采矿工程毕业设计翻译

附录外文翻译

APPLICATION OF BLASTING IN DRIVING TUNNEL

1 FRAGMENTATION

Fragmentation is the breaking of coal, ore,or rock by blasting so that the bulk of the material is small enough to load, handle and transport.Fragmentation would be at its best when the debris is not smaller than necessary for handling and not so large as to require hand breaking or secondary blasting .

Energy must be supplied to rock by direct or indirect means to fragment that rock and the type of loading system.Fragmentation energy is consumed by the main mechanisms: (1) creation of new surface area (fracture energy), (2)friction (plasticity) and (3)elastic wave enegy dispersion.

The loading method determines the relative proportions and the amount of energy consumed in fragmenting a given rock type. Unonfined tensile failure consumes the least energy with an increasing a,mount of energy required as the rock is more highly confined within a compressive stress field during fragmentation The way energy is applied by tools to cause rock or mineral fragmentation is important in determining fragmentation efficiency. To best design fragmentation tools and optimize fragmentation systems it would be desirable to know how rock properties influence breakage.

The strength of rock is influenced by the environmental conditions imposed on the rock.Those of most importance in rock are (1)confining pressure ,(2)pore fluid pressure, (3)temperature and (4)rate of load application .Increase in confining pressure, as with increasing depth beneath th earth's surface or under the action of a fragmentation tool, causes an increase in rock strength .Apparent rock strength decreases as porc fluid pressure increases, since it decreases the effect of confining pressure. Although chemical effects of pore fluids influence rock strength, they generally are small compared to the confining pressure effect, except for a small minority of rock types .Increase in rock temperature causes a decrease in rock strength.This effect is very small because of the small ambient temperature changes

found during mining. An increase in rate of load application causes an apparent increase in rock strength.

Rock exhibits directional properties that in fluence the way it breaks. These are embodied in the concept of rock fabric ,which connotes the structure or configuration of the aggregate components as well as the physical or mechanical property manifestations. Rock fabric ont only relates to the preferred orientation of mineral constituents and their planes of weakness, but also to the configuration of discontinuities, microcracks and pores.Joints and bedding planes have great influence on fragmentation at field scale.

Physical properties of rock (density,indentation,hardness,abrasivehardness and porosity ,)are frequently used in conjunction with mechanical properties to develop better empirical esti mations of rock fragmentation.

2 BLASTHOLE CHARGING METHODS

Drill hole charging can be carried out in different ways depending on whether the explosive used is in cartridges or in the form of loose material. The oldest charging method implies the use of a tamping rod and this system is still used to a very great extent .During the last 20years, compressed air chargers have been used and these machines provide both good capacity and also an improved level of charge concentration so that the drill holes are utilized to a higher degree. During the last few years semi-automatic chargers have been taken into use, primarily in underground work. Compressed air chargers for blasting powder in the form of loose material have also come into use on a large scale. As far as slurry blasting is concerned, special pumping methods have been developed through which charging capacity in the case of large diameter drill holes is practically good.

A tamping rod must be made of wood or plastic. It must not be too thick in relation to the drill hole diameter since this can crush and damage fuse or electric detonator cables during charging work. If a good degree of packing is to be obtained during charging with a tamping rod then only one cartridge at a time should be charged and tamped. The detonator must be correctly fed into the drill hole during charging work.

Compressed air chargers have been in use is Sweden for about 20 years. The first type consisted of aluminum pipes connected together and the cartridges were blown into the hole with an air pressure of 42 pounds per square inch .since that time the charging tube has been replaced by anti-static treated plastic hose of a special design.

A charger includes a foot-operated valve, reduction vavle with air hose, breech, connecting tube and charging hose.

The semi-automatic charger permits the continuous insertion of explosive cartridge at the same rate as they are charged in the hole by the hose .Instead of a valve being used ,the cartridges pass through an air lock between two flaps. The air pressure in the charging hose is retained while cartridges are pressure in the charging hose is retained while cartridges are beins inserted .The semi-automatic charger permits considerably higher charging capacity than the normal type of charger.

