Factors affecting stability of waste dumps in mines

ABSTRACT

With the increasing adoption of surface mining/open pit, problems of associated waste dump, instability of which affects resource recovery, mining cost, safety and environmental hazards, has become the matter of prime concern to planners and operators. Greater attention is therefore required to critically analyse the factors controlling slope failure of spoil heaps. The present paper deals with some of these parameters, their effect on dump stability and remedial measures called for.     

An expert system for slope stability assessment: Part I

ABSTRACT

Expert or Intelligent Knowledge Based Systems have proved themselves to be valuable mechanisms for using computers to transfer and utilise expert knowledge in the solution of everyday industrial problems, in a wide variety of engineering fields. Their application in the mining industry has to date been limited by the development of the facts and heuristics that represent the knowledge concerning mining problems, and which form the essential component, the knowledge base, of an expert system

This paper describes the development of a knowledge base for an expert system to aid in the prediction of potential slope stability problems in U.K. surface coal mines. It is the first of two papers that will describe the development and operation of the complete system.     

Slopes design in surface mines

ABSTRACT

Slopes design is part of surface mine planning Methods of slopes design are described in three parts. Overall slope angles are derived from geological, structural geomechanical, and water table data during the feasibility stage Variations of the safety factor to changes in slope angle are described in both cases of jointed rock mass and continuous rock mass Influences of slope curvature and underground workings upon stability are also mentioned Selection of basic slope types (geometry of benches) is then discussed. The problem of haul road insertion in the pit walls while saving slopes stability is tackled and a method proposed.     

Design of open pit coal mine slopes: An integrated approach

ABSTRACT

Many of the coal deposits of Western Canada exhibit intensely folded and/or faulted strata. Geological evaluation of such deposits is often difficult and uncertain, and interpretations are subject to significant modifications throughout the exploration, development and mining phases. Design and excavation of open pit slopes under such conditions can present a variety of operational and slope stability problems. Slope design approaches and excavation procedures which are flexible and capable of adapting to changing conditions are essential for rational slope development

This paper examines the problems associated with open pit coal mine slope design in complex geologic environments. A systematic approach to slope design which incorporates engineering geology assessments, slope stability analyses, economic evaluations and mining operational constraints is presented:, Slope design concepts which utilize a variety of slope development techniques, Including benching and artificial support are developed. The design process continues throughout the mining phase in an iterative cycle whereby slope designs are prepared and implemented, remedial measures are applied, existing slopes are documented and evaluated, and slope design concepts and subsequent slope designs are updated and modified as necessary.     

Examples of open pit mining instability

Abstract

Geotechnical technology for surface mining has become increasingly sophisticated as lower grade ore deposits are being developed. With larger and deeper open pits, more detailed and accurate investigation has become necessary during the past decade.

Many variables influence successful open pit operations. These include ore grade, metal price, development costs, construction costs, mine design, stability and operating costs. With the great increase in the size of open pits to depths over 600 ～ 800 meters, the determination of pit slope angle and control of wall stability has a major influence on project economics.

This paper briefly discusses preliminary considerations for pit slopes from a geotechnical standpoint to optimize economics and safety, describes recent developments in stability engineering and to illustrate a wide range of stability problems, typical examples are briefly reviewed.     

Editor's Page

ABSTRACT

Data is presented from a ground deformation monitoring program conducted at a surface coal mine over a two year period. Monitoring focused on the mining of a coal measures sequence on a footwall slope. Mining plans had aimed to isolate a remnant pillar block, 12500 m² in plan, carrying a 132kV pylon tower and thus to maintain the integrity of a cross-pit power line. Pillar deformation which arose from shear on inclined strata is reviewed and related to the excavation sequence by strike cut and dip cut mining, involving remedial backfill buttressing. The monitoring program was based principally on an array of borehole inclinometers, supported by ground tiltmeter and conventional survey methods. The paper discusses the performance of the monitoring practice and strategy adopted in this mine production environment.     

