Open Pit Mine Rock Dump Geotechnical Evaluation

Open pit mining generally involves moving large quantities of waste rock to disposal areas which are usually located near the mine. This waste rock must be disposed of in a safe, economical, and environmentally acceptable manner. The stability of the waste dump depends to a great extent on the physical properties of the underlying foundation. Information must be obtained to define and assess the strength, consolidation, distribution, topographic and hydrogeologic properties for the foundation materials. Methods for obtaining estimates of the material properties include: laboratory and field testing, back analysis, and indirect estimates from other material properties. Mining operations in mountainous terrain generally necessitate development of waste rock dumps on areas of moderate to steeply sloping terrain. The design and monitoring of these waste embankments are an integral part of the mine planning function, and present a challenge to the geotechnical engineer. Close coordination with mining operations is also required to ensure proper dump construction. Described is a case history of a large scale rail dump settlement episode which extended over an area of approximately 20 acres. Boundary and crest tension cracks closely followed original drainage topography leading to the belief that displacements were foundation soil (clay) related. Active and passive blocks were distinctly exhibited. Concentrated dumping with attendant foundation pore pressure buildup were principal causes for the settlement

Application of Groundwater modeling for designing a dewatering system: Case study of the Buvač Open Cast Mine, Bosnia and Herzegovina

This paper presents groundwatermanagement based on the results of groundwater modeling used to simulate theeffects of operation of three dewatering system scenarios of the Buvač open pitmine. Several aquifers exist within the Buvač limonite ore deposit region,which puts ore exploitation at risk. Groundwater modeling, was used tounderstand the groundwater regime within these aquifers. A previous numericalmodel (2007) was completed for the state of the groundwater regime prior to theopening of the open pit mine. During the last five years, the development ofthe open pit mine and associated activities have drastically modified the flowfield. The model was modified for the new conditions on the site, and with thenew data from the groundwater and surface water regime monitoring. The existingsystem of protection of the open pit mine from groundwater encompasses drainageof the alluvial aquifer and the ore body aquifer. This paper analyzes threescenarios of the open pit protection from groundwater for the period from 2013to 2024. The new model was used to simulate the effects of operation of thethree proposed dewatering systems. The differences in the effects of operationof the scenarios were quantified through the conditions of groundwater levelsand water budget. Recommendations have also been given for performingprediction calculations in the case of existence of drainage wells, with themost effective dewatering system determined from a hydrodynamic aspect. Theresults presented in this paper may be used for developing an effectivedewatering program

The Miocene Bükkábrány Fossil Forest in Hungary – field observations and project outline

The oldest, standing forest preserved as wood has been found at Bükkábrány, Hungary. An open-pit mine working Upper Miocene (Pannonian) lignite revealed sixteen stumps, 1.8 to 3.6 m diameter at base, preserved up to 6 m height, standing on top of the coal bed. Suddenly rising water level of Lake Pannon drowned the forest 7 Ma ago. Sand of a prograding delta covered the landscape, preserving the trunks in waterlogged condition. A brief review of the environment allowing preservation is provided here, and investigations in progress are outlined

EVALUATING GEOMECHANICAL UNCERTAINTY IN OPEN PIT MINE PLANNING

Open pit mine planning encompasses a variety of uncertainties. Uncertainty due to geomechanics is most critical for a safe operation in an open pit mine. Without sufficient knowledge of the geomechanical properties of the subsurface, a reliability analysis of the slope stability could be challenging. Slope stability is a crucial step in pit optimization since the cash flow analysis of a mine is constrained by a stable slope angle. However, obtaining a stable slope angle with certainty is difficult to achieve as geomechanical parameters are modeled using a very limited number of samples. This thesis proposes a method to integrate geomechanical uncertainty, specifically uncertainty regarding slope stability, in pit optimization through reliability-based analysis. This research explores gold deposit data received from exploration drilling in Alaska, with potential to build an open pit mine. The gold grade was estimated by ordinary kriging (OK) using exploration drilling data. Rock Quality Designation (RQD) is the only geomechanical data available from this deposit, and it was used to calculate cohesion, angle of internal friction, and unit weights of the rock. The uncertainty of the RQD was quantified for each rock type of the deposit. The probability density function (PDF) of RQD for each rock type was fitted using log-normal distribution. The uncertainty-based slope stability analysis was carried out using the limit equilibrium method. The reliability and failure probability of the different slope angles were calculated, and the maximum slope angle with 100% reliability is 50°. The cash flow for each slope angle was identified and assessed along with the probability of failure for three different factor of safety values. The results showed that the steeper the slope angle used, the more profit would be generated, but the probability of failure increased. In contrast, using shallower slopes did not generate as much profit, but the probability of failure was lower. A threshold slope angle of 51.5° was determined to be the highest angle that can be utilized without the probability of failure outweighing the profit generated

Three dimensional computational fluid dynamics models of pollutant transport in a deep open pit mine under Arctic air inversion and mitigation measures

