Reliability Assessment of an Open Pit Slope on Bong Iron Ore Mine

Slope stability on Bong mine is crucial for securing a balance in the gross national product of Liberia. The mine is being operated using conventional open pit methods with slope angles optimally designed to maximize ore stripping quantity. However, a working slope has displayed signs of uncertainty. The overall inclination of the slope is 56°, and the proposed maximal excavation is 315.42 m, but current depth in ore is approximately 50%. Based on the study of slope geological characteristics, the physical and mechanical parameters of rock mass and the geometrical calculation of stoping, the study is tailored on the mechanism of inspecting stress-strain behavior in response to seasonal variation of rock moisturization as a more suitable means of stope slope stability analysis in this case. This study took full account of local rainfall and other meteorological conditions. Slope stability is investigated via stereographic projections and stability assessment using the Shear Strength Reduction (SSR) method based on FLAC (Fast Lagrangian Analysis of Continua) numerical modeling technique in three dimensions to predict the stress-strain behavior of the open-pit slope and evaluate its stability state. Global stability has been analyzed under natural and saturated conditions and it is found that the slope is critically stable and needs proper attention.

Numerical investigations of rock bridge effect on open pit slope stability

In this study,the effect of rock bridges on rock slope stability was investigated by incorporating nonpersistent joint networks in numerical models,and the critical profiles of an open pit mine were analysed.Parallel deterministic networks of infinite and finite lengths,ubiquitous joint network model and Veneziano joint network model were used in order to simulate the rock fractures.Materials were modelled based on the generalised Hoek-Brown and equivalent Mohr-Coulomb failure criteria.The parallel deterministic infinite and the ubiquitous joint network models produced lower safety factors.The introduction of rock bridges along discontinuity planes in the parallel deterministic network and Veneziano joint network models significantly contributed to the stability and strain distribution,which should be considered in stability analysis of rock mass in open pit by rock slope practitioners.The results show the significance of joints in hard rock behaviour and the joints should be included in order to attain practical and realistic simulations.

Effects of Sublevel Open Stope Underground Mining on Surface and Open Pit Slopes

Underground mining is an economically viable option for exploiting ore reserves deemed uneconomic after open pit mining. However, underground development can have adverse effects on the above existing open pit slope walls. As a goal of this paper, identification and assessment of potential slope instabilities prior to underground development is crucial for safe and sustainable mining. Towards goal achieving, this paper gives a comprehensive parametric study to investigate the influence of sublevel open stope (SLOS) underground mining on the surface and open pit slope walls. By means of numerical simulation, the SLOS design is tried against the existing open pit followed by adjustments of important slope parameters which are overall slope height (OSH) and overall slope angle (OSA). We found that underground mining may induce slope failure, particularly on the hangingwall side of the pit. Subsidence is prominent on the hanging wall and the surface, whereas, the uplift dominates the footwall and pit bottom. Pit wall closure is observed during underground mining. Although the assigned dimensions in the parametric study show a negligible effect of OSH and OSA, the high OSH experience low subsidence in comparison with low OSH. Overall, the results demonstrate that the slope walls on the hanging wall side are mostly affected by the underground mining and high-stress concentration prevails near slope toes and pit bottom. Additionally, slope deformation decrease from pit bottom towards the slope crest and surface. The results of this study add knowledge to open pit and underground mining interaction.

Monitoring and Assessing Method for Blasting Vibration on Open-pit Slope in Hainan Iron Mine

A type of velocity sensor CD 1, an auto recording instrument on blasting vibration YBJ 1 and a random signal and vibration analysis system (CRAS) were used to monitor the particle vibration induced by blasting at open pit slope in Hainan Iron Mine. The attenuating rules of blasting ground vibration on slope were developed. By means of the analysis and calculation of the blasting vibration data at open pit slope and the vertical particle vibration velocity assessment method based on the concept of vibration strength, the empirical attenuating equations which can be used for predicting and estimating the damage of slope were derived.

Cut slope reinforcement technique in open-pit mines

The design and practice in supporting the cut slope of an open-pit mine wereintroduced, in which the high pressure grouting method was used in reinforcing the weak formation inthe slopes. Based on a detailed geological survey of the slope, a theoretical analysis was carriedout, and the design parameters were proposed, where the Tresca or Mohr-Coulomb yield criteria wasemployed. A patent technology, named 'Technology of high pressure and multiple grouting in differentlevels within a single hole', was employed in the construction. Anchor bars were also installed asgrouting proceeds. This method combines anchoring and grouting comprehensively and was foundsuccessful in practice.