Development of an air attenuation model for noise prediction in surface mines and quarries

ABSTRACT

Surface mining and quarrying produces a complex noise field. The noise generated by mining operations changes with time and is affected by the changing meteorological conditions in situ. Theoretical research on the attenuation of noise in air has formed the basis for the development of an air attenuation model. The methodology developed by the authors accounts for the prevailing temperature and relative humidity conditions in the area. The model also includes the evaluation of ray path curvature directly from long-term experimental wind velocity and temperature data, or indirectly in terms of the Net Solar Index and the wind velocity. This paper describes the air attenuation model, which was developed as an integral part of an environmental noise prediction system.     

Prediction of instability of slopes in an opencast mine over old surface and underground workings

Abstract

Jharia coalfield is a chief storehouse of prime coking coal in India. Earlier,many shallow seams were exploited by surface mining but when this method became uneconomical the mine operators resorted to underground method. However, due to various geotechnical problems, it was not possible to fully extract coal by underground method. Opencast mining is now being planned for extraction of coal locked in partially worked coal seam for ensuring maximum recovery. The major problem envisaged in conducting opencast mining insuch areas will be the stability of slope. In this paper, the technique adopted for simulation of 144 10 thick section of rock mass in equivalent material model is outlined. Old shallow surface excavation upto 33.0 m and later on underground workings were simulated in coal seam II/III. The span of the void was 160 m. An opencast excavation was conducted for recovering locked coal. The behaViour of slopes are reported here.     

Evaluating the effect of rock parameters on surface mine blasting by finite element analysis

ABSTRACT

The blasting process in surface mines involves extremely complex interactions. Utilizing Finite Element (FE) analysis, the affect of rock mass properties and discontinuity data can be fairly idealized and assessed. The purpose of this paper is to present the application of finite element methods to fragmentation due to blasting in surface mining operations. As a result, the prediction and extent of blasting will help the engineers engaged in surface mining and construction operations to use explosives efficiently.     

Applications of expert systems in equipment selection for surface mine design

ABSTRACT

The MINDER system (MINe Design using Expert Reasoning), has been developed to a prototype level in the Department of Mining Engineering, University of Nottingham. The Xi-Plus shell system has been used to create a multi-level expert system capable of accessing and controlling both commercially available mine planning software and 'in-house' programs. The expert system is used primarily for surface mining method selection and excavation and haulage equipment selection. Methods of storing knowledge, interrogating and controlling external programs, and reaching conclusions using multiple knowledgebases have been discussed in previous papers by the authors, and will be dealt with only briefly in this paper. This paper concentrates on the methods used to rank equipment, including relational operations (both with the knowledgebase and in external databases) and fuzzy logic techniques. The paper will include an example of the ranking of hydraulic excavators under UK surface coal mining conditions.     

Practical considerations for developing an automatically driven open pit mining machine: Compact bucketwheel excavator

ABSTRACT

The arc of electronic revolution is here bringing changes to mining technology. The surface mining Industry is keen to be part of this changing environment. Efforts are being directed towards developing automated mining equipment. This paper, using the compact bucket wheel excavator as an example examines the theoretical and practical parameters which must be considered in developing an automated machine.     

Ground control for highwall mining in the United States

Abstract

Highwall mining is an important coal mining method in the USA and may account for approximately 4% of total USA coal production. Highwall stability is the major ground-control-related safety concern in highwall mining. Engineering away the safety risk by decreasing the highwall slope angle may be the best solution to the hazard posed by vertical joints in highwalls. The Mine Safety and Health Administration (MSHA) requires a ground control plan that usually specifies the hole width, maximum hole depth, maximum overburden depth, seam thickness, web pillar width, barrier pillar width and number of holes between barriers. Design charts for these parameters are given. Web pillars containing pre-existing auger holes are analysed and a design chart for estimating their minimum width is also presented. Close-proximity multiple-split highwall mining, which caused several serious highwall failures, is analysed and recommendations are made. Finally, this study examined records from 5289 highwall miner holes with a total completed hole length of 780 300 m to understand the reasons for early pull out. Average loss was almost 20% of planned hole length, and only 35% of the holes reached the planned depth.     

