【作者】 李娜；

【导师】 潘一山； 王凯兴；

【作者基本信息】 辽宁工程技术大学 ， 力学， 2023， 硕士

【摘要】 煤层钻孔是防治煤矿冲击地压的重要技术措施,在以往的研究中,通常认为煤层钻孔可以降低巷道侧向高应力区的应力,以提高巷道围岩的稳定性,但是根据现场观察发现,煤层钻孔对巷道浅部围岩的整体稳定性页产生了破坏作用,减弱了巷道围岩的承载能力,增加了围岩对巷道支架的负荷,从而对巷道支护结构的稳定性和抗冲击能力产生影响。因此,研究煤层钻孔在冲击地压孕育和发生过程中防控冲击地压的实质,揭示其防冲机制,对于指导煤层钻孔的设计参数和巷道支护结构参数具有重要意义。本文通过研究钻孔煤样在静载条件下的变形破坏特征和弹性模量、冲击倾向性和冲击载荷条件下变形破坏特征及吸能量等力学性能,获得钻孔对于煤体物理力学性能的影响规律,基于冲击地压扰动响应失稳理论,分析煤层钻孔在冲击地压孕育和发生过程中起到的作用,揭示煤层钻孔防控冲击地压机理,最后结合数值模拟优化改进煤层钻孔参数。通过单自由面煤样准静载压缩实验,测试了无钻孔煤样、单孔煤样、双孔煤样以及三孔煤样弹性模量和冲击倾向性等力学性能、变形破坏特征等变化情况,发现无钻孔煤样破坏以剪切贯穿破裂为主,钻孔煤样以垂直钻孔间的裂隙贯穿破坏为主,多钻孔下还会形成水平钻孔间的裂隙,裂隙较为发育。钻孔条件下,随着煤样孔洞率的增大,煤样抗压强度、弹性模量逐渐降低,积聚弹性应变能的能力逐渐降低,同时煤样冲击倾向性也显著降低,改变了煤体的物理力学性质,使其异于原煤体介质。通过单自由面煤样冲击载荷下压缩实验,测试了无钻孔煤样、单孔煤样、双孔煤样以及三孔煤样吸能量等力学性能和变形破坏特征,发现无钻孔煤样及钻孔直径5mm条件时,冲击过程中煤样整体出现局部大裂隙发育,但冲击后煤样随着钻孔孔径增大和数量增多,即煤样的孔洞率逐步增加,相同冲击载荷下煤样的宏观裂隙更加发育,煤样破碎更加均匀。试验可以看出,孔洞率增加后,煤样在冲击破坏过程中表面能显著提升,具备更好的吸能效果。基于冲击地压扰动响应失稳理论,分析钻孔改变煤层钻孔区域煤体的孔洞率、抗压强度等物理力学性质后,巷道围岩介质性质变化时,煤层钻孔措施对巷道围岩失稳临界应力的影响,发现在巷道支架支护阻力为1MPa,钻孔区煤岩体强度为原煤体强度50%的条件下,若煤体单轴抗压强度?_c=10MPa,弹性模量与软化模量比E/?=1时,巷道临界失稳载荷增加量随着孔洞率增加呈线型下降趋势,能够起到很好的防冲作用。加密钻孔间距和加深钻孔深度可提高钻孔区煤体吸能量,同时钻孔煤体的密度小,冲击阻抗相对较小,将冲击波的正压持续时间和上升时间拉长,使冲击波的冲量减小,降低冲击载荷对巷道支护的冲击力,起到缓冲作用,避免巷道支护发生失稳破坏。较高的孔洞率可以使钻孔区具有良好的吸能缓冲效果,但其降低了煤体的弹性模量,使其在相同的载荷作用下产生更大的变形,增加了巷道的收缩量,增大了巷道围岩对巷道支护的压力,易造成巷道支护发生较大变形,甚至破坏失效,因此钻孔底端处的间距两倍与临界塑性软化区半径时最为合适。以某矿21404工作面现场钻孔措施为研究对象,通过FLAC3D数值模拟发现煤层钻孔可使巷帮围岩应力峰值向深处转移,随着钻孔深度的增加,峰值位置将进一步向深部转移,同时也小幅降低了应力集中区应力峰值;钻孔间距过大不仅无法起到防冲效果,钻孔间距过密会导致煤体强度下降,进而使得巷道围岩变形加剧。因此在巷道进行钻孔前需要合理设计煤层钻孔与巷道支护间的协调关系。结合本文相关研究成果,给出某矿21404工作面现场钻孔参数的设计方案。该论文有图83幅,表11个,参考文献54篇。更多还原

