Effect of drainage conditions on porewater pressure distributions and lining stresses in drained tunnels | |
| Author | Ponlawich Arjnoi |
| Call Number | AIT Thesis no.GE-07-06 |
| Subject(s) | Drainage--Simulation methods Tunnels |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering in Geotechnical and Geoenvironmental Engineering, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. GE-07-06 |
| Abstract | This study deals with the effect of drainage conditions on porewater pressure distributions and lining stresses in drained tunnels. Firstly, simple closed-form analytical solutions for the steady-state porewater pressure are derived within a common theoretical framework for two different boundary conditions (one for zero water pressure and the other for a constant total head) along the tunnel circumference by using the conformal mapping technique. The porewater pressure distributions between two solutions are generally similar. Correctly estimating the boundary condition along the tunnel circumference is shown to be important in a shallow drained circular tunnel. The numerical simulation of a drained circular tunnel under the steady-state groundwater flow condition is made to investigate the effect of porewater pressure distributions on lining stresses. Both of two different boundary conditions can equally be used in the numerical simulation for tunnel lining stress analyses. Secondly, the numerical simulation of the case study of the planned South Blue Line Extension subway tunnel is performed under the steady-state groundwater flow condition, is made for the single tunnel and twin-tunnel with four different drainage conditions (sealed, fully-drained with zero pressure or a constant total head, and invert only-drained) along the tunnel circumference. The effects of different drainage conditions on porewater pressure distributions, flow nets, and lining stresses are investigated. The values of bending moments, axial forces and stresses in the lining can be reduced using the fully-drained conditions. The maximum stresses in the lining for fully-drained conditions are almost 80% of those for sealed and invert only-drained conditions in the single tunnel. Also, the effect of fully-drained conditions in the twin tunnel is larger than that in the single tunnel. About 30% of maximum compressive stress and 55% of maximum tensile stress are reduced using the fully-drained conditions in the twin-tunnel |
| Year | 2008 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. GE-07-06 |
| Type | Thesis |
| School | School of Engineering and Technology (SET) |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Geotechnical Engineering (GE) |
| Chairperson(s) | Park, Kyung-Ho; |
| Examination Committee(s) | Bergado, Dennes T.;Noppadol Phien-wej;Giao, Pham Huy;Lee, In-mo; |
| Scholarship Donor(s) | RTG Fellowship Brain Korea 21 Fellowship; |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2007 |