Thesis
Numerical simulation of the performance of horizontal drains for subsurface slope stabilization
Washington State University
Master of Science (MS), Washington State University
2009
Handle:
https://hdl.handle.net/2376/101404
Abstract
Numerous slope failures are caused by heavy rainfall. During these rainfall periods, the ground water table rises up contributing to an increase in porewater pressure and a reduction in slope stability. Therefore, lowering of the ground water table is important for reducing the pore water pressure and increasing the stability of the slope. Installing horizontal drains is a very efficient and cost effective method for lowering the ground water table. The horizontal drains method has a well established theory, but there seems to be limited resources available for designing horizontal drains. The objective of this research is to develop design charts for optimal design of subsurface drainage systems. A finite difference based numerical simulator called TOUGH2 was used to model selected sites in the state of Washington. Simulated pressure values were matched to the site instrumentation data. The failure surface was located using XSTABL. A parametric study was conducted on a model slope to find optimal design parameters such as number of drains, elevation of drains, and spacing between drains. The study showed that the anisotropic permeability ratio is an important soil parameter in influencing the horizontal drain performance because it changes the profile of phreatic surfaces very much. It was found that slopes with higher ratios of permeability stabilized quicker than those with lower ratios of permeability. The study found that drains installed along the toe of the slide give more stability than those installed in higher elevations. The stability of the slope also increased with increasing length of drains and decreased when drains are spaced at larger intervals. Charts quantifying the changes have been developed. The length of drain extending longer than its intersection with the critical failure surface is found not to provide an increase in factor of safety.
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Details
- Title
- Numerical simulation of the performance of horizontal drains for subsurface slope stabilization
- Creators
- Marie Leony Pathmanathan
- Contributors
- Balasingam Muhunthan (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Civil and Environmental Engineering, Department of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; Pullman, Wash. :
- Identifiers
- 99900525284701842
- Language
- English
- Resource Type
- Thesis