Explosives in the form of the form of loose material, usually ammonium nitrate explosives(ANFO), require special chargers. Two types can be differentiated: pressrure vessel machines and ejector units. Pressure vessel machines are particularly suitable for crystalline An explosives with good charging capacity. Ejector units are operate by an ejector sucking up explosive from a container through a charging hose. The explosive is then blown through the charging hose into the drill hole .There are, also combined pressure ejector machines. The charging hose used for ANFO charging operations must conduct electricity and have a resistance of at least 1K?/m and max.30K?/M.

Nitro Nobel has developed a special pumping procedure which consists of a tanker vehicle which is used to pump explosive directly the drill holes. The charging capacity is very high in the case of large diameter drill holes.

3 CONTROLLED BLASTING TECHNIQUTES

Controlled blasting is used to reduce overbreak and minimize fracturing of the rock at the boundary of an excavation. The four basic controlled blasting techniques are: line drilling, presplitting, cushion blasting and smooth blasting.

Line drilling, the earliest controlled blasting technique, involves drilling a row of closely spaced holes along the final excavation line, providing a plane of weakness to

which to break. Line drill holes, 2or 4 diameters apart and contain no explosive. The blastholes adjacent to the line drillholes normally are loaded lighter and are on closer spacing than the other blastholes. The maximum depth for line drilling is about 30 ft .Line drilling involves no blasting in the final row of holes, and thus minimizes damage to the final wall.

Presplitting, sometimes called preshearing ,involves a single row of boreholes ,usually 2 to 4 in .in diameter ,drilled along the final excavation at a spacing of 6 to 12 borehole diameters .Dynamite cartridges 1to 1.5 in . in size on 1 to 2 ft .centers usually are string-loadde on detonating cord ,although special small-diameter cartridges with special couplers are available for total column loading .In unconsolidated formations ,closer spacings with lighter powder loads are required .The bottom 2 to 3 ft .of borehole usually is loaded somewhat heavier than the remainder .Stemming between and around the individual charges is optional .The top 2 to 3 ft . of borehole is not loaded ,but is stemmed. The depth that can bu presplit is limited by hole alignment ,with 50 ft .being about maximum .The presplit holes are fired before before the adjacent primary holes to provide a fracture plane to which the primary blast can break .In presplitting it is difficult to determine the results until the adjacent primary blast is shot .For this reason ,presplitting too far in advance is not recommended .Presplitting seldom is done underground.

Cushion blasting involves drilling a row of 2 – to 6-in .diameter boreholes along the final excavation line ,loading with a light well-distributed charge ,completely stemmed and firing after the main excavation is removed rather than before ,as in presplitting. The burden on the holes is slightly larger than the spacing .Wedges may be used to abut the charges to the excavation side of the borehole and minimize damage to the final wall .Eeplosive loading is similar to that in presplitting .Cushion blasting has been done to depths near 100 ft .in a single lift with the larger-diameter boreholes because alignment is more easily retained .Cushion blasting seldom is done underground.

Smooth blasting is the underground counterpart of cushion blasting .At the perimeter of the tunnel or drift ,closely spaced holes with a burden-to-spacing ratio

near 1.5:1 are loaded with light well-distributed charges .Smooth blasting differs from cushion blasting in that (1) except at the collar ,the charges are not stemmed and (2) the perimeter holes are fired on the last delay in the same round as the primary blast .Total column loading is most common ,although spacers may be used .The holes are stemmed to prevent the charges from being pulled out by the detonation of the previous delayed holes .Smooth blasting reduces overbreak in a drift and also provides a more competent back requiring less support .It involves more perimeter holes than does normal blasting.

Combinations of controlled blasting techniques are used .In unconsolidated rock,line drilling sometimes is desirable between presplit or cushion boreholes . Corners sometimes are presplit when cushion blasting is used.

4 TUNNEL BLASTING

The most common methed of driving a mining tunnel is a cyclic operation in three sequences:

(1)Drilling shot holes ;charging them with explosives and blasting.

(2)Removing the resulting muck pile.

(3)Inserting the tunnel linings into the newly excaved area; and advancing the ralls. ventilation arrangements, and power supplies ready for the next cycle of operations.

