Constraint Mechanism and Mechanical Characteristics of CFRP Partially Wrapped Coal Columns
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摘要: 碳纤维增强复合材料（carbon fiber reinforced plastic, CFRP）包裹是一种极具吸引力的煤柱加固技术。三向受压煤柱因侧向膨胀受限，其抗压强度明显高于单轴受压煤柱，在巷道中CFRP加固预留煤柱比未加固煤柱更具优势。为此，设计了不同CFRP层数和净间距比的煤圆柱试样，通过单轴压缩试验，测定了各试样的应力-应变曲线、峰值强度、极限应变等力学参数，深入探讨了CFRP约束对煤圆柱力学行为的影响，以及不同参数下煤圆柱的破坏模式。结果表明，CFRP条带约束煤圆柱和CFRP全约束煤圆柱表现出相似的力学特性。CFRP条带约束煤圆柱在单轴压缩下表现出显著的强化效果，随着净间距比的减小和CFRP层数的增加，煤圆柱的峰值强度和抗变形能力均显著增强。同时，CFRP的约束作用能够有效抑制煤圆柱的横向膨胀，改变其破坏模式，延缓破坏的发生。此外，基于Richart模型和Hoek-Brown模型，利用试验数据进行修正和对比分析，得到了CFRP条带约束煤圆柱的Richart修正强度模型。Abstract: Carbon fiber-reinforced plastic (CFRP) wrapping is a promising technique for enhancing the structural integrity of coal columns. When applied to coal columns in roadway environments, CFRP reinforcement offers significant advantages over unreinforced columns. Specifically, the compressive strength of coal columns subjected to triaxial compression is markedly higher than that of columns subjected to uniaxial compression, primarily due to the restricted lateral expansion in the former case. This study investigates coal column specimens with varying CFRP layer configurations and net spacing ratios, evaluating mechanical properties such as stress-strain behavior, peak strength, and ultimate strain through uniaxial compression testing. The research explores the impact of CFRP confinement on the mechanical performance and damage modes of coal columns under different conditions. The results indicate that coal columns confined by CFRP strips or fully wrapped with CFRP exhibit similar mechanical behaviors. CFRP strip confinement provides a notable strengthening effect under uniaxial compression, with peak strength and deformation resistant capacity significantly improved as the net spacing ratio decreases and the number of CFRP layers increases. Additionally, the CFRP reinforcement effectively mitigates lateral expansion, alters the failure mode, and delays the onset of damage. Furthermore, using the Richart and Hoek-Brown models, the study incorporates the test data for model refinement and comparative analysis, leading to the development of a modified Richart strength model for CFRP-constrained coal columns.
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Key words:
- carbon fiber-reinforced plastic /
- coal column /
- net spacing ratio /
- hoop strain /
- strength model
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图 5 不同净间距比下煤圆柱的应力-应变曲线
Figure 5. Stress-strain curves of coal columns under different net spacing ratios
图 6 不同包裹方案下试样抗压强度的比较
Figure 6. Comparison of compressive strength of specimens under different wrapping schemes
图 7 不同包裹方案下试样极限轴向应变的比较
Figure 7. Comparison of ultimate axial strain of specimens under different wrapping schemes
图 8 煤圆柱在不同高度处的环向应变
Figure 8. Circumferential strain of coal columns at different heights
图 9 不同约束形式下的煤圆柱受力模型
Figure 9. Force models of coal columns under different confinement
Elastic modulus/GPa Thickness/mm Tensile strength/MPa Ultimate tensile strain/% 47.54 0.167 918.07 1.94 
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表 2 A、B胶参数
Table 2. Parameters of A and B glue
Type Tensile strength/MPa Elastic modulus/MPa Elongation ratio/% Compressive strength/MPa A ≥40 ≥2 500 ≥1.5 ≥70 B ≥30 ≥1 500 ≥1.5 ≥70
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表 3 试验方案
Table 3. Test scheme
Group No. Specimen s/D L s/mm n b/mm 1 SC 0 3 2 SF-1 0 1 0 2 100 SF-2 0 2 0 2 100 SF-3 0 3 0 2 100 3 SP-1-0.700 0.700 1 35.00 2 10 SP-1-0.550 0.550 1 27.50 2 15 SP-1-0.400 0.400 1 20.00 2 10 SP-1-0.250 0.250 1 12.50 2 10 SP-1-0.125 0.125 1 6.25 2 15 4 SP-2-0.700 0.700 2 35.00 2 10 SP-2-0.550 0.550 2 27.50 2 15 SP-2-0.400 0.400 2 20.00 2 10 SP-2-0.250 0.250 2 12.50 2 10 SP-2-0.125 0.125 2 6.25 2 15 5 SP-3-0.700 0.700 3 35.00 2 10 SP-3-0.550 0.550 3 27.50 2 15 SP-3-0.400 0.400 3 20.00 2 10 SP-3-0.250 0.250 3 12.50 2 10 SP-3-0.125 0.125 3 6.25 2 15
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表 4 不同CFRP约束形式下煤圆柱的破坏模式
Table 4. Failure modes of coal columns under different CFRP confinement
L s/D Unconfined coal
column0 0.125 0.250 0.400 0.550 0.700 1 
2 
3 
Note: The areas circled by the white dashed lines in the table indicate localized crushing of the coal column, while the areas circled by the blue dashed lines indicate the fracture of the CFRP strips.
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