The design of slopes in open pit mines requires an in-depth understanding of the ground behavior to predict the potential failure mechanism and to better determine the stabilization measures. This study compares the critical slip surface defined by the limit equilibrium method (LEM), the limit analysis (LA), and the finite elements method (FEM) for the stability analysis to better approach the stability on a multi-layered slope. The safety factor, the size, and the location of the critical slip surface obtained from the applied methods are considered in the comparisons. This study highlights some features that affect the slope stability and presents a procedure for addressing the evaluation challenges in a multi-layered formation. Moreover, it presents some aspects of the upper-bound computation on the safety factor of a layered slope subjected to the effects of pore water pressures. Based on the obtained results, the critical slip surface defined by the limit equilibrium method compares well with the slip mechanism suggested by the limit analysis and the finite element approach. In view of the differences in the shape and location of the critical slip surface, as well as the values obtained for the safety factor, it is recommended that an engineer should analyze critical slopes using the finite element method in combination with the limit equilibrium or limit analysis method as a cross reference. The authors propose that in defining the potential failure mass, consideration must be given to the conducted field research and monitoring.

This article provides a comprehensive and chronological account of the technological advancements in alluvial gold mining. Gold has been a highly prized commodity throughout history and has played a significant role in humanity’s economic and cultural progress. The primitive methods of extracting gold from riverbeds were carried out in Ancient Anatolia and Ancient Greece. The earliest references to the extraction of gold from riverbeds can be traced back to the Argonautic expedition and the myth of the “Golden Fleece”. In this myth, fine gold particles were believed to be trapped within the skin of the fleece, thus alluding to the early practices of gold recovery from rivers. Since then, gold extraction and processing technologies have evolved. During the Roman Empire period, Emperor Augustus made significant advancements in hydraulic gold mining. He developed the “ground sluicing” method, which used water to wash away the overlying soil and expose the bedrock where gold deposits were located. Subsequently, the revolutionary pumps described by Georgius Bauer (Agricola) gained significant popularity during the Renaissance. Additionally, Spanish colonialists in America enhanced their techniques by observing the efficient methods employed by the indigenous populations. Finally, the “gold rush” era was perhaps the most crucial period in alluvial gold mining and took place in the rivers of America during the 19th–20th centuries. Today, technologies have evolved significantly, and exploring the evolution of primitive methods to the present is considered essential.

The island of Cyprus is famous for its rich deposits of volcanic mineralisation that yielded large quantities of copper, gold, and silver. The abandonment of the waste material in several dump sites during exploitation severely impacted the environment. A significant environmental issue is the acid mine drainage from the hydration of large barren piles that cover these old open pit mines. However, abandoned piles are still enriched in precious metals and perhaps even rare earth metals. These dump sites may form a new possible “deposit”, which may attract companies’ economic interest. Removing the stockpiles can be cost-effective, since the secondary extraction process is profitable, in addition to the benefits from the restoration of the natural environment. The case study considered here pertains to the North Mine of Mathiatis, where unmanned aerial vehicle (UAV) images were used to create not only a 3D topographic map but also to locate these dump sites and finally to create a 3D model of one of these waste stockpiles. The methodology proposed here to locate dump sites by using point cloud data (x, y, z, RGB) and high-resolution images provided by UAVs will assist in the secondary mining of old open-pit mines by defining the bottom and top stockpile surfaces. The reconstructed 3D waste piles can also be used to calculate the volume they occupy and other parameters, such as the gradient of slopes, that are essential for estimating the cost of possible restoration. The proposed methodology was applied to the stockpile STK1 with the most available drillhole data, and its volume was estimated at 56,000 m³, approximately.

This work provides historical information and examines changes in the methods and equipment used in gold recovery and processing operations. Alluvial gold recovery methods, mainly based on gravity separation combined with mercury (amalgamation), have been applied since the early days of mining. Historically, mining gold from the riverbeds was first implemented in Ancient Anatolia (also called “Asia Minor”) and Ancient Greece. As a first attempt to recover gold, the traditional immersion of sheepskin in river water to trap alluvial gold was developed. This technique has been considered a milestone in the famous myth of the Golden Fleece. Since then, gold extraction and processing technologies have evolved. In this respect, Emperor Augustus developed hydraulic gold mining during the period of the Roman Empire. Subsequently, the innovative machines of Georgius Bauer (Agricola) were widely used during the Renaissance, while Spanish colonialists in America improved their techniques by observing the efficient methods of the natives. Finally, the “American Gold Rush” era was perhaps the most crucial period of the alluvial gold mining process. It took place along the rivers of America during the 19th and 20th centuries. Today, in the technologically advanced society, various gold mining machines, including spiral and jig concentrators, provide higher production rates and less environmental harm.

Modifications in European environmental legislation requiring the minimization of the environmental footprint of mining operations have resulted in increased environmental costs and fewer investments in new surface mines. Due to the significant dependence of the global economy on mining, which provides raw materials and energy for most industries, it is essential to develop the necessary technologies for reducing pollutant emissions and exploitation costs. In open pit or underground mining operations, the highest cost comes from loading and hauling the extracted ore. Hence, the optimal combination of loading and hauling equipment has a significant impact on the production rate of the mine/quarry. The primary aim of this research is to improve the production of a surface mining operation by modifying the operational parameters (different dumping positions of materials) of the loading-hauling equipment in such a manner as to reduce fuel consumption and emitted pollutants. This aim is achieved by optimizing the hauling cycle by examining different scenarios utilizing stochastic simulation based on queue theory. The queue theory is a stochastic method commonly used to simulate the shovel-truck haulage system of a mine operation. This method has been implicated to estimate pollutants emitted in the atmosphere and propose alternative scenarios for reducing emissions normalized with the hauled material. The method is validated against actual data from a large open pit. The implementation of queue theory and estimating fuel consumption and greenhouse gas (GHG) emissions are derived from the $$M/M/1$$ and $$M/M/2$$ queue models. These two scenarios were examined for two different transportation routes and dumping positions. Based on these scenarios, it was found that the case $$M/M/1$$ with one electrical shovel having the nearest dumping position gives the minimum GHG emissions. Regarding the environmental impact, in all examined cases, the optimum truck fleet was the one with five trucks. From the productivity point of view, for the $$M/M/1$$ and $$M/M/2$$ scenarios, the number of trucks was six and eight, respectively. The greatest production was achieved in $$M/M/2$$ scenarios, with the one having the maximum distance to the dumping position being the one closest to actual data from the mine site. Another scenario, considering the implementation of the Trolley Assist haulage (TA) system resulted in a local minimum decrease by 54% for the $$M/M/2$$ TA Route 1 (longest) and for the $$M/M/2$$ TA Route 2 (shortest) by 62% of kg CO ₂ per tons of hauled material for the selected truck fleet size.