《毕业设计英文翻译部分2.doc》由会员分享，可在线阅读，更多相关《毕业设计英文翻译部分2.doc（17页珍藏版）》请在taowenge.com淘文阁网|工程机械CAD图纸|机械工程制图|CAD装配图下载|SolidWorks_CaTia_CAD_UG_PROE_设计图分享下载上搜索。
1、VERTICAL SHAFTS Ventical shafts are used especially for hoisting；they also serve as the entrance into and the exit from the mine , timbei and other material are transported through them, as well as filling material ,and they constitute the airways. The pipelinges for removing the water ,the elephone
2、 cable, etc.are all placed in them. If we hoist through them all he or eor coal,they form the main working shafts. When they serve for ventilation they are downcast (inlet) crup cast (outlet)shafts .Sometimes they serve only certain special purposes,e.g. the transport of filling material , as energe
3、ny exits,etc. Them auxiliary shafts. A shaft need not open on to the surfaceWhen It begins below the surface it is called an underground shaft(blind shaft) The return or up cast shaft often serves also for the transport of men and material，for the compressed airpiopeline，for the electric cables，Wate
4、r-pipesetc，.so that the main shaft is not disturbed by frequent repair sand can be used entirely for hoisting The performance of the shaft may be increased by increasing the hoisting speed，by shonening the time for loading and unloading，i.eby suitable equipment and circulation of the cars at the sha
5、ft stations in the mine and on the surface，and by employing multicompartment cagesAt present we have cages with up to eight compartmens，which can hoist a great number of truck sand a large body of workersIn the shaft there are two hoisting compartment side by sideA greater hoisting performance can b
6、e achieved also by the use of skips Vertical shafts are cut almost without exception through the bedsIn horizontal or slightly inclined beds we also traverse and explore by this means the overburden and ascertain its nature, which cannot be done by inclinesThat the vertical shaft traverses the overb
7、urden may on the other hard be a great disadvantage when the overburden include weak rock sauroted with waterUpon he nature of the rock through which the shafts are sunk depends the choice of their shape and manner of their support.SHAFT SINKING IN FIRM ROCK In conventional shaft sinking in firm roc
8、k， the sinking cycle consists of three basic operations， namely，drilling and blasting，mucking of the blasted material and when the placement of a concrete lining or support when necessary Is it important to achieve the greatest advance possible with a minimum or overbreak to the shaft sidewall ，cons
9、ident with maintaining the stabillty of he shaftThe depth of round to be blasted is controlled by proper coordination of the basic operations Full face shaft rounds (or advances) are generally preferred when mechanical type mucking is employed as it offers rapid advanceShot holes are generally drill
10、ed by hand held compressed air operated jack hammers Some improvements have been achieved in mechanization in this area by the use of shaft jumbos with multiple drills，particularly in large diameter shafts The process of removing the blasted materia1 from the shaft bottom is known as mucking Manual
11、or hand mucking，the method used extensively in the past，is very expensive today and is usually used only in small diameter shaftsAmong the mechanical types of mucking devices used today are Riddeg Muckers，Cryderman Mukers，Eimco 630 Mucker，Cactus Grab and Clamshell Mucking. The broken rock is loaded
12、into a bucket which is hoisted to the surface by a winchwe have to ensure that nothing falls into the shaft from aboveThis is done by putting a covering over the shaft collar so that only in the middle an opening is left through which the bucket can passThe bucket is steadied by rope guides while it
13、 is being hoisted Sometimes small cages holding one or two mine cars are used in sinking the shaft Infiltrating water has to be pumped outFor this purpose pumps are used Which can easily lowered into the shaft by cable or chain and hoisted out during blasting operationsSimilarly provision has to be
14、made for ventilation，usually by a ventilatio pipeline hanging on acableThe pipeline is lowered as the shaft is sunk, and is lengthened by adding further sections on the surface or，when it is a fixture，it is length end from below as the shaft is deepened. The workers must always have an escape way in
15、 case of sudden inflows of water or other accidentsFor This reason a safety ladder is lowered to the bottom of the shaftThis ladder is drawn up when blasting tackes place There are a number of shaft lining methods used todayCircular concrete lined shafts are the methods commonly constructed shaftsTh
16、e advantages associated with circular lined shafts are ability to achieve high sinking rates，greater strength for ground support, better air flow cha-racteristics through the shaft，lower maintenance cost, the ability to seal off unwanted air or gases and rehabi- litaion can be accomplished much easi
