Abhinav, Vyom2025-06-192025-06-192025-06-19http://hdl.handle.net/10393/50575https://doi.org/10.20381/ruor-31186Mining plays an essential role in shaping the modern society by providing the necessary raw materials for the development of technology, infrastructure, and other daily conveniences, while also promoting the economic growth of a country. However, this critical industry faces significant environmental challenges, particularly in terms of waste management. The process of mineral extraction generates an enormous amount of waste, known as tailings. Furthermore, a large volume of products made from mined mineral ultimately end up in municipal and industrial landfills before or after their lifecycle. Landfills contain materials ranging from electronic waste and construction debris to discarded clothing, food wastes, etc. As these materials decompose, they generate harmful leachate containing heavy metals and other toxic compounds, as well as greenhouse gases such as methane and carbon dioxide, which contribute to global warming. Such waste needs to be securely contained to prevent environmental contamination and ensure long-term stability. Engineered barriers systems, such as liners and covers, play a vital role in mitigating these environmental risks. These barriers serve as crucial components in preventing the escape of contaminants into the vadose zone or the atmosphere. Liners are installed at the base and side slopes of waste impoundments and help prevent the toxic substances from seeping into groundwater, surface water, soil, etc. Covers form the topmost layer of waste facilities once they have reached their maximum capacity. Covers aims to prevent ground infiltration of fluids and regulate gas emissions. The efficacy of these barrier systems depends on their material properties, such as hydraulic conductivity, mechanical characteristics, resilience towards natural seasonal stresses such as wet-dry cycles and freeze-thaw cycles, and desiccation cracking behavior. In alignment with this perspective and to promote sustainability through the reuse of tailings, recent studies have investigated the properties of compacted mixtures of bentonite-paste tailings (BPT) as a potential barrier material. Through the experimental study, it was found that BPT mixtures exhibit very low hydraulic conductivity, which is necessary to fulfill the requirement for barriers in a waste containment facility. This low hydraulic conductivity is further coupled with robust resistance of BPT towards natural stresses such as wet-dry and freeze-thaw cycles. However, mechanical characteristics (consolidation behavior and shear characteristics) of BPT, which are important geotechnical criteria for the design of liner and cover, are not known. No studies have addressed this research and knowledge gap. Thus, further research is required to address this knowledge deficiency. This study investigates the mechanical characteristics of bentonite-paste tailings mixtures in terms of consolidation and shear strength. The experimental program evaluates BPT mixtures with varying bentonite contents – 0%, 2%, 4%, and 8% – combined with synthetic tailings. One-dimensional consolidation tests revealed low compressibility and minimal volume change upon addition of bentonite. Moreover, direct shear testing showed improved shear strength and its parameters (cohesion and angle of friction) as bentonite content increases up to a threshold bentonite content (4%), indicating its strength under heavy loading conditions. However, in reality, barriers are often temporarily exposed to environmental conditions between the time of their installation and placement of waste. Moreover, during the operational phase, the waste placement can be either uniform, covering the entire region, or non-uniform. This can lead to the formation of desiccation cracks, which can significantly reduce the mechanical strength and impermeability, creating preferential pathways for contaminants to seep into the subsurface or escape into the atmosphere. However, no previous studies have examined the desiccation cracking behavior of BPT. Therefore, this study further investigates the desiccation cracking behavior of BPT mixtures, up to one wet-dry cycle, which is critical to ensure its suitable performance. Desiccation crack analysis showed a direct correlation between bentonite content and crack intensity, with increased bentonite content exhibiting more pronounced crack formation. The experimental program examining the performance of the proposed BPT barrier material reveals a complex interplay between mechanical strength and desiccation behavior. While the BPT mixtures exhibit favorable mechanical characteristics – low consolidation and high shear strength – suited for barrier applications, they also show susceptibility to desiccation cracking at higher bentonite contents, presenting a potential vulnerability to the very same improved mechanical and hydraulic properties. Therefore, the study suggests that optimizing the bentonite percentage needs careful consideration of the trade-off between mechanical performance and crack resistance. The findings from this study significantly contribute to understanding the behavior of BPT mixtures as engineered barriers and encourage further research to ensure their long-term efficiency in waste containment facilities.enAttribution 4.0 Internationalhttp://creativecommons.org/licenses/by/4.0/TailingsShear characteristicsConsolidationLinerCoverBentoniteWaste containmentDesiccation crackImage processingThesis