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Control Values and Influence Factors of a Water Head of the Secondary Lining in a Bored Subway Tunne
(1 School of Civil Engineering and Transportation, South China University of Technology, Guangzhou 510640; 2 State Key Laboratory of Subtropical Architecture Science, South China University of Technology, Guangzhou 510640)
Abstract Based on the features of secondary lining structures of bored subway tunnels in Guangzhou, the asymp?
totic failure process of secondary linings under external water pressure was studied through three-dimensional numerical simulation, corresponding control values of the water head of each force stage were obtained, and sensitivity analysis was conducted for parameters affecting control values of the water heads. Based on the measured results at the site, an analytic demonstration was carried out regarding the main reasons for the local collapse of the secondary lining of a certain bored subway tunnel. The results show that: 1) the water head of a secondary lining of a common single line bored tunnel of Guangzhou metro is 30 m under initial cracking; 2) cracking depth exceeds the thickness of the protective layer if the water head goes beyond 47 m; 3) concrete is crushed if the water head is more than 90m; 4) the reinforcement yields if the water head is larger than 90 m and the crack cuts through the section if the water head is larger than 95 m; 5) the control value of the water head should be set to 47 m to guarantee the durability of the secondary lining; 6) the control values could be improved effectively with reasonable reinforcement and thickness of the secondary lining; and 7) the main cause for local collapse of the secondary lining of a certain bored subway tunnel is insufficient thickness of the secondary lining under high external water pressure.
Abstract：
Based on the features of secondary lining structures of bored subway tunnels in Guangzhou, the asymp?
totic failure process of secondary linings under external water pressure was studied through three-dimensional numerical simulation, corresponding control values of the water head of each force stage were obtained, and sensitivity analysis was conducted for parameters affecting control values of the water heads. Based on the measured results at the site, an analytic demonstration was carried out regarding the main reasons for the local collapse of the secondary lining of a certain bored subway tunnel. The results show that: 1) the water head of a secondary lining of a common single line bored tunnel of Guangzhou metro is 30 m under initial cracking; 2) cracking depth exceeds the thickness of the protective layer if the water head goes beyond 47 m; 3) concrete is crushed if the water head is more than 90m; 4) the reinforcement yields if the water head is larger than 90 m and the crack cuts through the section if the water head is larger than 95 m; 5) the control value of the water head should be set to 47 m to guarantee the durability of the secondary lining; 6) the control values could be improved effectively with reasonable reinforcement and thickness of the secondary lining; and 7) the main cause for local collapse of the secondary lining of a certain bored subway tunnel is insufficient thickness of the secondary lining under high external water pressure.
YANG Xiao-Ping- 1 Xu- Rao- 1 Liu-Ting-Jin- 1,
2 Wu-Shang-Yong- 1
.Control Values and Influence Factors of a Water Head of the Secondary Lining in a Bored Subway Tunne[J] MODERN TUNNELLING TECHNOLOGY, 2017,V54(1): 96-104
2017, Vol. 54 