深部环境下坚硬顶板预裂爆破弱化机理研究
发布时间：2018-07-24 09:55
【摘要】：在实际的开采过程中,许多煤矿工作面顶板为坚硬的灰岩、砂岩或其他硬度更大的岩层。坚硬顶板条件下煤矿开采存在顶板大面积悬露、诱发冲击可能性增加等一系列问题,对于坚硬顶板采场一般需要采取强制放顶措施来控制顶板的垮落。预裂爆破强制放顶技术由于对煤层地质的适应性强,对缓解大面积来压效果显著,而被广泛运用。由于开采深度的增加,深部岩体将具有很高的地应力,从而使得深部岩体爆破损伤弱化机理与浅部不同。本文通过理论分析和数值仿真手段对深部环境下坚硬顶板预裂爆破弱化机理进行了相关研究。主要完成的研究工作如下:(1)归纳总结了坚硬顶板所具有的物理特性和破断特性。根据坚硬顶板采场特点,通过对坚硬顶板破断理论的简单推导,分析了坚硬顶板初次来压步距和周期来压步距的估算方法及相关破断位置。(2)综合各种理论探讨了岩体爆破破碎损伤机理。通过对爆破应力波的衰减特点及传播特点进行分析,得到了岩体先发生拉压变形,再发生剪切变形的破坏特征以及通低频阻高频的应力波传播特性。(3)运用ANSYS/LS-DYNA显式动力学有限元软件对岩体在单孔爆破荷载作用下的动力响应机理及裂隙发育规律做了数值仿真试验,并研究了弹性模量、岩层埋深的变化对岩体裂隙发育规律的影响,同时研究了双孔爆破岩体动力响应规律以及起爆延时对岩体爆破动力破碎效果的影响。分析表明:随着埋深的增加,爆破后产生的裂隙区半径减小,岩体的破碎损伤程度增大;随着弹性模量的增加,爆破后产生的裂隙区半径增大,岩体的破碎损伤程度增大;随着起爆延时的增加,爆破应力波的叠加作用减弱,爆破孔间形成的贯通裂隙区减小,岩体的破碎损伤程度降低。(4)以纳林河二矿3-1煤层首采工作面为工程背景,运用UDEC软件对坚硬顶板预裂爆破强制放顶过程进行了数值仿真分析。结果表明:采取预裂爆破强制放顶措施后,采场顶板初次来压垮落步距降幅接近50%,周期来压垮落步距降幅在25%到50%之间,顶板超前集中应力峰值减小5.1MPa;随着预裂高度的增加,采场初次来压步距逐渐减小,煤壁处压力及岩层超前支撑压力峰值逐渐降低,采场顶板的初次来压将经历两次释放的过程。在一定预裂高度范围内,采场顶板弱化效果明显,可以达到人为控制采场顶板破断垮落步距目的。
[Abstract]:In the actual mining process, the roof of many coal face is hard limestone, sandstone or other rock strata with greater hardness. A series of problems exist in mining under the condition of hard roof, such as large area hanging of roof, increasing possibility of induced impact and so on. For hard roof stope, it is necessary to take forced roof caving measures to control the collapse of roof. Presplit blasting forced caving technology is widely used because of its strong adaptability to coal seam geology and remarkable effect on relieving large area pressure. Because of the increase of mining depth, the deep rock mass will have high in-situ stress, which makes the mechanism of deep rock blasting damage weakening different from that of shallow rock mass. In this paper, the weakening mechanism of hard roof pre-splitting blasting in deep environment is studied by means of theoretical analysis and numerical simulation. The main works are as follows: (1) the physical and fracture characteristics of hard roof are summarized. According to the characteristics of hard roof stope, a simple derivation of breaking theory of hard roof is given. In this paper, the estimation methods of the initial pressure step and periodic pressure step of hard roof and the relative breaking positions are analyzed. (2) the damage mechanism of rock mass blasting breakage is discussed by synthesizing various theories. By analyzing the attenuation and propagation characteristics of blasting stress wave, it is obtained that the first deformation of rock mass occurs under tension and compression. Failure characteristics of secondary shear deformation and propagation of stress wave at low frequency and high frequency. (3) dynamic response mechanism and fracture development of rock mass under single hole blasting load are studied by ANSYS/LS-DYNA explicit dynamic finite element software. Numerical simulation test, The influence of elastic modulus and the change of rock stratum depth on the fracture development of rock mass is studied. The dynamic response law of rock mass and the effect of initiation delay on the dynamic fracture effect of rock mass blasting are also studied. The analysis shows that with the increase of burying depth, the radius of fracture area decreases after blasting, and the degree of fragmentation damage increases, and with the increase of elastic modulus, the radius of fracture zone increases after blasting, and the damage degree of rock mass increases. With the increase of detonation delay, the superposition of blasting stress wave weakens, the through fracture area between blasting holes decreases, and the degree of rock mass fragmentation decreases. (4) taking the first mining face of 3-1 coal seam in Nalinhe No. 2 Mine as the engineering background, UDEC software is used to simulate and analyze the forced caving process of hard roof pre-splitting blasting. The results show that after the presplit blasting forced roof caving, the drop distance of the first roof collapse is close to 50, the periodic collapse step drop is between 25% and 50%, the peak value of the roof leading concentration stress is reduced by 5.1 MPA, and with the increase of the pre-cracking height, the peak value of the roof leading concentration stress decreases by 5.1 MPa, and the peak value of the roof leading concentration stress decreases by 5.1 MPa with the increase of the pre-cracking height. The initial pressure step of stope decreases gradually, the pressure at coal wall and the peak value of rock support pressure gradually decrease, and the initial pressure of stope roof will go through the process of twice releasing. In the range of certain pre-splitting height, the weakening effect of stope roof is obvious, which can achieve the purpose of artificially controlling the stope roof breaking and falling distance.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TD327.2;TD235
