This study presents a comprehensive stability analysis of specific reservoir slopes at the Ajima Chacha Earthen Dam in Ethiopia, aiming to enhance the understanding of stability conditions under varying hydrological scenarios, both dry and wet. The stability assessments consider the inherent properties of slope materials, comprising both rock and soil. To facilitate this analysis, extensive field investigations were conducted alongside laboratory tests to gather critical data pertinent to the stability assessments of key slopes vulnerable to failure from multiple triggering mechanisms. Factors identified as predisposing these slopes to instability include surface water infiltration, weak geological formations, steep gradient angles, and high degrees of weathering in the slope constituents. The finite difference method was employed as the numerical framework for analyzing the selected critical slopes. Utilizing FLAC2D (Fast Lagrangian Analysis of Continua in Two Dimensions), the stress–strain response of the slope stratigraphy was meticulously examined, leading to the computation of safety factors for a two-dimensional slope model. Notable deformations were recorded in the soft rock units and the highly weathered materials within the slope profiles. The analysis revealed a concerningly low safety factor during wet conditions for the assessed slopes. Critical reservoir slopes (RS-1, RS-2, RS-3) have (1.32 1.24), (1.42 1.12), and (1.63 0.99) under dry and wet slope conditions respectively. The results from the numerical modeling of the reservoir slopes provide crucial insights for monitoring slope integrity, particularly in sensitive zones. These insights are essential for the long-term stability management of dam reservoir slopes, enabling the implementation of effective mitigation measures to ensure the safety and reliability of the dam infrastructure.

Currently, opal mining in Ethiopia significantly contribution to the socio-economic growth of the country. Wollo opal has good play of color and is highly competitive in the global opal market. However, due to less investment and traditional mining practices, illegal opal market transactions, and low value addition processes, the forex earned revenue and other socio-economic opportunities gained from the resource are not desirably enough. Thus, this study aims to explore opportunities, identify challenges, and forward effective suggestions for the sustainable mining of Wollo opal. Suggestions are important for increasing opal productivity, increasing mining safety, and improving job creation in future Wollo opal mining. The major identified challenges in Wollo opal mining are miners’ use of rudimentary mining tools, the collapse of underground mining holes, unlawful opal market chains, less value addition, the environmental impacts of mining waste, and miners’ health risk. On the bases of existing data on the production of opal and generated revenue from Wollo opal, quantitative and qualitative analyses were performed to elucidate the current opal marketing. On the bases of statistical data, processed opal resources had a great impact on revenue generation than rough opal resources did during the year from 2019_2023. However, the forex currency earned in a legal way was reduced and occasionally fluctuated from time to time because of the opal market being jammed by illegal collectors and contrabandists. On the bases of the forwarded suggestions for the current existing challenges the government and other mining stakeholders should take measurements for the sustainable mining and marketing of opal resources.

Stability analysis on underground excavation is crucially helps to reduce collapse risks and optimize resource extractions. In this study numerical method was employed for stability analysis on the selected opal mine drift. Intensive field investigation of rock mass characterization, geometry of current mine drift, discontinuity measurements, and insitu rock mass characterizations were done. The Delanta mining site opalized rock layer is naturally weak and unwelded to moderately welded, which is not easy for bolting and steel reinforcements. The Delanta opal resource is found in the deep cliffy gorge greater than 200 m depth from surface. To obtain compressive strength of intact rock properties, laboratory tests of rock samples were conducted. The insitu parameters and laboratory tested parameters were utilized for numerical stability analysis. The study shows stress conditions, deformation behavior and determine pillar dimensions based on the selected rock mass behavior which has critical importance on the safe mining operations. Stress–strain simulations were conducted on 1-m, 2-m and 3-m cross-section of natural rock pillar with 2 m height and 1.5 m width of mine excavation. The evaluated mine drifts have high deformability at the mine gate and less deformable inside the mine drift. Compressive strength of rock samples was low, and the generated deformation behavior of rock pillars is less while excavation move inside 100 m at MinchWuha mining drift. Based on the existing rock mass properties, the mine drift pillars are unstable in 1-m, and 2-m rock pillar dimensions. The mine excavation was more stable while the natural rock pilar dimensions increased to 3-m. The Delanta district mining system should design in room and pillar methods to reduce the risk vulnerability of miners and to increase the opal resource extraction efficiently. Natural rock support system would be better by creating rock pillar than man-made supports. Thus, mining system in the Delanta mine sites should be customized by implementing room and pillar mine systems, which increases the mining safety and resource extraction optimizations with sustainable mining.