Quantitative hazard assessment system(Has-Q) for open pit mine slopes

Rock slope hazard assessment is an important part of risk analysis for open pit mines.The main parameters that can lead to rock slope failures are the parameters traditionally used in geomechanical classifications,the slope geometrical parameters and external factors like rainfall and blasting.This paper presents a methodology for a hazard assessment system for open pit mine slopes based on 88 cases collated around the world using principal components analysis,discriminant analysis and confidence ellipses.The historical cases used in this study included copper,gold,iron,diamond,lead and zinc,platinum and claystone mines.The variables used in the assessment methodology are uniaxial compressive strength of intact rock;spacing,persistence,opening,roughness,infilling and orientation of the main discontinuity set;weathering of the rock mass;groundwater;blasting method;and height and inclination of the pit.While principal component analysis was used to quantify the data,the discriminant analysis was used to establish a rule to classify new slopes about its stability condition.To provide a practical hazard assessment system,confidence ellipses were used to propose a hazard graph and generate the HAS-Q.The discriminant rule developed in this research has a high discrimination capacity with an error rate of 11.36%.

Stability analysis of the sliding process of the west slope in Buzhaoba Open-Pit Mine

To study the stability of the west slope in Buzhaoba Open-Pit Mine and determine the aging stability coefficient during slide mass development, the deformation band of the west slope and the slide mass structure of the 34,600 profile are obtained on the basis of hydrology, geology, and monitoring data.The residual thrust method is utilized to calculate the stability coefficients, which are 1.225 and 1.00 under sound and transfixion conditions, respectively. According to the rock damage and fragmentation and the principle of mechanical parameter degradation, the mechanical models of the slide mass development of the hard and soft rock slopes are established. An integrated model for calculating the slope stability coefficient is built considering water, vibration, and other external factors that pertain to the structural plane damage mechanism and the generating mechanism of the sliding mass. The change curve of the stability coefficient in the slide mass development is obtained from the relevant analyses,and afterwards, the stability control measures are proposed. The analysis results indicate that in the cracking stage of the hard rock, the slope stability coefficient decreases linearly with the increase in the length Lbof the hard rock crack zone. The linear slope is positively correlated to rock cohesion c. In the transfixion stage of the soft rock, the decrease speed of the stability coefficient is positively correlated to the residual strength of the soft rock. When the slope is stable, the stability coefficient is in a quadratic-linear relationship with the decreased height Dh of the side slope and in a linear relationship with anchoring force P.

Application of open-pit and underground mining technology for residual coal of end slopes

Given the conditions of residual coal from the boundary of a flat dipping open-pit mine,which uses strip areas mining and inner dumping with slope-covering,we propose an open-pit and underground integrated mining technology for residual coal of end slopes.In the proposal a conveyance road and ventilation conveyance near the slope are built,corresponding to the pit mining area and the surface coal mine dump,as well as an interval haulage tunnel and air-inlet tunnel.The outcome shows that such mining method may reduce the effect to slope stability from underground mining,it does not affect the dumping advance and has a high recovery rate of residual coal resources.The working face is timbered by single hydraulic props,transported by a scraper conveyor and supported by coal walls.This method of mining is one of layered top coal caving,with high resource recovery,low production cost where positive economic benefit can be realized.

GIS-based 3D limit equilibrium analysis for design optimization of a 600 m high slope in an open pit mine

Combining the GIS （geographic information systems） grid-based data with four proposed column-based 3D slope stability analysis models, a comprehensive solution of a high-steep open-pit slope has been obtained. For six searching ranges, 19 critical slip surfaces of different sizes have been studied, in which the minimum 3D safety factor is 1.33. Comparison of 3D safety factors of designed and proposed slope plans shows for all the critical slip surfaces for the proposed plan, the smallest 3D safety factor is 1.33 under the most unfavorable condition. This means that the proposed plan of the high slopes, about 600 m, of an open pit （2-5° steeper than designed plan） is feasible.