17、er if an accident occurs in the shaftSHAFT SINKING IN UNSTABLE AND WATERBEARING GROUND Under Ground water is the principal cause of difficulties arising in singking a shaft in unstable ground， as sand ,gravel, clay or siltEven in dry soils, the removal of lateral support around an excavation may cau
18、se a fall，of flow, of the material into the excavated space, and when water is present, this tendency is great1y increasedThe first requisite the shaft is，therefore，a lining of wall； but if water pumped out， the groundwater will flow under the lining into the excavation，carrying with it the finer pa
19、rticles of the soil; or partially liquefied clay or si1t may be forced up into the shaft by the wuperincumbent weight. in such case, continued excavation and pumping may cause a continuous flow with slips and falls of the ground，distortion of shaft lining，subsidence of the surface around the shaft m
20、outh and settlement of the sinking equipment and adjacent buildingsThis situation may prevent further progress. except by a chance of method Hence sinking methods requiring pumping have been largely eplaced by those in which pumping is unnecessary Different methods of sinking in unstable ground have
21、 been adoptedAmong these are： 1Wood or steel sheet-ling, driven vertically around the sides of the excavation and braced bu horizontal tinmbers or steel beams 2Drop-shafts, with walls of reinforced concrete built above the surface, which sink as excavation advances. 3 Concrete diaphram wall, constru
22、cted by filling a ring of contiguous bored pile holes surrounding the shaft. 4 Freezing method, by which p protective wall of ice is formed in sufficient thickness to enable singing to proceed normally5 Cementation and grouting methods, with Which the liquid cement or chemicals are injected under pr
23、essure into flssures and cabities in the ground by means of boreholes and pumps 6Rotarydrilling method (or shaft boring)， With which all operation in shaft sinking are carried out by men working above ground and are performed through unstable and water-bearing ground without difficulty.FREEZING METH
24、ODFreezing method in shaft sinking was invented by FHPoetsch in 1883Its essential feature is the soledy flying, by freezing, of water-bearing ground in which the shaft is sunk. The freezing is sometimes continued into water bearing rock .This method has been much used in recent years To preare for t
25、he freezing a series of equally spaced boreholes ate drilled on a concentric circle enclosing the site of the shaft Heat is remive from the ground via probes( free tubes ) placed into the boreholes The probe itself consists of an external pope ,50 - 150 mm in diameter , closed at the lower end and c
26、ontaining an open ended inner tube of slifhtly shorter length(Fig5) The inner rube mau vary between 20 mm and 75 mm in diameter. The freezetubes are conneded to two circulation mains， in such a manner that cold brine may be pumped down the inner tube and a11owed to return along the annular space bet
27、ween the two tubes and thence through the collection main back to the refrigeration plantHere it is pumped through a chillernormaHy a shell and tube heat-exchanger-and is recooled and then delivered via a distribution main to the inner tubes of the probes. The coolant(brine)is therefore confined in
28、a closed ,recirc-ulatory flow path, industrial refrigeration plant is required to cool the brine. For ease of installtion, this is brought to site packaged into units, either skid or trailer mounted, The choice of equipment and refrigerant is a wide one: rotary or reciprocating compressors, using ei
29、ther Freon or ammonia as frfrigerants, are in common useCompound compression is often required to produce the necessary temperature depression. Abstracted heat is dissipated into a nearby watercourse if available, if not then into the atmosphere by forced-draught cooling towers or evaporative conden
30、sers. Such a system, with two-stage compressors, can ultimately lower the brine temperature to一40 if required, but a greater mechanical efficiencyis fained if design temperatures are limited to about一30(F1g5) The effect of circulaing a coolant through the complete system is to produce long pencils o
31、f frozen strata around each column, and these increase in girth intil, when they merge, a circular barrier of frozen ground is formed， known as to ice wall. Whilst this is happening several effects are observable in a centrally drilled pilot hole, which is lined with perforated casing tube. It will
32、be apreciated that as the freezing advances inwards, ice formation gives rise to a displancement of water and this in turn is reflected by a rise in level of the water in the pilot hole. Some of the water isFig. 5 Refvigeration system1-Cooling water; 2-High pressure refrigerant gas; 3Low pressure re
