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浅埋煤层大采高综采面矿压规律与支护阻力研究摘要：针对浅埋煤层大采高综采工作面采场顶板岩层的运动规律和采场矿山压力显现规律有其特殊性的特点，着重研究浅埋煤层大采高综采工作面的矿压显现特征及其规律、工作面采场围岩应力场、位移场及围岩塑性破坏场的分布规律以及大采高综采工作面煤岩组合力学模型及支护阻力。关键词：浅埋煤层，大采高，矿压显现规律，顶板结构，支护阻力0 引言能源是经济发展的动力，国家经济的持续快速发展导致能源需要高速增长。我国是一个煤炭资源丰富，油气资源相对短缺的国家，长期以来形成了以煤为主的能源生产和消费结构，20世纪煤炭在全国一次能源消耗中占75%左右，随着国家对天然气资源的开发，煤炭资源消耗比例将有所下降，根据资料分析在近几年的能源生产、消费总量构成中，煤炭比重占70%左右。但是每年的总量消耗成直线增加。根据专家陈清泰等预测2020年煤炭消费比例将控制在60%左右。其中煤炭总产量2008年为27.16108t，专家预测，2010年、2015年、2020年将分别达到29108t，33108t，35108t。我国未来一次能源消费中煤炭仍将占主导地位，2050年，煤炭在我国一次能源消费结构中的比例也不会低于35%。由此看出，我国未来几十年的经济发展动力脱离不了煤炭工业强有力的支持，煤炭工业仍将是21世纪我国能源工业的主力军。八十年代初，我国在陕北浩瀚的毛乌素沙漠下发现了储量丰富的煤田神府煤田。神府煤田探明储量2236108t，占全国探明储量的1/3,相当于70个大同、160个开滦，是我国目前探明储量最大的煤田，该煤田与美国的阿巴拉契业煤田、德国的鲁尔煤日等被称为世界七大煤田。以开发神府东胜煤田为中心的“神华工程”，是我国大型项目建设中总投资仅次于“三峡工程”的第二大工程，是国家“七五”、“八五”、“九五”计划重点建设项目。神东矿区目前各矿开采区域大部分集中于埋深在100150m。埋深浅、基岩薄、上覆厚松散沙层是煤层典型赋存特征。从1985年至今，神东公司在神东矿区先后建设11对大型现代化矿井，20052008年连续四年原煤产量超过1108t，连续几年创历史新高。神东公司的煤炭单产与效率、百万吨死亡率等技术经济指标已居于世界领先水平或世界先进水平，开创了中国煤炭工业发展新纪元。2008年12月，在一片对金融危机的惊恐声中，陕煤集团旗下陕西煤业股份有限公司正式成立，目前在神木矿区已成功建成4对现代化矿井。根据国家规划，这里是我国西部优质动力煤的供应和出口煤基地，且地理位置又具承东启西的作用，是国家煤炭工业的首选基地，对国民经济的发展具有重大意义。神东矿区目前大部分开采煤层的主要赋存特征是埋深浅于150m、薄基薄，厚风积沙覆层。突出特点是埋藏浅、薄基岩、地表为厚风积沙覆盖层，是典型的浅埋煤层。矿井初期实践表明，厚松散层下浅埋煤层采动形成的顶板结构和来压特征与普通非浅埋煤层具有明显区别，长壁回采工作面普遍出现台阶下沉现象，矿压显现强烈，表现出与普通非浅埋煤层不同的特点。大柳塔矿建井初期的试采工作面（C202），来压期间普遍出现350600mm的台阶下沉，第一个综采工作面（1203），埋深5060m，采高4m，支架阻力3500kN，初次来压期间工作面中部约90m范围顶板出现台阶下沉，矿压显现非常强烈，其中部31m范围内顶板台阶下沉量高达1000mm，来压猛烈，造成工作面部分支架被压死。1203工作面在开采过程中发生过涌水溃沙事故，工作面被淹，在地面南端出现24m深的倒锥形漏斗，瓷窑湾煤矿及上湾等煤矿也发生过大的涌水溃沙事故，最大涌水量为200m3/h，涌水时间长达12h，巷道中的泥沙平均厚度达2m以上，塌方约40000m3，地面出现很大的倒锥形沙漏斗。地方小煤窑大部分采用房柱式采煤方法，不仅采出率很低浪费煤炭资源，而且具有顶板大面积冒落的灾变危险，严重威胁井下工作人员和地面居住人员的安全。如大砭窑煤矿1994年7月发生大面积垮落，垮落面积约达3104m2；郭家湾煤矿1995年2月7日发生面积高达7104m2的大面积垮落；2008年7月，神木县赵家梁煤矿发生大面积冒顶，造成9人死亡；2009年10月16日神木县永兴乡高庄煤矿发生大面积冒顶事故，冒顶范围17104m2；原哈拉沟煤矿，由于煤层顶板上水和沙土层载荷的作用，工作面顶板经常发生切顶和水患，井下工作人员伤亡事故不断增加，最后不得不把长壁工作面改为房柱式采煤方法，而使矿井煤炭采出率降低为30%左右，造成煤炭资源的巨大浪费。其实神东矿区小煤窑由于长时间采用房柱式开采，未对悬露的大面积顶板进行放顶处理，煤柱长时间由于风氧化造成强度降低，所以矿区小煤窑顶板大面积冒落是必然的。所以近年来神木县相应上级管理并结合当地煤层实际赋存情况对小煤窑进行整合。目前神东煤炭公司部分综采工作面液压支架额定工作阻力已达12000kN，由第一个综采面(大柳塔矿1203工作面)所选3500kN液压支架到现在，公司选购的综采工作面支架阻力不断提高，先后使用过额定工作阻力为6000kN， 6708kN，7592kN，10800kN，12000kN等支架，到目前最大为16800kN。尽管公司所选支架工作阻力之大，但根据补连塔矿32206工作面与张家赤煤矿15201试采工作面矿压观测，额定工作阻力12000kN的ZY 12000/28/63D型两柱掩护式支架基本满足工作面顶板压力需要，根据统计初次来压与周期来压时，工作面中部测区60%的支架安全阀开启，说明矿井所选支架额定工作阻力富余系数并不大。通过对神东矿区浅埋煤层近十年来的回采经验进行总结，得出矿区开采引起的特殊岩层控制问题主要有：顶板覆岩出现全厚切落形成剧烈的矿山压力显现，导致支架被压死，地面出现台阶下沉；工作面煤壁前方出现直至地表的贯通裂隙，造成地面水、沙溃入井下，造成水资源严重流失，加剧了地表荒漠化程度，给本来就十分脆弱的生态环境带来严重的影响，若采取房柱式开采，则回采率低，且顶板大面积悬顶由于煤柱长期风氧化造成煤柱强度降低，所以工作面有顶板大面积冒落的隐患，对矿井安全生产带来灾难性危害。浅埋煤层大采高综采工作面支架额定工作阻力不断增加，由3500kN，7592kN，10800kN，12000kN，到目前最大达16800kN，使大采高综采工作面成套设备费用不断增加，为了进一步掌握神东矿区浅埋煤层综采工作面随着采高的不断增加支架额定工作阻力是否需要继续增大，论文综合运用现场实测与理论分析等研究方法，以“张家峁煤矿试采工作面矿压规律及地表移动观测技术研究”等课题为依托，对神东矿区浅埋煤层大采高综采工作面由于采动影响其上覆岩层垮落后形成的结构、矿压显现规律及合理的支护阻力进行了分析研究。为今后类似煤层回采提供科学的参考依据，为保证安全、高产、高效的开采提供理论指导。外文原文：Analysis for interaction of supports and surrounding rock of gateways in longwall mingingWU Yong-ping(Xian University of Science and Technology, Xi an710054, China)Abstract:Gateway supporting in long-wall mining has been a problem that restricts the mine production and safety, the paper sets up an interaction model between support and surrounding rock (rock mass structure) and probes the elementary theory about ground pressure behaviors of gateway. Based on the analysis of supporting theories, some new viewpoints about gateways supporting and ground pressure controlling are put forward.Keywords: support surrounding rock, interaction, gateway, long-wall miningIntroductionFor the gateways extracted in solid coal (rock) or having wide coal pillar in one side, the