Simulation of truck haulage systems in surface mines

ABSTRACT

Computer simulation can be used as a means of experimentation and evaluation of both truck allocation and dispatching problems especially when analytical methods are not suitable. The simulation language known as Q-GERT is introduced and evaluated in terms of its applicability to the modeling of surface mining activities. Through the analysis of a wide variety of situations, the program is proven to be an accurate modeling method.     

Groundwater Recharge Assessment in an Arid,Coastal, Middle Mountain Copper Mining District,Coquimbo Region,North-central Chile

Groundwater recharge processes operating in a portion of the western slope of the Chilean Coastal Cordillera (30°S) were assessed. The study takes advantage of the presence of the Cerro Brillador Mine (CBM), currently part of the Universidad de La Serena mining research center. Six factors—slope, solar exposure, drainage density, lineament density, geology and vegetation were characterized in a 12 km × 12 km area around the mine to identify the zones of greatest and least potential for groundwater recharge. The analysis indicates that approximately 66% of the total area presents favorable conditions for recharge. At a more local scale, the work focused on the CBM itself, an experimental facility where structural measurements in the interior and exterior of the mine, monitoring of the water level in the shaft, and sampling of mine water for chemical and isotopic composition were carried out. The chemical analysis highlighted the lack of acid drainage, despite the existence of pyrite (FeS₂) and copper-sulfate mineralization in the mine. The isotopic analysis showed that the groundwater has a similar signature to local precipitation. From this information, a simple conceptual model for the hydrogeology is proposed, in which precipitation rapidly recharges the mine along faults and joints with a preferential N-S strike, but is impounded by the Urrutia fault, which facilitates the storage of groundwater in the underground workings by acting as a flow barrier. A simple analysis suggests a recharge rate on the order of 5% of the average annual precipitation for the CBM area.

     

采动地表移动变形与建筑物损坏程度评价的再认识

实测数据分析的目的是认识地表移动规律和确定预计参数,而沉陷预计的目的是评价采动损坏程度。无论实测数据分析还是形变预计,地表倾斜、曲率和水平变形等主要指标都是基于下沉和水平位移2个移动分量;不均匀下沉在引起地表倾斜和曲率变形的同时,也会导致采动建筑物水平变形和破坏。通过分析起伏地形和不均匀沉陷在实时位形上对地表变形的作用关系,建立了地表水平和起伏条件下采动地表倾斜变形引起的地表水平变形表达式;以采动地表正曲率变形为例,分析确定了建筑结构长度、高度、最大挠度、挠度比与地表曲率的关系,定性给出了建筑结构顶部伸长量、拉伸变形及其影响规律;进一步分析了建筑结构与地基相互作用的反力分布以及拉伸和剪切作用下建筑物损伤破坏特征。在继承我国现行规范中采动建筑物损坏评价优点的基础上,针对硬性分级存在的不足以及I,IV级损坏再划分的模糊性,借鉴英国沉陷工程师手册中考虑建筑物结构长度影响的思想,建立了综合考虑水平变形、建筑物结构长度和挠度比的采动损坏分等定级指标体系;实验结果分析表明,同等采动地表变形条件下建筑结构越长其损坏越严重,证明该指标体系的损坏程度评价结果比现行规范中单纯考虑地表变形的方法更科学、客观,同时消除了原来I,IV级损坏再划分的模糊性和不确定性。     

Change in the local thermal field due to the removal of the coal layer,Velenje depression,Slovenia