The Influence of Earthquakes on Open-Pit Slope Stability

Estimation of stability of natural slopes, embankments, dams and open-pit slopes during earthquakes are complex and non-linear problems, therefore physical modeling is used for decision of it. As a result of physical modeling the pattern of seismic vibrations impact based on the movement process of probable collapse prism delineated by the most stressed plane of sliding has been established. Particular recommendations on the basis of safety factors selection in seismoactive zones are given.

Geotechnical Approach for Slope Design and Management Strategy for Nchanga Open Pit,Zambia

Rock slope stability is a very important research area for many geo-engineers concerned with civil or mining works.Slope stability of pits,roads,tailings dams and other embankments is very cardinal as it directly impacts on the working or utilization of these facilities.After a spate slope failures at the Nchanga Open Pits,a challenge arose to investigate the design parameters that have been in use.This research

Factor of safety of strain-softening slopes

Stability analysis of strain-softening slopes is carried out using the shear strength reduction method and Mohr-Coulomb model with degrading cohesion and friction angle.The e ffect of strain-softening behavior on the slope factor of safety is investigated by performing a series of analyses for various slope geometries and strength properties.Stability charts and equations are developed to estimate the factor of safety of strain-softe ning slopes from the results of traditional stability analysis based on perfectly-plastic behavior.Two example applications including an open pit mine in weak rock and clay shale slope with daylighting bedding planes are presented.The results of limit equilibrium analysis and shear strength reduction method with perfectly-plastic models were in close agreement.Using perfectly-plastic models with peak strength properties led to overly optimistic results while adopting residual strength properties gave excessively conservative outcomes.The shear strength reduction method with a strain-softening model gave realistic factors of safety while accounting for the process of strength degradation.

露天边帮开采中充填方式的探讨

针对我国露天边帮开采充填的现状,结合井工开采充填的方式,介绍了矸石充填、膏体充填和高水充填3种边帮充填方式的优缺点,探讨了3种井工开采充填方式应用到露天边帮开采充填的可行性,为露天边帮开采充填设计者提供了一些思路。

基于数值模拟的神延西湾露天煤矿边坡稳定性分析

西湾露天煤矿是国家能源集团的大型露天煤矿,煤炭产量高,产品质量优,在历年的能源保供任务中承担重要角色,西湾露天煤矿在开采过程中形成工作帮、边帮、排土场等边坡,较原始状态的边坡,稳定性存在不确定的因素。西湾露天煤矿地下水储量丰富,尤其是东端帮火烧岩边界,地下水对岩土的分界面及地层的强度影响较大,边坡长期受涌水影响,岩层裂隙发育,孔隙变大,易造成边坡失衡;地表主要成分为砂土,局部遇水流沙,保安平盘留设困难,易发生片帮、坍塌、滑坡事故。本文通过对各个地层的岩性、构造、层理和地下含水体进行综合分析,使用极限平衡法、有限元分析法验算西湾露天煤矿边坡稳定系数,确定露天边坡的边坡角、爆破方式、平盘高度、平盘宽度等重要边坡稳定参数,保证边坡的稳定性,提高采剥效率,对露天煤矿的安全生产具有重要意义。

大型绿色砂石矿山高边坡稳定性分析与监测设计研究

露天矿山高陡边坡的安全稳定具有重要意义。蕲春县石鼓冲绿色建材基地项目建设的特大型绿色砂石矿山露天开采后将形成高度超过450 m,坡度达60°的高陡边坡。本文对矿山高陡边坡进行工程地质分区,利用GeoStudio进行多工况的边坡渗流分析和稳定性评价,基于稳定性评价结果开展矿区边坡的分期监测方案研究,构建了多要素分期监测网络。提出的矿区高陡边坡稳定性分区评价方法和分期监测方案有助于有效管控边坡地质灾害风险。

断裂构造和结构面对露天高陡边坡破坏模式影响研究

为研究断裂构造和结构面对露天高陡边坡破坏模式的影响,以湖南某锂多金属矿为工程背景,采用现场调查和理论分析等手段进行调查与分析。矿区断裂构造以近SN向断裂为主干构造,其间发育NE向断裂、近EW向断裂、NW向断裂、弧形断裂及不同的节理裂隙,构成矿区的基本构造格架;通过现场调查测得岩体结构面产状,统计分析得到不同岩体的优势结构面:粗中粒斑状黑云母花岗岩3组、中细粒斑状黑云母花岗岩2组和云英岩2组;采用赤平投影法分析断裂构造和结构面对露天高陡边坡破坏模式影响。结果表明:F2断裂构造在Ⅳ区可能发生平面破坏;粗中粒斑状黑云母花岗岩第三组优势结构面在Ⅲ区可能发生平面破坏;Ⅲ、Ⅳ区粗中粒斑状黑云母花岗岩第二组、第三组优势结构面组合,与坡面相切后可能发生楔体破坏。

