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paramount adj. 最高的，至上的；首要的， tortuous adj. 弯弯曲曲的 brass n. 黄铜
spad n. 矿山井下测量用钉
damp adj.潮湿的，不完全干燥的
galvanic adj. 流电的，抽搐的，以流电所产的 corrosion n. 腐蚀；受腐蚀的部位 loose-leaf活页
facilitate vt.使便利，减轻…..的困难 meticulously adj.极仔细的；一丝不苟的 neatness n.整洁，干净
graphics n.图样；图案；绘图；图象 plotter n.绘图仪，绘图机
perpendicular adj垂直的；成直角的 fireproof adj.耐火的，防火的 vault n.拱顶，地下室
microfilm n.(拍摄文件等用的）缩微肢卷
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Unit 2 Surface Mining 露天采矿 (9) Introduction 简介
Surface mining is the predominant exploitation procedure worldwide，producing in the United States about 85% of all minerals, excluding petroleum and natural gas. Almost all metallic ores (98% )，about 97% of the nonmetallic ores, and 61 % of the coal in the United States are mined using surface methods ( U. S. Geological Survey, 1995 ； Energy Information Administration, 2000 )，and most of these are mined by open pit or open cast methods. In open pit mining, a mechanical extraction method, a thick deposit is generally mined in benches or steps, although thin deposits may require only a single bench or face. Open pit or open cast mining is usually employed to exploit a near-surface deposit or one that has a low stripping ratio. It often necessitates a large capital investment but generally results in high productivity, low operating cost, and good safety conditions. The open pits views are showed in Fig. 2.1. Fig_ 2.1 Open-pit views ( Photos were obtained from www. google, com) The aqueous extraction methods depend on water or another liquid ( e. g. dilute sulfuric acid, weak cyanide solution, or ammonium carbonate) to extract the mineral. Placer mining is used to exploit loosely consolidated deposits like common
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Other factors that can influence pit limits are existing surface infrastructures, such as townships,river,etc ,
In order to enhance the stability of a slop within the pit and for safety reasons berms may be left. A berm is a horizontal shelf or ledge within the ultimate pit wall slope. The berm interval, berm slope angle, and berm width are governed by the geotechnical configuration of the slope. The overall pit slope angle is the angle at which the wall of an open pit stands, as measured between the horizontal and an imaginary line joining the top bench crest with the bottom bench toe.
For the duration of open pit mining, a haul road must be maintained into the pit. A spiral system is an arrangement whereby the haul road is arranged spirally along theperimeter walls of the pit so that the gradient of the road is more or less uniform from the top to the bottom of the pit. A zigzag system is an arrangement in which the road surmounts the steep grade of a pit wall by zigzagging，generally on the footwall side of the pit. The choice of spiral or zigzag is dependent upon the shape and size of the ore body, truck economics, and pit slope stability.
Haul road width is governed by the required capacity of the road and type of haulage unit. The grade may be defined as the the road in terms ofdegrees from the horizontal or percentage of rise to the horizontal.
The angle ofrepose or angle of rest is the maximum slope at which a heap of loose material will stand without sliding.
The suboutcropdepth represent the depth of waste that has to be removed before any ore is exposed. This waste is often referred to as preproduction stripping.
Vocabulary
open pit露天坑 bench n. 平台
stripping ratio aqueous adj. 剥采比 dilute adj. 水的，水成的
cyanide n. 贫化的稀释的冲淡的氰化物 ammonium carbonate碳酸铵 placer mining淘洗采矿 hydraulicking水力采矿
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erosive adj. 侵蚀性的，腐蚀性的 solution mining 溶浸釆矿 chloride n. 氯化物 leaching n. 堆浸 waste rock 废石 scheduling n. 进度计划 crude adj. 天然的，未加工的 slope n. 边坡，斜坡，斜面 terminology n. 专门用语，术语 shovel n. 铲子；锹，铲运机 bench slope 平台 toe n. 脚趾；足尖部 crest n. 顶，峰 pit limits 采坑境界 berm n. 台阶 berm slope angle 台阶坡面角 geotechnical adj. 岩石力学的 haul vt.&vi. 拖，拉，运输 Spiral adj. 螺旋形的 gradient n. 道路的斜度，坡度 zigzag adj. 锯齿形的，之字形的，Z字形的 haulage n. 货运业，运费 (10) Open Pit Blasting Technology 露天爆破技术 Drilling and Blasting is by far the most economical means to fragment and move material. The initial blast design depends mainly on the hardness of the rock, the geologic structure of the rockmass, the location of the mine relative to vibration sensitive structures, available drilling equipment and the excavation rate and capacity of the mining equipment. A high level of field controls must be continuously maintained in order to gain reliable quantitative data that can then be used to refine the blast design.
To begin，a well-designed blast consists of a quantity of explosives placed into a series of blastholesdrilled into a rockmass. The amount of explosive energy generated by the explosives must be adequate to overcome the tensile strength of the rockmass.
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This series of blastholes must then be detonated in a controlled sequence as to control the burden and spacing dimensions between adjacent holes. A well-designed blast will efficiently utilize the explosive energy in order to result in optimum fragmentation and
burden movement. One of the negative impacts of blasting is ground and air vibration. Proper burden spacing design dimensions maintained through accurate field controls typically will yied reduced ground vibrations as the energy is used to fragment and move rock and not to create excessive ground vibrations through energy over- confinement. A well designed blast is showed as Fig. 2.2.
1.Surface Blast Design
Surface blast designs require the selection of hole spacing S，burden B, charge weight W or powder factor PF, top-hole stemming length T, and subgrade drilling depth J. Design parameters are shown in Fig. 2. 3. Borehole patterns are drilled square (S/B = 1) or rectangular (S/B> = 1) on center or offset ( staggered ) ? The sequence of hole initiation timing, S/B ratio, actual timing between charge detonations, and number of blasthole rows determine the shape of the broken rock pile as well as the degree of rock fragmentation.
An empirical approach is taken in blast design as blasting is a never-ending process of fine-tuning and modifications. This approach is necessary due to the many factors that cannot be controlled, such as geology and explosive loading conditions.
Borehole diameter and burden are perhaps the most important factors used in design. Burden values should be selected based on geology and explosive energy output. Usually hole diameter is set by the drill rig capacity, which is matched to the range of hole depths anticipated for the job. It is desirable to select a size that will provide an adequate powder factor (the ratio of explosive quantity used to the yield ofrock breakage) for breskage while distributing the explosive evenly throughout the hole depth.
Fragmentation and particle size distribution are a function of hole diameter and burden.The capacity of the excavation equipment dictates the required fragmentation.Thecharge length to charge diameter ratio for a cylindrical charge should be five or