most unfavorable situation is to regard surrounding rock mass as loose medium, but even in this condition rock mass structure like arch can still form during a certain period, and its calculating theories is well-known.When the gateways of long-wall face are influenced by face advancing, in acute interval of working influenc zone (at the intersection region of face with gateways), because cover strata moves severely, the simple arch structure will be not formed in lower strata, but a 4-demensions rock structure which extends deeper and relatives with time- coal is formed. The structure can be described as formula (1) and has following characteristics:F (x, y, z, t) = 0 (1)(1) When gateways are ones driving along adjacent goaf or reserved for next face, the catch-borders of the structure will be solid coal one side of face, waste falling and compacted behind face and adjacent goaf, so its extending range will be very large.(2) The rock structure moves forward in the way of “forming -destabilizing forming again as the face advancing.(3) At the intersection of face with gateways, rock structure is regarded a flat cowl of its long axis along face line and short one along axial line of gateways.1. Analysis of internal stress of the rock structureSupposing t= t0 in formula (1) and the rock structure is shown as Fig. 1.Getting any element from the model shown in Fig. 2, the distribution of its internal stress are shown as Fig. 1, and the equilibrium differential equation of the element can be obtained from Fig. 2.Fig.1 model of rock structure in gatewaywhere, Nx, Ny, Sxy, Syx are film internal stress; Mx, My, Mxy, Qx, Qy are bending moments, twisting moments and shearing forces; q0 is uniform distributed load acting upon the rock structure coming from cover strata (upper strata); p0 is re-loading providing by supports in gateway.Fig.2 Mechanical model of elementAssuming curved surface equation of rock structure (as shown in Fig. 1) consists of two parabolic surfaces translating each other:.Then, maximum vector height of neutral surface is obtained, f=fa+fb, and its curvature and curve radii along x, y are separately:Where, fa, fb are separately vector heights of parabola of parallel rank xoz and yoz.Analysis the rock structure using plate-cowl theories, we can obtain its internal stresses and displacements shown as follows: （2）And near board of x=0, x=a, its vertical displacements are:Its corresponding bending moments areSimilarly, bending moments near border y=0 and y=b also can be obtainedWhere, K1, K2, Ks, , , are factors of internal stresses relating with Thomsons function; E is elastic modulus of rock; h is cross-section thickness of structure (flat cowl); ， According to formula (2) (4), we can draw distribution states of internal stresses in rock structure as shown in Fig. 3.Fig.3 Internal stresses distribution of rock structure2. Relation between the movement of rock structure and ground pressure behaviorBecause the coalface advances continuously, the deformation of the structure as (flat cowl) relates with time as formula(1)，so the damage of lower strata within range of structure extending increases gradually as time passing, which has been changing and overall strata of rock structure will change and which is a dynamic process in ground pressure behavior, from forming to its limiting equilibrium state of rock structure takes a period, so the velocity of face advancing (speed of the structure moving) can have the moving characteristics of cover strata changed. When face advances very fast, the influence of ground pressure behavior of main roof (cover strata) acting upon rock