煤炭特殊開采外文文獻(xiàn)翻譯、中英文翻譯、外文翻譯,煤炭,特殊,開采,外文,文獻(xiàn),翻譯,中英文 英語(yǔ)原文 COAL MINING UNDER SPECIAL CONDITIONS SECTION1 LONGWALL MINING TECHNIQUES FOR MINIMIZING SURFACE STRUCTURAL DAMAGES Longwall mining is a relatively new mining method in the United States. Early trials in the eastern and central coal fields were not successful, mainly because, among others, the face supports did not have sufficient capacity. It was not until in the late 1960s , when the high capacity self-advancing powered supports became available,that longwall mining was successfully reintroduced. Since then the number of mines employing the longwall method has been steadily increasing. It has reached approximately 7.5％ in 1981. One of the major concerns for longwall mining is the extent of surface subsidence and its induced surface structural damages. The experiences have been that room and pillar mining with low recovery ,e.g. no pillar mining can be implemented such that no measurable surface subsidence occurs during the period of underground mining, although subsidence may occur long after (say 40~50 years)mining. In contrast, the general concept about longwall mining is that since there is a complete extraction of coal in a longwall panel, there will be much large surface subsidence and thus structural damages. This is to some extent justifiable because past research has demonstrated that surface subsidence due to longwall mining occurred even when the seam depth was close to 1000 ft. and that minor ctackings could occur in a residential house depending on the type and location of the residential house within the panel. In other words under longwall mining there could be some damage to some surface structures such as houses. But it can be protected such that the damages are so minor that except minor crackings, the houses are practically the same before and after mining. Therefore in dealing with the protective measures for surface structural damages due to underground longwall mining it must be recognized that mearly all surface structures can be completely protected if the cost is not the subject. But this is not necessary . Instead, there should be a compromise between the cost to be expended and the degree of damages the structures will be sustained. In anticipation of the development of longwall mining, the authors have been studying the subsidence problems that have occurred in major coal producing countries in the world. In this paper various mining techniques that have been successfully employed for reducing surface structural damages are reviewed and presented. Protective Measures for Surface Structures It is well known that underground mining will induce movements and deformation of the overburden strata and surface. As a result, surface structures within the movement basin will be subjected to deformation. In general it is uncommon to adopt measures that will completely eliminate structural deformations because it’s extremely costly and difficult to accomplish . The technical methods that are normally employed can be divided into two categories : Methods for protecting the structural elements of the structures and protective mining methods for reducing surface movements. The basic principle is that a small amount of deformation is allowed to occur. Within this limit, the structure maintains its normal