露天煤矿采排空间边坡稳定性及陡帮开采方案研究

为了提升露天煤矿采排空间边坡稳定性并优化陡帮开采策略,本文通过介绍矿区概况,详细分析了露天煤矿采排空间边坡的稳定性因素,针对性地设计了陡帮下部边坡外扩法与边坡内缩法两种开采方案,并进行了剥采比的计算与方案比选。基于安全性、经济性及开采效率的考量,提出了最适宜的陡帮开采方案。研究结果表明,该方案有效增强了边坡稳定性,降低了开采成本,提高了资源回收率,为露天煤矿的可持续开采提供了科学依据和技术支持。

基于高精准定位技术的露天矿铲装设备安全管控

受露天矿特殊开采工艺的影响,铲装设备极易在作业过程中发生安全事故。针对露天矿企业对铲装设备管理存在的巡检盲区大、响应不及时等问题,基于高精准定位技术提出了铲装设备高边坡、交叉作业管控方案。铲装设备高边坡作业管控方案结合地形数据,利用定位技术,通过现场测量与作业调度、实时监控与报警、现场处理与记录核查,实时监测铲装设备作业高度并判断是否超出安全范围。铲装设备交叉作业管控方案则通过作业前的作业间距确认、调度计划审核、作业间距巡查等实时监测作业间距。提出的管控方案实现了铲装设备作业间距和挖掘高度的安全精细化管理,有效降低了露天矿开采事故的发生风险,保障了作业正常进行,提升了作业效率。

露天矿边坡稳定性的层次分析-模糊综合评价耦合分析

露天煤矿台阶所构成的边坡对矿山资源生产及运输发挥着重要的作用,也承载着煤炭外运的任务,其稳定性对矿山连续生产具有重要意义。文章在边坡地质调查和监测信息分析的基础上,充分考虑边坡几何形态、地质信息、气象水文信息、现场监测信息等指标,以层次分析法确定边坡稳定性分析的指标权重,基于隶属度最大原则确定边坡稳定性状态,建立了多源信息融合的边坡层次分析-模糊综合评价模型。将该模型应用于扎哈淖尔露天煤矿北帮边坡稳定性分析中,最后基于数值模拟对模型进行了验证。研究表明,北帮边坡基本稳定,基于数值模拟得出扎哈淖尔露天煤矿北帮边坡滑移面安全系数为1.121,模型结果与数值模拟结果所得到的边坡稳定性状态吻合度较好,验证了模型的有效性。该模型可以充分考虑多重信息对边坡稳定性分析的贡献,从而更全面准确分析边坡稳定性。

基于InSAR-COMSOL的露天矿边坡稳定性分析及形变预测

露天矿地表形变特征的快速、准确分析及形变趋势精准预测是推进矿山绿色安全生产的重要保障。针对当前形变监测技术存在的时空采样率低、成本高,预测模型参数难确定等问题,以东鞍山露天铁矿为工程背景,提出了一种融合短基线子集干涉测量(SBAS-InSAR)技术和COMSOL有限元模拟的边坡稳定性分析和形变预测一体化方法。首先,利用SBAS-InSAR技术处理2018年5月—2020年6月获取的62景Sentinel-1A升轨SAR数据,获取了该区域2 a内地表形变时间序列,分析了其形变时空演化特征。然后,采用COMSOL Multiphysics软件模拟外界强降雨影响下的典型沉降区域边坡稳定性状况,探讨了坡体损伤裂化规律及形变机理。基于此,利用粒子群算法(PSO)优化长短期时间记忆(LSTM)网络,搭建了形变时序预测最优模型,开展典型沉降区的形变时序预测,并引入平均绝对误差和均方根误差作为预测精度评价指标。结果表明:矿区西部沉降相对严重,年均沉降速率高达47.8 mm/a,形变速率与区域降雨量存在显著相关性。相较于传统形变预测模型,PSO-LSTM模型的2种误差至少降低了14%和36%,且能够有效反映采区地表形变波动趋势,为滑坡灾前预警提供了新思路。