Mine Slope Research Articles

SVNN-ANFIS approach for stability evaluation of open-pit mine slopes

The stability of the open-pit mine slope has an important impact on the safe operation and benefits of the mining company. This paper proposes a single-valued neutrosophic number-based adaptive neuro fuzzy inference system (SVNN-ANFIS) approach to evaluate the open-pit mine slope stability. In the method, it utilizes the single-valued neutrosophic number concept for expressing the truth, indeterminate, and falsity information of influencing factors/indices (slope height, slope angle, potential slip plane angle, cohesion, internal friction angle and rock density) of the open-pit mine slope stability by truth, indeterminate, and falsity membership functions. Then, three ANFISs are used to obtain the corresponding relations between the influencing factors and the slope stability in truth, indeterminate, and falsity situations. Finally, the truth, indeterminate, and falsity output of the three ANFISs, i.e., a SVNN output, whose score value can be used to evaluate the slope stability through a score function of SVNN. The application results of the proposed approach have reflected that the training accuracy reaches 99.20% and the testing accuracy reaches 97.62%. Therefore, the established SVNN-ANFIS method provides a new effective way for evaluating open-pit mine slope stability in the uncertain environment.

Study on the Weakening Law and Classification of Rock Mass Damage under Blasting Conditions

To study the effects of declining mechanical parameters caused by blasting excavation on slopes, we introduced the damage degree index Ds, and established a relationship between Ds and the disturbance factor D in the Hoek–Brown criterion, along with a basic quality index BQ for the rock mass. We then explored the change law for the degree of rock damage Ds as a function of the disturbance factor D. We also used a phosphate mine slope in Guizhou Province for reference, and analyzed the process of damage evolution of the slope based on the RHT (Riedel-Hiermaier-Thoma Constitution) in LS-DYNA (Yunnan, China). Results showed a direct relationship between the GSI value in the Hoek–Brown criterion and the initial damage degree of the slope. As Ds increases, D increases exponentially. However, the compressive strength, elastic modulus, cohesion, and internal friction angle decreased nonlinearly, and the tensile strength of the rock mass decreased linearly. Among these parameters, the compressive strength decreased the most rapidly, while the internal friction angle decreased slowly. We also established a new grade for rock self-stabilization with Ds as the evaluation standard. Thus, these results may provide a theoretical basis for determining the mechanical properties of rocks for future slope protection and stability evaluations.

PT. GAG NICKEL NICKEL MINING SLOPE STABILITY ANALYSIS USING BISHOP METHOD

It is important to understand the condition of the slopes formed and the FK values obtained from the results of slope analysis to provide a safe FK value based on standard requirements for nickel mining slopes. The problems found in the study are, what variables are used in calculating FK values as well as the presence of safe FK values and level geometries that are ideal for mining activities. Thus, the results of one of the main variables used to calculate the slope balance are the Bishop method, and get FK values from one different method, namely 1.144 by looking at the characteristics of the soil and rocks.

Remote Real-Time Monitoring System for Mine Slope Based on Cloud Computing

A remote real-time monitoring system was developed for the remote real-time monitoring of mine slope deformation and internal forces. The system is based on cloud-computing technology and a 5S multimedia streaming monitoring data transmission system. It has now been applied to an open-pit iron mine in Nanfen to monitor the horizontal displacement of potential sliding surfaces. Compared with geometric monitoring methods in traditional geodetic surveying, the results show that this monitoring system has higher accuracy (0.01 mm) and the ability to monitor in real time for 24 h. These features can realize early warnings of mine slopes from multiple dimensions, and provide a guarantee for safe, continuous and the efficient production of mines. In addition, it can provide a certain reference for the prevention and control of mine slope disasters, and is beneficial to the application of information-based early warning technology.

Failure of Rock Slopes with Intermittent Joints: Failure Process and Stability Calculation Models

