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A Study of Stress Evolution During Construction of
Extra-Large Cross Section Railway Tunnels
(Key Laboratory of Transportation Tunnel Engineering, Ministry of Education, School of Civil Engineering, Southwest Jiaotong University, Chengdu 610031)
Abstract In order to study the stress evolution of a rock mass during tunnel construction, the curve, reflecting the three-dimensional stress of the rock mass, was utilized in combination with the Mohr-Coulomb criteria to demonstrate the stress path and define the safety factor. In this paper, using the Wumenshan Tunnel 2 as an example, FLAC3D software is applied to analyze the evolution of the stress path and safety factor during construction of an extra-large cross section railway tunnel. Results show that during construction of extra-large cross section railway tunnels, the following are true: the evolution of the stress path and safety factor of the rock mass at both sides of the tunnel acts with a certain degree of symmetry during partial construction; while advanced to monitoring points spaced at 3m, the stress value and safety factor at the monitoring points are sharply decreased due to excavation and the deflection of the principal stress takes place; after the completion of the primary support, the stress value and safety factor are certainly increased and tend to be stable; earlier installation of all primary supports is useful to control the evolution of rock stress; the safety factor at the sidewalls is less than 1.0 for a long time, to which more attention shall be paid; when the working face passes through each monitoring point, the safety factor measured at each monitoring point tends to be stable and more than 1.0, which shows the tunnel construction is safe based on this computation.
Abstract：
In order to study the stress evolution of a rock mass during tunnel construction, the curve, reflecting the three-dimensional stress of the rock mass, was utilized in combination with the Mohr-Coulomb criteria to demonstrate the stress path and define the safety factor. In this paper, using the Wumenshan Tunnel 2 as an example, FLAC3D software is applied to analyze the evolution of the stress path and safety factor during construction of an extra-large cross section railway tunnel. Results show that during construction of extra-large cross section railway tunnels, the following are true: the evolution of the stress path and safety factor of the rock mass at both sides of the tunnel acts with a certain degree of symmetry during partial construction; while advanced to monitoring points spaced at 3m, the stress value and safety factor at the monitoring points are sharply decreased due to excavation and the deflection of the principal stress takes place; after the completion of the primary support, the stress value and safety factor are certainly increased and tend to be stable; earlier installation of all primary supports is useful to control the evolution of rock stress; the safety factor at the sidewalls is less than 1.0 for a long time, to which more attention shall be paid; when the working face passes through each monitoring point, the safety factor measured at each monitoring point tends to be stable and more than 1.0, which shows the tunnel construction is safe based on this computation.
ZHAO ,
Bin,
Zhang-Hui-Jian etc
.A Study of Stress Evolution During Construction of
Extra-Large Cross Section Railway Tunnels
[J] MODERN TUNNELLING TECHNOLOGY, 2014,V51(1): 70-76
2014, Vol. 51 