This research focuses on landslides caused by rainfall, earthquakes, and their combined effects. In many tropical regions, slopes are not fully saturated, meaning the soil contains both water and air. When rainfall enters such slopes, it changes water pressure, reduces soil suction, and weakens the slope, potentially leading to failure. Traditional slope stability methods often do not fully consider these unsaturated soil conditions. Earthquakes can further increase the risk, especially when the slope is already weakened by rainfall. This study, therefore, examines how slopes behave under combined rainfall infiltration and seismic shaking. The thesis uses numerical analysis to study changes in the factor of safety, pore-water pressure, degree of saturation, internal stress, and slope deformation during rainfall. It also evaluates how rainfall-affected slopes respond to earthquakes and proposes a simplified method to estimate slope safety that considers both earthquake and seepage forces. Since soil properties, rainfall, groundwater conditions, and failure information are uncertain in real situations, the study also develops probability-based and Bayesian methods to estimate landslide risk more clearly. Overall, this work helps improve landslide hazard assessment and supports the development of early warning systems, evacuation plans, and safer slope design methods.

The study focuses on improving the understanding of slope stability in mine overburden dumps, which are highly prone to landslides and failures due to weak shear strength characteristics. Conventional laboratory testing methods used for determining shear strength parameters such as cohesion and friction angle often fail to represent the true field conditions because of sample disturbance, exclusion of large particles, and changes in natural compaction during sampling and handling. To address these limitations, a new in-situ large-scale direct shear apparatus which can be easily assembled at the test site was developed (patented) with a 60 cm shear box capable of testing dump materials in their undisturbed state directly at the site. The study involved extensive field investigations such as density, moisture content tests, and direct shear tests over a period of 1.5 years. In addition to field tests, laboratory tests such as particle size analysis, Proctor compaction, XRD, UCS, and direct shear tests were performed. Results showed significant differences between in-situ and laboratory samples. In-situ samples exhibited much higher bulk density and friction angle, while laboratory samples showed artificially higher cohesion and lower friction angle due to the dominance of fine particles and loss of natural particle interlocking. Numerical slope stability analysis further revealed that slopes analyzed using in-situ parameters had a much lower probability of failure compared to those analyzed using laboratory parameters. This indicates that in-situ testing provides more realistic and reliable data for slope design and disaster risk reduction. The developed methodology can therefore help geotechnical engineers and mining professionals design safer and more optimized slope stabilization and mitigation measures, ultimately reducing the risk of landslides and associated disasters in mining areas.

Mercury (Hg) and lead (Pb) are two gravely threatening substances wreaking havoc on global ecosystem. They are found predominantly in water bodies due to their exorbitant discharge from various anthropological sources. In that context, adsorption is a simple, cost effective technology that is capable of removing these toxic heavy metals from wastewater and addresses the global concern of freshwater availability and usage. The present research work introduces seven novel materials (nanoparticles or composite), namely, NH2-UiO-66-SH_C, PBS2, APAN5-BS0.75, FE-TA, Fe-LAA1, aHAp-S and C-aHAp-S, which were designed specifically for Hg and Pb adsorptive purposes with tuned sulfur or nitrogen functionalities due to their targeted affinity for these heavy metals. These adsorbents belong to different categories, such as, metal organic frameworks (NH2-UiO-66-SH_C, Fe-TA and Fe-LAA1), chalcogenides (PBS2), hydroxyapatite (aHAp-S), polymeric mixed matrix media (APAN5-BS0.75) and charcoal based composite (C-aHAp-S). The synthesis strategies employed to produce these materials included hydrothermal, solvothermal, co-precipitation, anti-solvent induced polymeric phase inversion methods thereby, creating a diverse, flexible and versatile approach to material design and application studies. Leading edge techniques were used to characterize the physical as well as chemical intricacies of the produced adsorbents. Additionally, their high selectivity (in presence of interfering co-ions and counter ions) and effective reusability emphasized their remarkable performance. NH2-UiO-66-SH_C, PBS2, Fe-TA and APAN5-BS0.75 showed excellent Hg removal capacities of 885 mg/g, 832 mg/g, 1223 mg/g and 130 mg/g, respectively, while Fe-LAA1, aHAp-S and C-aHAp-S reported Pb binding capacities of 508.2 mg/g, 1282 mg/g and 200 mg/g, respectively. The present thesis is an effort to enrich the existing pool of materials in the domain of adsorption with newly developed adsorbents for the removal of inorganic mercury and lead in water. Their superior capacities and selective binding ability emphasize their wide prospect in water treatment applications.