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Time effects in rock-support interaction: a case study in the construction of two road tunnels
ARTICLE IN PRESS
International Journal of Rock Mechanics & Mining Sciences 41 (2004) 540
SINOROCK2004 Paper 3B 20
Time effects in rock–support interaction: a case study in the construction of two road tunnels Ling Xu, Hongwei Huang* Department of Geotechnical Engineering, Tongji University, Shanghai, China
Abstract With the development of China, more and more rock road tunnels will be constructed. During design and construction, it is necessary to understand the mechanics of the tunnel structure in terms of time effects. These have been researched in rock over the years with most studies focussing on different kinds of rock in laboratory tests. There has been little research on time effects in situ. In this paper, the deformation and contact pressure with time during the construction of tunnels were analyzed. Two long rock road tunnels in Yunnan province, China, are taken as examples in this paper: one is Dafengyakou tunnel and the other is No.1 Yuanjiang tunnel, which are both double lane tunnels with separate up and down lines. Dafengyakou tunnel, about 3300 m long, and No.1 Yuanjiang tunnel, about 1000 m long, have the same net height 7.2 m and width 10.90 m. After the contact pressure between the initial and secondary lining, and crown displacement of the initial lining were analyzed, the time effect was carefully investigated. For example, the change of contact pressure with time can be divided into two stages, and in both stages, the change satisfies a hyperbolic rule. The typical increment of contact pressure in the second stage is shown in Fig. 1, where the numbers, such as 1695, 1654, etc., are the codes of the pressure cells. The relation between crown displacement and time satisfies an exponential rule. The time-dependent modulus of concrete, rock creep and tunnel excavation can cause large changes in the contact pressure. For the deformation of the initial lining, the reinforcement adopted can decrease the ultimate value but, because of the inherent characteristic of the weak rock and abundant underground water, the deformation requires a long period to become stable. The obtained conclusions will be helpful for the future construction of rock road tunnels in China.
Increment of contact pressure (MPa)
Keywords: Rock tunnel; Deformation; Contact pressure; Creep; Time-dependent; Time effect
0.12 1695 1654 1681 1634 1690 Fitting curve of 1695 Fitting curve of 1654 Fitting curve of 1681 Fitting curve of 1634 Fitting curve of 1690
0.1 0.08 0.06 0.04 0.02 0 -0.02 0
100
200
300 400 500 Increment of time (days)
600
700
800
Fig. 1. Typical curves of the contact pressure between the initial and secondary lining versus time.
*Corresponding author. Tel./fax: +86-21-65982986. E-mail address: [email protected] (H. Huang). For full length paper see CD-ROM attached. doi:10.1016/j.ijrmms.2003.12.128
International Journal of Rock Mechanics & Mining Sciences 41 (2004) 540
SINOROCK2004 Paper 3B 20
Time effects in rock–support interaction: a case study in the construction of two road tunnels Ling Xu, Hongwei Huang* Department of Geotechnical Engineering, Tongji University, Shanghai, China
Abstract With the development of China, more and more rock road tunnels will be constructed. During design and construction, it is necessary to understand the mechanics of the tunnel structure in terms of time effects. These have been researched in rock over the years with most studies focussing on different kinds of rock in laboratory tests. There has been little research on time effects in situ. In this paper, the deformation and contact pressure with time during the construction of tunnels were analyzed. Two long rock road tunnels in Yunnan province, China, are taken as examples in this paper: one is Dafengyakou tunnel and the other is No.1 Yuanjiang tunnel, which are both double lane tunnels with separate up and down lines. Dafengyakou tunnel, about 3300 m long, and No.1 Yuanjiang tunnel, about 1000 m long, have the same net height 7.2 m and width 10.90 m. After the contact pressure between the initial and secondary lining, and crown displacement of the initial lining were analyzed, the time effect was carefully investigated. For example, the change of contact pressure with time can be divided into two stages, and in both stages, the change satisfies a hyperbolic rule. The typical increment of contact pressure in the second stage is shown in Fig. 1, where the numbers, such as 1695, 1654, etc., are the codes of the pressure cells. The relation between crown displacement and time satisfies an exponential rule. The time-dependent modulus of concrete, rock creep and tunnel excavation can cause large changes in the contact pressure. For the deformation of the initial lining, the reinforcement adopted can decrease the ultimate value but, because of the inherent characteristic of the weak rock and abundant underground water, the deformation requires a long period to become stable. The obtained conclusions will be helpful for the future construction of rock road tunnels in China.
Increment of contact pressure (MPa)
Keywords: Rock tunnel; Deformation; Contact pressure; Creep; Time-dependent; Time effect
0.12 1695 1654 1681 1634 1690 Fitting curve of 1695 Fitting curve of 1654 Fitting curve of 1681 Fitting curve of 1634 Fitting curve of 1690
0.1 0.08 0.06 0.04 0.02 0 -0.02 0
100
200
300 400 500 Increment of time (days)
600
700
800
Fig. 1. Typical curves of the contact pressure between the initial and secondary lining versus time.
*Corresponding author. Tel./fax: +86-21-65982986. E-mail address: [email protected] (H. Huang). For full length paper see CD-ROM attached. doi:10.1016/j.ijrmms.2003.12.128