Abstract Rock slopes with intermittent joints in open-pit mines are complex geological bodies composed of intact rock and discontinuous structural planes, and their stability analysis are necessary for mine disaster prevention. In this study, a series of base friction tests were performed to determine the failure process and displacement field evolution of rock slopes with intermittent joints using the speckle technique of a noncontact measurement system. Next, stability calculation models of the slopes were established from the energy perspective using the plastic limit analysis theory, and the effects of the joint inclination angle and coalescence coefficient of rock bridges on the slope stability were evaluated. The four main conclusions are as follows: (1) The failure of rock slopes with intermittent joints shows the feature of collapse-lower traction-upper push. (2) Based on the failure modes of rock bridges in slopes, the failure of rock slopes with intermittent joints could be divided into three types: tensile coalescence (type A), shear coalescence (type B), and tensile–shear coalescence (type C). (3) Among the three slope types, the stability of the type A slope is significantly influenced by rock cohesion, whereas that of the type B slope is significantly influenced by joint cohesion. The stability of type C slope is significantly influenced by the joint inclination angle and joint friction angle. (4) The local-stable slope is unstable while the first through-tensile crack in the zone of the potential sliding body higher than the critical instability height appeared. This study guides the stability evaluation and instability prediction of jointed rock slopes in open-pit mines.

From Climate Conditions to the Numerical Slope Stability Analysis of Surface Coal Mines

A new perspective is presented for evaluating the slope stability of coal and lignite mines due to rainfall. The case of Greek lignite mining areas is employed to illustrate the methodology. Initially, past climatic records of rainfall are documented and analyzed; rainfall intensity varies from light (0.8 mm/h) to heavy (up to 9 mm/h). Few extreme phenomena are documented, with the maximum intensity being 17 mm/h. Furthermore, climatic projections of future trends are performed with open-access tools to anticipate possible deviations from the baseline conditions. Although the mean temperature is expected to increase, projections show that the past rainfall range is not expected to change. Finally, the effect of rainfall infiltration on the stability of a typical open-pit lignite mining slope is investigated by finite element analysis. The precipitation range defined by the environmental analysis is used. The SF is practically constant for the lower rainfall intensities (0.8–2.2 mm/h). For the higher intensities of 6.4 mm/h, 9 mm/h, and 17 mm/h, the SF decrease is almost the same (from 2.08 to 1.9), with reduction rates of 8.3%, 8.9%, and 9.3%, respectively. The effect of the critical geotechnical properties—groundwater table depth, unsaturated zone properties, and soil permeability—is also examined for a complete evaluation.

Study on Three-Dimensional Dynamic Stability of Open-Pit High Slope under Blasting Vibration

AbstractThe propagation process of blasting vibration has always been a difficult problem affecting the stability of high slopes in open-pit mines. Taking the Jianshan Phosphorus Mine as the research background, combined with engineering geological investigation, field blasting test, blasting vibration monitoring, numerical simulation technology, and theoretical analysis, the three-dimensional dynamic stability of the adjacent high slope after blasting vibration was systematically studied. In our study, a small-diameter buffer shock-absorbing blasting technology near the slope was proposed, which greatly improved the production efficiency. Through regression analysis of a large amount of vibration test data, the law of blasting vibration propagation in Jianshan stope and Haifeng stope was obtained. In addition, by establishing four three-dimensional geomechanical numerical models, the slope’s own frequency, damping characteristics, and dynamic response acceleration distribution after detonation were studied, respectively. On the other hand, under the action of Ei Centro wave with 8-degree seismic intensity, the maximum total acceleration and maximum total displacement of the slope were calculated and analyzed. Both the explosion unloading of the 8-degree earthquake and the Ei Centro wave simulation results showed that the high slope near the Jianshan Phosphorus Mine was generally in a stable state. Thus, this study can provide technical support and theoretical guidance for mine blasting.

Geological Survey and Comprehensive Analysis of a Dangerous Slope in the Weibei Limestone Mine

Abstract There are abundant limestone resources in Weibei area. However, under the influence of a complex geological environment and harsh external environment, they often suffer from various types of serious geological disasters, which seriously threaten the safety of the people in the mining area and the development of mining resources. Therefore, it is urgent to carry out relevant governance. Firstly, combined with the field engineering geological data of a typical limestone quarry slope in Weibei, this paper makes a detailed geological survey of the study area. Then, the geometric model of the limestone mine slope is established to analyze the stress relationship between each block and its failure mode. Finally, a deep Newtonian force monitoring and early-warning system is set up in the dangerous area of large deformation of the slope to carry out the early warning treatment of reinforcement. The results show that (1) limestone is the main component of the mine, followed by mudstone, with developed joints and fissures, broken rock mass, and high hidden danger of engineering geological disasters; (2) in addition to bending and toppling failure on the surface of the mine slope, there are three failure modes: toppling failure along the joint surface, combined failure along the joint and plane, and failure along the outward structural plane; and (3) the NPR anchor cable is used to strengthen the slope, and the real-time monitoring of the slope force changes is realized, which has a particular reference significance for the study of similar significant deformation failure mechanisms of the slope and imminent slide warning.

