综放回采巷道围岩力学特征实测研究

通过对综放面回采巷道围岩的深部位移、表面位移、应力分布以及支架荷载的实测分析，得出综放面回采巷道围岩力学特征分布规律．研究表明，临近工作面巷道围岩处于支承压力降低区，支架荷载下降，但支架和围岩变形最剧烈，表明巷道围岩处于岩石峰后的力学状态．围岩变形主要发生支承压力影响区，合理的巷道支护应能控制采动影响剧烈阶段的围岩变形，顺槽支护设计理念应从载荷控制向变形控制转变．     

深部巷道围岩间隔性区域断裂研究

深部巷道围岩间隔性区域断裂现象,与浅部围岩破裂状态有显著不同,用浅部岩体力学的弹塑性理论不能很好的解释这一现象．采用能量平衡分析方法,研究了深部巷道围岩间隔性区域断裂结构的形成机理,分析了岩石形成这一有序结构的过程,并给出了结构的序列关系．结果表明：深部巷道围岩断裂位置不出现在巷道周边,而出现在围岩内部的弹性能分布不稳定极值点处;深部巷道围岩间隔性区域断裂是深部岩体在高地应力作用下由开挖卸载引起的一种自然响应,岩石力学性质的非稳定性是巷道围岩出现这种断裂的自身原因;深部巷道围岩间隔性区域断裂序列关系跟巷道半径、围岩所处的应力状态、围岩的黏聚力和内摩擦角有关．     

巷道冲击地压软化区能量极值判别准则及试验研究

为了解决目前巷道冲击地压理论研究对于能量分析的不完善,对冲击地压危险性判别难以定量化的问题,基于弹塑性力学理论,建立了圆形巷道弹塑性软化力学模型,得到了圆形巷道发生冲击地压的围岩软化区能量解析解;提出了巷道冲击地压发生的软化区能量极值判别准则,给出了巷道冲击地压发生的临界软化区能量、临界软化区半径、临界巷道收缩位移及临...     

巷道蝶形破坏理论及其应用前景

以弹塑性力学中孔洞围岩破坏的平面应变模型为基础,研究了圆形巷道围岩塑性区形态和扩展规律.提出了巷道围岩蝶形破坏理论,该理论建立了巷道围岩破坏形态与非等压区域应力场的力学模型,阐明了巷道围岩破坏具有圆形、椭圆形和蝶形3种基本形态,给出了巷道围岩3种基本破坏形态的数学界定标准和应力围岩判别准则,从应力环境、围岩条件、支护阻力3个方面阐述了蝶形塑性区具有方向性、突变性、变异性、蝶叶缺失和跃透、支护微效性等基本特性.在论述蝶形塑性区工程意义的基础上,探讨了该理论在巷道围岩控制、动力灾害防治、煤与瓦斯共采等工程领域的应用前景,介绍了大变形巷道蝶叶型冒顶机理、蝶型冲击地压机理、蝶叶型煤与瓦斯突出机理、煤与瓦斯共采中钻孔蝶形卸压增透机制等新认识和新方法.     

深埋巷道破裂围岩位移分析

针对深埋巷道围岩普遍处于破裂状态的特点，采用非连续变形分析（DDA）软件对巷道围岩松动圈非连续体位移影响因素的变化规律进行了模拟研究．分析了用锚杆、锚索和注浆加固以增加围岩破裂面的黏结力、抗拉强度和内摩擦角的数值朱减少位移量的机理，提出了非连续体巷道失稳破坏的判断标准，并对埋深1159m的大松动圈围岩巷道的非连续体位移进行了定量计算和实地观测．实测结果与DDA软件计算值比较吻合，说明对于深埋巷道破裂围岩采用DDA方法进行位移计算和支护参数设计是可行的．     

应变软化与扩容特性极弱胶结围岩弹塑性分析

极弱胶结岩体具有显著的峰后应变软化与体积扩容变形特性,这是造成极弱胶结地层巷道围岩产生大变形的主因.基于极弱胶结岩体应变软化与扩容特性,建立了考虑岩体应变软化与扩容特性的围岩弹塑性力学模型,分析了力学计算模型、扩容系数、软化系数及支护抗力对围岩塑性区范围与位移的影响规律.将巷道围岩塑性区及位移的理论解答与数值计算结果进行了对比分析,验证了极弱胶结岩体扩容大变形本构模型的适用性.结果表明:考虑极弱胶结岩体的扩容和应变软化特性使得分析更加合理准确,研究成果对极弱胶结地层巷道支护设计与施工具有一定指导意义.     

