冲击矿层的层裂板模型及实验研究

片帮型冲击矿压是煤壁局部失稳，与煤壁层裂板结构的形成有关，分析了煤壁层裂板结构形成及压曲失稳破坏规律，给出了裂纹扩展，贯通的应力判据以及随后形成的层裂板结构压曲失稳的条件，并据此对冲击矿井进行模拟试验研究，实验结果与理论分析基本一致。     

冲击矿压模拟试验研究

采用相似材料和煤质材料模拟煤矿冲击矿压发生的过程和现象,揭示了煤壁局部突然失稳形成片帮型冲击矿压的机制,即巷道附近压应力集中区内裂纹平行壁面扩展、贯通,形成层裂板结构,在一定压力下发生压曲破坏。此外,试验采用三维模型和现场煤样,更接实际情况,为此类试验提供了新的途径。     

动力扰动导致巷道围岩层裂结构及冲击矿压的数值模拟

煤矿生产中存在着大量的动力扰动,常导致采矿巷道和采场围岩局部失稳,诱发冲击矿压发生。在一定条件下,动力扰动可简化为平面应力波。针对片帮型冲击矿压,采用数值方法模拟应力波作用下巷道围岩层裂结构的形成过程,探讨巷道围岩层裂结构的形成与巷道埋深、岩体弹性模量及应力波强度、时程特性的关系,进而讨论“小进尺、弱爆破”可减小扰动应力波诱发冲击矿压的机制,得到一定地质条件下动力扰动诱发冲击矿压的条件。     

煤矿岩爆发生机制研究

 博士学位论文摘要　以煤矿岩爆为工程背景, 采用岩石力学、断裂力学、粘弹性力学、稳定理论以及试验模拟相结合的方法,从煤岩体结构局部失稳的角度, 提出并建立了煤矿片帮型岩爆的力学模型。在理论分析和试验研究方面作了一些新的探索和尝试, 取得了下列主要研究结果:(1) 以岩石裂隙演化及其力学特性的研究为出发点, 着重研究了受自由表面影响的近壁面裂纹的扩展条件与扩展方向。研究表明, 在压应力集中区内, 近自由表面的裂纹在低侧压(或无侧压) 时, 将平行于壁面沿最大压力方向扩展, 在一定的压力下,受自由表面的影响, 这种扩展是不稳定的。通过滑移开裂裂纹模型, 给出了近壁面两种情况下裂纹扩展的临界应力计算公式。(2) 通过对巷道和采场围岩的受力分析, 定义了由壁面到煤体深处的应力过渡区。在高压应力(包括采动应力) 作用下, 过渡区内裂纹将扩展贯通, 并在一定范围内形成顺壁层裂结构区, 讨论了层裂结构区的尺度。提出并建立了煤矿片帮型岩爆的力学模型———层裂板模型, 即认为巷道或采场壁面的局部稳定是由高应力集中区内形成的层裂板结构区的稳定控制的, 片帮型岩爆是煤壁层裂板结构区的局部压屈。分析了层裂板结构两种约束状况下的稳定性。(3) 考虑裂纹的亚临界扩展, 研究了裂纹扩展的时间相关性, 讨论了裂纹贯穿前壁面位移与时间的关系。(4) 基于板梁结构和层裂板模型, 采用线粘弹性本构关系, 研究了煤矿片帮型岩爆的时间延迟问题, 这是对岩爆发生的时间延迟研究的一个新的尝试。得到了不同载荷水平下, 板梁结构和层裂板模型失稳的延迟时间计算公式。此外, 简单讨论了缓慢底鼓与急剧底鼓的机制以及扰动应力对岩爆发生的影响。(5) 用研制的相似材料模型和煤块混合模型, 对煤矿岩爆进行了模拟试验研究, 验证了本文建立的层裂板模型的正确性和适用性。试验成功地模拟了巷道或采场岩爆的过程。壁面及顶底板的相对位移变化的记录曲线表明, 岩爆发生时, 位移曲线发生相应的突跳, 这种现象在一定的间歇后, 可再次发生, 反映了岩爆的间歇性和动力失稳的特征。试验后的壁面观测发现, 残存壁面呈层裂结构, 突出物为片状块体。此外, 还对相似材料模型和煤块混合模型的试验现象和结果进行了对比分析, 认为后者更能反映实际状况。混合模型在此类试验中是首次使用, 为该类试验模型制作提供了新的途径。(6) 以三河尖煤矿岩爆为例, 运用层裂板模型对片帮型岩爆发生机制进行了分析。通过模型的实例估算, 得到了发生岩爆的临界深度与该矿当时的开采深度相一致的结果, 这表明层裂板模型对片帮型岩爆机制的分析是合适的。     

井巷围岩的延迟失稳机理分析

针对煤矿井巷围岩层状结构特征和流变特性,建立了围岩延迟失稳的粘弹性板屈曲模型,用粘弹性理论分析了具有层状（裂）结构特点的围岩延迟失稳特性,讨论了扰动载荷对围岩稳定性的影响以及冲击矿压发生的时间延迟问题,并进行了简单的实例计算,其结果对工程实践有一定的参考价值。     

