大采高工作面煤壁稳定性分析及控制分析

发布时间：2018-05-25 22:05

本文选题：大采高工作面 + 煤壁破坏机理　；参考：《中国矿业大学(北京)》2017年博士论文

【摘要】：我国自1978年引进国外大采高综采设备以来,系统地研究了大采高工作面综合机械化采煤方法及其成套装备技术,并达到了世界领先水平。然而,煤壁片帮、端面冒顶等工作面围岩稳定性问题一直是大采高工作面开采实践中最棘手的技术难题。近年来,随着装备制造技术和生产管理水平的提高,大采高工作面一次采出厚度增大至7-8 m,工作面长度和开采深度也进一步加大,采场采出空间和工作面开采强度显著增大,因此大面积、大深度的煤壁片帮问题更加突出。大采高工作面煤壁片帮问题严重威胁工作面人员的安全、影响工作面设备的正常使用和维护、降低工作面产量和煤矿经济效益。因此,研究大采高工作面煤壁破坏机理及其影响因素、寻求工作面煤壁的稳定性控制技术,是大采高工作面开采实践中亟待解决的关键问题。论文以煤壁破坏机理及其影响因素、采场系统刚度对煤壁稳定性的影响机制为研究内容,综合运用了理论分析、数值模拟、实验室力学基础试验、相似模拟试验、工程实践等方法,研究了大采高工作面日益突出的煤壁片帮问题。建立了煤壁稳定性力学模型,分析了大采高工作面煤壁破坏机理,得到了煤壁稳定性与顶板载荷、煤壁等效集中力、等效弯矩、护帮板作用力、护帮板长度、煤体内聚力、内摩擦角等影响因素的关系;结合试验手段和数值计算,分析了煤中裂隙对煤体力学参数和承载能力的弱化作用,及煤中裂隙对煤壁破坏特征的影响;根据工作面推进方向上的“采空区-液压支架-工作面煤壁”采场系统刚度关系,建立了采空区刚度动态演化的数值模型和支架-煤壁系统刚度力学模型,进行了煤壁稳定性三维相似模拟试验,研究了采空区承载性能、煤体GSI、采高、煤壁集中力、煤壁弯矩、支架刚度等对煤壁稳定性的影响机制;构建了基本顶关键岩块冲击模型,结合现场工程实践,总结和提出了煤壁稳定性控制原则及煤壁片帮防治措施,取得了以下主要结论:(1)建立了煤壁稳定性力学模型,采用能量法中基于位移变分原理的Ritz法对煤壁破坏机理进行了研究,求解了工作面煤体的应变能和外力势能,得到了工作面前方煤体的位移场和应力场分布云图,其中最大位移和最大应力均出现在工作面煤壁上部,即最容易发生煤壁片帮的位置。(2)根据莫尔-库仑屈服条件定义了工作面前方煤体的稳定性系数k:当k0时煤体处于破坏状态,当k=0时煤体处于极限平衡状态,当k0时煤体处于稳定状态。根据煤体稳定性系数云图中k0的包络范围,模拟出现场实践中3种常见的煤壁片帮形式:煤壁上部片帮、煤壁上下部同时片帮、煤壁整体片帮;结合煤壁稳定性力学模型和煤体稳定性系数,对顶板载荷、煤壁等效集中力、煤壁等效弯矩、护帮板作用力、护帮板长度、煤体内摩擦角、煤体内聚力等煤壁破坏影响因素进行了敏感度分析,其中煤体内聚力、顶板载荷、煤壁等效集中力、煤壁等效弯矩对煤壁破坏的影响较大。(3)进行了预制裂隙型煤试件的实验室力学参数试验,试验结果表明:相比于无裂隙的完整试件,含裂隙试件在压力作用下试件表面产生大量的次生裂隙,试件破碎程度高;节理迹长、节理层间距、节理连通率对煤体的力学参数弱化效应显著,试件峰值强度当量和弹性模量当量介于0.5-0.85之间;结合煤壁稳定性力学模型,煤体损伤变量对煤壁水平位移及煤壁破坏面积具有较高的敏感度。(4)采用3DEC建立了含节理煤层大采高工作面煤壁稳定性数值模型,研究了节理-煤壁方位角α、节理层间距s、横向层理对煤壁稳定性的影响,模拟结果表明:随着节理-煤壁方位角α的增大,煤壁最大位移逐渐减小,但当α增大到一定程度时,对煤壁位移的影响不再明显,因此在条件允许的情况下,布置工作面时应尽量使工作面倾斜方向与节理走向相互垂直;随着节理层间距s的增大,煤壁位移减小,但当s增大到一定程度时,对煤壁位移的影响不再明显;当煤层中含有横向层理时,煤壁位移仅略微增大,故横向层理的影响较为有限。(5)工作面推进方向上的“采空区-液压支架-工作面煤壁”采场系统刚度对采场支承压力分布规律、工作面围岩稳定性及破坏具有显著影响。采用PHASE 2D和FLAC 3D构建了采空区刚度动态演化的数值模型,完整地模拟出了工作面前后方增压区、减压区、稳压区的支承压力分布特征。数值模型中,随着工作面的推进和顶板跨距的增大,工作面超前支承压力、煤体塑性区宽度、煤壁位移场等表现出先增大后稳定的演化规律。(1)PHASE 2D数值模拟结果显示:当采空区刚度较大时,工作面超前支承压力较小,支承压力峰值距煤壁距离缩短,煤壁塑性区宽度及煤壁最大位移减小,因此提高采空区刚度有利于增大煤壁稳定性;增大煤体GSI、降低工作面采高,工作面超前支承压力增大,但支承压力影响范围减小,塑性区宽度和煤壁位移降低。(2)FLAC 3D数值模拟结果显示:在工作面倾斜方向上,工作面中部超前支承压力和煤壁破坏深度较工作面端部更大,因此煤壁破坏具有工作面中部集中效应;由于采空区刚度及其对上覆岩层的承载能力小于实体煤,故当前工作面在靠近已采工作面的端部(较当前工作面靠近接续工作面的端部)的超前支承压力和煤壁破坏深度均有所增大,因此煤壁破坏具有采空区影响效应。在生产实践中,当前工作面中部和当前工作面靠近已采工作面的端部是煤壁破坏的重点防治区域。(6)基于弹性地基梁理论建立了支架-煤壁系统刚度力学模型,求解了工作面前方煤体及液压支架顶梁的挠曲线方程,计算结果表明:工作面前方煤体垂直位移、煤壁垂直位移、支架活柱回缩量与支架刚度呈非线性负相关,增大支架刚度、提高煤层地基系数,能够有效降低工作面煤体及支架的变形量;但当支架刚度增加到一定程度后,支架对顶板、煤壁变形的控制作用逐渐减弱。(7)基于煤壁稳定性力学模型和支架-煤壁系统刚度力学模型,设计了大采高工作面煤壁稳定性三维相似模拟试验,分析了煤壁集中力、煤壁弯矩、支架刚度对煤壁破坏特征、顶板下沉规律、煤壁运移规律的作用,揭示了顶板-支架-煤壁系统协调变形规律及支架刚度对煤壁破坏的影响机制。试验结果表明:(1)在煤壁集中力的作用下,当顶板千斤顶加载22次时,煤壁发生整体片帮。片帮时顶板最大下沉量为27 mm,顶板下沉速率快;煤壁水平位移小,从水平位移开始增长到煤壁发生片帮所经历的时间间隔为200 s,煤壁水平位移变化速率快;煤壁片帮具有突发性,即煤壁在短时间内累积了较小的垂直位移和水平位移即可触发煤壁片帮。(2)在煤壁弯矩的作用下,当顶板千斤顶加载26次时,煤壁发生整体片帮。片帮时顶板最大下沉量为35 mm,顶板下沉速率较快;煤壁水平位移开始增长到煤壁片帮发生所经历的时间为500 s,煤壁水平位移变化速率较快;煤壁片帮具有一定的突发性。(3)当支架刚度较小时,顶板千斤顶加载81次后,煤壁发生整体片帮。支架增阻期间顶板下沉速率较慢,但支架卸载期间顶板下沉显著,并呈现阶梯式下沉规律,下沉梯度为5 mm,片帮时顶板最大下沉量为47 mm;煤壁水平位移大,从水平位移开始增长到煤壁发生片帮的时间间隔为1200 s,煤壁水平位移变化速率较慢;在支架的支护作用下,煤壁在较长的时间内累积了较大的垂直位移和水平位移,最终引发煤壁片帮。(4)支架刚度增大后,当顶板千斤顶加载86次时,煤壁仅发生局部片帮。支架增阻期间顶板下沉缓慢,并呈现阶梯式下沉规律,下沉梯度为3-3.5 mm,片帮时顶板最大下沉量为35 mm;煤壁水平位移量较大,水平位移开始增长到煤壁发生片帮的时间间隔为1400 s,煤壁水平位移变化速率缓慢,煤壁片帮现象有所缓解。(5)支架刚度进一步增大后,顶板千斤顶加载87次时未发生煤壁片帮现象,工作面仅出现局部破碎情况。顶板下沉慢,阶梯下沉梯度为2 mm,片帮时顶板最大下沉量为25.55 mm;煤壁水平位移小,水平位移变化速率慢。因此当支架刚度足够大时,煤壁在有限的时间内所积累的垂直位移和水平位移较小,不足以触发煤壁片帮。(8)建立了周期来压期间基本顶关键岩块冲击力学模型,确定了直接顶、支架、工作面煤体的刚度对顶板载荷、煤壁集中力、煤壁弯矩的影响作用,总结和提出了缓解顶板载荷、降低煤壁集中力、控制基本顶破断岩块回转的煤壁稳定性控制原则;根据王庄煤矿8101大采高工作面支架工作阻力利用率不高的现状,指出了支架升柱时间短、供液不充分、初撑力不足的问题,提出了增大液压支架刚度和初撑力、提高护帮板使用率、工作面煤壁注浆、优化工作面回采工艺的的煤壁片帮防治措施,取得了良好的煤壁片帮控制效果。