33、frigerant gas; 4-Brine pump; 5-Freese tubes; 6-Expansion valve; 7-Liquid refrigerantalso explled outwards through fapa in the ice wall, but on closure the rate of expulsion via the central hole becomes regular and can be correlated with the estimated thickening of the ice wall according to the rate
34、of heat extraction provided by the refrigeration plant, Measure-ments of water quantities and temperature in the pilot hole are therefore extremely helpful in diagnosing the state of affirs at deptn ,and in deciding at what time the ice wall reaches this stage when sinking can safrly proceed. During
35、 excavation refrigeration is maintained ,gene-rally in excess of the level required to offset heat transference from the warmer strata surrounding the shaft. CEMENTATl0N ANDGROUTING METHODS Mine shafts often intersect strong aquifers which risk inundation of the shaft unless some form of water contr
36、ol can be introduced. In sedimenrary formations theaquifers are often roughly horizontal. The aquifers may consist of open joins or cracked and fissured rock arising from tectonic action ,or from porous rocks such as sand-stones. In shaft sinking，when water flowing into a section of deepening shaft
37、exceeds a few litres a second ,work becomes slow and increasingly difficult ,In some sites the potential water-flow to a shaft may be 100 liters a second and moreThe singking then becomes impracticable without previous ground treatment .The commonest way of suppressing water inflow is by cement or b
38、y chemecal grouting before shaft sinking commences. The presence of aquifers at a potential shaft site is established before comstruction commences by sinking an exploratory test hole and analysing the results of rock cores and of in-situ water tests. Plans for the treatment of the aquifer zones are
39、 then made. The process of injecting liquid cement or chemicals under pressure into fissures and cavities in the ground is called cementation or grouting. A number of small- diameter bore boles are put down around the shaft from the ground suiface or from the shaft excacation, through which cement o
40、r chemical grout is forced by means of pumps. The grout most commonly used for jointed and fissured rock is cement frout .Thick cement slurries of the consistency of a mortar will not penetrate passages narrower than a few centimeters and the grout used for fine rock very dilute suspension .Typicall
41、y the ratio of water to cement may be as low as eight to one at least during the early stages of injection. When fissures becomes narrower than about 250microns, the individual cement particles quickly block the entrances to the fissures and treatment is ineffective. Accordingly the cement grout is
42、replaced or supplemented with a chemical grout whenever the rock encountered comprises fine fissures or the fine pores of open granular rocks such as sandstones. Chemical grouts take many forms. In general ,they consist of solutions of gel-forming chemicals .At the time of mixing and injection the s
43、olutions are normally true ffluids and should contain no suspended particles. Once the frout has been injected ,the chemical reactions lead to stiffening of the fluid to form a gel structure while blocks the pores and staunches water inflow. A wide class of chemical grouts is based on sodum sili-cat
44、es. Other chemical grouts are based on polymerization action involving variously: lignins, tannins, urea formal-dehyde ,resorcinol formaldehyde, acrtlamides, uretbanes etc. Detiled choice depends on a balance between cost and such engineering properties as hifh initial fluidity,gel-times achievable
45、,gel strength longevity and relative toxicity. In any actual grouting project decisions need to be made before and during the actual injectionThese include the seiection of grout，hole spacing, stage length .sequence of injection, quantity of grout and acceptable levels ofinjection pressure.ROTARY DR
46、ILLING METHOD(or ShaftBoring)Rotarydrilling techniques often provide an efficient and convenient method for constructing shafts .The drilling rigs that have been wsed to excavate shafts were usually the same as those used for drilling deep oil and fas wells. However ,the drilling assembly, drill pip
47、e and the other drilling tools are of a special design to meet the requirements for excavating large holes. As the use of rorary drilling of large diameter holes has increased, knowledge and experience gained has resulted in hole diamcter and depth limitations becoming less restrictive. The followin
48、g advantages accrue from the use of blind hole shaft drilling equipment; Safety-All operations are controlled at the surface so that no workmen are needed in the shaft .This makes the technique safer than other methods. Ground Water-Drilling down the hole through water bearing formation is carried out routinely without interruptions. Caving Formations-Rotary drilling ,by vritue of the hydrostatic pressure exerted on the walls of the hole by the myd column,