国投哈密一矿8.0Mta新井设计含5张CAD图.zip
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英语原文COAL MINING UNDER SPECIAL CONDITIONSSECTION1 LONGWALL MINING TECHNIQUESFOR MINIMIZING SURFACE STRUCTURAL DAMAGESLongwall 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 highcapacity 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 4050 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 its 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 basin1 center zone; 2inner edge zone; 3outer edge zone1. Center zoneThis is located directly above the center portion of the gob. Surface subsidence is maximum possible and uniform. There are no visible cracks.2. Inner edge zoneThis 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.3. Outer edge zoneThis 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 PROTECTINGSURFACE STRUCTURESThe 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 58 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 characteristica 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 developoed 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 ExtractionAs mentioned earlier, both nonuniform subsidence and horizontal deformation concentrate on the edge of the mevement 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 ExtractionThe 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 1190 of the static ones , with mostly from 4060. 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 ExtractionWhen 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 ExtractionSince 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 ExtractionWhen 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.中文译文煤炭特殊开采第一部分 为尽量减少地表结构损害的长壁开采技术在美国，长壁开采是一个相对较新的采矿法。早期在东部和中央煤田试验没有成功，这主要是因为，没有足够的支护能力支护工作面。但直到1960年代后期，当使用自移式液压支架时，长壁开采法重新获得了成功。从那以后使用长壁开采法的煤矿的数量稳定地增加，在1981年达到了大约7.5。长壁开采法主要关注之一就是地表下沉及它导致的地表结构损坏的程度。以往的经验是：具有较低回采率的房柱式开采，例如不开采煤柱，可使地下回采期间不出现可测到的地表下沉，尽管这种下沉可能在开采很久以后（如4050年）发生。与此相反，长壁开采的一般概念是，由于在长壁开采的区段中煤的完全采出，会有较大范围的地表下沉，从而造成地面建筑物破坏。这在一定程度上是合理的，因为过去的研究已经表明，地面沉降是由于采用了长壁开采法，既使当开采深度接近1000英尺，住房是否出现裂缝还取决于住宅房子的类型和所处的位置。换句话说长壁开采可能会使一些建筑物表面结构产生损坏，如房屋。但是，这种损坏能够防止，以使裂缝小到可以接受的程度，采后的房屋与采前相比实际上没有区别。因此，必须认识到，在处理由于地下长壁开采导致地表结构损伤的保护措施时，如果费用不是问题，所有的地表建筑物都能够得到完全保护。但是，这是没有必要的。相反，应该在所花费用和建筑物将经受的破坏程度这两者之间综合权衡考虑。在长壁开采的预期发展中，作者一直在研究发生在世界上主要产煤大国的沉降问题。本文回顾并提出了已成功地减少表面结构损伤的各种采矿技术。地表建筑物的保护措施众所周知，地下采矿会引起上覆岩层的移动和地表的变形。其结果是，在地表移动盆地中的建筑物将发生变形。一般采取的是完全消除结构变形的措施，因为它非常昂贵，所以难以完成。通常被使用的技术方法可以被划分成二个类别： 保护建筑物结构元素方法和保护性开采方法，减少地表移动。 基本原则是允许发生少量变形。在这一限度内，保持其拥有和采矿之前一样的正常的结构功能。为保护结构元素使用的所有方法的宗旨是结构尽可能承受长壁开采法导致的变形。那些被保护的建筑物的维护费用远远低于那些无保护的。通常的做法是，预测地表的变形量，其次是评价建筑物在允许发生的变形量的基础上的损坏强度，最后，采取适当的保护措施。保护性开采方法应该是减少地表和建筑物发生变形。其中包括部分回采和充填回采，以及任何其他采矿方法，利用地表的移动和变形特征实现高比例的回收利用。在正常情况下，在一组建筑物下采煤应当考虑采取保护地表和地表建筑物的采煤方法。在国外的经验已经证明，这些因素在经济合理和技术上是可行的。只要采取适当的开采保护措施，长壁开采法将以其低成本，高效益和高回收率而被广泛采用。当地表移动的特征被更好地了解和掌握后，保护地表建筑物的采矿方法从条带开采或房柱式开采，到正面长壁开采，后来由长壁充填开采到长壁垮落采煤法。在许多情况下，对长壁垮落法进行合适的设计，使其工艺过程合理，再采取配套的保护地表建筑物的措施，将会收到令人满意的效果。表面移动和变形的特征 当长壁开采法的影响波及到地表时，比采空区面积大的地表盆底在地面形成，在平或接近平的接缝中，当采空区被重新压实后，在地表移动盆地中形成了三个区域（图1）：图1地表移动盆地1中心区；2内缘区；3外缘区1、中心区-这是位于采空区正上方的中心部分。地面沉降是最大的可能和统一。没有明显的裂缝。2、内缘区-这是位于采空区上方靠近地表移动盆地边缘的部分。沉陷并不统一。表面凹面向上，并向盆地中央倾斜。这一地区受到压缩，通常没有出现裂缝。3、外缘区这是位于地表移动盆地边缘之外和在坚固煤体之上。地面沉降并不统一。表面凸并向地表移动盆地中央倾斜。这里受到拉应力作用，被拉伸。当拉伸应变超过了允许值时，表面出现裂纹。第二部分 保护地表建筑物的开采技术由地下长壁开采引起的地面建筑物的破坏程度不仅取决于建筑物的变形特征，而且取决于相当数量的变形量。每一点的相
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