structure will be decrease relatively (or influencing beside range of the structure) and it doesnt threaten gateway supporting. In addition, in lower strata within range of the structure extending, rock structure can t damage and deform at once because of face advancing fast, so loading of gateways surrounding rock will be reduced. On the contrary, if face advancing very slowly or stop advancing, range of the structure extending (top of cowl) in vertical direction will constantly increase and loading of Gateways surrounding rock will duplicate. The gateways reserved for next face of which has violent ground pressure behavior and is very hard to support is a typical example.3. Analysis of supporting patterns in gatewayIn general, supporting patterns of gateway in long wall mining may be simply put into classes: (1) They are active type and passive one classified by their supporting characteristics. The active includes various bolting and strengthening supporting, and the passive includes different framed timbers. (2) They are rigid supporting and yielding classified by their structure characteristics. The rigid includes various rigid framed timbers and common bolting, and yielding includes yielding framed timbers and yielding bolts. (3) They are also wooden, steel (including wire rope and reinforced bar), bamboo and concrete supports classified by their materials.In our mining districts, there exists large difference in geological conditions (lithological properties, working depth, etc) and in mining technical conditions (length of face, speed of face advancing, patterns of gateway supporting, etc)，so the supporting patterns in gateway are different also, but in general, rigid framed timbers are most widely used. Therefore, a great deal of studies in theory and tests are being done, and in 510 years state of gateway supporting in practice of production will be much changed.According to the studies as described in the paper, we put forward such views as follows.3. 1 Studying and testing about action mechanism of the bolt supporting in gateway of long wall mining should be go onFor the gateways, protected by rock mass (solid coal) both sides, theories and applications in practice of the bolt supporting are all very ripe,even for gateways extracted along adjacent goaf in boom roof beam(plate), the bolts possess still partial supporting action to cover strata because of combined beam formed in lower strata. But for the gateways extracted along adjacent goaf of longwall mining, especially, in conditions of high mining height, cover strata moving violently, big deformation of lower strata and the gateway rserved for next face, the characters of bolt such as its length and yielding measurement require studying and testing further according to forming and moving rules of gateway rock structure(such as range of the structure extending, bearing borders, its mechanisms of deformation and damage, etc), so as to ensure their reliabilities. For example in same cross-section of gateway, traditional bolts with same length wouldnt suit the strutture characteristics of flat cowl, the supporting effect predetermined is not reached, so it requires using the bolt with different lengths and yielding measurements.3.2 Using different patterns in accordance with different conditions of surrounding rock deformationAs known above, when the deformation of surrounding rock in gateways is below 200 mm, the common bolts and rigid framed timbers may be used, but if it is more than 200 mm, the supporting patterns chosen just now will be extremely not suitable.Assuming active force produced by unit width