[Abstract]:Since the introduction of foreign large mining high mechanized mining equipment in China in 1978, the comprehensive mechanized coal mining method and complete set of equipment technology for large mining face have been systematically studied, and the world leading level has been reached. However, the stability of the surrounding rock of the working face, such as the coal wall section and the end face, has been the most difficult technique in the mining practice of the large mining face. In recent years, with the improvement of equipment manufacturing technology and production management level, the thickness of the mining face of large mining height increased to 7-8 m, the length of working face and mining depth increased further, the mining intensity of mining area and working face increased significantly, so the large area and large depth of coal wall slaving problem became more prominent. The problem of coal wall section of working face seriously threatens the safety of staff in working face, affects the normal use and maintenance of working face equipment, reduces the output of working face and the economic benefit of coal mine. Therefore, the study on the mechanism of coal wall failure and its influencing factors and the stability control technology of coal wall in the working face are the mining face of large mining face. In this paper, the mechanism of coal wall failure and its influencing factors, the influence mechanism of the stiffness of the stope system on the stability of the coal wall are studied, and the theoretical analysis, numerical simulation, the laboratory mechanics basic test, the similar simulation test and the engineering practice are used to study the increasingly prominent working face of the large mining height. The mechanical model of coal wall stability is established, and the failure mechanism of coal wall is analyzed. The relationship between the stability and roof load of the coal wall, the equivalent concentrated force of coal wall, the equivalent bending moment, the force of the retaining wall, the length of the retaining plate, the cohesion of the coal body, the internal friction angle and so on; The weakening effect of the cracks on the mechanical parameters and bearing capacity of coal body and the influence of the cracks in coal on the damage characteristics of the coal wall are analyzed, and a numerical model of the dynamic evolution of the stiffness of the goaf and the stiffness of the support coal wall system is established according to the stiffness relationship of the mining area system of the "goaf - hydraulic support - working face coal wall" in the direction of the working face. A three dimensional simulation test of the stability of coal wall is carried out by the degree of mechanical model. The bearing performance of the goaf, the coal body GSI, the coal wall concentration force, the coal wall bending moment, the rigidity of the coal wall, and so on, the impact mechanism of the coal wall stability are studied. The impact model of the key rock block is constructed and the stability control of the coal wall is concluded and put forward. The main conclusions are as follows: (1) the mechanical model of coal wall stability is established. The failure mechanism of coal wall is studied by Ritz method based on the principle of displacement and variation in energy method. The strain energy and external force potential of coal face are solved, and the displacement field and stress field of coal body in front of the working face are obtained. The maximum displacement and maximum stress