特厚煤层综放工作面变宽煤柱段巷道掘进期间围岩矿压显现特征分析

为了掌握大同煤矿集团有限责任公司塔山煤矿特厚煤层综放工作面变宽煤柱段巷道掘进期间围岩变形破坏特征,采用现场实测、数值模拟及理论分析方法,分析了变宽煤柱段巷道掘进期间围岩矿压显现规律,研究了变宽煤柱段巷道围岩应力场及煤岩体能量分布特征,揭示了特厚煤层变宽煤柱段巷道掘进期间巷道矿压显现机理。研究表明:特厚煤层变宽煤柱段巷道掘进期间伴随有声响、震动、冒顶、片帮等强矿压现象,主要发生在煤柱宽度22.4～47.9 m段;侧向应力及煤体能量集中分布于距采空区边缘30～40 m处,呈"带"状分布,随着煤柱宽度的增大,巷道围岩侧向应力及围岩积聚的能量曲线表现出先增后减的趋势,在煤柱宽度约35 m时应力和能量均达到最大值,分别为24.27 MPa和7.29×10~5 J;巷道掘进使砌体梁结构的力学平衡状态受到破坏,引起围岩应力的快速动态调整,当煤岩体中的静载荷与采掘活动引起的动载荷叠加值超过煤岩体的承载极限时,煤体中集聚的大量弹性应变能以动能形式释放从而引起巷道矿压显现。     

康家湾 矿深部难采矿体采场稳定性及结构参数优化研究

采用大型有限元分析软件——ANSYS对康家湾．矿深部难采矿体典型采场顶板的稳定性及其对采场围岩力学状态的影响进行数值模拟、非线性分析，对9种典型采场结构模型的模拟结果进行了比较分析，根据分析结果结合采掘效率和开采成本等因素确定了采场最优结构参数，并对当前采矿方案提出修正和调整建议，以便更清楚地掌握深部地压变化规律，有效地进行地压管理，实现深部破碎带矿体及顶板不稳固矿体的安全高效开采．     

应变非线性软化的预应力衬砌隧洞弹塑性应力解

基于岩体单轴应变非线性软化本构模型,采用全量理论将其推广,获得考虑中间主应力影响的复杂应力状态下的岩体等效应力和等效应变关系,由此对灌浆式预应力衬砌隧洞进行弹塑性分析.指出预应力作用下围岩可能处于弹性或弹塑性两种状态,给出了两种情况下围岩压力、塑性区半径及衬砌应力的解析计算式,得到了围岩产生塑性变形的临界灌浆压力,并结合某工程进行了具体分析.     

体元-区域-系统冲击地压模型及应用

基于弹塑性力学和损伤力学原理,考虑到煤岩体内部存在大量节理裂隙,在弹塑脆性模型的基础上增加了结构面单元,构建了体能势函数,建立了能量的积聚、耗散与煤岩动态变形破裂过程之间的联系,并以此为依据从能量角度建立了体元-区域-系统冲击地压模型.结果表明:冲击地压是含结构面煤岩体组成的力学平衡系统在外界扰动作用下的失稳现象;基于该模型分析了煤岩系统在不同应力状态下变形破坏的演化规律及相应的地球物理信号特征;对跃进煤矿23130掘进工作面电磁辐射监测数据进行分析,验证了该模型的正确性.     

A dynamic ejection coal burst model for coalmine roadway collapse

In this study, we established a dynamic ejection coal burst model for a coalmine roadway subject to stress, and held that the stress concentration zone at the roadway side is the direct energy source of this ejection. The formation and development of such burst undergoes three stages:(1) instability and propagation of the cracks in the stress concentration zone,(2) emerging of a layered energy storage structure in the zone, and(3) ejection of coal mass or coal burst due to instability. Moreover, we figured out the initial strength of periodic cracks is parallel to the maximal dominant stress direction in the stress concentration zone and derived from the damage strain energy within the finite area of the zone based on the Griffith energy theory. In addition, we analyzed the formation process of the layered energy storage structure in the zone, simplified it as a simply supported restraint sheet, and calculated the minimum critical load and the internally accumulated elastic energy at the instable state. Furthermore, we established a criterion for occurrence of the coal burst based on the variational principle, and analyzed the coal mass ejection due to instability and coal burst induced by different intensity disturbances. At last, with the stratum conditions of Junde Coalmine as the model prototype, we numerically simulated the load displacement distribution of the stress concentration zone ahead of the working face disturbed by the main roof-fracture-induced dynamic load during the mining process as well as their varying characteristics,and qualitatively verified the above model.     

