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附錄A
液壓支架
液壓支架被用來支護工作面頂板。他們在立即前移支護系統(tǒng)里通常從事以下幾步工作，為了盡可能快地支撐新暴露空間。在正常的支撐重要條件下，支架的頂梁是通過立柱的支撐阻力緊緊地靠著來阻止頂板巖層。當切割和通過幾個支撐單位超過支架時，立柱降柱和向前移動一段距離，通過液壓推進油缸的縮回來達到與切割的深度相等。推進油缸靠在工作面輸送鎦槽上，它的位置是通過支架的推進油缸的推進力來保持不變，作用在支架的兩邊。支架一推進到設(shè)計的位置，支架就立即重新靠在頂板上。最后，支架的推力油缸試圖向前推進輸送機和為下一次切割做準備。
描述的順序步驟就是為了單個支架的推移，在方向上要垂直于工作線。但是沿著工作線的方向，在采煤機通過輸送機之后，輸送機不會立即推移很大一段距離，由于鎦槽的剛性。因此第四步通常是在采煤機通過之后的一段時間，導(dǎo)致了彎曲或矩形的方向。
在采區(qū)推進期間，鎦槽向?qū)ǔＪ清^桿支架。但是在尾部巷道一排或兩排垛子被支撐去輔助頂板螺栓。在后退式采煤期間，在下順槽T型接口的頂板（伸出工作面的距離達到了152m）一般是通過某些類型的支架來進行加固，以提高支護密度來處理向前移動和向旁邊移動的支座壓力。
現(xiàn)代長壁采煤工作面使用自移式液壓支架（這種支架在這本書中通常被稱為液壓支架）。液壓支架不僅支撐頂板，推移工作面刮板輸送機，和它自己的移動前進，而且為了所有相互聯(lián)系的采煤活動提供安全的環(huán)境。因而液壓支架成功的選擇和應(yīng)用是長壁開采成功的選擇和應(yīng)用是長壁開采成功的前提條件。此外，由于需要大量的液壓支架，為液壓支架所投入的資金通常超過為長壁工作面所投入的初期資金的一半。因而從技術(shù)和經(jīng)濟兩方面觀點看，液壓支架是長壁工作面非常重要的設(shè)備。
液壓支架的分類
現(xiàn)代液壓支架的使用可以追溯到20世紀50年早期。自從那時起，隨著液壓支架在世界上的應(yīng)用，在不同的國家已經(jīng)有了不計其數(shù)的設(shè)計模型和不計其數(shù)的液壓支架被制造。但是不幸的是液壓支架仍然沒有一致的分類體系。
在這一段一個簡化的分類被使用。液壓支架是由四大主要部分組成（頂梁、掩護梁、立柱和底座）。這些組成部分的使用是相互聯(lián)系的，為了便于分類。在這一方面，兩個因素是最重要的：（a）是否存在掩護梁---如果包括掩護梁，那么這種支架就是掩護型的，否則它就是節(jié)式或垛式支架；（b）立柱的數(shù)量和類型---立柱的負載量通常與立柱的數(shù)量成正比例，因而確定支架的立柱數(shù)量是重要的。此外，立柱被安裝的方式是重要的；例如，在支護頂板方面，在頂梁和底座之間垂直的安裝立柱有最高的應(yīng)用效率然而在底座和掩護梁之間傾斜的安裝立柱卻有著最低的效梁。
根據(jù)這個概念，有四種類型匠液壓支架，那就是，節(jié)式，垛式，掩護式和支撐掩護式，隨著他們的發(fā)展演變而來的。然而，必須強調(diào)的是每種類型的發(fā)展趨勢都是為了在應(yīng)用方面讓液壓支架變的容易區(qū)分。
這四種類型的液壓支架不僅可以用于后退式長壁回采工作面和前進式開采工作面，還
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可以用于標準方式、滯后支護方式和即時支護方式。
對于標準支護方式，采煤機作切割或分段運動，工作面輸送機由裝在液壓支架上的推移千斤頂推動前進。液壓支架比輸送機先移動。對于滯后式支護方式，支架不可能靠近輸送機，因為有一個裝置自動的使支架前端與輸送機保持一定的距離。這就要求要有貫穿工作面的緩溝，并且采用前進式標準支護，比如：先推動刮板輸送機，然后再讓液壓支架前進。
對于即時支護方式，液壓支架在截煤機過去之后立即跟隨刮板輸送機前進，液壓支架前面的頂板有足夠的長度來支護采過和將要采的頂板部分。在液壓支架前進以后，刮板輸送機也被推移前進。
節(jié)式支架
節(jié)式支架是通常使用在地下的單體液壓支柱的擴展。因此節(jié)式支架是在現(xiàn)代自移式液壓支架中發(fā)展出的第一種類型的液壓支架。它包含兩排串列的液壓支柱，在頂部由單個或兩個扇形頂梁所連接。兩個扇形頂梁可以在兩個立柱之間或前柱的前面以任意的角度鉸接。兩個液壓支柱的底座可能是一個環(huán)形的鋼鐵滑必履焊接在每個立柱的底部或整個底座連接兩個立柱。如果鋼鐵滑履被使用，那么彈簧板連接著立柱就用來提高穩(wěn)定性。