appear on the top of the coal wall on the working face. (2) according to the Mohr Coulomb yield conditions, the stability coefficient of the coal body in front of the working face is defined k: when the coal body is in the state of failure when K0, when the coal body is in the limit equilibrium state, when K0 is in the coal body. According to the envelope range of K0 in the coal body stability coefficient cloud, 3 kinds of common coal wall sheet help forms in field practice are simulated: the upper part of the coal wall, the upper and lower part of the coal wall and the whole wall of the coal wall, combined with the stability mechanics model of coal wall and the number of coal stability system, the load of the roof, the equivalent concentrated force of the coal wall and the equivalent of the coal wall. The sensitivity analysis of the bending moment, the force of the retaining plate, the length of the retaining plate, the friction angle of the coal body and the cohesion of coal in the coal wall, including the cohesion of the coal, the load of the roof, the equivalent concentrated force of the coal wall and the equivalent bending moment of the coal wall have great influence on the failure of the coal wall. (3) the Laboratory mechanical parameters of the prefabricated crack briquettes are tested. The test results show that a large number of secondary cracks are produced on the surface of the specimen under pressure action compared to the complete specimen without fissure, the fracture degree of the specimen is high, the length of the joint, the spacing of the joint layer, the joint rate of joint on the mechanical parameters of the coal body is significant, and the peak strength equivalent and the modulus of elasticity of the specimen are in the 0.5-0.85. In connection with the mechanical model of coal wall stability, the damage variable of coal body has high sensitivity to the horizontal displacement of coal wall and the damaged area of coal wall. (4) a numerical model of the stability of coal wall with a large mining face with joint coal seam is established by 3DEC. The influence of the azimuth angle of the joint - coal wall, the spacing of the joint layer of S, and the lateral bedding on the stability of the coal wall The simulation results show that the maximum displacement of coal wall decreases with the increase of the azimuth of the joint - coal wall azimuth, but when the alpha increases to a certain extent, the effect of the coal wall displacement is no longer obvious. Therefore, when the condition is allowed, the working face should be arranged as far as the inclined direction of the working face is perpendicular to the joint direction; with the spacing of the joint layer s The displacement of coal wall decreases, but when the s increases to a certain extent, the influence of the coal wall displacement is no longer obvious; when the coal seam contains transverse bedding, the displacement of the coal wall only slightly increases, so the lateral bedding is more limited. (5) the stope stiffness of the "goaf - hydraulic support - working face coal wall" in the direction of the working face Bearing pressure distribution law, the stability and failure of surrounding rock has significant influence. A numerical model of dynamic evolution of the stiffness of the goaf is constructed by PHASE 2D and FLAC 3D, which completely simulates the distribution characteristics of the support pressure in the turbocharging area, the pressure reducing area and the stable pressure area behind the work. The increase of