Rock burst risk evaluation based on equivalent surrounding rock strength

On-site investigations consistently show that the rock burst inherent to coal seams varies greatly with coal seam thickness. In this study, impact factors related to coal seam thickness and surrounding rock strength were analyzed and a corresponding rock burst risk assessment method was constructed. The model reflects the influence of coal seam thickness on the stress distribution of surrounding rock at the roadway. Based on the roadway excavation range, a stress distribution model of surrounding roadway rock is established and the influence of coal seam thickness on rock burst risk is analyzed accordingly. The proposed rock burst risk assessment method is based on the equivalent surrounding rock strength and coal seam bursting liability. The proposed method was tested in a 3500 mining area to find that it yields rock burst risk assessment results as per coal seam thickness that are in accordance with real-world conditions. The results presented here suggest that coal seam thickness is a crucial factor in effective rock burst risk assessment.     

煤岩动力灾害的弱化控制机理及其实践

煤岩动力灾害的实质是能量积聚与耗散的自组织临界过程，当煤岩体中所积聚的弹性能达到其极限冲击能时，就会发生冲击矿压．实验室研究发现，弹脆性煤体是能量积聚与耗散的主体，顶板关键层（坚硬厚层砂岩顶板）的运移则会导致能量积聚与耗散，加速失去动态平衡．以煤岩冲击倾向性与顶板强度及厚度的关系为基础，依据能量积聚与耗散理论，提出了煤岩动力灾害的强度弱化机理，即通过钻孔卸压与深孔卸压爆破来弱化煤岩体的强度，降低煤岩体的聚能能力，释放煤岩体中所积聚的大量弹性能，使得煤岩体中所积聚的弹性能达不到最小冲击能，同时利用电磁辐射监测仪来检验煤岩体强度弱化治理的效果，以达到消除或降低冲击危险的目的．通过在三河尖煤矿9202高冲击危险工作面的生产实践，充分证明了这种技术的有效性．     

Numerical simulation study on hard-thick roof inducing rock burst in coal mine

In order to reveal the dynamic process of hard-thick roof inducing rock burst, one of the most common and strongest dynamic disasters in coal mine, the numerical simulation is conducted to study the dynamic loading effect of roof vibration on roadway surrounding rocks as well as the impact on stability. The results show that, on one hand, hard-thick roof will result in high stress concentration on mining surrounding rocks; on the other hand, the breaking of hard-thick roof will lead to mining seismicity, causing dynamic loading effect on coal and rock mass. High stress concentration and dynamic loading combination reaches to the mechanical conditions for the occurrence of rock burst, which will induce rock burst. The mining induced seismic events occurring in the roof breaking act on the mining surrounding rocks in the form of stress wave. The stress wave then has a reflection on the free surface of roadway and the tensile stress will be generated around the free surface. Horizontal vibration of roadway surrounding particles will cause instant changes of horizontal stress of roadway surrounding rocks; the horizontal displacement is directly related to the horizontal stress but is not significantly correlated with the vertical stress; the increase of horizontal stress of roadway near surface surrounding rocks and the release of elastic deformation energy of deep surrounding coal and rock mass are immanent causes that lead to the impact instability of roadway surrounding rocks. The most significant measures for rock burst prevention are controlling of horizontal stress and vibration strength.     

A review of energy associated with coal bursts

A coal burst is defined as a rapid expulsion of coal(and potentially gas) from the boundary of the roadway. Rock and coal fractures together with micro seismic vibration is a common occurrence during mining, however, it is very uncommon for coal and rock to be propelled into the roadway. Irrespective, such occurrences do occur and appear to require significantly more energy than is available from strain energy release during coal cutting. The sources of energy which can contribute to the propulsion of coal from the face or ribs are typically strain energy from the surrounding ground, seismic energy from a rapid rupture of the ground in the vicinity, or rapid expansion of gas from within the burst source area. The aim of this paper is to briefly review the bursts which may be related to strain energy, seismic energy and gas energy.     

