Deformation analysis of transversely isotropic coal-rock mass with porous and cracks

Coal-rock as a typical sedimentary rock has obvious stratification,namely it has transversely isotropic feature.Meanwhile,deformation leads to coal-rock mass having the characteristics of different porous and crack structures as well as local anisotropy.Equivalent axial and circumferential strain' formulas of the pure coal-rock mass specimen with a single crack were derived through the establishment of equivalent mechanical model of standard cylindrical coal-rock specimen,and have been widely used to a variety of media combined different structures containing multiple cracks.The complete stress strain curve of a real coal-rock specimen was obtained by the CTC test.Additionally,according to the comparison with the theoretical value,the theoretical mechanical model could well explain the deformation characteristics of coal-rock mass and verify its validity.Further,following features were analyzed:strain normalized coefficient and elastic modulus(Poisson's ratio) in vertical and parallel direction to the stratification,stratification angle,porosity,pore radius,normal and tangential stiffness of crack,and the relationship of different crack width with different tangential stiffness of crack.Through the analysis above,it substantiate this claim that the theoretical model with better reliability reflects the transversely isotropic nature of the coal-rock and the local anisotropy caused by the porous and cracks.

Similarity model tests of movement and deformation of coal-rock mass below stopes

For a study of the movement and deformation of coal-rock mass and low protected seams below a stope,as well as for fracture developments and rules of evolution of permeability,we designed a plane strain model test stand to carry out model tests of similar materials in order to improve the effect of gas drainage from low protected seams and to measure the movement and deformation of coal-rock mass using a method of non-contact close-range photogrammetry.Our results show that 1) using paraffin melting to take the place of coal seam mining can satisfy the mining conditions of a protective seam;2) coal-rock mass under goafs has an upward movement after the protective seam has been mined,causing floor heaving;3) low protected seams become swollen and deformed,providing a good pressure-relief effect and causing the coal-rock mass under both sides of coal pillars to become deformed by compression and 4) the evolution of permeability of low protected seams follows the way of initial values→a slight decrease→a great increase→stability→final decrease.Simultaneously,the coefficient of air permeability increased at a decreasing rate with an increase in interlayer spacing.

Dynamic Failure Model of Thin Coal and Rock Mass under Uniform Impact Load

During the excavation of deep coal and rock mass, the radial stress of the free face changes from three-dimensional compression state to two-dimensional stress, bearing the combined action of dynamic disturbance and static load at the same time. With that, many mines suffer from dynamic disasters, such as coal and gas outburst, rock burst and rock caving during deep mining excavation, which is often accompanied by plate crack, spalling and other disasters, seriously affecting the stability of stope and roadway. Taking thin rectangular coal and rock mass as the research object, the dual equation of the free vibration was derived and the exact solution model of the free vibration was established with the use of Hamilton dual system. Based on the action characteristics of the uniform impact load, the effective mode of the forced vibration was obtained by using the Duhamel integral principle and the orthogonality of the mode function. Based on the third strength theory and the numerical simulation results, the dynamic damage process and development trend of coal and rock mass were analyzed under uniform impact load. It was concluded that the starting position of dynamic damage can be judged by the first order main mode, and the development direction and trend of the damage can be judged by the fifth and sixth order main modes. It was concluded that the vibration mode functions of coal and rock mass with four side fixed (C-C-C-C), the two sides fixed and simply supported on the other (S-C-S-C) are mainly composed of three modes that are the first order (dominant frequency), the fifth order and the sixth order, from which the dynamic damage mechanism is preliminarily studied.

Mechanics analysis on the conditions of rock burst occurrence in the coal mass of roadway rib

According to the rock burst features occurred in the coal mass of roadway rib in one mine,the mechanics model of coal mass and roof structure system along the edge of goaf was founded to analyze the stress of roof rock layer,so the subside curve of roof rock layer was deduced.Furthermore,the stability of coal and rock system were analyzed,the critical load and critical resistance zone were used to judge the danger degree of rock burst occurrence.The influence of coal mass strength,brittleness degree,coal seam thickness,roof thickness,suspending length,equivalent shear module on the critical load, critical resistance zone was confirmed.So the rock burst occurrence conditions of coal mass in roadway rib mainly depend on mining depth,coal seam thickness and hard roof and floor,which are decided by the above studies,and successfully applied in prediction and prevention of rock burst in this mine.

