Quantitative study on grouting plugging effect of loaded fractured coal sample based on CT scanning
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摘要: 针对现有注浆煤岩体裂隙结构和注浆效果研究不能定量表征的问题，利用自主搭建的受载煤岩体注浆试验系统开展了不同受载破裂煤样（单轴和劈裂）的注浆试验，采用工业CT扫描设备对破裂煤样注浆前后的裂隙结构进行了CT扫描，应用图像分析软件VG Studio MAX对CT扫描数据重建模型所得到的数字煤样进行裂隙精准提取，对受载破裂煤样注浆前后三维裂隙形态和结构进行了数字化定量分析。结果表明：① 单轴加载破裂煤样主裂隙由煤样顶部两侧贯穿至煤样底部并汇聚，裂隙宽度基本保持不变，煤样主要在剪切应力作用下破裂，整体破碎程度较大，主裂隙网络伴生较多的小裂隙；注浆前后50 mm以上裂隙由1条转为0，总裂隙体积由12 000 mm3减小为5 700 mm3，降幅为52.5%，表明单轴破裂煤样裂隙结构相对不利于浆液扩散流动。劈裂破坏煤样主裂隙由顶部沿竖直方向向下延伸至煤样中下部，裂隙宽度较大，然后向一方倾斜45°继续延伸，裂隙宽度逐渐变小；注浆前后50 mm以上裂隙由2条转为0，总裂隙体积由3 430 mm3减小为312 mm3，降幅为90.9%，表明劈裂破坏煤样裂隙结构有利于浆液的流动和充填。② 注浆前后单轴加载破裂煤样渗透率由57×10−14 m2下降到1.2×10−14 m2，下降了97.9%；注浆前后劈裂破坏煤样渗透率由75×10−14 m2下降到1.3×10−14 m2，下降了98.3%，表明注浆对不同破坏形式煤样均具有显著的堵漏降渗效果。 ③ 对比2种煤样注浆前后裂隙体积和渗透率变化情况可以看出，虽然单轴加载破裂煤样注浆浆液仅充填了部分裂隙，但渗透率与原始煤样差别很小，表明通过阻隔漏气通道的连通性，即可有效封堵裂隙并取得良好的注浆封孔效果。研究结果可为破裂煤体注浆量化分析及煤层注浆封堵效果评价提供有益参考。Abstract: The existing research on the fracture structure and grouting effect of grouting coal and rock mass cannot be quantitatively characterized. In order to solve the problem, the self-built grouting test system for loaded coal and rock mass is used to carry out the grouting test of different loaded fractured coal samples(uniaxial and splitting). The CT scanning of the fractured coal sample before and after grouting are carried out by using industrial CT scanning equipment. The image analysis software VG Studio MAX is used to accurately extract the fractures of the digital coal sample obtained from CT scanning data reconstruction model. The digital quantitative analysis of the three-dimensional fracture morphology and structure of the loaded fractured coal samples before and after grouting is carried out. ① The results show that the main fracture of the fractured coal sample under uniaxial loading penetrates from both sides of the top of the coal sample to the bottom of the coal sample and converges. The fracture width is basically unchanged. The coal sample is mainly fractured under the action of shear stress. The overall degree of fragmentation is large. The main fracture network is accompanied by more small fractures. The number of fracture above 50 mm is changed from 1 before grouting to 0 after grouting. The total fracture volume is reduced from 12 000 mm3 to 5 700 mm3 by 52.5%. It shows that the fracture structure of fractured coal sample under uniaxial loading is not conducive to slurry diffusion flow. The main fracture of splitting failure coal sample extends downward from the top to the middle and lower part of the coal sample along the vertical direction. The fracture width is large. And then the fracture tilts 45° to one side and continues to extend. The fracture width gradually narrows. The number of fractures above 50 mm is changed from 2 before grouting to 0 after grouting. The total fracture volume is reduced from 3 430 mm3 to 312 mm3 by 90.9%. It shows that the fracture structure of splitting failure coal sample is conducive to the flow and filling of slurry. ② The permeability of fractured coal sample under uniaxial loading is decreased from 57×10−14 m2 before grouting to 1.2×10−14 m2 after grouting by 97.9%. The permeability of splitting failure coal sample is decreased from 75×10−14 m2 before grouting to 1.3×10−14 m2 after grouting by 98.3%. It shows that grouting has a significant effect of plugging leakage and reducing seepage on coal sample with different failure forms. ③ The change of fracture volume and permeability of two kinds of coal samples before and after grouting are compared. It shows that although the grouting slurry of fractured coal sample under uniaxial loading only fills part of the fracture, the permeability difference is very small compared with the original coal sample. This result indicates that by blocking the connectivity of the air leakage channel, the fractures can be effectively blocked and a good grouting hole sealing effect is achieved. The research results can provide useful references for quantitative analysis of grouting in fractured coal and evaluation of grouting plugging effect in coal seam.
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图 3 单轴加载破裂煤样裂隙结构
Figure 3. Fracture structure of fractured coal samples under uniaxial loading
图 5 单轴加载破裂煤样注浆后裂隙结构
Figure 5. Fracture structure of fractured coal samples under uniaxial loading after grouting
图 6 劈裂破坏煤样注浆后裂隙结构
Figure 6. Fracture structure of splitting failure coal samples after grouting
图 7 单轴破裂煤样注浆前后裂隙数量占比
Figure 7. Fracture number ratio of fractured coal samples under uniaxial loading before and after grouting
图 8 单轴破裂煤样注浆前后裂隙体积占比
Figure 8. Fracture volume ratio of fractured coal samples under uniaxial loading before and after grouting
图 9 劈裂破坏煤样注浆前后裂隙数量占比
Figure 9. Fracture number ratio of splitting failure coal samples before and after grouting
图 10 劈裂破坏煤样注浆前后裂隙体积占比
Figure 10. Fracture volume ratio of splitting failure coal samples before and after grouting
表 1 试验煤样工业分析参数
Table 1. Industrial analysis parameters of test coal samples %
煤样编号 水分 灰分 挥发分 煤样1 1.28 8.63 7.60 煤样2 1.72 7.49 7.37 
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表 2 煤样注浆前后基本数据对比
Table 2. Comparison of coal sample basic data before and after grouting
煤样
破坏注浆前
质量/g注浆后
质量/g原煤渗透
率/10−14 m2受载破裂渗
透率/10−14 m2注浆后渗透
率/10−14 m2劈裂 289 305 1.1 75 1.3 单轴 295 308 0.8 57 1.2
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