distance, the overbearing pressure of the working face, the width of the coal body plastic zone and the displacement field of the coal wall first increase and then the stable evolution law. (1) the results of PHASE 2D numerical simulation show that, when the rigidity of the goaf is large, the overbearing pressure of the working face is smaller, the peak value of the supporting pressure is shorter than the coal wall distance, the width of the plastic zone of the coal wall and the largest coal wall. When the displacement is reduced, the rigidity of the goaf is beneficial to increase the stability of the coal wall; increase the coal body GSI, reduce the height of the working face, increase the front support pressure of the working face, but reduce the influence range of the support pressure, the width of the plastic zone and the coal wall displacement. (2) the FLAC 3D numerical simulation results show that the middle of the working face is ahead of the working face in the direction of the face. The support pressure and coal wall failure depth is greater than the end of the working face, so the coal wall failure has the central effect in the middle of the working face; because the rigidity of the goaf and the bearing capacity of the overlying rock are less than the solid coal, the current working face is near the end of the working face near the present working face near the end of the working face. Pressure and coal wall failure depth have increased, so coal wall failure has the effect of goaf. In the production practice, the current working face and the present working face near the end of the working face are the key prevention areas of the coal wall failure. (6) based on the elastic foundation beam theory, the stiffness mechanics model of the support coal wall system has been established, and the solution is solved. The calculation results show that the vertical displacement of coal body in front of the working face, the vertical displacement of coal wall, the nonlinear negative correlation of the back shrinkage of the support column and the stiffness of the support, increase the stiffness of the support and the coefficient of the foundation of the coal seam, and can effectively reduce the deformation of the coal body and the support of the working face; but when the coal body and the support are reduced, the deformation of the coal face and the support can be effectively reduced. After the stiffness of the support is increased to a certain degree, the control of the support to the roof and the deformation of the coal wall gradually weakened. (7) based on the mechanical model of the stability of the coal wall and the stiffness model of the support - coal wall system, a three-dimensional similarity simulation test of the stability of the coal wall in a large mining face was designed, and the coal wall concentration force, the coal wall bending moment, and the stiffness of the support on the coal wall were analyzed. The bad characteristics, the roof subsidence law and the action of the coal wall movement, reveal the mechanism of the coordination deformation of the roof support coal wall system and the influence mechanism of the support stiffness on the failure of the coal wall. The test results show that (1) the coal wall has a whole wall when the top plate jack is loaded 22 times under the action of the coal wall concentrated force. For 27 mm, the roof subsidence rate is fast, the horizontal displacement of coal wall is small, the time interval from the horizontal displacement to the coal wall is 200 