Interaction mechanism of the interface between a deep buried sand and a paleo-weathered rock mass using a high normal stress direct shear apparatus

In order to evaluate the feasibility of safe mining close to the contact zone under reduced security coal pillar conditions at a coal mine in eastern China, the interaction mechanism of the interface between deep buried sand and a paleo-weathered rock mass was investigated in the laboratory by direct shear testing. A DRS-1 high pressure soil shear testing machine and orthogonal design method were used in the direct shear tests. Variance and range methods were applied to analyze the sensitivity of each factor that has an influence on the mechanical characters of the interface. The test results show that the normal pressure is the main influencing factor for mechanical characteristics of the interface, while the lithological characters and roughness are minor factors; the shear stress against shear displacement curve for the interface shows an overall hyperbola relationship, no obvious peak stress and dilatancy was observed.When the normal pressure is 6 MPa, the shear strengths of interfaces with different roughness are basically the same, and when the normal pressure is more than 8 MPa, the larger the roughness of the interface, the larger will be the shear strength; the shear strength has a better linear relationship with the normal pressure, which can be described by a linear Mohr–Coulomb criterion.

Numerical modeling on strain energy evolution in rock system interaction with energy-absorbing prop and rock bolt

The interaction mechanism between coal and rock masses with supporting materials is significant in roadway control, especially in deep underground mining situations where dynamic hazards frequently happened due to high geo-stress and strong disturbed effects. This paper is to investigate the strain energy evolution in the interaction between coal and rock masses with self-designed energy-absorbing props and rock bolts by numerical modeling with the finite difference method. The interaction between rock and rock bolt/prop is accomplished by the cables element and the interface between the inner and outer props. Roadway excavation and coal extraction conditions in deep mining are numerically employed to investigate deformation, plastic zone ranges, strain energy input, accumulation, dissipation,and release. The effect on strain energy input, accumulation, dissipation, and release with rock deformation, and the plastic zone is addressed. A ratio of strain energy accumulation, dissipation, and release with energy input a, β, γ is to assess the dynamic hazards. The effects on roadway excavation and coal extraction steps of a, β, γ are discussed. The results show that:(1) In deep high geo-stress roadways, the energyabsorbing support system plays a dual role in resisting deformation and reducing the scope of plastic zones in surrounding rock, as well as absorbing energy release in the surrounding rock, especially in the coal extraction state to mitigate disturbed effects.(2) The strain energy input, accumulation is dependent on roadway deformation, the strain energy dissipation is relied on plastic zone area and disturbed effects, and strain energy release density is the difference among the three. The function of energyabsorbing rock bolts and props play a key role to mitigate strain energy release density and amount, especially in coal extraction condition, with a peak density value from 4×10^(4) to 1×10^(4)J/m^(3), and amount value from 3.57×10^(8) to 1.90×10^(6)J.(3) When mining is advanced in small steps, the strain energy accumulation is dominated. While in a large step, the released energy is dominant, thus a more dynamic hazards proneness. The energy-absorbing rock bolt and prop can reduce three times strain energy release amount, thus reducing the dynamic hazards. The results suggest that energy-absorbing props and rock bolts can effectively reduce the strain energy in the coal and rock masses, and prevent rock bursts and other hazards.The numerical model developed in this study can also be used to optimize the design of energyabsorbing props and rock bolts for specific mining conditions.

Compositional and Structural Study of Macerals in Coals and Source Rocks Using SIMS

The authors applied the Secondary Ion Mass Spectrometry (SIMS) technique to the analysis of compositions and structures of vitrinites fusinites, fusinites bitumens and graptolites in the hydrocarbon source rocks with different maturities dscribed their SIMS spectral characteristics and found that different macerals have differnt spectra which, reflected the compositional and structural differences of macerals. Moreover, the change bod of parameter CH2+/CH3+ can be used for the evaluation of thermal evolution regularity of macerals in the hydrocarbon source rocks The study results show that the SIMS technique is a powerful means for microara analysis of macerals in coals and source rocks. It is certain that the study level of macerals can be raised by detailed study of SIMS results of SIMS results of macerals.