浅埋房式采空区下长壁采场动载矿压发生机制

为了揭示浅埋房式采空区对下位煤层开采矿压显现的控制机制,降低工作面过房式采空区的动压显现强度和压架风险,以神东矿区霍洛湾煤矿2-2煤层房式采空区下3-1煤层长壁开采工作面动压特征为研究对象,将3-1煤层覆岩结构分为四类,利用理论分析和相似材料模拟等方法,系统研究了不同覆岩结构类型运动特征、力学模型及对3-1煤层长壁工作面的动压控制机制。结果表明:房式采空区稳定房柱下易形成上下位关键层双悬臂梁结构,双悬臂梁结构协同失稳是形成动载矿压的主要原因;房柱失稳区主关键层形成的不稳定砌体梁结构及靠近大煤柱未失稳的房柱随下位煤层开采滑落失稳是导致长壁工作面动载矿压发生的原因;当3-1煤层工作面上覆前方为房柱失稳区时,工作面推出集中煤柱时的动载矿压是由于大煤柱两侧关键块已提前滑落失稳,两关键块间无作用力,倒梯形岩柱与亚关键层联合失稳作用结果;当3-1煤层工作面上覆前方为房柱稳定区时,工作面推出集中煤柱时,动载矿压是由房柱失稳所致。     

长壁工作面采空区见方形成异常来压的微震监测研究

上覆岩层的断裂失稳下沉是造成工作面矿压显现的根源。采用微震监测技术对长壁工作面见方期间围岩破坏的整个过程进行监测,研究长壁工作面见方期间微震事件动态信息与岩层运动及矿压显现间的关系,揭示大能量微震事件发生和工作面围岩异常矿压的物理力学机制。同时,统计研究采场煤壁片帮和支架工作阻力的动态变化规律。微震监测与宏观矿压观测综合对比研究表明,见方期间的开采影响范围比正常开采时大,围岩释放能量也达到极大值。研究结果证实了采空区见方期间工作面将发生异常矿压,能够为见方期间冲击地压、煤与瓦斯突出和底板突水等矿井动力灾害防治提供针对性的指导。     

大空间远近场结构失稳矿压作用与控制技术

针对大同石炭系坚硬顶板特厚煤层开采造成的强矿压显现及控制难题,通过现场实测和理论分析,揭示了大空间远、近场岩层失稳破断的强矿压显现机制,提出了坚硬顶板控制技术。研究表明:近场岩层破断失稳造成工作面复合周期来压显现,远场结构失稳是工作面强矿压的主要影响因素,临空开采、煤柱赋存条件下,高位结构破断回转、应力集中更复杂,采场矿压显现更强烈。提出井上下、远近场协同控制坚硬岩层技术体系,通过采用井下近场预裂和地面远场压裂的坚硬岩层弱化技术,减弱远、近场坚硬岩层的矿压作用,控制工作面强矿压显现,开辟了采场矿压控制的新途径。     

覆岩关键层运动诱发冲击的规律研究

基于岩层运动关键层理论,研究了覆岩关键层破断规律,从力学机理上分析了覆岩关键层正"O-X"型破断时,矿山压力达到最大值,极易导致强矿震、冲击矿压的发生。利用微震监测系统,对关键层破断诱发冲击矿压进行定位分析,证明了高能量级别的矿震大多数发生在工作面推进过程中覆岩关键层处于正"O-X"型破断位置。研究表明由关键层运动破断诱发冲击矿压前后,微震事件的时空演化规律、前兆信息显著。研究结果为利用岩层运动理论与微震监测相结合的方法预测冲击矿压奠定了基础。     

冲击地压的一维层裂模型

提出了煤层冲击地压的一维模型.该模型把煤体破坏分为两个阶段层裂和失稳,并用支承压力分布特征描述煤体的失稳破坏.该模型描述了重力场条件下的冲击煤层失稳机制.     

Vibration, buckling and parametric instability behaviour of plates with centrally located cutouts subjected to in-plane edge loading (Tension or compression)

The vibration, buckling and parameterc instability behaviour of a plate with internal opening subjected to in-plane compressive or tensile periodic edge loading are studied. Different shapes and sizes of the cutout are considered. Compression and tension buckling results are discussed. The vibration analysis for this problem shows that for certain parameters of tensile loading and the opening, the frequency of the plate initially rises' with the load, but then begins to decrease with increasing tension showing the onset of tension buckling. Dynamic instability behaviour of the plate under compressive and tensile loading shows that the instability regions are affected by the size, shape of the opening and the loading parameters. Instability behaviour due to all the parameters are discussed.     