Mine Slope Stability Based on Fusion Technology of InSAR Monitoring and Numerical Simulation

In this paper, the slope of the open pit of Dahongshan iron ore mine in Yunnan is taken as the research object, the safety coefficient and settlement values of the slope under natural and rainfall conditions are derived by the finite element software Midas/GTS, and the surface settlement versus time is produced by fusing the InSAR monitoring results of the study area for a whole year to judge the stability of the open pit slope. The results show that the settlement and deformation areas shown by numerical simulation and InSAR monitoring results are consistent; the comparison between InSAR monitoring results and rainfall intensity shows that the cumulative value of slope settlement has a high correlation with heavy rainfall. The safety coefficients of the slopes of the open pit under natural conditions and rainfall conditions are 1.50 and 1.21, the cumulative value of settlement in InSAR monitoring data for one year is 18.4 mm, and no obvious large deformation area is found. The use of numerical simulation combined with InSAR monitoring can realize the analysis of the stability of the slope of the open pit mine.

Monitoring slope stability in surface mines: are low-cost UAVs used for excavated rock volume calculations capable of early detection of displacements?

This paper tries to assess the ability of UAVs equipped with RGB cameras to monitor the stability of the specific slopes in the surface lignite mines of Ptolemaida basin. For this purpose, the results of high measurement accuracy surveying, which was applied based on a series of target prisms placed on the crests of mine benches, are compared with the displacements detected by subtracting successive digital terrain models produced using UAVs equipped with RGB cameras in combination with RTK processing.

EQUIVALENT GEOLOGICAL STRENGTH INDEX (GSI) APPROACH WITH APPLICATION TO ROCK MASS SLOPE STABILITY

A considerable amount of slope stability analysis has been observed in jointed rock masses in which the GSI (Geological Strength Index) estimated at the outcropping level is considered input data to define the rock mass strength. However, this procedure is unsuitable when the rock outcrop scale and the slope scale are significantly different (e.g. open-pit slopes), resulting in an overestimated rock mass strength. For this reason, and in the absence of criteria to modify the GSI based on the scale effects, in this research, a new GSI version is proposed, called GSIe or “equivalent GSI”. To define an expression for obtaining the GSIe in terms of the rock mass properties, comparative stability analyses were conducted in a series of hypothetical slopes using two approaches: the first considers the rock mass as a discontinuous medium of rock blocks separated by discontinuities; the second considers the rock mass as an equivalent continuous medium characterized by an equivalent GSI. For the adequate equivalent GSI value, evaluated in each analyzed slope, the safety factor and the failure surface are similar in both approaches. In conformity with the results, a GSIe formulation in terms of the slope height, the spacing, the intact rock strength, the persistence, and the joint conditions has been proposed. Finally, the formulation was validated by applying it in five cases of mining slopes where the failure occurred.

Monitoring of geotechnical facilities through DLT solution

The article states the objectives of geotechnical monitoring in an open cast mine and discusses the main measurement methods. Distributed ledger technology (DLT) is recommended for monitoring and sharing data on the condition of the mine slopes between private and public organizations. Private DLT implementation is chosen because confidential corporate data is shared. A conceptual model for communication among the Mining Company, the responsible institutions and regulatory authorities has been suggested. It has been established that there is a possibility of leakage of personal data according to the GDPR.

Remote monitoring techniques for rehabilitated slope

AGL Loy Yang has been intensively engaged and involved in research in the area of rehabilitated mining slopes. A proposal was raised to turn the Loy Yang mine pit into a lake after decommission (in three decades) to achieve safe and stable rehabilitation of the mines. The slope stability of these rehabilitated slopes is one of the major concerns. The slopes are hardly failed spontaneously. Instead, they usually provide indications of distress (cracks and erosion) over some time. Therefore, an ongoing monitoring system may provide valuable time to mitigate the progression of the failure. Distributed optical fibre sensing (DOFS) and unmanned aerial vehicle (UAV) are emerging new and innovative technologies for remote monitoring a large civil structure for early warnings, alerts and decision making. Both DOFS and UAV have been recently deployed at Loy Yang rehabilitated trial site. The preliminary results have demonstrated their reliability and practicality for these rehabilitated slope monitoring techniques. These remote sensing techniques are compared and discussed in terms of slope monitoring application.