s, the horizontal displacement of coal wall is fast, and the coal wall section is sudden, that is, the small vertical displacement and horizontal displacement of coal wall can trigger the coal wall section. (2) coal Under the action of wall bending, when the roof jack is loaded 26 times, the coal wall takes a whole slice. The maximum subsidence of the roof is 35 mm, the roof subsidence rate is faster. The coal wall horizontal displacement begins to grow to the coal wall section, the time is 500 s, the horizontal displacement of the coal wall is faster, and the coal wall section has a certain burst. (3) When the support stiffness is small, the top plate jack is loaded 81 times after the roof is loaded. The top plate sinking rate is slower, but the roof subsidence rate is slow during the support increase, but the roof subsidence is remarkable, and the downward gradient is 5 mm, the maximum subsidence of the roof is 47 mm, the horizontal displacement of the coal wall increases from the horizontal displacement. The time interval between the coal wall and the coal wall is 1200 s, and the change rate of the horizontal displacement of the coal wall is slow. Under the support of the support, the coal wall accumulates a large vertical displacement and horizontal displacement in a long time. (4) when the stiffness of the support is increased, the coal wall only takes part in the local section when the jack is loaded 86 times. The roof subsidence is slow and the subsidence gradient is 3-3.5 mm, the maximum subsidence of the roof is 35 mm, the horizontal displacement of the coal wall is larger, the horizontal displacement begins to increase to 1400 s, the change rate of the coal wall horizontal displacement is slow, and the ganging phenomenon of coal wall is relieved (5). (5 ) when the stiffness of the bracket is further increased, there is no coal wall segment phenomenon when the roof jack is loaded 87 times. Only local breakage occurs in the working face. The roof subsidence is slow, the gradient of the staircase is 2 mm, the maximum subsidence of the roof is 25.55 mm, the horizontal displacement of the coal wall is small and the horizontal displacement is slow. So when the stiffness of the support is large enough, coal The vertical displacement and horizontal displacement accumulated in a limited time are not enough to trigger the coal wall section. (8) the impact mechanical model of the key rock block is established during the period of periodic pressure. The influence of the stiffness of the direct top, the support and the coal face on the roof load, the coal wall concentration force and the coal wall bending moment is determined. To solve the roof load, reduce the coal wall concentration force, control the principle of the stability control of the coal wall of the broken rock block at the top of the top, and according to the present situation of the low utilization rate of the working resistance of the support in the 8101 large mining face of Wang Zhuang coal mine, points out the problem that the supporting column time is short, the supply fluid is insufficient and the initial brace force is insufficient, and the stiffness of the hydraulic support and the initial support are raised. Force, improve the utilization rate of the retaining wall, the coal wall grouting in the working face, optimize the control measures of the coal wall section of the coal wall, and obtain the good control effect of the coal wall section.
【学位授予单位】：中国矿业大学(北京)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TD823;TD323

【参考文献】