Experimental study on correlation between compressibility and permeability of on-load lignite pore structure
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摘要:
为分析褐煤受载孔隙结构可压缩性与渗透率的相关性，采用单轴压缩在线核磁共振测试方法，测试得到了褐煤受载过程T2图谱演化曲线及其渗透率，研究了不同应力水平下褐煤孔隙结构的可压缩性系数与渗透率的关系。根据T2图谱计算发现，褐煤内小孔、中孔、大孔的占比分别为50%～60%、20%～30%、5%～20%，其中小孔可划分为吸附孔，中孔和大孔可划分为渗流孔。在褐煤受载破坏的全过程中，煤体孔隙变化主要集中在渗流孔，吸附孔虽占比超过50%，但对于煤体宏观变形的贡献几乎可以忽略。渗流孔的可压缩性较强，可压缩系数变化值达到0.07～0.23，而吸附孔的可压缩系数变化值仅为0.01～0.02。煤体的渗透率变化趋势与渗流孔可压缩系数变化趋势一致，相关系数均大于0.893，煤体骨架的可压缩性与渗流孔可压缩性的线性关联证明了煤体渗透率随应力的变化，主要取决于渗流孔。
Abstract:In order to analyze the correlation between compressibility and permeability of lignite bearing pore structure, the T2 pattern evolution curve and permeability of lignite loading process were tested by uniaxial compression online NMR test method, and the relationship between compressibility coefficient and permeability of lignite pore structure under different stress levels was studied. According to the calculation of T2 map, it is found that the proportion of small holes, medium holes and large pores in lignite is 50%～60%, 20%～30% and 5%～20%, respectively, of which small pores can be divided into adsorption pores, and mesopores and macropores can be divided into seepage pores. In the whole process of load failure of lignite, the pore changes of coal body are mainly concentrated in seepage pores, and although the adsorption pores account for more than 50%, their contribution to the macroscopic deformation of coal body can be almost ignored. The compressibility of the seepage hole is strong, and the change value of compressible coefficient reaches 0.07～0.23, while the change value of compressible coefficient of adsorption pores is only 0.01～0.02. The change trend of coal permeability is consistent with the change trend of the compressibility coefficient of seepage holes, and the correlation coefficients are greater than 0.893, and the linear correlation between the compressibility of coal skeleton and the compressibility of seepage holes proves that the change of coal permeability with stress mainly depends on the seepage pores.
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Keywords:
- lignite /
- compressibility /
- permeability /
- pore structure /
- uniaxial compression
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图 2 单轴加载应力应变、渗透率及T2谱图
Figure 2. Stress strain, permeability, and T2 spectrum under uniaxial loading
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图 5 渗透率与渗流孔可压缩性关系
Figure 5. Relationship between permeability and compressibility of seepage hole
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图 6 骨架可压缩性与渗流孔可压缩性关系
Figure 6. Relationship between compressibility of framework and compressibility of seepage hole
表 1 试样物理参数
Table 1 Physical parameters of samples
试样 体积/cm3 孔隙度/% Aad/% Vdaf/% FC/% S1 23.75 19.1 9.36 7.25 81.63 S2 23.94 16.65 S3 24.09 17.37 
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