构造煤和煤与瓦斯突出关系的研究

Causality between tectonic coal and coal and gas outbursts

  • 摘要: 构造煤是原生煤经过长期的强烈挤压,剪切变形后形成的,其具有黏聚力低、强度低和渗透率低等特点。长期以来,中国乃至全球的大部分煤与瓦斯突出事故都发生在构造煤层中,但是其根本原因尚未明确。为了揭示构造煤与突出的内在关系,对构造煤与原生煤的孔隙结构、甲烷吸附、解吸、扩散、渗流和力学性质进行了系统性的回顾与对比,并结合突出能量进行了定量分析。结果表明,由于构造作用,构造煤比原生煤具有更大的总孔隙体积和比表面积,其中大孔受到的影响最为显著。此外,构造煤的吸附/解吸能力和扩散系数普遍较高,而抗压强度和弹性模量则普遍较小。在突出激发阶段,煤体破碎依赖于应力能的释放,此时破碎煤体释放的大量解吸瓦斯是突出后续发展的重要能量来源,特别是小于临界粒径的突出煤体,起到了决定性作用。然而,能量分析表明,若要满足临界粒径的要求,原生煤所需应力条件远高于构造煤,甚至会远超过目前采掘深度的应力水平。因此,原生煤难以提供足够的能量支撑突出的发展。在实际情况中,即使首先发生破碎的是原生煤或者岩石,突出的持续发展也强烈依赖于破碎比功更低和解吸能力更强的构造煤,表明构造煤不仅仅是更易于突出,更是突出发展的一个必要条件。此外,就构造煤的储层特性而言,在实验室中获得的构造煤渗透性能显著高于现场获得的结果(差异可达2个数量级),其主要原因可归结为实验室中重构的构造煤样品无法还原构造煤的原始物理性质。因此在未来的研究中,除了仍需要对构造煤体的孔隙结构进行系统性的研究外,探究构造煤样品重构的新方法也具有重要意义。

     

    Abstract: Tectonic coal is formed after the intact coal being subjected to long-term intense squeezing,shearing and deformation It is characterized by brittle or ductile damaged coal body,with the characteristics of low cohesion,low strength and low permeability The existence of a causal link between outbursts and tectonic coal is widely accepted Recent observations have also indicated that most of the outburst cases in China and the world occurred in tectonic coal seams However,the mechanism is not yet clear In order to reveal the internal connection between tectonic coal and outburst,reservoir properties,including pore structure,adsorption,diffusion,permeability and geomechanical properties of the tectonic coal are reviewed in detail and compared with those of the intact coal It was found that tectonic coal in general shows larger total pore volume and specific surface area than intact coal for larger pores due to tectonism,and the impact on macropores is the most significant In addition,the adsorption/desorption capacity and diffusion coefficient of tectonic coal are generally high,while the compressive strength and elastic modulus are generally low Further analysis shows that the release of stress energy is the key to coal crushing,and the existence of coal particles smaller than the critical size is crucial-However,to reach the critical particle size,the stress conditions required for intact coal are much higher than tectonic coal and may even far exceed the stress levels of current mining depths Hence,the development of outbursts strongly relies on tectonic coals In this case,the existence of tectonic coal is a necessary condition for outburst development,rather than easier to outburst In addition,in terms of the reservoir characteristics of tectonic coal,the permeability obtained in the laboratory is significantly higher than the results obtained in the field (up to two orders of magnitude)The reason can be attributed to the fact that using reconstituted samples for tectonic coal in the laboratory may not fully replicate the original physical properties of tectonic coal It is suggested that in addition to systematic research on the pore structure of tectonic coal,it is also of great significance to explore new methods for the reconstruction of tectonic coal samples

     

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