A new criterion of coal burst proneness based on the residual elastic energy index

To evaluate the coal burst proneness more precisely, a new energy criterion namely the residual elastic energy index was proposed. This study begins by performing the single-cyclic loading-unloading uniaxial compression tests with five pre-peak unloading stress levels to explore the energy storage characteristics of coal. Five types of coals from different mines were tested, and the instantaneous destruction process of the coal specimens under compression loading was recorded using a high speed camera. The results showed a linear relationship between the elastic strain energy density and input energy density, which confirms the linear energy storage law of coal. Based on this linear energy storage law, the peak elastic strain energy density of each coal specimen was obtained precisely. Subsequently, a new energy criterion of coal burst proneness was established, which was called the residual elastic energy index(defined as the difference between the peak elastic strain energy density and post peak failure energy density).Considering the destruction process and actual failure characteristics of coal specimens, the accuracy of evaluating coal burst proneness based on the residual elastic energy index was examined. The results indicated that the residual elastic energy index enables reliable and precise evaluations of the coal burst proneness.     

坚硬顶板型冲击矿压灾害防治研究

针对兖州矿区济三煤矿6303工作面的冲击矿压问题，分析了冲击矿压发生的主要原因及影响因素．根据现场条件和数值模拟分析，提出了采用顶板爆破解除冲击矿压危险的技术措施，并确定了爆破参数．采用矿用钻孔窥视仪并配合电磁辐射法和钻屑法对爆破进行了效果检验．结果表明，通过顶板爆破措施可以破坏工作面上方坚硬厚层砂岩顶板的完整性，提前释放顶板聚集的弹性能，减弱和消除了工作面的冲击矿压危险，胜，保证了工作面的安全生产．现场实践证明，该项技术对具有坚硬顶板型冲击矿压的防治效果明显．     

顶板岩层对冲击矿压的影响规律研究

采用模拟试验方法研究了顶板岩层对煤体应力状态的影响,并根据震动能量对煤体的破坏效应和在岩体中的传播衰减规律,从能量角度分析了煤层上方不同厚度和强度的顶板岩层对煤体冲击的影响程度.结果表明,顶板释放的能量与岩层强度呈对数关系、与顶板厚度呈指数关系,坚硬、厚层顶板岩层会对煤体产生更为强烈的扰动,使冲击矿压危险性明显升高.另外,具有一定厚度和强度且距离煤层较近的老顶岩层运动产生的冲击载荷对煤体的影响作用较大.某矿一个工作面的冲击矿压防治工程实践表明,对该煤层上方的顶板岩层实施爆破弱化处理技术措施后,可有效降低工作面回采过程中的冲击危险性.     

Simulation of the relationship between roadway dynamic destruction and hypocenter parameters

Many factors can induce rock burst. Shock energy and shock distance are two key factors affecting rock burst. The 32101 roadway of the Xingcun coal mine, which has a tendency for rock burst, was used as an example. The dynamic module of Itasca's FLAC (Fast Lagrangian Analysis of Continua) 2D explicit finite-difference software was used to simulate the roadway's destruction. The vibration velocity and displacements of the rock surrounding the roadway were modeled for different shock energies and hypo-center distances. The simulation results indicate that the vibration velocity and displacement of rock surrounding the roadway have a quadratic relationship to the shock energy and a power law relationship to the distance of the hypocenter from the roadway. A dynamic view of the process was obtained from a series of "snap-shots" collected at 100 different time steps. This shows an isolat-ing "river" is first formed at the hypocenter. The region above the "river" is a low stress zone while below the "river" a high stress zone exists. This high stress zone surrounds the ribs of the roadway in a "double ear" pattern. Continuous and repeated action of the high stress in the "double ear" shaped zone destroys the roadway.     

Selected elements of rock burst state assessment in case studies from the Silesian hard coal mines

Exploitation of coal seams in the Upper Silesian Coal Basin is conducted in complex and difficult conditions. These difficulties are connected with the occurrence of many natural mining hazards and limitations resulting from the existing in this area surface infrastructure. One of the most important problems of Polish mining is the rock burst hazard and reliable evaluation of its condition. During long-years' mining practice in Poland a comprehensive system of evaluation and control of this hazard was de-veloped. In the paper the main aspects of rock burst hazard state evaluation will be presented, comprising: 1) rock mass inclination for rock bursts, I.e., rock strength properties investigation, comprehensive parametric evaluation of rock mass inclination for rock bursts, prognosis of seismic events induced by mining operations, methods of computer-aided modelling of stress and rock mass deformation parameters distribution, strategic rock mass classification under rock burst degrees; 2) immediate seismic and rock burst hazard state evaluation, I.e., low diameter test drilling method, seismologic and seismoacoustic method, comprehensive method of rock burst hazard state evaluation, non-standard methods of evaluation; 3) legal aspects of rock burst hazard state evaluation. Selected elements of the hazard state evaluation system are illustrated with specific practical examples of their applica-tion.