Optimum Design of Municipal Solid Waste (MSW) Dumps: A Reliability-based Approach

K V N S, Raviteja and Basha, B Munwar (2018) Optimum Design of Municipal Solid Waste (MSW) Dumps: A Reliability-based Approach. PhD thesis, Indian institute of technology Hyderabad.

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Abstract

The increase of population, rapid urbanization and improved living standards of the people have all led to the exponential growth of municipal solid waste (MSW) generation in India as well as in the rest of the world. The scarcity of enough land and capital, it is always a challenge to establish a new landfill facility. Consequently, the authorities are being forced to use the existing MSW landfills though they exceeded their design capacities turning out them to massive MSW dumps. The continuous dumping of MSW leads to steeper slopes which pose a threat to the MSW slope stability. Improper compaction practices, lack of daily soil/geosynthetic covers, the absence of drainage and leachate collection systems at the dump sites accelerates the chances of catastrophic failures in MSW dumps. The MSW is a highly heterogeneous and complex material and subjected to various stress conditions due to placement and compaction practices, leachate/pore fluid pressures, decay and disintegration, physical, chemical and biological changes. It is necessary to study and understand the variability associated with the geotechnical properties of the MSW to deliver safer designs. The construction of a landfill commences with installation of soil and GMB liners to avoid the contaminant transport. The design without considering uncertainties associated with the shear parameters of the MSW and the soil-liner interface friction angle may yield potentially misleading conclusions in terms of slope safety levels. The deterministic approaches ignoring the variability of these design parameters, which are random in nature, may cause a higher or lower probability of failure of the system. It can also be noted that the factor of safety approach yields either too conservative or unsafe designs. The framewor been proposed for the reliability-based design optimization (RBDO) of anchor trenches and MSW slopes. A logical framework is also developed to efficiently incorporate the variability associated with unit weight, cohesion, and friction angle of MSW and the soil-liner interface friction angle. Reliability-based designs mostly represent the random variables using Gaussian or lognormal distributions, which may not be capable of representing the experimental data precisely. The statistical analysis has been conducted on the experimental data collected from various studies reported during 1971-2017. Then, a new method is proposed to optimize the mean and standard deviation of the distributions using the compiled data based on quantile error, percentile error, and cumulative distribution function error. The MSW in a landfill is directly rested over the side slope of the anchor trench. Therefore, the stability of the MSW slopes is dependent on the stability of geomembrane (GMB) liners installed at the bottom of the MSW landfill. The dissertation provides an optimized design methodology for various types of anchor trenches in the reliability framework. A design methodology is developed for computing the anchorage capacity and GMB tensile force using the RBDO. More importance is given to the design of the V-shaped anchors in the current study. A logical framework has been proposed to consider the variability associated with the design parameters based on Qian et al (2002) and Villard and Chareyre (2004) approaches. This study also proposes a new procedure for the application of load resistance factor design (LRFD) using target reliability-based design optimization (TRBDO) of anchor trenches. The study presents the RBDO methodology for the slope stability in MSW dumps using the Morgenstern-Price method of slices. A comprehensive framework is proposed to evaluate the reliability index considering the variability associated with the stability number and friction angle of MSW. The location of the critical center and critical failure surface may be different when the variability associated with MSW are considered for the reliability analysis. Therefore, efforts have been made to locate the critical slip surfaces by minimizing the reliability index of MSW slopes. The reliability based LRFD is developed to compute the load and resistance factors for stability number and friction angle of MSW. The properties of MSW are strongly correlated in horizontal direction compared to the vertical direction. The anisotropic spatial variability associated with the unit weight, cohesion, and friction angle of MSW is also accounted. Inverse Gaussian and Gaussian random fields for stability number and friction angle of MSW, respectively, are developed by employing the square root exponential decaying Gauss-Markov correlation function and Cholesky decomposition technique. The reliability analysis of ten MSW dumps slopes is provided which highlights the importance of accounting variability of the shear strength of MSW. The details the dumps/landfills are viz: Ghazipur dump (Delhi), Leuwigajah dump (Indonesia), Cruz Almas dump (Indonesia), Payatas dump (Philippines), Bandeirantes landfill (Brazil), Muribeca landfill (Brazil), Este’s landfill (Itlay), Okhla dump (Delhi), Meethotamulla dump (Sri Lanka) and Koshe dump (Ethiopia). Overall, the proposed reliability-based design methodology exhibits promising features, wide applicability for the design of geosynthetic anchor trenches and MSW slopes. The design charts provided from the spatial and non-spatial analysis are relevant to both practicing engineers, and offers enough confidence in dealing with the uncertainty and judgment. The proposed methodology can also be adopted in the Geoenvironmental design and practice for the development of the sustainable design of MSW slopes.

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IITH Creators:
IITH CreatorsORCiD
Basha, B MunwarUNSPECIFIED
Item Type: Thesis (PhD)
Uncontrolled Keywords: MSW Slopes, Spatial Variability, Optimum Design, Reliability Analysis
Subjects: Civil Engineering
Divisions: Department of Civil Engineering
Depositing User: Team Library
Date Deposited: 31 Oct 2018 04:38
Last Modified: 31 Oct 2018 04:38
URI: http://raiith.iith.ac.in/id/eprint/4505
Publisher URL:
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