The basic principle of tunnel blasting ,in its simplest term, is to loosen a volume of the virgin rock in such a way that when it is removed the line of the tunnel has advance in the correct direction with as nearly as possible the correct cross-section.

The dilling pattern in which the holes to receive the explosives are drilled into the working face is designed so that :the holes are easy to drill; the minimurd total quantity of explosive is required ;and the periphery of the space left after the blast conforms as nearly as possible to the required tunnel section.

A blast round consists of cut ,relief, breast and trim holes . The cut portion is the most important . The objective of the cut is to provide a free face to which the remainder of the round may break.

The two general types of cuts are the angled cut and the burn .These can be used

in combinations to form various other cuts .Angled cuts are more advantageous than burn in wide headings ,due to the fewer boles and less explosive required per foot .A disadvangtage is the possibility of large pieces of rock being thrown from the ―V‖.

The wedge or V-cut consists of two holes angled to meet or nearly meet at the bottom . The cut can consist of one or several Vs, either verticao or horizontal .For deeper rounds or hard-breaking rock ,double Vs can be used .The smaller is called the baby cut . It is useful in small https://www.360docs.net/doc/4f17295096.html,rge-diameter burn holes provide excellent relief in big headings .Burn cuts permit deeper rounds than angled cuts and , due to the increased advance per round ,may prove more economical .In burn cuts ,the holes must be drilled parallel , with proper spacing ,and 0.5 : 1 ft deeper than the remainder of the round .Usually ,one or more holes (large-diameter) are left unloaded to provide relief for the loaded holes . Various combinations of spacing ,alignment and holes loaded are possible.

Innumerable typesofblastingrounds are used in underground headings .Even in the same heading the round may have to be altered as different rock charateristics develop.An important factor in any round is the firing sequence .In general ,the holes are fired so that each hole or series of holes is blasted to the free face provided by the preceding holes .The depth of drift rounds depends on the complete drifting cycle and drift size.A general rule is that a round will not break much deeper than the least cross-sectional dimension of the drift . Rounds can be arranged that provide certain muck-pile shapes and positions for more efficient loading and cycles . In drifts requiring close support , rounds can be arranged to prevent damage.

爆破在井巷掘进中的应用

1 破岩理论

破岩是用爆破的方法把煤、矿石或岩石破碎，使大部分物料的块度足够小，满足装载、处理和运输的条件。碎块不要小到不便于装运，也不要大到需要手工破碎或二次爆破，这样的破岩才算最佳。

为了破岩，必须用直接或间接的方式向岩石施加能量。能量的大小取决于岩石的性质和装药系统的类型。消耗能量的主要机理有：(1)形成新的表面(破岩能量)；(2)摩擦(塑性)；(3)传播弹性波能。

上述方面的相对比例和所消耗的能量决定于装药的方法和需破碎岩石的性质。无约束时岩石拉伸破坏所消耗的能量最少，在破岩过程中如岩石受到较高的压应力场的约束时，破岩需要能量有所增加。用机械传递能量使岩石或矿石破碎的方法，对于决定破岩效率十分重要。为了设计出最好的破岩机器和最佳的破岩系统，需要尽可能地弄清楚岩石性质是如何影响破岩的。

岩石的强度受到周围环境的影响，其中最重要的因素是：(1)约束力；(2)空隙中的流体压；，(3)温度；(4)加压的速度，约束力的增加(如随着高地表深度的增加或在破岩机具的作用下而使其增加)，使严石的强度增加。随着孔隙流体压力增加，岩石的视强度就降低因为它减弱了约束力的作用。虽然孔隙流体的化学作用对岩石的强度有影响，仅和约束力作用比较，除少数几种岩石外，一般都比较小。岩石温度的增加使岩石的强度降低。但这种效应非常小，因为采矿的时候周围温度变化小。加压的速度增加，使岩石强度显著增加。

岩石具有影响其破碎方式的方向性。这体现在岩石的结构上，包括集合岩石组分的结构或形状以及岩石的物理特性或机械特性岩石的结构不仅与矿物组分的方向及其薄弱面有关，而且与其非连续性、微观裂隙和孔隙

