Graduation Semester and Year
Summer 2026
Language
English
Document Type
Thesis
Degree Name
Master of Science in Civil Engineering
Department
Civil Engineering
First Advisor
Dr. MD Sahadat Hossain
Abstract
Landfill leachate threatens groundwater quality in low-lying coastal Bangladesh, where a shallow water table and a discontinuous natural clay barrier heighten contamination risk beneath municipal solid waste sites. At the Chakaria Landfill in Cox's Bazar District, a cement-bentonite slurry wall was proposed as a vertical cutoff to control seepage, but its reliability under the site's high-groundwater condition had not previously been evaluated in probabilistic terms.
This study evaluated the wall's performance using a two-dimensional SEEP/W finite-element seepage model, a validated response surface (RSM) equation relating seepage rate to wall permeability, thickness, depth, and a Hasofer-Lind first-order reliability (FORM) analysis built on that equation. Fifty deterministic SEEP/W simulations were used to develop and validate the RSM model, which achieved a validation R² of 0.83 and a mean absolute percentage error of about 18%.
The Slurry wall proved highly effective, reducing seepage by roughly 84% to over 99% across the groundwater conditions examined. Permeability was the dominant control, with reduction rising from about 19% at 1E-07 m/s to about 87% at 1E-11 m/s; depth was second, rising from about 17% at 4 m to about 86% once the wall reached 27.5 m and keyed into the underlying stiff clay; thickness had only a minor effect, improving reduction from about 85% to 89% across the range studied. Sensitivity analysis confirmed this same ranking: permeability first, depth second, thickness a distant third.
Reliability analysis set an allowable seepage rate of 69.56 gal/day/acre at the target reliability index of 3, corresponding to a failure probability of about 0.135%. Reliability declined as the RSM model's own uncertainty grew, dropping to the target index once its coefficient of variation reached about 19%, and declined further as field construction variability in permeability, depth, and thickness increased, requiring progressively more conservative design values to sustain the target index.
The Chakaria slurry wall performs most reliably when it combines low, uniform permeability with sufficient embedment into the stiff clay layer; thickness and foundation-layer arrangement act mainly as secondary safeguards. A reliability-based framework offers a more defensible basis than deterministic analysis alone for specifying seepage-control barriers at coastal, high-groundwater landfill sites.
Keywords
Slurry wall, Seepage control, Landfill, SEEP/W, Response surface methodology, Reliability analysis, First-order reliability method
Disciplines
Civil Engineering | Geotechnical Engineering
License
This work is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 4.0 International License.
Recommended Citation
Bhandari, Shishir, "Reliability-based Performance Evaluation of Slurry Wall for Leakage Control at Chakaria Landfill, Bangladesh" (2026). Civil Engineering Theses. 6.
https://mavmatrix.uta.edu/civilengineering_theses2/6