surrounding rock of the structure (as shown in Fig. 2) is Pr and relevant reactive force of supports is Ps, then in process of interaction between supports and rock structure, the reloading upon the structure supplied by supports may be described: (1) Pr Ps, supports possess only capacity of load-bearing and restricting; (2) Pr Ps, some constructional elements (such as beam) of the support will he damaged, it makes re-loading upon the structure supplied by the support lost P0=P in formula (2) (4) and also makes restricting force upon “part of bearing surrounding rock” of the structure weaken, as known from characteristics of internal stresses of the structure, right now, not only internal stresses and displacements of the structure will increase but also its hearing borders moves into further parts of surrounding rock because its restricting conditions change suddenly, a part of load former borne by the structure will transfer to the support and cause the deformation and damage of the support further increasing, finally, it will lead to destabilize wholly of system between support and surrounding rock, and gateway will he deformed and damaged heavily.When the deformation of surrounding rock is above 200 mm, yielding supports should he used (an overwhelming majority of gateway belongs to this case in the gateways reserved for next face or extracted along adjacent goaf).For the supports working in yielding, when Pr Ps, the support doesnt occur deformation and damage at once but yielding among structure elements of it and during the period, the re-loading upon the rock structure supplied by the support will decrease in a certain degree and time, p0 decrease in formula (2) (4)，the internal stresses and displacements of the rock structure will change in certain degree. Because the support doesn t lose majority of its supporting force but yielding in working state, so its re-loading and restricting upon the rock structure is a process fitting to dynamic change of the rock structure, it doesnt cause internal stresses and displacements of the rock structure change suddenly and bearing borders of the rock structure also dont move into deeper, so it doesnt lead the rock structure to destabilize in large area. During the process, loading upon the support produced by the rock structure will slowly increase because its movement is controlled and restricted. When the rock structure moves to a certain state, the support will yield again and repeat the whole process above until working face passed through.3. 3 Application of active supportingTraditional framed timbers belong to passive supporting type, that is to say, they are types waiting for loading, it makes surrounding rock occur deformation, damage and layer separation early, and not only makes surrounding rock which is natural bearing body change to loading body, but also impels the rock structure formed in upper strata to destabilizing and destroying. As known as analysis before, to change deformation degree and engage condition of surrounding rock in certain area, either can impel the rock structure to form in part of surrounding rock near gateway surface or can strengthen restricting to the rock structure supplied by the surrounding rock both sides of gateway and can also raise stability of the structure in itself.The support can either change the distribution of internal stresses and displacements of the rock structure (manifested by re-loading force p0) or can restrict to “the part of surrounding rock” supporting the rock structure. We can change and adjust re-loading force p0 in two ways. One is choosing yielding supports in higher working resistance. Another is having the support a setting load in its mounting, so as to impel the rock structure to form and stabilize in early and reduce the intensity of ground pressure manifestation.3. 