functions as well as it did before mining. The objective of any methods employed for protection of the structural elements is that the structures can tolerate the deformation induced by longwall mining. The repair cost for those protected structures will be much less than those unprotected ones. The normal practice is to predict the potential amount of surface deformation, followed by evaluating the intensity of damage based on the allowable amount of deformation for the structures. Finally, the proper protective measures are adopted. The protective mining methods should be such that they reduce the amount of deformation occurred on the surface and the structures. These include partial and backfill mining and any other mining methods that achieve high percentage of recovery by making use of the deformational characteristics of surface movements. Under normal conditions, mining under a group of surface structures should consider the protective mining methods and the corresponding methods for protecting the structural elements of the surface structures. Experiences in foreign countries have demonstrated that such considerations are economically reasonable and technically feasible. As the characteristics of surface movements become better known, the preferential mining techniques for surface structural protection changes from strip mining or room and pillar mining to full face longwall mining; and later from longwall backfilling to longwall caving method. In many cases, the longwall caving with proper designs and procedures, coupled with the protective measures for structural elements has achieved satisfactory results. Characteristics of the Surface Movements and Deformations When the effects of longwall mining have reached the surface, a surface basin which is larger in area than that of the gob area is formed on the surface. In the flat or nearly flat seams, there are three zones in the final surface movement basin when the mined-out area (or gob ) has reached the critical one (Fig.1): Fig.1 Surface movement basin center zone; 2—inner edge zone; 3—outer edge zone Center zone—This is located directly above the center portion of the gob. Surface subsidence is maximum possible and uniform. There are no visible cracks. Inner edge zone—This is located above the gob near the panel edge. Subsidence is not uniform. The surface is concave upward and dips toward the center of the basin. This area is subjected to compression and usually no cracks appear. Outer edge zone—This is located beyond the panel edge and above the solid coal. Surface subsidence is not uniform. The surface is convex and dips toward the center of basin. It is subjected to tension. When the tensile strain exceeds the allowable value, surface cracks appear. SECTION 2 MINING TECHNIQUES FOR PROTECTING SURFACE STRUCTURES The intensity of damage to the surface structures due to underground longwall mining depends not only on the characteristics but also the amount of the deformation. The amounts of movement and deformation for each point on the movement basin vary. Therefore the relative position of surface structures in the movement basin affect the intensity of structural deformation. Surface curvature and horizontal strain are the two major causes for structural damages. Generally speaking, when the structures are located