通常節(jié)式支架包含兩排或三排立柱。首先移動的那排立柱是輔助的立柱，后來移動的是主要的立柱。有一個雙作用油缸安裝在每排立柱之間。油缸的活塞連接到了輔助立柱上，氣缸連接到了主要立柱上。在支架推移期間，主要立柱支撐頂板而輔助立柱是低的并且通過活塞向前推。達到了新的位置時，輔助立柱支撐頂板而主要立柱是低的并且通過氣缸向前推。每次前移的距離是在20到36英寸之間。
因此節(jié)式支架是非常簡單的，不僅不是更加的靈活而且結(jié)構(gòu)上不穩(wěn)固。在兩塊頂梁之間有相當大的地方，不允許破落的頂板石塊落在那里。因此，節(jié)式支架不適合用在支撐力弱的頂板上。節(jié)式支架已經(jīng)變的極少使用因為它們不穩(wěn)固而且需要經(jīng)常維修。
垛式支架
在垛工支頂架里，頂梁是一整塊和底座可能是一整塊也可能是由后端梁和前端梁上的鋼鐵桿連接的兩個分開的零件。在這兩種情況里，一塊大的空地方是在中心的左邊，為了定位雙作用液壓缸，用來在整個機構(gòu)里推拉刮板輸送機和垛式支架。都分別不同于節(jié)式支架，這個裝置也用在掩護工和支撐掩護式支架中。
此外，所有的立柱都垂直地安裝在底座和頂數(shù)值之間。立柱的三到六個，但是四柱的垛式支架是遠遠落后于最流行的垛式支架。六柱垛式支架的前面兩個立柱和后面四個立柱都設(shè)計的有細小縫隙，被一個通道分開。因為六柱垛式支架也在頂興的后部安裝一個擋矸板。擋矸板由幾個矩形的鐵板組成，水平的連接在兩端。
在大多婁的垛式支架里，在立柱和頂梁，立柱和底座之間都有鉸接的連接口。但是為了增加縱向的穩(wěn)定性，在底座和每個立柱之間用一個箱形的鐵架來進行加固。在箱形鐵架的頂部，每個立柱的周圍都安裝一個立柱復(fù)位裝置。
垛式支架適用于中硬頂板。當頂板外伸進了采空區(qū)并且要求人工放頂，垛式支架就會給采空區(qū)提供通道。
掩護式支架
掩護式支架，十七世紀早期的一種新的發(fā)明，以在后部，底座和頂梁之間增加一個掩護梁為特征。掩護梁，一般是傾斜的，鉸接到頂梁并且底座給了掩護工支架穩(wěn)定的支撐，這是勝過節(jié)式支架和垛式支架的一個主要的優(yōu)點。它也完全密封采空區(qū)和阻止矸石以免進入支架工作面的一邊。因此，掩護式支架工作面通常是干凈的。
掩護式支架的立柱通常是傾斜的，可以為交通提供更多的窨。因為頂梁，掩護梁和底座都是相互連接的，它可以很好地阻止水平力以免立柱產(chǎn)生彎曲。因此，不像在節(jié)式或垛式支架晨的固定的約束力，掩護式支架的立柱和頂梁，立柱和底座之間都采用銷連接，這就可能使立柱的傾斜角度隨采煤高度的變化而變化。立柱的壓力只有垂直分力可以用來支撐頂板，掩護式支架實際的裁荷量也隨采煤高度的變化而變化。
掩護是液壓支架有很多種類。在下面的介紹中，有六項可以用來給掩護是液壓支架分類，這六項可實現(xiàn)所有類型掩護式液壓支架統(tǒng)一術(shù)語的發(fā)展。頂梁端部的運動軌跡，液壓立柱的定位于定向，液壓立柱的數(shù)目，頂梁的幾何形狀，以及其他的可以任意選擇的設(shè)計方法和理念都可以用專業(yè)術(shù)語詳細的說明。
頂梁端部的運動軌跡的形式
這是公認的最普遍的對掩護是液壓支架的分類方法。基于這種標準，掩護是液壓支架可以分為三種類型：雙紐線形，圓弧形和橢圓形。
雙紐線形：這是最常用的一種類型。掩護梁和底座通過含有四個鉸鏈的雙紐線形運動的連桿連接起來。隨著掩護式液壓支架立柱的升起和下降，選擇好雙紐線桿的尺寸，就可以使頂梁前端近乎垂直的作上升和下降運動，這樣就可以保持頂梁前端與煤壁之間未支撐的距離為一常量，這種特性對很好控制頂板來說是廣泛考慮的最合乎要求的。當采煤高度有明顯限制時，頂梁前端垂直運動。頂梁、掩護梁、雙扭線桿和底座的尺寸及位置的布置都嚴格約束了這種限制。如超出這個限制，頂梁前端將會迅速的遠離采煤線，從而產(chǎn)生一個很大的未支護面積。
圓弧形：在圓弧形掩護式液壓支架中，掩護梁和底座之間通過單一的鉸接連接。當液壓支架立柱升起時，頂梁的前端將按圓弧型軌跡遠離煤壁，這樣使未支護面積增大。這就是大多數(shù)用戶所考慮的，圓弧型式掩護式液壓支架最不合適的地方。但在實際應(yīng)用中，如果煤層厚度變化幅度較小，則頂梁、掩護梁和底座的尺寸及位置可以按這種形式設(shè)計，未支護面積處的縱向距離變得不重要。另外，當降低液壓支柱時，未支護面積將會減少。
橢圓形：在橢圓形掩護式液壓支架中，掩護梁和底座采用這種方式連接，當液壓支架的立柱作上升和下降運動時，支架頂板的前端沿橢圓形軌跡運動。這種形式的液壓支架現(xiàn)在已經(jīng)很少應(yīng)用了。