【Abstract】 The technology of coal seam drilling is an important measure to prevent rock burst in coal mine.By changing the physical and mechanical properties of the surrounding rock near the roadway and improving the hole rate(It’s the volume of the borehole divided by the coal sample volume.)of coal body in the drilled area,the energy absorption and buffering performance can be enhanced.Absorb the energy amplified by the breaking of far-field surrounding rock,thereby protecting the stability of tunnel support.At the same time,drilling is used to reduce the elastic modulus of coal body in the drilling area,reduce the stress concentration of the surrounding rock in it,transfer the peak stress area of the tunnel surrounding rock to the deep part of the coal seam,improve the stability of the tunnel surrounding rock system,and prevent deformation and damage of the tunnel support caused by high stress.Firstly,the paper studies the deformation and failure characteristics and mechanical properties such as elastic modulus,bursting liability and energy absorption of borehole coal sample under static and dynamic loading,and obtains the law of the influence of borehole on the physical and mechanical properties of coal body.Then based on the instability theory of rock burst disturbance response,this study reveals the role of coal seam drilling during the formation and occurrence of rock burst,and reveals the mechanism of coal seam drilling to prevent and control rock burst.Finally,the parameters of coal seam drilling are optimized and improved by numerical simulation.Through a single free surface coal sample quasi-static compression experiment,the changes of mechanical properties,deformation and failure characteristics,such as elastic modulus,bursting liability and so on,without boreholes,single boreholes,double boreholes and three boreholes were tested.It is found that the failure of it is mainly shear through fracture,while the fracture of drilled coal samples is the fracture between vertical boreholes,and the fracture between horizontal boreholes will be formed under many boreholes,and the fracture is relatively developed.Under the drilling condition,with the increase of the hole ratio of the coal sample,the compressive strength and elastic modulus of the coal sample gradually decrease,and the ability to accumulate elastic strain energy gradually decreases.Simultaneously,the bursting liability of coal sample decreases significantly,which changes the physical and mechanical properties of coal body and makes it different from the raw coal body medium.Through the compression experiment under the impact load of single free face coal sample,the energy absorption mechanical properties and deformation and failure characteristics of coal sample without borehole,single hole,double hole and three holes are tested.It is found that under the condition of undrilled coal sample and borehole diameter of 5mm,local large fractures are developed in the whole middling coal sample during impact.However,after the impact,the pore ratio of the it gradually increases as the borehole diameter and quantity increase.Under the same impact load,the macroscopic cracks of the coal sample are more developed,and the coal sample fragmentation is more uniform.It can be seen that with the increase of pore ratio,the surface energy of coal samples in the impact failure process is significantly improved,which has a better energy absorption effect.Based on the rock burst disturbance response instability theory,the influence of coal seam drilling measures on the critical stress of roadway surrounding rock instability is analyzed when the medium properties of roadway surrounding rock change after drilling changes the porosity rate and compressive strength of coal body.It is found that under the condition that the roadway support resistance is 1MPa and the strength of coal and rock in the drilling area is 50%of the strength of the original coal body,if the mechanical parameters of the coal body are?_c=10MPa,E/?=1,the increase of the critical instability load of the roadway shows a linear downward trend with the increase of the porosity,which can play a good anti-scour role.The energy absorption of coal body in drilling area can be increased by spacing and deepening of drilling depth.At the same time,the density of the drilling coal body is small,and the impact impedance is relatively small,which prolongs the duration and rise time of the positive pressure of the shock wave,reduces the impulse of the shock wave,reduces the impact load in the impact force of the tunnel support,avoiding the instability and damage of the tunnel support.The higher pore ratio allows the borehole area to have a good energy absorption buffer effect.But it reduces the elastic modulus of the coal body,causing it to undergo greater deformation under the same load,increasing the shrinkage of the tunnel,and increasing the pressure of the surrounding rock on the tunnel support,which can easily cause significant deformation or even failure of the tunnel support.Then the spacing at the bottom of the borehole 2?is the most suitable.Taking the on-site drilling pressure relief measures of 21404 working face in a certain mine as the research object.Through FLAC3D numerical simulation,it is found that the coal seam drilling can make the stress peak shift to the depth of the roadway wall rock.With the increase of the depth of the drilling,the peak position will be further shifted to the depth.At the same time,the stress peak in the stress concentration area is slightly reduced.Too large spacing of boreholes not only fails to play an anti-scour effect,but also too dense spacing of boreholes will lead to the decline of coal strength and further aggravate the deformation of roadway surrounding rock.Therefore,it is necessary to reasonably design the coordination relationship between coal seam drilling and tunnel support before drilling and pressure relief in the tunnel.Combined with the relevant research results of this paper,the designing scheme of pressure relief parameters of in-situ drilling in 21404 working face of a mine is given.There are 83 pictures,11 tables and 54 references in this paper.更多还原