赵庄矿大断面煤巷层状顶板变形失稳机理及控制技术

发布时间：2018-04-12 16:24

本文选题：层状顶板 + 变形失稳　；参考：《中国矿业大学(北京)》2017年博士论文

【摘要】：巷道顶板稳定性控制是实现矿井安全高效生产的基础。随着煤炭开采规模和开采强度的增加,矿井向大型化、集约化、机械化发展,掘进大断面巷道成为煤炭行业发展的必然趋势。对于在煤层中掘进的大断面巷道由于煤层强度一般较低,且顶板具有典型的层状特征,当顶板层理、裂隙发育,分层厚度小,层间黏结程度低,煤帮完整性差时,巷道冒顶和片帮等安全问题较为突出,使巷道顶板维护变得更加困难。本文以赵庄矿布置在煤层中的开拓大巷为工程背景,综合采用现场调研、理论分析、数值模拟和现场工程试验等方法,系统研究了弱黏结、薄分层、含多层软弱夹层顶板的变形破坏规律,揭示了典型条件下大断面煤巷层状顶板变形失稳机理和锚索破断失效原因,基于上述研究成果提出了以保证顶板岩梁连续性和抑制巷道顶角破坏为核心,以长锚杆、短锚索、长锚索为主导的多层次顶板控制技术,主要取得以下结论:大断面煤巷典型变形破坏特征为:顶板下沉剧烈、冒顶事故频发;煤壁极易片帮、内挤显著;锚索破断率高,支护结构损坏严重;巷道返修量大、维护成本高;局部存在底鼓现象。大断面煤巷顶板内部层理、裂隙发育,层间黏结程度低,自身稳定性差,顶板跳跃性、非连续性破坏现象较多,离层较明显,内部含多层泥页岩夹层或煤线。顶板泥岩粘土矿物含量高,遇水易碎裂软化;煤帮松软,破坏范围大。煤巷顶板具有典型的层状特征,岩体力学性质受到岩性与结构面的联合制约。以顶板岩梁理论为基础,根据层状顶板特征,考虑层理面和软弱夹层的影响,阐明了层状顶板离层的形成及扩展过程;顶板离层的形式可分为三种:连续离层、间隔离层以及无离层;并指出采用合理的支护方式阻止层间剪切作用,能够抑制顶板离层、减小顶板下沉量。根据顶板层理发育程度,将层状顶板分为两类,揭示了大断面煤巷层状顶板重力驱动型失稳和离层挠曲型失稳机理;并指出层状顶板离层、挠曲,导致巷道顶角处易产生剪应力集中,并在该处产生剪切破碎带,随着顶板挠曲的发展,剪切破碎带以一定角度向上扩展,直至达到较坚硬岩层,围岩变形加剧,锚索承受载荷增加,发生破断,支护强度不足,诱发顶板切落式失稳冒落。煤帮作为巷道顶板岩梁的载体,煤帮不同的破坏程度和破坏范围将对顶板岩梁提供不同的支撑方式。合理地增大煤帮的支护强度,减小煤帮塑性区范围,使煤帮为顶板提供可靠的支撑,可抑制顶板有害变形的产生,有利于煤帮的维护。对于大跨度顶板、超高松软煤帮巷道应坚持“顶帮协同控制”的原则,保证围岩的长期稳定。软弱夹层极易导致顶板的沿层破坏,使顶板出现大范围的离层;软弱夹层位置距离巷道顶板越远到对顶板变形的影响越小,但巷道顶板具有穿层破坏特性,当软弱夹层在其开挖影响范围内时,之间即使具有相对坚硬的岩层阻隔,软弱夹层也会破坏。软弱夹层数量增加后,层状顶板被切割成的分层顶板数量越多,抵抗变形的能力越低,顶板破坏范围增大,使冒顶高度和冒顶风险增加。煤巷顶板裂隙水的存在和空气湿度的季节循环,加剧顶板风化碎裂,造成锚索托板锚空,预应力损失,加剧顶板下沉变形,锚索破断失效,支护强度降低极易引发顶板失稳。此类巷道掘出后必须及时喷射混凝土层,密闭围岩隔绝空气和水,防止围岩风化、潮解剥落,降低工程岩体强度劣化。锚索预应力损失、破断失效导致其工作状态发生改变,是引发顶板变形失稳的主要因素,对于大变形巷道围岩控制时必须使支护结构的力学性能与围岩的大变形相匹配。大断面煤巷层状顶板锚索失效主要是索体破断,索体破断位置主要发生在托板孔口处和顶板2m范围内,其中发生在托板孔口处的破断主要是由于顶板非均匀变形使托板翻转,造成锚索弯折剪切破断。锚索拉伸试验断口多为杯锥状,具有明显的颈缩,断口基本平齐,断裂位置较为集中,为典型的韧性断裂;锚杆轴向承载能力一般低于锚索,但其具有较高的延伸率,适应围岩大变形的能力强。对比分析了不同类型锚索以及锚杆的剪切力学性能,锚索剪切过程中受力较为复杂,锚索剪切试验中钢丝断口以斜切断口为主,同时含有颈缩拉伸断口、旋涡状扭转断口,以及拉剪复合断口。锚索剪切破断时砂浆试块接触面错动位移受索体类型、预应力、锚固方式和砂浆试块强度的制约;全长锚固锚索支护系统的剪切刚度优于未锚固锚索;锚杆支护系统具有较高的初期剪切刚度,有利于增大顶板层间剪切阻抗,抑制顶板离层。采用FLAC3D软件和改进的pile单元模拟锚索(可承受弯矩和施加预紧力)分析层状顶板与锚索的相互作用关系,得出布置在顶板不同位置的锚索其受力状态存在差异:顶板锚索越靠近帮部,受到的层间剪力越大,轴向拉力越小;而越靠近巷道顶板中部,锚索受到的轴向拉力越大,层间剪力越小;锚索破断是顶板层间剪切错动与竖直下沉共同作用的结果,靠近巷道帮部的顶板锚索主要是剪切破断,而靠近顶板中部的锚索以拉伸破断为主。长时间服务的巷道锚索受局部腐蚀影响时,易产生应力腐蚀断裂和腐蚀疲劳断裂。根据锚索不同的破断原因,提出了相应的控制对策。分析了目前巷道支护存在的主要问题:主观臆断性强,对顶板变形失稳机理认识不清,支护对策针对性差;对巷道围岩地质条件和应力环境认识不充分,巷道支护方式“一刀切”,造成区域支护强度不足冒顶隐患大和过度支护材料浪费严重;对巷道矿压监测重视不够,对围岩局部大变形处理不及时;锚杆与锚索协调支护理论缺乏深入、系统的研究,锚杆与锚索不能协同承载;缺乏对巷道服务时间因素的考虑,对时间因素影响下工程岩体强度劣化和支护结构力学性能劣化考虑不足。并提出大断面煤巷层状顶板控制思路。分析了锚杆锚索预应力、锚固长度、杆体长度和索体长度对围岩控制效果的影响规律,其中预应力对围岩主动支护效果起重要作用;锚杆极限锚固力随着锚固长度的增加成指数关系增加;合理地增加锚杆的长度有利于控制下位顶板岩层的离层错动;锚索长度增加后不利于对其中部围岩的控制,适当降低锚索的长度有利于预应力在围岩中叠加扩散,增加围岩控制效果。根据大断面煤巷层状顶板不同区域岩体冒顶风险以及承载特性,划分为非稳定层、亚稳定层和稳定层,同时根据不同区域岩体变形特征,提出了以保证顶板岩梁连续性、抑制巷道顶角破坏为核心的多层次支护技术。多层次支护技术以“长短结合、强弱结合、疏密结合”的支护系统为依托,选取典型的巷道,根据工程地质条件选择3.2m的长锚杆、5.4m的短锚索、7.4m的长锚索联合支护顶板,形成连续的预应力承载结构,并使护表构件与之相配套,加强煤帮的控制,支护完成后及时喷射混凝土层抑制围岩强度劣化。现场监测表明,新支护方案实现了围岩的长期稳定,取得了较好的支护效果。