本文编号：2141000
[Abstract]:In the actual mining process, the roof of many coal face is hard limestone, sandstone or other rock strata with greater hardness. A series of problems exist in mining under the condition of hard roof, such as large area hanging of roof, increasing possibility of induced impact and so on. For hard roof stope, it is necessary to take forced roof caving measures to control the collapse of roof. Presplit blasting forced caving technology is widely used because of its strong adaptability to coal seam geology and remarkable effect on relieving large area pressure. Because of the increase of mining depth, the deep rock mass will have high in-situ stress, which makes the mechanism of deep rock blasting damage weakening different from that of shallow rock mass. In this paper, the weakening mechanism of hard roof pre-splitting blasting in deep environment is studied by means of theoretical analysis and numerical simulation. The main works are as follows: (1) the physical and fracture characteristics of hard roof are summarized. According to the characteristics of hard roof stope, a simple derivation of breaking theory of hard roof is given. In this paper, the estimation methods of the initial pressure step and periodic pressure step of hard roof and the relative breaking positions are analyzed. (2) the damage mechanism of rock mass blasting breakage is discussed by synthesizing various theories. By analyzing the attenuation and propagation characteristics of blasting stress wave, it is obtained that the first deformation of rock mass occurs under tension and compression. Failure characteristics of secondary shear deformation and propagation of stress wave at low frequency and high frequency. (3) dynamic response mechanism and fracture development of rock mass under single hole blasting load are studied by ANSYS/LS-DYNA explicit dynamic finite element software. Numerical simulation test, The influence of elastic modulus and the change of rock stratum depth on the fracture development of rock mass is studied. The dynamic response law of rock mass and the effect of initiation delay on the dynamic fracture effect of rock mass blasting are also studied. The analysis shows that with the increase of burying depth, the radius of fracture area decreases after blasting, and the degree of fragmentation damage increases, and with the increase of elastic modulus, the radius of fracture zone increases after blasting, and the damage degree of rock mass increases. With the increase of detonation delay, the superposition of blasting stress wave weakens, the through fracture area between blasting holes decreases, and the degree of rock mass fragmentation decreases. (4) taking the first mining face of 3-1 coal seam in Nalinhe No. 2 Mine as the engineering background, UDEC software is used to simulate and analyze the forced caving process of hard roof pre-splitting blasting. The results show that after the presplit blasting forced roof caving, the drop distance of the first roof collapse is close to 50, the periodic collapse step drop is between 25% and 50%, the peak value of the roof leading concentration stress is reduced by 5.1 MPA, and with the increase of the pre-cracking height, the peak value of the roof leading concentration stress decreases by 5.1 MPa, and the peak value of the roof leading concentration stress decreases by 5.1 MPa with the increase of the pre-cracking height. The initial pressure step of stope decreases gradually, the pressure at coal wall and the peak value of rock support pressure gradually decrease, and the initial pressure of stope roof will go through the process of twice releasing. In the range of certain pre-splitting height, the weakening effect of stope roof is obvious, which can achieve the purpose of artificially controlling the stope roof breaking and falling distance.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TD327.2;TD235
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