Slope Stability Of The Middle Stack Of An Open Pit (original) (raw)
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Stability assessment and slope design at Sandsloot open pit, South Africa
Sandsloot open pit is located on the northern limb of the Bushveld Igneous Complex. It is the largest open pit platinum mine in the world. Three major joint sets have been recognized at Sandsloot, which are related to the regional tectonic history. They have an important influence on slope stability in the open pit, notably in terms of planar and wedge failures. Detailed geological and geotechnical data are often a notable unknown factor in the design and operation of an open pit, the lack of which may pose a significant risk to the mining venture. As data are accumulated and used effectively, so the risk of unforeseen conditions is reduced, and accordingly safety and productivity is increased. Usually, the geotechnical work undertaken at an open pit mine is in connection with improving slope stability. At Sandsloot open pit geological and geotechnical data have been obtained by face mapping, scanline surveys, from exploration drillholes and from laboratory tests. Such data have been used to delineate different geotechnical zones in which different types of slope failure have occurred. These are the usual types of slope failure associated with rock masses, namely, planar, wedge, toppling and circular failures. Analysis of the data has allowed optimum design parameters to be developed for these zones which has led to improved slope stability. In other words, this has allowed slope management programmes to be initiated, as well as slope optimization of the hangingwall. The latter resulted in an improved slope configuration and an increase in the ultimate angle of the wall by 71. This has resulted in substantial savings, as well as an improvement in safety. r
Stability Analysis and Failure Mechanisms of Open Pit Rock Slope
Journal of the Civil Engineering Forum
Rock mass in nature tend to be unideal, for it is heterogeneous, anisotropic and has discontinuity. The discontinuity makes anisotropic strength and stress in the rock mass, and also controls the changing of the elastic properties of rock mass. This condition results to disruptions in the rock mass strength balance, and finally drives the slopes to collapse. This study aims to determine the slope failure mechanisms in the area of case study, as well as its variations based on the Rock Mass Rating (RMR), Geological Strength Index (GSI), Slope Mass Rating (SMR), kinematic analysis, numerical analysis and monitoring approach slope movement in a coal mine slope applications. The site investigations were implemented to obtain information about slope collapse. Prior to the collapse, the slope inclination was 38° with of 94 meters height, strike slope of N 245 E and direction of slope surface of 335°. After the collapse, the slope was became 25º; and after the collapse materials were clear...
Model Study of Slope Stability in Open Pit by Numerical Modeling Using the Finite Element Method
Aspects in Mining and Mineral science, 2018
Open pit slope stability analysis has been performed to assess the slope deformation, state of stresses at critically instable failure zones, different failure modes and safe functional design of excavated slopes using the numerical modeling technique as finite element method. In the evaluation of slopes, the factor of safety values still remain the main indexes for finding out how close or far slopes are from failure. The evaluation can be done my means of numerical methods such as the finite element method. In the finite element method, the latter analysis, the so-called shear strength reduction (SSR) technique can be applied. The angle of dilatancy, soil modulus or the solution domain size is not critical parameters in this technique. The safety factor can be obtained, assuming a Mohr-Coulomb failure criterion, by reducing the strength parameters incrementally, and starting from unfactored values. In this paper we have based our study on element modeling finished using the software Plaxis, the model used is that of Mohr-Coulomb.
Risk Assessment of Open Pit Slope Design at PT Adaro Indonesia
2014
Risk assessment of open pit slope stability is an important aspect to be considered in a decision making of slope design. The risk of slope failure that occurred on the slopes of the mine affect two factors namely the failure probability (FP), and consequences (C) of slope failure. FP is obtained from the collection of the value of Safety Factor (SF) < 1 compared to the total value of SF, while the consequences is estimated from the sectional area multiplied by the width of slope failure. Physical and mechanical properties of sandstone was collected from PT Adaro Indonesia, and tested by “Kolmogorov-Smirnov (K-S)” fitting method to obtain an assumed theoretical distribution that be sued with the character of the original distribution data. “Monte Carlo (MC)” and “Latin Hy- percube (LH)” sampling method is used as a tool to generate sample data, and both methods were compared. Finally Validation is conducted in order to propose an acceptable criteria of FP for single slope of sand...