[Abstract]:The roadway roof stability control is the basis for safe and efficient production of coal mine. With the increase of coal mining scale and strength of mining, mine to large-scale, intensive, mechanization, large section roadway has become the inevitable trend of the development of the coal industry. For large section roadway in coal seam excavation of the coal seam because of low strength, and has the typical characteristics of the layered roof, when the roof bedding, fissures, layer thickness, interlayer bonding degree is low, coal poor integrity, roadway caving and sloughing and other security problems are more prominent, the roof of the tunnel maintenance becomes more difficult. In this paper, Zhaozhuang Mine layout in Coal Exploration Major lane as the engineering background, combined with field survey, theoretical analysis, numerical simulation and field engineering test method, system of weak bonding, thin layered, the deformation failure law of soft interlayer containing multilayer roof, exposing the The mechanism of instability and failure of cable breaking deformation under typical conditions of large section roadway roof, based on the above research results to ensure the continuity of the roof and roadway damage suppression as the core put forward angle, with long bolt, short anchor, anchor for multi-level roof dominant control technology, mainly made the following conclusion: large section roadway deformation and failure characteristics of typical roof subsidence: severe, frequent accidents easily; the coal wall spalling, squeeze significantly; anchor breaking rate is high, the supporting structure was damaged; roadway repair capacity, the maintenance cost is high; the drum phenomenon exists in the local bottom coal roadway roof inside. Bedding, fracture, interlayer bonding degree is low, its poor stability, roof jumping, non continuity damage phenomenon more obvious internal separation, with multiple layers of mudstone and shale or coal line. Clay mineral content of roof high, the water easily broken Softening; coal soft, damage range. Roof of coal roadway with layered typical characteristics, mechanical properties of rock mass by lithology and structure of the joint constraints. In roof rock beam theory, according to the characteristics of layered roof, considering the influence of bedding surface and soft interlayer, expounds the formation and propagation process of layered roof separation; the roof separation form can be divided into three types: continuous separation, isolation layer and separation layer; and points out that the reasonable support means to prevent the interlaminar shear effect, can inhibit the roof separation, reduce roof subsidence of roof layer. According to the barber education, the layered roof is divided into two categories, reveals the large cross section coal Xiang bedded roof of gravity driven instability and flexible separation mechanism of instability; and pointed out that the layered roof separation, deflection, roadway leading vertex is easy to produce stress concentration, and shear fracture zone in the area, with the roof deflection The development of shear fracture zone at a certain angle extended upward until it reaches the hard rock, the surrounding rock deformation intensifies, anchor load increase, break and support strength is insufficient, cutting down type instability induced by roof caving coal. As a carrier of roadway roof rock beam, destruction degree and range of different coalside will provide support for different roof beam. The increase of coal for supporting strength, reduce coal for the plastic zone, which help to provide reliable support for the coal roof, can