Thesis (Ph.D.) University of Alaska Fairbanks, 2015As open pit mines continue to grow deeper and productivity continues to increase, the management of air pollution can become challenging. One of the challenges, common during winter in deep open pit mines operating in the Arctic, is the occurrence of atmospheric inversion. In itself, inversion is not hazardous. However, due to the emission of gases and particulates during the mining process, the air within the pit can be severely contaminated, rather quickly, leading to serious health and safety consequences. The problem is complex and any solution approach will require a good understanding of the interaction of the aerodynamic movement of air, the air inversion process, the meteorology, the pollutant sources, and the application of mechanical ventilators in open pit mines. Scientific literature related to open pit mine ventilation, particularly with respect to air inversion, is practically non-existent in the English literature. This is perhaps the first account of a three dimensional computational fluid dynamics (CFD) model of pollutant transport in an actual open pit mine under an Arctic air inversion. Advanced technology has made computers faster and more powerful, which allows computational fluid dynamics (CFD) procedures to be applied to many air flow problems. Thus, a CFD approach can be used to understand the transport of contaminant in the pit during inversion by using several turbulence models. An array of data is required to develop CFD models for open pit mine ventilation. The meteorological conditions within deep open pit mines are significantly affected by temperature and roughness conditions, which ultimately generate complex dispersion phenomena including separation of air flow and its recirculation. For the application of CFD, various data such as pollutants concentrations, temperature, velocity, pit contours, equipment locations, and radiation (shortwave and longwave) were collected from the selected open pit mine and the weather stations located nearby. Analysis of the weather data showed that inversions are due to elevated inversions in the selected open pit mine. Because an exact flow situation in open pit mines is not known a-priori, open pit air flow simulation and pollution transport are often highly sensitive to the type of flow model employed. It is therefore necessary to investigate various turbulent models to identify the appropriate model that will simulate the flow phenomena with reasonable accuracy and predict the contaminant distributions within the pit. Dispersion models differ in their assumptions and structures as well as in the algorithm used and as a result, predictions vary from model to model. Furthermore, it is also important to investigate the behavior of a CFD model when simulating complex phenomena, such as the transport and distribution of contaminants in an open pit mine under an Arctic air inversion. The simulation of an enhanced period of turbulence in the stable boundary layer (SBL) is of particular interest because traditional air pollution dispersion models cannot explicitly treat intermittent turbulence events, and yet the SBL is often the worst-case scenario in open pit pollution transport.Realizable κ-ε and Large Eddy Simulation (LES) models were used for understanding flow of gaseous contaminants. The 2010 pit configuration was used to develop models for understanding the gaseous transport under air inversion. During an inversion, turbulence is dominant at the bottom of the pit, while in the middle portion of the pit turbulence is intermittent and flow over the upper portion of the pit is mostly laminar. The realizable κ-ε model tends to over-predict the contaminant concentration, whereas, the LES model under-predicts the level of pollutant concentrations. Validation of the developed model was performed using the 2013 pit configuration. Despite the complex synoptic situations, the different meteorological input data and the fast changing conditions, the simulation results from the validation model were in good agreement regarding the dispersion of pollutants and other turbulent variables. Pollutant concentration values in the selected locations showed differences, but remained within the same order of magnitude in most cases. Removal of the harmful pollutants from the pit is significantly important for the health and safety of the mine workers. The mitigation models were developed for both the 2010 and the 2013 pit configurations. Several remedial measures such as the use of mechanical ventilators in forcing and exhaust mode, push-pull ventilation and a novel approach of using cloud cover were considered. Mitigation efforts employing mechanical means were unsuccessful in removing or diluting the contaminants to a safe level. The novel approach of using cloud cover over an open pit mine showed promise. With this approach, the model showed that the inversion could be lifted and pit could be cleared of all pollutants

Comparing Exploration Plans for a Porphyry Copper Open-Pit Mine

This paper uses stylized features of several open-pit copper mines in BC, Canada to build a toy model to compare different exploration plans. Assuming an ore body is there, would one exploration plan find it faster than others or more cheaply? This paper compares the results generated by three different exploration plans with the same budget, where key parameters are calibrated to mines in BC. A first plan drills holes on a uniform distribution across the search space and produces results that are worth less than they cost. A second plan uses a geochemical survey to narrow the area of drilling and yields greater value from exploration than the cost. A third plan includes a seismic survey before the geochemical and drilling, which yields less value than the second plan but increases the confidence that the drilling is in the right spot

An “Unexpected” Rock Failure in a Limestone Open Pit Mine

On 28th October 2004 a rock failure occurred in a limestone open pit quarry in Tuscany (Italy). The phenomenon evolved slowly with the collapse of about 1000 cubic meters. The complex failure mechanism mainly involved plane sliding along stratifications with rotation and block toppling. The phenomenon continued to evolve slowly and on 3rd November failure extended to the neighbouring portion of rock with a total collapse of about 5000 cubic meters of rock. Failure analysis took advantage of an accurate characterization of geology, geometry and mechanical properties of the collapsed rock mass. Such analysis led to the conclusion that the failure has been caused by the concurrence of various factors, namely: - unfavourable dip and dip directions of stratification which daylight in the slope face; - possible reduction of the angle of shear resistance available along stratification especially as a consequence of intense rainfall and vibrations

Rules of Risk Management - Case Study of Open Pit Mine

The issue of human factor risk and rules and regulations in open pit mine is a main focus of this paper in order to develop predictive models of behavior of workers in relation to compliance with the procedures and rules. Presented survey was conducted in open pit coal mine, as high-risk system, involving 476 mineworkers. The survey was in the form of a questionnaire, consisting of 45 questions, aimed to fmd out the opinions of the mining workforce about risk attitude generally as well as about safety rules and regulations

Rules of Risk Management - Case Study of Open Pit Mine

The issue of human factor risk and rules and regulations in open pit mine is a main focus of this paper in order to develop predictive models of behavior of workers in relation to compliance with the procedures and rules. Presented survey was conducted in open pit coal mine, as high-risk system, involving 476 mineworkers. The survey was in the form of a questionnaire, consisting of 45 questions, aimed to fmd out the opinions of the mining workforce about risk attitude generally as well as about safety rules and regulations