的构造有关。在现场，节理和层理对破岩有很大影响。人们经常综合利用岩石的物理性质(密度、压痕，硬度、磨蚀硬度、孔隙度)和机械性质，来谋取更好的破岩效果。

2 装药方法

炮眼装药的方式可根据所采用的炸药是药卷或散装而有所不同。最古老的装

药方法是用炮棍装药，这种方法至今仍广泛使用。在过去二十年中，压风装药器已被采用，这些装药器既提高装药效率，同时又改进装药密度，因此炮眼的利用率较高。近几年来采用了半自动装药器，主要用于井下作业。装填散装药的压风装药器也已大规模地投入使用。就浆状炸药而论，已发明了一些专用的泵送方法，这种方法对于大孔径炮眼的装药能力实际上是很高的。

炮棍必须用木或塑料做成。但炮棍与钻孔相比不能做得太粗，因为这在装药作业中有可能捅坏和损坏导火索或电雷管脚线。用炮棍装药时，若想装填得好，那么一次只能装填并捣实一个药卷。装药时雷管必须送到炮眼中的准确位置。

压风装药器在瑞典已使用了大约二十年。第一种装药器由几节铝管连接而成并用42磅／英寸2的压风把药卷吹入炮眼。后来这种装药管由专门设计的经抗静电处理的塑料软管所代替。一台装药器包括脚踏阀，带风管的减压阀、分风管、连接管和装药软管。

半自动装药器可连续装填药卷，其装药速度与软管装药速度相同。这种半自动装药器不用阀门，而是让药卷通过一个位于两个闸门之间的气室。装药时装药钦管中的风压不变。半自动装药器的装药能力比普通的装药器高得多。

散装炸药一般为硝铵炸药(铵油炸药)，需要专用装药器。有两种不同的装药器：压力罐式装药器和注药器。压力罐式装药器特别适用装填结晶的销铵炸药，其装药能力较高。注药器的操作是用一个喷射器经—很软管把炸药吸出，然后再通过这根装药软管将炸药吹入炮眼入。还有一些由压力罐和注药器组合的装药器。装填铵油炸药的装药软管必须能导电，其电阻最小为1千欧米。最大为30千欧米。

奈特罗诺贝尔(硝化诺贝尔)公司曾创造一项专用泵送炸药的工艺，它包括一台直接把炸药泵入炮眼的槽车。向大直径炮眼装药时其装药能力极高。

3 控制爆破

控制爆破用于减少巷道超挖和使围岩震裂减至最小程度。摔制爆破的四种基本方法是：轮廓线钻眼法、预裂爆破法、缓冲爆破法和光面爆破法。

轮廓线钻眼法，是最早的控制爆破法，这种方法是沿巷道(最终)轮廓线打一排紧密相邻的钻眼，形成一个有利于破碎的薄弱面。布在轮廓线上的钻眼直径为2英寸或3英寸。眼距通常相当于2~4个炮眼直径，不装药。靠近轮廓线钻眼的

炮眼，起装药量及眼距均比其他炮眼小。轮廓线眼的最大深度大约为30英尺。由于轮廓线钻眼法的最后一排眼不爆破，因而对岩壁的破坏最轻。

预裂爆破，有时又称为预剪切爆破，是在巷道的轮廓线上钻一排炮眼，其直径一般为2至4英寸眼距为炮眼直径的6~12倍，显然市场上可买到柱状装药所需的小直径药卷和专用的连接器，但一般仍采用直径为l—11／，英寸的代那买特药卷，间隔装药，药卷间隔为1~2英尺，以导爆线串系起来。在松软岩层中，要求眼距小—些，装药量少一些。眼底2~3英尺处的装药量略比其余部分要多一些。单个药卷之间及其周围是否充填炮泥可随意确定。孔口2~3英尺处不装药，但要充填炮泥。预裂爆破的深度受炮眼排列的限制，最大深度约为50英尺。预裂炮眼比邻近主炮眼先起爆，以形成有利于主炮眼爆破的裂面。预裂爆破中在邻近主炮眼爆破之前很难判断其效果。因此建议预裂的超前距离不要太大。预裂爆破很少在井下使用。