Pit Slope Configuration for Open Pit Mining – A Case Study
American journal of science, engineering and technology, 2024
To achieve stable pit wall slopes, it is imperative to obtain a fair knowledge of the rock mass characterisation before designing the pit. Insufficient knowledge of the competency of the country rock could lead to using unsupported slope configuration in the design process which can consequently lead to slope failure. In this study, the geomechnical properties of the Bremen-Nkosuo concession are analysed using Bieniawski's classification scheme to determine the Rock Mass Rating (RMR) for defining safe pit slope configuration of the Nkosuo pit. The findings show that the rockmass are best described as 'fair' for the two main lithologies existing at the concession. Subsequently, localised adjustment factors are applied to the calculated RMR to arrive at Mining Rock Mass Ratings (MRMR). These MRMR values are correlated with 50 m fixed stack height and 1.2 safety factor to determine optimum Bench Slack Angle (BSA) of 54° and 57° for host sedimentary and granitic rocks respectively. For individual benches, optimum slope design configurations were 10 m, 800, and 6.6 m respectively for bench height, bench face angle and catch berm for metasedimentary rocks. Likewise, that for granitic formation were 10 m bench height, 800 face angle and 6.0 m catch berm width. These configurations are in conformance with mineral and mining regulations of Ghana. Slope stability assessment was performed which included Slope Mass Rating (SMR), Kinematic and Limit equilibrium analysis. From the analysis, multi-bench scale slope instability occurrence was found to be rare but single-double scale could be possible at the western wall of the planned pit with probability of failure of about 0.4. Presplit and trim shots perimeter blasting techniques are recommended to maintain the integrity of the final pit walls at certain areas.
IOP Conference Series: Earth and Environmental Science
Batu Hijau is a gold mine which is now run and managed by PT Amman Mineral Nusa Tenggara (PT AMNT) with open mining method. The located in Sekongkang District, West Sumbawa Regency-West Nusa Tenggara Province. The geological structure aspects are interesting as objects in this study, due to the condition is very tight and become to trigger for the slope failure. Slope stability is one of the important terms for supporting in open pit mining activities. One of the slope failure indication is the failure caused by the structure. Geological structure analysis performed with kinematic analysis which takes into account the probability of failure and type of failure. The probability of Failure can count by structure orientation, the orientation of the mine slope design, and friction angle with using dips 6 software. The percentage of slide obtained from the ratio between the critical point from the critical zone with the total critical point in stereographic projection. The count applied in all geotechnics domain with inputting of parameter structure orientation, the orientation of the mine slope design, and friction angle. The result shows between 0% to 2.63% of planar failure. The percentages show probability of failure but still in the safe category with 10% safety limit. Slope safety factor counts manually based on the mathematical formula applied to all domains in Batu Hijau Open Pit Mining. The result shows the value between 1.04 to 1.905 on planar failure. This value shows the condition of slope in the research site is stable.
Study of Slope Stability (Open Pit Mining, Algeria)
International Congress and Exhibition" Sustainable Civil Infrastructures: Innovative Infrastructure Geotechnology", 2017
The objective of our work is the study of the influence of the dynamic load due to the use of the explosive in the stability of the slope of an open pit mine, for this purpose we used the method of limit equilibrium to calculate the value of the safety factor through the geotechnical software SLIDE. On the one hand the calculation was carried out under static loading and on the other hand the dynamic loading is taken into account, which allowed us to conclude that the dynamic load influences the safety coefficient. Finally, a proposal to stabilize the slope at through a reprofiling of the bench is presented.
Probability Methods for Stability Design of Open Pit Rock Slopes: An Overview
Geosciences, 2021
The rock slope stability analysis can be performed using deterministic and probabilistic approaches. The deterministic analysis based on the safety concept factor uses fixed representative values for each input parameter involved without considering the variability and uncertainty of the rock mass properties. Probabilistic analysis with the calculation of probability of failure instead of the factor of safety against failure is emerging in practice. Such analyses offer a more rational approach to quantify risk by incorporating uncertainty in the input variables and evaluating the probability of the failure of a system. In rock slope engineering, uncertainty and variability involve a large scatter of geo-structural data and varied geomechanical test results. There has been extensive reliability analysis of rock slope stability in the literature, and different methods of reliability are being employed for assessment of the probability of failure and the reliability of a slope. Probabi...
AN APPLICATION OF POINT ESTIMATION METHODS TO ASSESS OPEN PIT SLOPE STABILITY
XIV Congreso International de Energia Recursos Minerales, 2018
Open pit slope stability is typically assessed using deterministic methods. A single value for the factor of safety is calculated using a single set of input parameters and is assumed to represent the overall stability of the slope. A limitation of the deterministic approach is that it does not account for the natural variability of the input parameters or the uncertainty caused by sampling. The probability associated with the factor of safety is often not estimated and, although the input parameters are typically average values of existing data, this probability may be small because the likelihood of the average values occurring simultaneously is usually low. Reliability based methods overcome some of the limitations of deterministic methods by incorporating the natural variability of key input parameters and allowing the evaluation of cumulative distribution functions that can be used to quantitatively describe the likelihood of achieving or not achieving a certain factor of safety. In the latter case, the probability of failure can be assessed and represents the likelihood of having, for example, a rock discontinuity with persistence greater than a certain length, dip steeper than a certain angle, or strength lower than certain values. This paper presents a feasibility level geotechnical study undertaken using point estimation methods in combination with discrete fracture network modelling and limit equilibrium methods to evaluate the probability of failure of a proposed open pit slope. This paper describes the process followed to develop the probability density and cumulative distribution functions for the factor of safety by taking into account the natural variability in orientation, continuity, and strength of rock discontinuities. The statistical distribution of the factor of safety is presented and is used to assess the pit slope stability in terms of probability of failure and acceptable risk tolerance.