支撐掩護式支架
支撐支架組合了支撐式和掩護式支架的特點。它具有這兩種支架的優(yōu)點。
如果四個立柱或六個立柱都安裝在頂梁和頂座之間，這就叫支撐掩護式支架。經(jīng)常四柱或六柱的支撐掩護式支架，它們所有的立柱都是垂直的并且是平行的。其他的形成了V形或X形。一些頂單獨的一塊，一些是兩塊并且同液壓油缸鉸接在一起。支撐掩護式支架有最高的支撐效率。他們適用于硬頂板。
液壓支架的組成
現(xiàn)代的液壓支架不管形式如何，都是由以下五個常見的部分組成：
1.承載部分：包括頂梁、底板、掩護梁、連桿和連接銷
2.液壓千斤頂：包括液壓柱塞其作用是：（a）推移刮板輸送機和移動液壓支架（b）操作前梁或護幫板（c）平衡或限制頂梁的位置（d）操作輔助裝置例如立柱和側(cè)護板的復(fù)位裝置，尤其是操作立住更為重要。
3.控制和操行部分：它包括了內(nèi)部的控制閥例如液壓支柱中的單向閥和安全閥，單位控制閥，高壓液壓管路。
4.輔助裝置：它包括了支架的推進，立柱的縮回，擋矸板，護幫板，底座的抬起和照明等。
5．液壓液體介質(zhì)：乳化液 其作用是用于運行液壓支架
附錄B
Powered supports
Powered roof supports are used to support the roof at the face.They work in several steps mostly in the immediate forward support (IFS) type in order to support the newly exposed roof as soon as possible. In normal supporting condition the canopy of the support is set tightly against the roof strata,by the supporting resistances of the hydraulic legs. When the cutting machine cuts and passes several support units beyond the support in question, the support legs are lowered and pulled forward for a distance equal to the width of cut (web) by retracting the hydraulic advancing ram. The advancing ram acts against the face conveyor panline, whose position is held unchanged by the advancing rams, forces of the supports that are set on both sides of the support to be advanced. As soon as the support has been advanced to the designed position, the support is immediately reset against the roof. Finally, the advancing ram of the support in question is extended to push the conveyor forward and becomes ready for the next cut.
The sequential steps described are for the advance of an individual support in the direction perpendicular to the faceline.But along the faceline direction, the conveyor cannot be advanced in a sharp step immediately after the shearer has passed it, due to the rigidity of the panline. Thus the fourth step is usually sometime after the shearer,s pass, resulting in a curved or snaked section.