基于数字图像相关方法的煤岩表面应变场及裂纹演化特征

基于数字图像相关方法,开展了煤岩体试样单轴压缩破坏的裂纹演化特征及破坏过程研究,分析了试样破坏过程的表面应变场、变形局部化带的拉伸位移演化和错动位移演化特征,精细化分析煤岩体变形破坏过程。研究结果表明:(1)根据试样的应力-应变曲线特征,将试样分为缓慢破坏型和瞬间破坏型。缓慢破坏型试样的破坏过程较为平稳,裂纹宽度较小。瞬间破坏型试样破坏过程较为剧烈,表面裂纹宽度增加,表现出明显的岩爆现象。(2)加载过程中,缓慢破坏型试样先产生应变集中后,裂纹沿变形局部化带扩展延伸并逐渐贯通;瞬间破坏型试样在应力峰值后试样表面瞬间产生宏观裂纹。(3)试样表面应变演化特征与加载过程中应力变化特征对应,反映了裂纹扩展规律。缓慢破坏型试样在加载过程中表面应变变化过程较为缓慢,并在后期呈现波动状态;瞬间破坏型试样在应力峰值点处,拉伸应变瞬间突增达到峰值,导致试样破坏。

原生层理结构影响下煤岩组合体超声波及CT扫描分析

为研究原生层理结构对煤岩组合体波速及力学性质的影响,并提升室内获取煤岩波速及力学参数的精确性、快速性及便捷性,在室内对不同原生层理倾角的煤岩组合体开展了多层位多方位的超声波及CT扫描测试。基于超声波测试数据,获取了原生层理结构影响下煤岩组合体不同层位的波速及波速比变化特征;结合CT扫描及三维重构技术,应用煤岩灰度分布频数数据,提出了不同层位CT灰度均值的计算方法,获得了不同原生层理倾角下煤岩组合体不同层位灰度及煤岩含量的变化规律,建立了煤岩CT灰度均值与波速、力学参数的关系;构建了考虑层理倾角与煤岩含量效应的煤岩组合体纵波波速计算模型,并应用测试数据进行了对比验证。结果表明:①含原生层理的煤岩组合体波速及波速比与层理倾角线性相关,随层理倾角增加,组合体的纵波波速近似线性减小,而波速比的分布范围增大;②不同层理倾角下组合体的CT灰度均值与波速线性相关,随CT灰度均值增高,煤岩组合体波速线性增加;③煤岩组合体的密度随CT灰度均值增加线性增高,其动态弹性模量及剪切模量则与CT灰度均值均呈三阶多项式关系,并随CT灰度均值增高趋于增大;④层理倾角与煤岩含量相比,组合体波速对煤岩含量的敏感性更高,煤岩含量相近则波速受层理倾角响变化最大。

基于贝叶斯-响应面法的煤矿开挖过程中不同含水状态岩体力学参数分析

在煤炭开挖过程中,准确评价不同含水率条件下岩层的力学参数,对于制定有效的排水方案,降低工作面顶板水害风险至关重要.然而,由于地层分布不均匀,试验测量误差等因素的影响,岩石参数往往呈现不确定性,进而降低了计算煤层开挖时上下岩层不均匀沉降和塌陷等问题的可信度.鉴于以上出现的问题,提出了一种基于贝叶斯更新参数的神经网络的响应面建模方法.该方法采用ACO-BP神经网络建立响应面,并通过贝叶斯公式进行参数的更新,以此建立高置信区间的响应面模型.以正交试验数据为样本,建立传统多项式响应面和神经网络响应面模型,并使用确定系数(R^(2))、20%误差对两种响应面模型进行验证和对比分析.结果表明:相比于多项式响应面,神经网络响应面模型的预测数据误差值更小,具备更高的预测精度和更强的寻找非线性关系的能力,同时利用贝叶斯更新参数的方法,降低了BP神经网络陷入局部最优的缺陷,能更好地进行岩体力学参数的预测和分析.使用神经网络响应面的方法对陕西榆林锦界煤矿31301工作面3-1煤层进行分析,得到孔隙率、含水率、抗压强度与弹性模量之间的非线性关系,并对弹性模量进行预测,预测值和实际值的拟合度可达到0.92,以此来验证了方法的可行性.