4 To control rock structure movement by means of strengthening support in its entiretyAs known from complexity of ground pressure behavior at the intersection area of face with gateways as well as the rock structure forming and changing with coal face advancing, loading upon the gateway support are not only pressure but also torque force, thrusting force. The damage and deformation of the rock structure includes either destabilizing in cross-section of gateway or destabilizing swing and rebound along axial line of gateways. Proved by underground measuring in mines, great majorities of supports, in gateway are not crushed directly, but are pushed over and distorted firstly, then destabilize so as to lose its supporting capacity entirely, and soon afterwards involve adjacent to supports to bring about damage like “chain reaction”.Since ground pressure behavior in gateway results from cover strata moving entirely because of driving and mining, the support which produces re-loading should certainly unite a complete structural group in order to balance each other. Therefore, avoiding by all means to use individual supporting body to support surrounding rock, but should have all a unit to consist of a complete one strictly and timely. About this point, the braces used between framed timbers in Europe are worth to pay attention to, certainly, other manners of relation between two supports may be also considered.4. Brief conclusions(1) Surrounding rock of gateway exists a cowl structure, the ground pressure behavior in gateways is mainly produced from its moving.(2) The key to control ground pressure behavior of gateway is to control the rock structure moving, and the ways which can be used are “supporting actively, supporting entirely and using different patterns in accordance with different conditions”, etc.中文译文：长壁工作面开采中巷道支护与围岩之间相互关系的分析伍永平（西安科技大学，西安710054，中国）摘要：巷道支护在长壁工作面开采中一直是制约矿井生产和安全的问题，本文建立了一个巷道支护和围岩（岩体结构）相互作用的模型，并且探索了地压显现的基本理论。在对已有理论分析的基础上，提出了一些关于巷道支护和地压控制的新观点。关键词：围岩支护，相互作用，巷道，长壁工作面开采前言在固体煤（岩），或在一侧宽煤柱中掘进巷道，最不利的情况是把围岩认定为松散介质，但即使在这种情况下扁平罩形岩石结构仍然可以形成一段时期，其计算理论是众所周知的。当工作面巷道受到工作面推进影响时，在工作中的影响区的急性间隔区（工作面与巷道的交汇处），因为上覆岩层移动剧烈的影响，简单的扁平罩形结构将不能形成，但四维的岩石结构，延伸更深，并且时间和煤的关系正在形成。结构可以描述为公式（1）具有以下特点：F (X，Y，Z，T) =0 （1）（1）当巷道是沿相邻采空区掘进或为下个工作面保留，巷道的移动边界将是工作面一侧的固体煤，浪费下降工作面后面的相邻采空区压实，所以其延伸范围将是非常大。（2）随着工作面推进，围岩平衡结构以“形成不稳定再次形成”的方式前进。（3）在工作面与巷道的交汇处，围岩结构被认为是其长轴沿工作面方向和短轴沿巷道轴线的扁平罩形结构。1围岩结构的内应力分析假设公式（1）中t = t0，岩石结构如图1所示。从图2所示的模型取出任何元素，其内应力分布如图1所示。该元素的平衡微分方程可以从图2得到。图1 巷道围岩结构模型其中，Nx，Ny，Sxy，Syx为薄膜内应力；Mx，My，Mxy，Qx，Qy分别为弯矩，扭力矩和剪切力；Q0是来自上覆岩层并作用于岩石结构上的均匀分布载荷，P0为重新加载的巷道支撑力。图2 围岩结构力学模型假设岩石结构的曲面方程（如图1）由两个相互解释的抛物面组成：然后，得到中性面的最大载体高度，f=fa+fb，它的曲率和曲线半径沿X，Y轴，分别是：其中，fa，fb分别是平行于xoz和yoz的抛物线的向量大小。使用扁平罩形结构理论分析围岩结构，我们可以得到其内部的应力和位移如下式所示： （2）当x= 0，x = A，邻近板的垂直位移是：其相应的弯矩是：同样，靠近边界y = 0和y= b时的弯矩也可以得到：其中K1，K2，Ks，是与汤姆逊的函数相关的内应力的元素；E是岩石的弹性模量，h是结构截面厚度（扁平罩形）：。根据公式（2）（4），我们可以得出岩石结构内应力的分布状态，如图3：图3 围岩结构内应力分布2巷道变形和地压显现之间的关系由于采煤工作面的连续推进，如公式（1）所示巷道结构变形是与时间有关的，所以巷道变形影响范围内的下部岩层的破坏随着时间的推移逐渐增加，巷道结构已经改变，并且巷道整体围岩结构将发生变化，在地压显现中，这是一个动态过程，从开始变形到平衡状态需要一段时间，所以工作面推进速度（巷道变形速度）可以由上覆岩层移动特性来决定。当工作面推进非常快，老顶的矿压显现对巷道的影响将相对减少，而且不会破坏到巷道支护。此外，在巷道变形影响范围内的底板围岩中，岩石结构不会马上破坏变形，因为工作面推进速度快，所以巷道围岩的载荷将会减少。相反，如果工作面推进速度非常缓慢或停止前进，结构在垂直方向上的影响范围将不断增加，且巷道围岩的载荷加倍。保留巷道为下一工作面服务，相邻工作面开采时，巷道将会发生强烈的矿压显现，很难支护，这是一个典型的例子。3巷道支护模式分析在一般情况下，长壁工作面巷道支护可以简单的分类：（1）根据其支护特点可以分为主动型和被动型。主动支护包括各种锚杆支护和加强支持，被动支护包括不同的框架木材。（2）根据其结构特点可以分为刚性支护和柔性支护。刚性支护包括各种刚架木材和锚杆支护，柔性支护包括柔性木材和柔性锚杆支护。（3）根据支护材料可以分为木材，钢材（包括钢