During panel development the panel entries are roof bolted as usual. But in the tailentry one or two rows of cribs are erected to supplement the roof bolting. During retreating mining, the roof at the headentry T-junction area (up to 500 ft (152m) outby the face) is generally reinforced with supports of some type to increase support density to cope with the moving front and side abutment pressures.
Modern longwall mining employs hydraulic powered supports at the face area. The supports not only holds up the roof, pushes the face chain conveyor(AFC), and advances itself, but also provides a safe environment for all associated mining activities. Therefore its successful selection and application are the prerequisite for successful longwall mining. Furthermore, due to the large number of units required, the capital invested for the power support usually accounts for more than half of the initial capital for a longwall face. Therefore both from technical and economic points of view, the powered support is a very important piece of equipment in a longwall face.
Classification of powered supports
The application of modern powered supports can be traced back to early 1950s. Since then, following its adoption in every part of the world, there have been countless models design and manufactured in various countries. But unfortunately, there still is no uniform system of classification.
In this section a simplified classification is used. Since a powered support consists of four major components (i. e , canopy, caving shield, hydraulic legs and props, and base plate), the ways by which they are interrelated are used for classification. In this respect, two factors are most important: (a) presence or absence of caving shield- if a caving shield is included, the support is a “shield” type, otherwise, a frame or a chock; (b) number and type of arranging the hydraulic legs- since support capacity is generally proportional to number of hydraulic legs, it is important to specify the number of hydraulic legs that a support has. Furthermore, the way the hydraulic legs are installed is important; for example, a vertical installation between the base and the canopy has the caving shield has the least efficiency in supporting the roof.
Based on this concept, there are four types of powered support, that is, the frame, chock, shield and chock shield, in order of evolution of their development. However, it must be noted that the trend of development in each type is such that it becomes less distinguishable in terms of application.
The four types of roof supports can be obtained for either longwall retreating or advancing systems, and they are available in standard, one-web-back, and immediate forward support (IFS) versions.
With the standard system, the wining machine takes a cut or a slice, and the armored face conveyor is pushed over by the hydraulic rams that are fixed to the support units. The support units then are advanced sequentially to the conveyor. With the one-web-back system, a support is set back from the conveyor by a device that automatically keeps the leading edge of the support at a fix distance from the conveyor. This allows easy access though the face and employs the standard method of advancing; i. e , pushing the conveyor first, and then advancing the support.
With the IFS system, the support units is advanced to the conveyor immediately after the cutting machine has passed, and the forward canopy of the support units is long enough to the support both the recently and newly exposed roof sections. After the supports have been advanced, the conveyor is pushed over.
Frame
The frame support is an extension of the single hydraulic props conventionally used underground. Thus it is the first type developed in modern self-advancing hydraulic powered supports. It involves setting up two hydraulic props or legs vertically in tandem that are connected at the top by a single or two segmented canopies. The two segmented canopies can be hinge-jointed at any point between the legs or in front of the front leg. The base of the two hydraulic legs may be a circular steel shoe welded at bottom of each leg or solid base connecting both legs.
Generally, a frame support consists of two or three sets of hydraulic legs. The set moving first is the secondary set, the set moving later is the primary set. There is a double-acting ram installed between each set. The piston of the ram is connected to the secondary set and the cylinder to the primary set. During support advance, the primary set is set against the roof while the secondary set is lowered and pushed forward by the piston. Having reached the new position, the secondary set is against the roof while the primary set is lowered and pulled forward by the cylinder. The distance of each advance ranges from 20 to 36 in.(0.50 ~ 0.91m)
The frame support is very simple, but more flexible or less stable structurally. There are considerable uncovered spaces between the two pieces of canopy which allows broken roof rock to fall through. Consequently, the frame support is not suitable for a weak roof. Frames have become seldom used because they are less stable and require frequent maintenance.
Chock
In a chock support, the canopy is a solid piece and the base may be either a solid or piece or two separate parts connected by steel bars at the rear and/or the
front ends. In both cases a large open space is left at the center for locating the double-acting hydraulic ram which is used to push and pull the chain conveyor and the chock in a whole unit, respectively, a distinctive difference from the frame support. This setup is also used in the shields and chock shields.
Again, all hydraulic legs are installed vertically between the base and the canopy. The number of legs ranges from three to six, but the four-leg chocks are by far the most popular ones. The six-leg chocks are designed for thin seams with two legs in the front and four legs in the rear, separated by a walkway. For the six-leg chocks, the canopy is generally hinge-jointed above the walkway. Most chock are also equipped with a gob window hanging at the rear end of the canopy. The gob window consists of several rectangular steel plates connected horizontally at both ends.