Warning Model of the Ionic Rare Earth Mine Slope Based on Creep Deformation Time Series

This paper takes the actual working conditions of leaching mining, with the Xikeng Rare Earth Mine in Anyuan County as the research object. The slope surface monitoring as a technical means is used to analyze the deformation characteristics, including cumulative displacement, velocity, and acceleration, and the leaching slope and establish an early warning system to assist with leaching production. The study shows that there are three stages in the process of ionic rare earth mine slope deformation, i.e., the initial stage with deformation velocity in 0.15 to 0.30 mm∙h-1, the speed of the uniform deformation stage fluctuating but maintaining at -0.15 to 0.15 mm∙h-1, and the accelerated deformation stage when the velocity and acceleration are 3 to 10 times or more than those of the initial deformation stage. The practice had proved that the monitoring system responded positively when an alarm based on the Local Outlier Factor (LOF) was issued so that the production process was in a safe state and no large-scale landslide disaster occurred. This study will provide theoretical and technical support for the safe and efficient mining of rare earth in situ leaching.

Experimental Investigation of Porous and Mechanical Characteristics of Single-Crack Rock-like Material under Freeze-Thaw Weathering

Freeze-thaw weathering changes the pore structure, permeability, and groundwater transportation of rock material. Meanwhile, the change in rock material structure deduced by frost heaving deteriorates mechanical properties of rock material, leading to instability and insecurity of mine slopes in cold regions. In this paper, rock-like specimens containing prefabricated cracks at different angles and having undergone various freeze-thaw cycles are used as the object. Their pore structure, compressive mechanical properties, strain energies, failure characteristics, and the connection between pore structure and mechanical properties are analyzed. Results show that the porosity, spectrum area of mesopores, and spectrum area of macropores increase with the increase in freeze-thaw cycles, while crack angle shows no obvious influence on pore structure. Peak stress and elastic modulus drop with the increase in freeze-thaw cycles, while peak strain shows an increasing trend. Peak stress and elastic modulus decrease in the beginning, and then increase with the increase in crack angle, while peak strain shows a reverse trend. Elastic strain energy and pre-peak strain energy drop with the increase in freeze-thaw cycles. Elastic strain energy decreases first, and then increases with the increase in crack angle. The correlation between the spectrum area of macropores and elastic modulus is the strongest among different pores. Elastic modulus and peak stress decrease with the increase in macropore spectrum area, and peak strain increases with the increase in macropore spectrum area.

On the design of the fiber reinforced shotcrete applied as primary rock support in the Cuiabá underground mining excavations: A case study

The Cuiabá mine is an underground gold operation located in Sabará (Minas Gerais, Brazil), which began to use fiber reinforced shotcrete as rock support since 2012. In order to carry on a mechanical analysis and to design the steel and polypropylene fiber reinforced shotcrete linings, the work in hand presents an experimental investigation on the mechanical behavior of the applied composite material inside the Cuiabá mine. Through standardized panel tests, the paper evaluates the toughness performance levels for each studied fiber reinforced shotcrete and applies the current design guidelines for mining works. Based on the rock mass classification of the analyzed mine slopes, while the use of 4.2 kg/m3 of polypropylene fiber volume fractions seems to be suitable where fair rock quality is observed, the addition of 25 kg/m3 of steel fibers is more indicated where severe ground movement is expected. On the other hand, a mismatch between the standardized panel tests (ASTM C1550 and EN 14488-5) on the shotcrete design guidelines was also assessed in the present research. The analyzed fiber reinforced shotcrete received different classifications depending on the used standardized panel test, resulting on an overestimation of the PP fiber reinforced shotcrete for the square panel tests. Safety factors can be applied in order to mitigate the possible mismatch between square and round panel tests.

Variable Weight Matter–Element Extension Model for the Stability Classification of Slope Rock Mass

