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Synthetical analysis on monitoring of Wushaoling railway tunnel
Tunnelling and Underground Space Technology incorporating Trenchless Technology Research
Tunnelling and Underground Space Technology 21 (2006) 363–364
www.elsevier.com/locate/tust
Synthetical analysis on monitoring of Wushaoling railway tunnel Zhichun Liu, Wenjiang Li, Sumin Zhang, Yongquan Zhu School of Civil Engineering, Shijiazhuang Railway Institute, Shijiazhuang, China
Comparison between the soft rock and rigid rock shows that the former has less elastic modulus and strength. Therefore, the deformation in soft-rock tunnel is much larger than in rigid-rock tunnel. The monitoring should be strengthened especially in the soft rock tunnel with large deformation, for there are no feasible measure in the current relative code for design and construction. Also, many inconsistencies exist between the code and the practice. Wushaoling railway tunnel, the longest single-track railway tunnel in China, is the key project of Lanzhou–Xinjiang railway line. It goes through four regional faults (F4–F7). The geological and geostress condition are complicated. According to the characteristics of soft rock tunnel with large deformation in the complicated stress field, the comprehensive monitoring is executed during the construction in Wushaoling tunnel. Based on the measured results of the settlement of arch crown, the horizontal convergence, the axial force of rock bolt, the surrounding rock pressure and the steel liner plate stress, followings are analyzed: shotcrete stress and the stress and pressure of secondary lining, the relation between surrounding rock pressure and displacement, the distribution rule of displacement, the coefficient of lateral pressure, the shared ratio of secondary lining pressure, the construction time of secondary lining, etc. Such information is feedback for the construction in time. The tunnel deformation is very large, and the max. horizontal convergence reaches to 1209.38 mm in left line of F7 fault, and the max. deformation rate is 167.53 mm. The tunnel has all characteristics of large-deformation tunnel, i.e. large deformation, high early deformation rate, and long duration. The max. of lining deformation is 13.30 mm. The max. of lateral pressure coefficient, i.e. k, is 1.563, the min. is 0.842. The max. of the shared ratio of secondary lining pressure, i.e. m, is 44.2%, the min. is 28.2%. The lining bears partial loading. The k and m are illustrated in Table 1. In large-deformation tunnel region, the construction time of secondary lining should be rectified according to the measured deformation. The construction time of secondary lining is shown in Table 2. Table 1 Statistical result of k and m Region
Line
k
m
F4 fault Silurian slate with phyllite rock F7 fault
Right line Right line Right line Left line
0.842 0.967 1.563 1.251
32.2% 28.2% 39.7% 44.2%
Table 2 The construction time of secondary lining Items
General deformation
Classification of large deformation I
II
III
UM/B UR/UL UM/UL VF/UM
<3% 80–90% 55–62% <0.5%
3–5% 70–80% 47–55% 0.5–1.0%
5–8% 65–75% 43–51% 0.5–1.5%
>8% 60–70% 39–47% 0.5–2.0%
Notes: where UM is monitoring deformation, and B is tunnel width, and UL is limit deformation after initial support construction, and UR is the actual deformation emerged before lining construction, and VF is deformation rate before lining construction. Because of the actual deformation (UR) consist of not only the monitoring deformation (UM), but also the elastic deformation and the lost deformation in measure, the UR is larger than UM. And UL can be worked out according to calculation and monitoring of each region. doi:10.1016/j.tust.2005.12.180
364
Abstracts / Tunnelling and Underground Space Technology 21 (2006) 363–364
The tunnel deformation has been controlled to a certain extent after modification of design and construction, and stabilization of the supporting structures. The measure has provided the basis of the modification of support parameters and the construction time of secondary lining. The results have given the basis data of subsequent research, and have accumulated experience of design and construction of very long tunnel on complicated geostress condition. Keywords: Soft rock tunnel with large deformation; Monitoring; Surrounding rock pressure; Construction time of secondary lining; Synthetical analysis
Tunnelling and Underground Space Technology 21 (2006) 363–364
www.elsevier.com/locate/tust
Synthetical analysis on monitoring of Wushaoling railway tunnel Zhichun Liu, Wenjiang Li, Sumin Zhang, Yongquan Zhu School of Civil Engineering, Shijiazhuang Railway Institute, Shijiazhuang, China
Comparison between the soft rock and rigid rock shows that the former has less elastic modulus and strength. Therefore, the deformation in soft-rock tunnel is much larger than in rigid-rock tunnel. The monitoring should be strengthened especially in the soft rock tunnel with large deformation, for there are no feasible measure in the current relative code for design and construction. Also, many inconsistencies exist between the code and the practice. Wushaoling railway tunnel, the longest single-track railway tunnel in China, is the key project of Lanzhou–Xinjiang railway line. It goes through four regional faults (F4–F7). The geological and geostress condition are complicated. According to the characteristics of soft rock tunnel with large deformation in the complicated stress field, the comprehensive monitoring is executed during the construction in Wushaoling tunnel. Based on the measured results of the settlement of arch crown, the horizontal convergence, the axial force of rock bolt, the surrounding rock pressure and the steel liner plate stress, followings are analyzed: shotcrete stress and the stress and pressure of secondary lining, the relation between surrounding rock pressure and displacement, the distribution rule of displacement, the coefficient of lateral pressure, the shared ratio of secondary lining pressure, the construction time of secondary lining, etc. Such information is feedback for the construction in time. The tunnel deformation is very large, and the max. horizontal convergence reaches to 1209.38 mm in left line of F7 fault, and the max. deformation rate is 167.53 mm. The tunnel has all characteristics of large-deformation tunnel, i.e. large deformation, high early deformation rate, and long duration. The max. of lining deformation is 13.30 mm. The max. of lateral pressure coefficient, i.e. k, is 1.563, the min. is 0.842. The max. of the shared ratio of secondary lining pressure, i.e. m, is 44.2%, the min. is 28.2%. The lining bears partial loading. The k and m are illustrated in Table 1. In large-deformation tunnel region, the construction time of secondary lining should be rectified according to the measured deformation. The construction time of secondary lining is shown in Table 2. Table 1 Statistical result of k and m Region
Line
k
m
F4 fault Silurian slate with phyllite rock F7 fault
Right line Right line Right line Left line
0.842 0.967 1.563 1.251
32.2% 28.2% 39.7% 44.2%
Table 2 The construction time of secondary lining Items
General deformation
Classification of large deformation I
II
III
UM/B UR/UL UM/UL VF/UM
<3% 80–90% 55–62% <0.5%
3–5% 70–80% 47–55% 0.5–1.0%
5–8% 65–75% 43–51% 0.5–1.5%
>8% 60–70% 39–47% 0.5–2.0%
Notes: where UM is monitoring deformation, and B is tunnel width, and UL is limit deformation after initial support construction, and UR is the actual deformation emerged before lining construction, and VF is deformation rate before lining construction. Because of the actual deformation (UR) consist of not only the monitoring deformation (UM), but also the elastic deformation and the lost deformation in measure, the UR is larger than UM. And UL can be worked out according to calculation and monitoring of each region. doi:10.1016/j.tust.2005.12.180
364
Abstracts / Tunnelling and Underground Space Technology 21 (2006) 363–364
The tunnel deformation has been controlled to a certain extent after modification of design and construction, and stabilization of the supporting structures. The measure has provided the basis of the modification of support parameters and the construction time of secondary lining. The results have given the basis data of subsequent research, and have accumulated experience of design and construction of very long tunnel on complicated geostress condition. Keywords: Soft rock tunnel with large deformation; Monitoring; Surrounding rock pressure; Construction time of secondary lining; Synthetical analysis