缓冲爆破法是沿岩道轮廓线钻一排直径为2~6英寸的炮眼，眼中装入均匀分布的小药卷，完全堵满炮泥，起爆顺序与预裂爆破不同，要在主炮眼起瀑之后周边眼才爆破。炮眼的最小抵抗线(光爆层厚度)略大于眼距。可利用楔子把药卷固定在眼中靠近爆破自由面一侧，以减少爆破对岩壁的损坏。这种方法的装药方式与预裂爆破法相似。因为钻大直径炮眼容易准直，所以缓冲爆破法采用大直径炮眼时一次爆破深度以达一百英尺。但缓冲爆破在井下很少使用。

光面爆破法就是井下的缓冲爆破法。巷道周边的密集炮眼的光爆层厚度(周边眼的抵抗值)与眼距之比L接近1.5：1。周边眼中装上分布均匀的小药卷。光面爆破与缓冲爆破的区别在于：(1)除炮眼口外，药卷不用充填炮泥；(2)周边眼在一茬炮眼中最后一段起爆。虽然药往中也可采用间隔物(间隔装药)，但最常用的是柱状装药。孔底装药量稍多一些。炮眼均填以炮泥，以防止(在延期爆破中)光爆炮眼爆轰时将药包带出。光面爆破减少巷道的超挖，增强围岩稳定性并减少支护量。但比普通方法需要多钻一些周边眼。

各种控制爆破方法可结合使用。在松软岩石中，有时需要轮廓线钻眼方法与预裂法或缓冲爆破法结合使用。当采用缓冲爆破法时，有时需要在转角处用预裂法爆破。

4 井巷爆破

最常用的岩巷掘进方法是三个工序的循环作业：

(1)钻炮眼、装炸药和爆破。

(2)装岩(将爆破的岩堆装运出去)。

(3)安装支架，支护刚掘出的巷道，敷设接长轨道、风管和电缆，为下个循环作好准备工作。

简而言之，岩巷爆破的基本原则是，把岩体上一部分岩石破碎下来，当装走爆落的岩石后，巷道按正确的方向前进，其断面尽可能地接近设

计断面。

炮眼布置设计要做到：便于钻跟，耗用炸药最少，爆破后所形成的巷道断面尽可能接近设计要求。

一组炮眼由掏槽眼、扩槽眼、辅助眼和周边眼组成。掏槽眼最重要。掏槽眼的作用是为炮眼组的其他炮眼提供一个自由面，便于爆破。

常用的两种掏槽方式是斜角眼掏槽和直眼掏槽。这两种掏槽方式可以联合组成其他各种掏槽方式。在较大断面巷道中，斜角眼掏槽比直眼掏槽优越，因为炮眼数目少掏，每掘进一英尺巷道所需炸药量少。其缺点是“v”形掏槽有可能抛出大块岩块。

楔形掏槽或v型掏槽内成对的斜角炮眼在底部相遇或接近相遇组成。楔形掏糟可由一个或几个v型槽构成垂直或水平楔形掏槽。对于深度较大的炮眼或难于爆破的岩石，可采用复式楔形掏槽。较小的掏槽称为小槽。它适用于小断面巷道。

大直径掏槽直眼在大断面巷道中可为良好的扩槽创造条件。采用直眼掏槽，炮眼组的深度可比斜眼掏槽大一些，因为每茬炮的进度增加了，证明其更为经济。直眼掏槽的槽眼要平行，眼距要适当，其深度要比其他炮眼深1／2~1英尺。一般有一个或一个以上槽眼(大直径眼)不装药、为其他装药槽眼提供自由面。槽眼间距，布置及装药槽眼可采用各种组合形式。

井下巷道掘进中炮眼布置有无数种。甚至在同一巷道中，随着岩石性质的变化也要改变炮眼布置。对任何一组炮眼来说，重要的因素是爆破顺序。一般来说，炮眼引爆的顺序应使每个炮眼或一组炮眼随前一响炮眼所形成的自由面爆破。每茬炮的深度取决于整个掘进循环和巷道的断面尺寸。一般规律是，一茬炮的深度不要超过巷道最小断面尺寸太多。炮眼布置要使爆破下来的岩石堆的形状及位置

有利于更有效地装运和循环作业。对用需用密集支架的巷道，炮眼布置要能够预防破坏。