in an area where subsidence is uniform, there will be no induced stress in and subsequently no damage to the structures. Of course if the uniform subsidence causes the water table to rise leading to long-term flooding or excessive moisture, it will be weaken the structures and restrict their normal use. It has been demonstrated that if a structure is located at the center portion of the surface movement basin under critical or supercritical area, regardless of the amount of subsidence, the damages to the structure will be light and can be used as normal. Almost all of the coal mines in the US are extracting flat or near flat seam in single pass (or slice). The average thickness varies from 5～8 ft. with little or no faulting. Housing density over the mines is much less than other countries. Therefore, longwall mining with special techniques can be effectively adopted for safe extraction of coal under surface structures. The most important item is , based on the characteristic of surface movement and deformation, how to make use of the adaptability of the structure and attempt to eliminate or reduce the effects of the factors that are detrimental to structural stability. In this respect, researchers in China , Poland and UK have developed considerable experiences. In the following sections the principles developed in those countries will be illustrated and adapted by considering the current state-of-the-art and expected development in the US. Complete Extraction As mentioned earlier, both nonuniform subsidence and horizontal deformation concentrate on the edge of the movement basin. This due to the fact that a corresponding surface deformation is formed in response to the edge of the mined-out area and that if the edge does not change position, surface deformation changes from dynamic to static in which the deformation reaches its maximum value. Therefore each permanent edge of the gob induces a larger surface deformation zone. In complete extraction, the coal underneath the structures is completely extracted so that surface deformation will be milder. Continuous Extraction The face must be advanced uniformly and continuously. It should not be stopped for a long period. Because the instantaneous or dynamic surface deformations on the edge of the movement basin above a moving longwall are only about 11％～90％ of the static ones , with mostly from 40％～60％. Furthermore the dynamic movement and deformation decrease gradually and disappear as the face moves away. If the face stops for a long time, a permanent gob edge will form and transform the dynamic to static movement and deformation. The amount of increase in deformation due to the transformation may be sufficient to cause structural damages. When the face encounters some structural geological changes such as faults or when it has reached the property boundary, the face is liable to stop and forms the permanent gob edges. In order to avoid its occurrence, based on the results of the premining geological surveys, preparatory works can be performed in advance on both sides of the fault so that longwall mining can be done continuously on both sides. The amounts of surface movement and deformation vary with the rate of face advance. It is generally considered that as the rate of face advance increases, the subsidence rate will increase