In most chock supports, there are hinge joint connections between the legs and the canopy and between the legs and the base. But in order to increase the longitudinal stability, it is reinforced mostly with a box-shaped steel frame between the base and each leg. A leg restoring device is installed around each leg at the top of the box-shaped steel frame.
The chocks are suitable for medium to hard roof. When the roof overhangs well into the gob and requires induced caving, the chocks can provide access to the gob.
Shield
Shields, a new entry in the early seventies, are characterized by the addition of a caving shield at the rear end between the base and the canopy. The caving shields, which in general are inclined, are hinge-jointed to the canopy and the base making the shield a kinematically stable support, a major advantage over the frames and the chocks. It also completely seals off the gob and prevents rock debris from getting into the face side of the support. Thus the shield-supported face is generally clean.
The hydraulic legs in the shields are generally inclined to provide more open space for traffic. Because the canopy, caving shield, and base are interconnected, it can well resist the horizontal force without bending the legs. Thus, unlike the solid constraint in the frame/ chock supports, the pin connections between the legs and the canopy , and between the legs and the base in a shield support make it possible that the angle of inclination of the hydraulic legs varies with the mining heights. Since only the vertical component of hydraulic leg pressure is available for supporting the roof, the actual loading capacity of the shield also varies with the mining heights.
There are many variations of the shield supports. In the following, six items are used to classify the shields , which enables a unified terminology to be developed for all kinds of shields. The types of motional traces of the canopy tip, leg positions and orientation, number of legs, canopy geometry, and other optional designs and devices can be clearly specified by the terminology .
Types of motional traces for the leading edge of the canopy.
This is the most commonly recognized way of classifying the shield. Based on this criterion, there are three types, lemniscate, caliper , and ellipse.
Lemniscate. This is the most popular type. The caving shield and the base are jointed by two lemniscate bars which have a total of four hinges. As the hydraulic legs are raised and lowered, the dimentions of the lemniscate bars are selected such that the leading edge of the canopy moves up and down nearly vertically , thus maintaining a nearly constant unsupported distance between the face-line and the leading edge of the canopy .This is a feature that is widely considered most desirable for good roof control . There are clear limits of mining height within which the leading edge of the canopy moves nearly vertically. These limits are strictly controlled by the dimentional and positional arrangements of the canopy, caving shield, lemniscate bars, and the base. Beyond these limits, the edges will move rapidly away from the face-line creating a large unsupported area.
Caliper. In a caliper shield, the caving shield and the base are connected by a single hinge .When the hydraulic legs are raised, the leading edge of the canopy moves in an arc away from the face, thus increasing the unsupported area. This is considered by most users the least desirable feature of the caliper shield .But in practice if the seam thickness varies little, the dimentional and positional arrangement of canopy, caving shield, and the base can be so designed that the distance change of unsupported area will not be significant. On the other hand, when the legs are lowered, it reduces the unsupported area.
Ellipse. In this type the caving shield and the base are so connected that when the hydraulic legs are moved up and down, the leading edge of the canopy follows an elliptical trace. This type is seldom used.
Chock shield
The chock shield combines the features of the chocks and the shields. As such it possesses the advantages of both.
If all of the four or six legs are installed between the canopy and the base, it is called a chock shield. There are regular four or six-leg chock shields in which all legs are vertical and parallel. Others form V or X shapes. Some canopies are a single piece and some are two pieces with a hydraulic ram at the hinge joint. The chock shield has the highest supporting efficiency. They are suitable for hard roof.
Common elements of powered supports
The modern powerd supports, regardless of the types ,consist of the following five common components:
( 1 ) Load-bearing units. These include the canopy, base plate, caving shield, lemniscate bars, and joint pins.
( 2 ) Hydraulic rams. These include the hydraulic rams for ( a ) pushing the chain conveyor and advancing the powered support, ( b ) operating the front canopy or face guards, ( c ) balancing or limiting the position of the canopy, and ( d ) operating other auxiliary equipment such as leg recovering devices and side shideds, and above all, operating the legs.
( 3 ) Control and operating Units. These include internal control valves such as check and yield valves in the hydraulic legs, unit control valve, and high pressure hydraulic tubings.
( 4 ) Auxiliary devices. These include support advancing,leg recovering, gob windows, face guards, base-lifting, lighting, and so on.
( 5 ) Hydraulic fluid. This is the emulsion for operating the powered supports.
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