安顺煤矿煤岩电磁辐射测试技术研究

随安顺煤矿开采深度的加深,工作面回采时异常动力灾害发生的危险性显著提高。为防范灾害事故,可基于煤岩受载破坏过程电磁辐射强度与煤岩破坏的相关性,采用电磁辐射仪测试煤岩体的损伤破坏状态,对煤岩体动力灾害事故危险性进行预测,通过设置三采区轨道下山、四采区轨道风门0~300 m处为对照组,对四采区轨道、回风、胶带三条下山掘进巷道进行煤岩电磁辐射测试,并对其监测数据进行规律分析。研究结果表明:掘进作业严重影响巷道内应力分布与煤岩破坏状态,靠近掘进点的部位所受应力扰动更为明显,掘进较深、支护稳定的巷道所受影响较小;巷道危险区的煤岩电磁辐射强度相对较高;存在断层时,断层周围电磁辐射信号较强;掘进煤巷的应力受扰动情况比岩巷更加稳定,且所受应力普遍较小。

水力割缝对不同厚度“三软”煤层巷道围岩扰动影响研究

赵家寨煤矿开采煤层在水力割缝过程中受到较大扰动,围岩强度降低,导致煤厚较大且分布不均的“三软”煤层巷道更加难以控制。基于14205工作面岩石力学参数,理论分析确定水力割缝合理参数,借助COMSOL Multiphysics构建不同煤厚条件下水力割缝模型,数值模拟得到了水力割缝对煤层应力、位移影响规律。结果表明:顶煤厚度对于受水力割缝扰动后巷道顶板稳定性有着重要影响,应力特征的主要影响因素为割缝的形态、位置,煤层越厚其变形量越小,水力割缝对煤体的损伤范围主要与割缝位置相关,巷道受扰动范围为两帮各5 m,托顶煤为2 m厚时,顶部煤体受破坏程度最大,巷道稳定性最差,当托顶煤厚度超过4 m时巷道稳定性得到良好改善,在煤体损伤范围内巷道顶部变形量最大,需要加强支护力度。研究结果为不同厚度“三软”煤层水力割缝扰动下巷道围岩稳定性分析提供基础。

基于煤层挥发分的狐偃山岩体隐伏形态特征研究

为了寻找狐偃山岩体隐伏形态特征,基于侵入岩体侧畔煤层挥发分的空间变化特征,刻画侵入岩体在煤系地层中的隐伏形态特征机理;依据西山煤田狐偃山岩体附近469组煤层挥发分数据及前人研究结果,通过制作研究区内02^(#)、2^(#)、6^(#)、8^(#)、9^(#)煤层挥发分等值线图、垂直挥发分变化方向剖面图,研究了煤层挥发分与侵入岩体距离关系。结果表明:狐偃山侵入岩体侧畔依次出现接触变质带、恒温变质带、耗散变质带及正常煤带,岩体影响带宽度在7 km左右,其中接触变质带的宽度在1 km以内,恒温变质带宽度在4~5 km范围内,耗散变质带宽度在2~4 km范围内;狐偃山侵入体在煤系中的隐伏形态为一大型岩体,其中9^(#)煤层下伏有多个小型岩株,煤层自上而下遭受岩体烘烤影响的程度逐渐增大。

瓦斯抽采钻孔孔周煤岩体损伤破坏试验

为研究瓦斯抽采钻孔蠕变失稳特性,采用数字散斑系统观测孔周煤岩体裂纹在扩展过程中的损伤破坏及蠕变过程,得到孔周煤岩体的损伤演化及蠕变力学特性规律。将煤样破坏分为缓慢型、间断型和瞬间破坏型,3个类型的煤样损伤破坏产生的裂隙主要由沿x方向应变引起,其中在不同的发育阶段损伤累积增加导致裂隙发育程度也不同,最终形成了煤样表面的不同破坏类型。在恒载应力下,随着蠕变时间推移,煤岩体的变形能力、变形空间都逐渐减弱,映射了现场的孔周煤岩体的抗压抗变形能力与蠕变时间的关系。