but the dynamic deformation will decrease. This is beneficial for structural protection. Therefore, the long-term face stoppage at each weekend results in larger static movements and deformations. Selected Extraction When there are multiple seams under a group of surface structures, it is not necessarily to extract in descending order . Rather based on the seam intervals,predicted surface deformation and structural ability to resist deformation, etc., the deeper and thinner seam may be selected for extraction first. The other seams are extracted later as experiences gain for that area. Limited Thickness Extraction Since the amount of surface movements and deformations increase with the increase in mining height, under certain conditions, only a portion of the seam thickness shoule be extracted. The thickness of extraction will be based on the predicted surface deformation to be tolerated by the structures. If the seam thickness varies considerably, the thickness of extraction as established before must be implemented uniformly. Simultaneous Extraction When surface structure are located on both sides of the mine boundaries or a fault, the coal should be extracted simultaneously on both sides in order to reduce the ill-effects associated with a permanent gob edge. Simultaneous extraction is also an effective method for extracting coal seams on both sides of a fault that is underneath a group of surface structures. If there are many surface structures on the areas to be undermined, one or several mining techniques described in this paper should be adopted to minimize the damage. 參考文獻(xiàn)： [1] 蔣國(guó)安、呂家立.《采礦工程英語(yǔ)》. 徐州：中國(guó)礦業(yè)大學(xué)出版社，1998. 中文譯文 煤炭特殊開采 第一部分 為盡量減少地表結(jié)構(gòu)損害的長(zhǎng)壁開采技術(shù) 在美國(guó)，長(zhǎng)壁開采是一個(gè)相對(duì)較新的采礦法。早期在東部和中央煤田試驗(yàn)沒有成功，這主要是因?yàn)椋瑳]有足夠的支護(hù)能力支護(hù)工作面。但直到1960年代后期，當(dāng)使用自移式液壓支架時(shí)，長(zhǎng)壁開采法重新獲得了成功。從那以后使用長(zhǎng)壁開采法的煤礦的數(shù)量穩(wěn)定地增加，在1981年達(dá)到了大約7.5％。 長(zhǎng)壁開采法主要關(guān)注之一就是地表下沉及它導(dǎo)致的地表結(jié)構(gòu)損壞的程度。以往的經(jīng)驗(yàn)是：具有較低回采率的房柱式開采，例如不開采煤柱，可使地下回采期間不出現(xiàn)可測(cè)到的地表下沉，盡管這種下沉可能在開采很久以后（如40～50年）發(fā)生。與此相反，長(zhǎng)壁開采的一般概念是，由于在長(zhǎng)壁開采的區(qū)段中煤的完全采出，會(huì)有較大范圍的地表下沉，從而造成地面建筑物破壞。這在一定程度上是合理的，因?yàn)檫^(guò)去的研究已經(jīng)表明，地面沉降是由于采用了長(zhǎng)壁開采法，既使當(dāng)開采深度接近1000英尺，住房是否出現(xiàn)裂縫還取決于住宅房子的類型和所處的位置。換句話說(shuō)長(zhǎng)壁開采可能會(huì)使一些建筑物表面結(jié)構(gòu)產(chǎn)生損壞，如房屋。但是，這種損壞能夠防止，以使裂縫小到可以接受的程度，采后的房屋與采前相比實(shí)際上沒有區(qū)別。 因此，必須認(rèn)識(shí)到，在處理由于地下長(zhǎng)壁開采導(dǎo)致地表結(jié)構(gòu)損傷的保護(hù)措施時(shí)，如果費(fèi)用不是問題，所有的地表建筑物都能夠得到完全保護(hù)。但是，這是沒有必要的。相反，應(yīng)該在所花費(fèi)用和建筑物將經(jīng)受的破壞程度這兩者之間綜合權(quán)衡考慮。 在長(zhǎng)壁開采的預(yù)期發(fā)展中，作者一直在研究發(fā)生在世界上主要產(chǎn)煤大國(guó)的沉降問題。本文回顧并提出了已成功地減少表面結(jié)構(gòu)損傷的各種采礦技術(shù)。 地表建筑物的保護(hù)措施 眾所周知，地下采礦會(huì)引起上覆巖層的移動(dòng)和地表的變形。其結(jié)果是，在地表移動(dòng)盆地中的建筑物將發(fā)生變形。一般采取的是完全消除結(jié)構(gòu)變形的措施，因?yàn)樗浅０嘿F，所以難以完成。通常被使用的技術(shù)方法可以被劃分成二個(gè)類別： 保護(hù)建筑物結(jié)構(gòu)元素方法和保護(hù)性開采方法，減少地表移動(dòng)。 基本原則是允許發(fā)生少量變形。在這一限度內(nèi)，保持其擁有和采礦之前一樣的正常的結(jié)構(gòu)功能。 為保護(hù)結(jié)構(gòu)元素使用的所有方法的宗旨是結(jié)構(gòu)盡可能承受長(zhǎng)壁開采法導(dǎo)致的變形。那些被保護(hù)的建筑物的維護(hù)費(fèi)用遠(yuǎn)遠(yuǎn)低于那些無(wú)保護(hù)的。通常的做法是，預(yù)測(cè)地表的變形量，其次是評(píng)價(jià)建筑物在允許發(fā)生的變形量的基礎(chǔ)上的損壞強(qiáng)度，最后，采取適當(dāng)?shù)谋Ｗo(hù)措施。 保護(hù)性開采方法應(yīng)該是減少地表和建筑物發(fā)生變形。其中包括部分回采和充填回采，以及任何其他采礦方法，利用地表的移動(dòng)和變形特征實(shí)現(xiàn)高比例的回收利用。 