisation numérique de l’apport du renforcement par boulonnage du front de taille des tunnels. Can. Geotech. J. 2005, 42, 1656–1674. [Google Scholar] [CrossRef]
- Peila, D. A theoretical study of reinforcement influence on the stability of a tunnel face. Geotech. Geol. Eng. 1994, 12, 145–168. [Google Scholar] [CrossRef]
- Anagnostou, G.; Serafeimidis, K. The dimensioning of tunnel face reinforcement. In Proceedings of the 33rd ITA-AITES World Tunnel Congress; Barták, J., Hrdina, I., Romancov, G., Zlámal, J., Eds.; CRC Press (Taylor & Francis): Prague, Czech Republic, 2007; pp. 291–296. [Google Scholar]
- Anagnostou, G.; Perazzelli, P. Analysis method and design charts for bolt reinforcement of the tunnel face in cohesive-frictional soils. Tunn. Undergr. Space Technol. 2015, 47, 162–181. [Google Scholar] [CrossRef]
- Wong, H.; Subrin, D.; Dias, D. Extrusion movements of a tunnel head reinforced by finite length bolts-a closed-form solution using homogenization approach. Int. J. Numer. Anal. Methods Geomech. 2000, 24, 533–565. [Google Scholar] [CrossRef]
- Wong, H.; Subrin, D.; Dias, D. Convergence-confinement analysis of a bolt-supported tunnel using the homogenization method. Can. Geotech. J. 2006, 43, 462–483. [Google Scholar] [CrossRef]
Pre-Reinforcement Technology | Construction Safety | |||||
---|---|---|---|---|---|---|
Stable Arch | Stable Working Face | Stability of Arch Foot | Groundwater Control | |||
Advance payments | Advance bolt | √ | √ | |||
Pipe shed | √ | √ | ||||
Horizontal rotary jet pile | √ | √ | ||||
Reinforcement of excavated surfaces | Core soil reserved for annular excavation | √ | ||||
Shotcrete on excavated surface | √ | |||||
Anchor of excavated surface | √ | |||||
Grouting of excavated surfaces | √ | |||||
Reinforcement of arch foot | Anchor bolt reinforcement | √ | ||||
Reinforcement of locked pile | √ | |||||
Grouting reinforcement of arch foot | √ | |||||
Temporary inverted arch | √ | |||||
Groundwater control | Drainage measures | Surface drainage | √ | √ | √ | |
Drainage | √ | √ | √ | |||
Waterproofing measures | Grouting | √ | √ | √ | ||
Freeze | √ | √ | √ | |||
Formation reinforcement | Contact grouting | √ | √ | √ | ||
Full section grouting | √ | √ | √ | |||
Joint grouting | ||||||
Surface pre-grouting | √ | √ | √ | √ |
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Han, K.; Wang, X.; Hou, B.; Cao, C.-y.; Lin, X.-T. Stability Analysis of Tunnel Face Reinforced with Longitudinal Fiberglass Dowels Together with Steel Pipe Umbrella. Symmetry 2020, 12, 2069. https://doi.org/10.3390/sym12122069
Han K, Wang X, Hou B, Cao C-y, Lin X-T. Stability Analysis of Tunnel Face Reinforced with Longitudinal Fiberglass Dowels Together with Steel Pipe Umbrella. Symmetry. 2020; 12(12):2069. https://doi.org/10.3390/sym12122069
Chicago/Turabian StyleHan, Kaihang, Xuetao Wang, Beibei Hou, Cheng-yong Cao, and Xing-Tao Lin. 2020. "Stability Analysis of Tunnel Face Reinforced with Longitudinal Fiberglass Dowels Together with Steel Pipe Umbrella" Symmetry 12, no. 12: 2069. https://doi.org/10.3390/sym12122069