注浆加固在破碎煤岩体中的应用与研究

破碎煤岩体注浆加固对控制围岩稳定具有重大意义,分层注浆效果检验是检测注浆工程合格的重要环节。通过设计分层注浆方案,选择合理的注浆材料、注浆压力以及注浆量,从浆液填充率、钻孔电视探测、分段注水、巷道检测4个方面进行注浆效果检验。结果表明,分层注浆工艺裂缝的浆液填充率可达90%以上,孔隙率低于10%,填充效果优于传统注浆工艺。

积水采空区破碎煤岩体渗流特性试验研究

掌握积水采空区破碎垮落带煤岩体渗流规律对矿井瓦斯安全高效开采至关重要。利用气水两相可调控流动试验系统,采用稳态渗透法开展了积水采空区破碎煤岩体应力-渗透率试验,得到了不同块径、不同积水量条件下渗透参数随轴向载荷的变化特征,揭示了积水采空区破碎煤岩体渗流规律。结果表明:煤样应变随着载荷应力的增加逐渐增大;相同积水量条件下,不同块径煤样渗透率随着载荷的增大呈指数式递减;相同块径条件下,不同积水量的煤样渗透率随载荷的增大呈减小的趋势,且随着载荷的增大,积水量对渗透率的影响逐渐减小。

掘锚一体机快速掘巷期间粉尘诱因及防控装置设计研究

基于2204胶带运输平巷快速掘巷期间粉尘源严重的问题,采用现场调研的方法揭示了掘进工作面迎头区粉尘源严重主要是滚筒截割机械构件顺时针快速切割煤岩体所致。受滚筒截割机械构件运移、迎头区巷道横断面80%以上的空间被占用等因素影响,导致了工作面迎头区粉尘量增加和扩散影响范围变广。基于“抑、控、除、净”的粉尘防控思路,从高效率降尘喷雾系统、掘锚一体机机载控除尘系统和风流净化机械装置等多方面对粉尘防控装置进行了优化设计。现场工业性应用结果表明:掘锚一体机回风侧5.0 m位置总粉尘和呼吸性粉尘的降尘效率分别为90.6%和86.5%,风流净化机械装置后方5.0 m位置总粉尘和呼吸性粉尘的降尘效率分别为97.7%和97.3%,掘进工作面的作业环境得到了显著的改善。

基于科氏质量流量计的微米级煤尘和岩尘颗粒分类方法

【目的】岩尘的粒径比煤尘的小得多,更容易被吸入到肺中,危害较大。为了解决煤尘和岩尘混合颗粒的分类问题,提出一种微米级煤尘和岩尘混合颗粒的测量方法。【方法】首先采用环形静电传感器进行前端流体流量的测定,根据科氏质量流量计的测量原理,研究测量管两侧的时间差和流体的质量流量的关系;其次采用ANSYS有限元软件进行双向流固耦合,验证对煤尘和岩尘混合颗粒进行分类的可行性;最后对测量管进行静力学分析以及数值模拟分析,实现科氏质量流量计对微米级煤尘和岩尘混合颗粒的分类判别。【结果】在科氏质量流量计的同一个测量管道入口处,颗粒的流入速度与测量时间差正相关;谐振式U型管的激振频率应为二阶振型对应的固有频率113.11 Hz;当煤尘和岩尘颗粒混合粒径不同时,静力学参数和时间差随着煤尘的体积分数的增大而减小,并且全岩尘和全煤尘的时间差明显与混合颗粒的不同;当煤尘和岩尘混合颗粒粒径相同时,时间差随着煤尘的体积流量增大而增大,关系曲线的陡度也随着增大。当煤尘体积分数<50%时,煤尘和岩尘的混合颗粒的粒径越大时间差越大;当煤尘体积分数≥50%时,煤尘和岩尘的混合颗粒的粒径越大时间差越小。【结论】煤尘颗粒和岩尘颗粒具有鲜明且不同的分类判别特征,微米级煤尘和岩尘混合颗粒分类具有可行性,可实现科氏质量流量计对煤尘和岩尘混合颗粒的实时在线精确分类。