ABSTRACT

In this paper we attempt to estimate, using the results of simulations, changes in the local thermal field after removal of the coal layer and thus, to establish the influence that mining has had in the area of the Velenje depression, Slovenia. Intensive mining and coal exploitation has been ongoing in the Velenje depression for many years. Subterranean activities affect the thermal field in this area. The exploitation of the useful material substance represents a disturbance in the low temperature system of the area. In this manner the isolation layer, e.g. coal, is removed. The coal layer acts as an isolation barrier in this case, which is clear on the basis of the results of die first model. According to these results, the temperature at the observation point, which lies close to the coal surface is 18.6°C In the second simulation model the coal layer was replaced with material, which was stored above the coal layer. The surface was sunken and filled up with precipitant water. The coefficient of heat conductivity for the rock of change consisting of sand, gravel and fine sandstone is approximate 3.5 times higher than the coefficient of heat conductivity for coal. Consequently, the temperature at the observation point is 24.3°C. The PORFLOW software package (Runchal & Sagar) was used for the simulation. The program is an extensive mathematical model for the simulation of multiphase fluid flow, heat transfer and mass transport problems in variably saturated porous or fractured media. Results obtained through calculations in the first model are compared with the results of well logging and bottom hole temperature (BHT) measurements, which had been carried out in the drill holes near the observed section. The results obtained through calculation show good agreement with the measured results. Some differences appear in the lower part of the profile under 1200 m; I believe this is because the geological structure and the thermal properties of solids in that depth are only estimates.     

Tailings revegetation - on non-ameliorated substrate

ABSTRACT

The Westonia open pit gold mine, 320 km east of Perth, Western Australia (31°18'S, 118°42'E) was decommissioned in July 1991. Normandy Mining Pty Ltd seeded in May-June I993, the entire surface of the tailings storage facility. The rehabilitation objective was to stabilise the tailings structure. Tailings slurry had been pumped into three Cells at different periods throughout mining operations. The near surface layer of tailings is most significant from a rehabilitation perspective, as it is where plants are growing. Vegetated areas have lower salinity than areas lacking vegetation (8.23 compared with 47,39 dS m^?1 ECe). Revegetation density averages 1.734 stems m^?2 in October 1999 and foliage cover is 30%. Nine chenopods were recorded in October 1999 with Maireana brevifolia, Atriplex undulata and A. leniiformis more prevalent. Grasses continue to show accelerated establishment. A cryptogamic cover prevalent over the upper surfaces of ‘raw’ tailings appears to be enhanced under established vegetation where moisture levels and the soil nutrient status are inherently higher. The tailings profile in the centre of the third cell (vegetation absent) showed similar changes in salinity to previous samplings. The surface sample in April 1999 (102 dS m^?1) was less saline than the April 1998 sampling (225 dS m^?1). The layer between 0.1 m and 0.4 m remains extremely saline, i.e. range 83-150 dS m^?1 ECe. Around the perimeter of his cell the tailings is coarser, and sampling of the profile to 0.3 m depth gave salinities from 5 to 20 dS m^?1 ECe.     

3D deformation effect and optimal excavated design of surface mine

The three-dimensional (3D) deformation effect of the slope engineering under the step-by-step excavation for the Antaibao surface mine was analyzed using the FLAC^3D technique. An optimal excavated scheme with a relatively steeper slope angle of 47° instead of 30° was successfully implemented at the west wall in the geological section 73200 of the mine area, where the 3D effect of the nonlinear large deformation of the slope was taken into account. Based on the above research conclusion, put forward the countermeasures of shortening mining length, excavating by different regions, timely foot backfilling to protect the excavated slope, and monitoring and feedback adjustment by studying the nonlinear effect. The results show that these countermeasures are effective in controlling maximum deformation and increasing the stability of the slope.     

Simulation models for surface mines

ABSTRACT

The ease and speed of constructing computer simulation models using the GPSS programming language is discussed. GPSS is a computer programming language and so each problem requires a separate program to be written. However, this is not a problem since the programs can be written in a matter of hours or days. This is the case for even the most complicated mining situations

The examples presented here represent three different mining situations from actual mines in Australia. It is shown that the GPSS language provides a rapid, inexpensive and very accurate method of simulating a variety of surface mining operations.     

受采动影响的山体边坡安全论证

准确分析地下采矿对地表山体边坡的影响,具有重要的现实意义。本文以冀东某地下铁矿开采为实例,通过数值模拟和数值微分方法,分析计算了受采动影响的山体边坡倾斜变形大小,为评价边坡上的构筑物安全提供了定量的分析依据。经过实践验证,其分析方法较为准确、方便。