The slope stability in an open-pit mine is closely related to the production safety and economic benefit of the mine. As a result of the increase in the number and scale of mine slopes, slope instability is frequently encountered in mines. Therefore, it is of scientific and social significance to strengthen the study of the stability of the slope rock mass. To accurately classify the stability of the slope rock mass in an open-pit mine, a new stability evaluation model of the slope rock mass was established based on variable weight and matter–element extension theory. First, based on the main evaluation indexes of geology, the environment, and engineering, the stability evaluation index system of the slope rock mass was constructed using the corresponding classification criteria of the evaluation index. Second, the constant weight of the evaluation index value was calculated using extremum entropy theory, and variable weight theory was used to optimize the constant weight to obtain the variable weight of the evaluation index value. Based on matter–element extension theory, the comprehensive correlation between the upper and lower limit indexes in the classification criteria and each classification was calculated, in addition to the comprehensive correlation between the rock mass indexes and the stability grade of each slope. Finally, the grade variable method was used to calculate the grade variable interval corresponding to the classification criteria of the evaluation index and the grade variable value of each slope rock mass, so as to determine the stability grade of the slope rock. The comparison results showed that the classification results of the proposed model are in line with engineering practice, and more accurate than those of the hierarchical-extension model and the multi-level unascertained measure-set pair analysis model.

Freeze-Thaw Effects on Stability of Open Pit Slope in High-Altitude and Cold Regions

The cycle of the freeze-thaw action must be taken into account in the stability analysis of an open pit slope in the high-altitude and cold regions, because the natural process of freeze-thaw poses a significant effect on mechanical properties of the rock mass. To achieve this purpose, a linear relationship between the geological strength index (GSI) and the Tianshan slope rock mass rating (TSMR) system is established considering the effect of the freeze-thaw action by introducing a freeze-thaw correction coefficient δ. The GSI value is modified for rock mass in high-altitude and cold regions. The improved Hoek-Brown criterion considers the influences of the freeze-thaw action and steep and gentle slopes. The research outcome is applied in the No. 4 minefield open pit coal mine in the Muli mining area. Numerical calculations are performed by inputting rock mass mechanical parameters obtained in traditional and modified criterions, to discuss the influences of the freeze-thaw action on the stabilities of both the present mining slope and the final slope at the end of the designed mining. The results show that the safety factors of the original slope are 2.33 and 1.67, respectively, while after the modification, they are 2.14 and 1.61, respectively. In terms of the No. 4 minefield open pit coal mine, the slope stability meets the design requirement, although taking the freeze-thaw cycle into account.

Experimental study of the shear failure of granite based on full-field-strain monitoring using digital image correlation

Shear failure is a common failure form of engineering rock mass. As a typical engineering rock mass, granite is widely present in reservoir dams, mine slopes, mine roadways, and other projects in China. Therefore, in this study, the direct shear testing of granite was conducted by taking granite as the research object and using an RLW-3000 shear creep biaxial testing machine. The complete process of shear failure was monitored by using digital image correlation non-contact full-field strain measurement technology, and the spatial evolution of the shear-failure process of granite was assessed by analyzing the main strain nephogram in combination with the main strain–time variation curves. The spatiotemporal evolution of strain during the shear-failure process of granite was studied to reveal the shear-failure mechanism of the material. Results show that the strain nephogram of granite during shear failure could be divided into four stages: uniform strain distribution, strain-localization band generation, strain band expansion, and strain-band expansion acceleration. Strain localization is an important feature of the shear failure of a rock mass; it is characterized by the uneven distribution of strain on the surface of the specimen and the appearance of strain-concentration bands, which indicate the initiation and propagation of macroscopic shear cracks. According to the principal strain–time curve obtained, the principal strain curve exhibits a sharp upward trend when strain localization occurs, and the stress is approximately 76%–79% of the peak stress. The space–time evolution characteristics of the above strain reflect the spatiotemporal variations in the stress field on the surface of the specimen, and the spatial extension of the banded strain-concentration area corresponds to the formation and development of shear failure in the rock. Therefore, the direction of the spatial development of shear microfractures can be predicted by capturing the spatial development of strain-localization bands. The results of this work provide an important theoretical basis and guidance for reservoir dam seepage prevention, highway and mine slope support, and goaf face instability early-warning systems.

Q-slope application to coal mine stability

The Q-slope classification system is used to assess the stability of excavated rock slopes and provide an indication of long-term stable, reinforcement-free slope angles. Q-slope is based on over 500 rock slope case studies from mines, road and rail cuts hosted in igneous, sedimentary and metamorphic rocks around the world. Q-slope has successfully been applied to slopes ranging from less than 5 m to more than 250 m in height in both civil and mining environments since its introduction in 2015. This paper describes the application of Q-slope to excavated coal mine slopes which are often hosted in complex, interbedded sedimentary strata. Q-slope application to coal mine slopes is compared to the likelihood of failure calculated by the Slope Stability Assessment Methodology (SSAM). A relationship between Q-slope and SSAM is also provided.