inhibit the harmful deformation of roof coal, to help the maintenance. For the long-span roof, super high soft coal roadway help should adhere to the "hangwall cooperative control" principle, to ensure the long-term stability of the surrounding rock. The weak interlayer can easily lead to the destruction of the roof layer along the roof, the large scale separation; weak interlayer distance between the roadway roof and roof deformation of far more. Ring is small, but has the failure characteristics of roadway roof wear layer, when the influence of excavation in soft interlayer between range, even with a relatively hard rock barrier, soft interlayer will be destroyed. The increase in the number of weak interlayer, layered roof number of layered roof was cut into more and more low ability to resist deformation. The roof damage range increased, the height of caving and caving risk. The seasonal cycle of coal roadway roof crevice water and air humidity, intensified roof weathering fragmentation caused by cable anchor plate, prestress loss, intensified roof subsidence deformation, cable breaking failure, supporting strength reduction can easily lead to instability. This kind of roadway roof to must be timely shotcrete, rock closed isolated from the air and water, to prevent rock weathering, deliquescence spalling, reduce the engineering rock strength deterioration. Prestress loss, breaking failure leads to the work. State change, is a major factor for instability of the roof deformation, for large deformation and mechanical properties of surrounding rock control of large deformation of surrounding rock roadway supporting structure must be matched. Large section roadway roof anchor failure is mainly cable breaking, cable breaking occurs mainly in the orifice plate and the roof in the range of 2M, which occurs when the broken plate orifice is mainly due to the inhomogeneous deformation of roof plate turning, bending shearing break caused by cable. Cable tensile test fracture is cup cone, with obvious necking, fracture basic flush, fracture location is more concentrated, is typical ductile fracture bolt; the axial load capacity is generally lower than the anchor, but extends its high rate, ability to adapt to the large deformation of surrounding rock. The comparative analysis of different types of anchor bolt, shear mechanical properties, shear stress of anchor cable Complex fracture shear test with anchor wire oblique fracture, with necking tensile fracture, spiral torsion fracture and tensile shear fracture. Anchor shear rupture mortar block contact surface displacement by the cable body type, prestress, anchorage and mortar control block strength; anchoring cable supporting system of shear stiffness better than the anchor cable; initial shear bolting system has high rigidity, can increase the roof shear resistance, inhibition of roof separation. Using pile FLAC3D software unit and improved analog cable (which can be subjected to bending and preload) analysis of the interaction between the layered roof with the anchor, the anchor roof arranged in different positions of the stress state are different: the roof cable is close to the part by the interlayer shear increases, axial