双T型板的应用及其屈曲特征分析

介绍了双T型板的应用现状,施工流程等。通过有限元对双T型板进行屈曲特征分析,得出其所能承受的极限荷载,近似得出双T型板所能承受的地震强度等级。     

Parametric instability of edge cracked plates

The presented paper deals with the parametric instability behavior of a simply supported rectangular plate with a crack emanating from one edge, subjected to in-plane compressive periodic edge loading. The problem is reduced to computing the free vibration frequencies and the corresponding mode shapes and substituting them into an integral equation based formula, which leads to a compact matrix form. Once the components of this matrix are found, the rest of the computation, i.e., establishing regions of instability, buckling loads and modified frequencies, is straightforward and fast. Several plates, each with a different dimension and crack length size are analyzed using this approach. The comparison of results with those of finite element models is found to be in close agreement.     

Buckling analysis of cracked plates using hierarchical trigonometric functions

The present paper deals with the estimation of buckling loads of plates with cracking damages. The hierarchical trigonometric functions are used to define the displacement function of the cracked plate. Selective choosing of the trigonometric functions satisfies the various boundary conditions of a plate bounded by support members in a continuous plated structure. Moreover, the analysis of the cracked plate can be carried out with a minimum number of equations accurately. In the present paper, the buckling loads of plates with various types of cracks, such as edge crack and central crack, are estimated under uniaxial compressive load, biaxial compressive load and in-plane shear load. The results are found to correlate well with those obtained using a finite element method.     

Buckling of cracked functionally graded plates under tension

Buckling of functionally graded cracked plates under tension has not been investigated so far. In this paper critical buckling load of functionally graded plates containing a crack has been obtained using classical plate theory through the finite element method. Displacement in vicinity of crack tips has been approximated using previous solutions related to bending of cracked plates. Effect on buckling of plate under uni-axial and bi-axial tension of different parameters, such as plate dimensions and material properties, are studied. Results show that the critical load decreases as material gradient index increases, while bi-axial loading leads to higher critical loads compared to uni-axial case.     

钢框架板柱体系叠层升板施工仿真分析

叠层升板是由传统的逐层提升改为一次提升两块板的提升方法。利用自主开发的基于ANSYS有限元程序的升板模拟仿真程序并以4层升板结构为例,对叠层升板过程中框架结构的屈曲载荷、柱的轴力、柱底弯矩、混凝土板的应力分布等进行分析并与传统升板进行比较。结果表明,在群柱稳定性得以保证的前提下,叠层升板在优化施工工序、降低工程造价、缩短施工周期等方面具有显著的优势和良好的经济效益。     

Lateral, local and distortional buckling of I-beams

A theoretical study of the elastic buckling modes of I-section beams under various loading conditions is presented.

The analysis is based on energy considerations and the energy equations governing instability are derived using plate theory to allow for distortion of the cross-section. The resulting analysis is able to predict lateral, local and distortional buckling modes.

The results are compared with classical lateral buckling solutions based on beam theory.     

Thermal buckling analysis of rectangular composite plates with temperature-dependent properties based on a layerwise theory

Thermal buckling analysis of rectangular composite multilayered plates under uniform temperature rise is investigated using a layerwise plate theory. von Karman strain–displacement equations are employed to account for large deflections occurrence. It is already proven that the layerwise theory results are compatible with the three-dimensional theory of elasticity results. The accuracy of the present results is increased by substituting each layer by many virtual sub-layers. The final governing equations are not simplified or linearized. Material properties are assumed to vary with temperature. Hermitian finite element formulation is used to ensure a C¹ continuity for the lateral deflections. No semi-analytic solution is employed to reduce the problem to an eigenvalue one. Layerwise formulations are usually displacement-based. Therefore, force or moment boundary conditions (e.g. simply supported boundary condition), are approximately satisfied. A FEM algorithm is presented to exactly incorporate the boundary conditions. A proposed numerical scheme and a modified Budiansky instability criterion presented by the author are used to determine the buckling temperature in a computerized solution. Finally, results of the present techniques are compared with the results of the high-order theories presented by some well-known researchers and the influences of various geometric and mechanical properties parameters of the composite plate on the buckling temperature are studied.     

底板工程裂缝控制的技术措施

提出从结构设计、材料及施工方面对底板结构进行裂缝控制的技术措施,指出UEA-H混凝土可控制大体积混凝土结构裂缝的出现,介绍了底板施工阶段的温度裂缝控制计算并对UEA-H混凝土的作用进行了评价。     

Buckling analysis of thin circular FG plates made of saturated porous-soft ferromagnetic materials in transverse magnetic field

This study presents the buckling analysis of soft ferromagnetic FG circular plates made of poro material. Equilibrium and stability equations of a poro circular plate in transverse magnetic field are derived. This study analyzes the poroelastic instability of clamped edge ferromagnetic plates subjected to magnetic loadings. The geometrical nonlinearities are considered in the Love–Kirchhoff hypothesis sense. In this paper the effect of pore pressure on critical magnetic field of plate and the effect of important parameters of poroelastic material on buckling capacity are investigated. Also the compressibility of fluid and porosity on the buckling strength are being investigated.