在正常情況下，在一組建筑物下采煤應(yīng)當(dāng)考慮采取保護(hù)地表和地表建筑物的采煤方法。在國(guó)外的經(jīng)驗(yàn)已經(jīng)證明，這些因素在經(jīng)濟(jì)合理和技術(shù)上是可行的。只要采取適當(dāng)?shù)拈_采保護(hù)措施，長(zhǎng)壁開采法將以其低成本，高效益和高回收率而被廣泛采用。當(dāng)?shù)乇硪苿?dòng)的特征被更好地了解和掌握后，保護(hù)地表建筑物的采礦方法從條帶開采或房柱式開采，到正面長(zhǎng)壁開采，后來(lái)由長(zhǎng)壁充填開采到長(zhǎng)壁垮落采煤法。在許多情況下，對(duì)長(zhǎng)壁垮落法進(jìn)行合適的設(shè)計(jì)，使其工藝過(guò)程合理，再采取配套的保護(hù)地表建筑物的措施，將會(huì)收到令人滿意的效果。 表面移動(dòng)和變形的特征 當(dāng)長(zhǎng)壁開采法的影響波及到地表時(shí)，比采空區(qū)面積大的地表盆底在地面形成，在平或接近平的接縫中，當(dāng)采空區(qū)被重新壓實(shí)后，在地表移動(dòng)盆地中形成了三個(gè)區(qū)域（圖1）： 圖1地表移動(dòng)盆地 1—中心區(qū)；2—內(nèi)緣區(qū)；3—外緣區(qū) 1、中心區(qū)--這是位于采空區(qū)正上方的中心部分。地面沉降是最大的可能和統(tǒng)一。沒有明顯的裂縫。 2、內(nèi)緣區(qū)--這是位于采空區(qū)上方靠近地表移動(dòng)盆地邊緣的部分。沉陷并不統(tǒng)一。表面凹面向上，并向盆地中央傾斜。這一地區(qū)受到壓縮，通常沒有出現(xiàn)裂縫。 3、外緣區(qū)—這是位于地表移動(dòng)盆地邊緣之外和在堅(jiān)固煤體之上。地面沉降并不統(tǒng)一。表面凸并向地表移動(dòng)盆地中央傾斜。這里受到拉應(yīng)力作用，被拉伸。當(dāng)拉伸應(yīng)變超過(guò)了允許值時(shí)，表面出現(xiàn)裂紋。 第二部分 保護(hù)地表建筑物的開采技術(shù) 由地下長(zhǎng)壁開采引起的地面建筑物的破壞程度不僅取決于建筑物的變形特征，而且取決于相當(dāng)數(shù)量的變形量。每一點(diǎn)的相當(dāng)數(shù)量的移動(dòng)和變形在地表移動(dòng)盆地范圍內(nèi)變化。因此，地面建筑物在地表移動(dòng)盆地的相對(duì)位置影響建筑物的結(jié)構(gòu)變形強(qiáng)度。 表面曲率和橫向應(yīng)變是引起建筑物結(jié)構(gòu)損壞的兩個(gè)主要因素。一般來(lái)說(shuō)，當(dāng)建筑物位于地表沉降一致的區(qū)域時(shí)，在建筑物內(nèi)部不引起應(yīng)力，因而，建筑物也不會(huì)受到破壞。當(dāng)然，如果統(tǒng)一的沉降導(dǎo)致地下水位上升，導(dǎo)致建筑物長(zhǎng)期水浸或浸入過(guò)量水分，這將削弱建筑物的結(jié)構(gòu)和限制其正常使用。已經(jīng)證明，如果一個(gè)建筑物，坐落于地表移動(dòng)盆中心部分超臨界或領(lǐng)域下，不論沉陷量有多大，對(duì)建筑物造成的損害將很輕，建筑物可作為正常使用。 幾乎所有的美國(guó)煤礦，提取在平的或接近平的單向(或切片的)的縫。平均厚度不同，從5～8英尺很少或根本沒有斷裂。在礦區(qū)周圍的住房密度遠(yuǎn)遠(yuǎn)小于其他國(guó)家。因此，長(zhǎng)壁開采的特殊技術(shù)可以有效地在地面建筑物下安全開采。 最重要的一條是，根據(jù)地表移動(dòng)和變形的特征，如何利用結(jié)構(gòu)的適應(yīng)性和如何設(shè)法消除或減少那些不利于結(jié)構(gòu)穩(wěn)定的因素的影響。在這方面，中國(guó)，波蘭和英國(guó)的研究人員已經(jīng)取得了相當(dāng)可觀的經(jīng)驗(yàn)。在下面的部分將對(duì)在那些考慮目前工藝水平的國(guó)家制定的以及在美國(guó)預(yù)期發(fā)展的原則加以說(shuō)明。 全部回采 如前所述，這兩個(gè)不均勻沉降和水平變形集中在地表移動(dòng)盆地的邊緣。這是由于相應(yīng)的地表變形形成于采空區(qū)的邊緣，并且，如果采空區(qū)的邊緣不改變位置，地表變形將在變形量達(dá)到最大值時(shí)由動(dòng)態(tài)變?yōu)殪o止。因此，每一個(gè)采空區(qū)的永久邊緣導(dǎo)致一個(gè)更大的表面變形區(qū)域。在全部回采工藝中，建筑物下的煤應(yīng)當(dāng)全部回采才能使地表變形變得平緩，從而使建筑物變形減小到最小。 連續(xù)回采 回采工作面必須連續(xù)一致地推進(jìn)。它不能停止太長(zhǎng)時(shí)間。長(zhǎng)壁開采的工作面形成的地表移動(dòng)盆地的邊緣處的地表變形是瞬時(shí)的和動(dòng)態(tài)的，其中只有百分之十到百分之九十是出于靜態(tài)的，最多達(dá)到百分之四十到百分之六十。此外，隨著工作面向前推進(jìn)，地表動(dòng)態(tài)移動(dòng)和變形逐漸減少直至消失。如果回采工作面停采了很長(zhǎng)時(shí)間，采空區(qū)將被逐漸壓實(shí)，采空區(qū)的范圍逐漸被確定，形成一道永久的邊緣。大量的地表變形將會(huì)形成對(duì)建筑物的損害。 當(dāng)回采工作面遇到某些地質(zhì)構(gòu)造如地質(zhì)斷層或是當(dāng)工作面推進(jìn)到井田邊界時(shí)，工作面將停止推進(jìn)，采空區(qū)的邊界隨即產(chǎn)生。為了避免這樣的情況發(fā)生，可以根據(jù)地質(zhì)勘測(cè)的結(jié)果提前在地質(zhì)構(gòu)造地帶的兩側(cè)同時(shí)布置工作面，這樣長(zhǎng)壁開采就可以在兩邊同時(shí)連續(xù)地進(jìn)行。 相當(dāng)數(shù)量的地表移動(dòng)和變形隨工作面推進(jìn)速度的變化而變化。人們普遍認(rèn)為，隨著工作面推進(jìn)速度的增大，地表沉降的速度也將增大，但地表的動(dòng)態(tài)變形將會(huì)減小。這有利于地表建筑物的保護(hù)。 有選擇的開采 當(dāng)一組地面建筑物下有煤層群時(shí)，不一定按照嚴(yán)格的順序逐層開采。而是根據(jù)煤層間隔距離，預(yù)測(cè)地表的變形量和建筑物抵抗變形破壞的能力，賦存較深和較薄的煤層可以首先被開采。其他煤層可以根據(jù)先開采煤層時(shí)取得的經(jīng)驗(yàn)而后開采。 限厚開采 相當(dāng)數(shù)量的地表移動(dòng)和變形隨著開采深度的增加而增加，在一定條件下，只有某一厚度的煤層可以被開采。煤層開采的厚度將根據(jù)預(yù)測(cè)的地表的變形量以及建筑物抵抗變形破壞的能力而定。如果煤層的厚度變化較大，應(yīng)當(dāng)始終保持先前確定的開采厚度開采。 同時(shí)開采 當(dāng)?shù)孛娼ㄖ镂挥诰镞吔缁虻刭|(zhì)構(gòu)造地帶的兩側(cè)時(shí)，應(yīng)當(dāng)在兩側(cè)布置工作面同時(shí)開采，以減小采空區(qū)邊緣帶來(lái)的不利影響。同時(shí)也是一種在一組地面建筑物下有效地開采斷層兩側(cè)的開采方法。 如果某些地方有很多地面建筑物被破壞，應(yīng)該采取在本文中描述的一個(gè)或幾個(gè)采礦技術(shù)以使地面建筑物的損害減到最小。