tension is smaller and closer to the roof; In the middle, the axial force of anchor has a larger interlayer shear is smaller; anchor is broken roof interlayer shear interaction and vertical sinking the roof cable near the sidewall is mainly shear fracture, while near the roof of central cable tensile breaking. Cable tunnel long time service local corrosion effect, easy to produce stress corrosion cracking and corrosion fatigue fracture. According to different break reason, put forward the corresponding countermeasures. The article analyzed the current problem of roadway support are: the subjective nature of the instability mechanism of strong, clear understanding of the deformation of roof, supporting measures for poor; geological conditions of surrounding rock and the stress of environmental awareness is not sufficient, roadway "caused by regional support strength is insufficient and the hidden dangers of excessive waste of roof supporting materials is serious; for rock pressure monitoring does not pay attention to Enough, on the rock of local large deformation processing is not timely; bolt and cable supporting coordination theory lack of in-depth, systematic study of bolt and cable cannot load; lack of roadway Business Hours factors, the factor of time under the influence of rock strength deterioration and supporting structure mechanical property deterioration and lack of consideration. The coal roadway roof control method. The analysis of layered prestressed anchor rod, anchor length, body length and body length of cable influence on control effect of surrounding rock, the prestressed plays an important role in the active supporting effect of rock bolt; anchoring force with the increase of anchorage length exponentially increase; reasonable increase of bolt the length of the roof strata is helpful to control the separation fault; cable length increase is not conducive to the control of the surrounding rock, appropriate to reduce the length of the anchor to pre stress in The superposition of diffusion in the surrounding rock, increase the control effect of surrounding rock. According to the large section roadway roof in different areas of layered rock mass caving risk and bearing characteristics, divided into non stable layer, sub stable layer and stable layer, and according to the different regional characteristics of rock deformation, put forward to ensure the continuity of the roof beam, vertex damage is the core of the inhibition of roadway multi level support technology. Multi level support technology in "combined with the length, strength, density combination supporting system based on typical roadway, according to the engineering geological conditions of long anchor 3.2m, short cable 5.4m, 7.4M long cable anchor supporting the roof, forming a continuous prestressed load-bearing structure and, the surface protecting component matching, strengthening the control of coal, after supporting timely shotcrete inhibit the rock strength deterioration. The monitoring results indicate that the new scheme can support the long-term stability of surrounding rock It has achieved good support effect.

【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】：TD322.4;TD353

【参考文献】