Mechanical characteristics and permeability evolution rule of coal under loading-unloading conditions
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摘要: 基于自主研發的煤巖熱流固耦合試驗系統,在考慮實際開采方式的條件下,進行軸壓升高和圍壓降低的加卸載試驗,分析研究不同加卸載速率下原煤的力學特性和滲透演化規律.結果表明:加卸載過程中,軸向應力的加載速率越大,峰值應力附近的曲線平臺越長,峰值應力、軸向應變和環向應變也越大,體應變則越小.不同加卸載速率比下含瓦斯煤變形模量均先迅速減小后緩慢減小,到破壞時再迅速降低,而后逐漸保持穩定趨勢;在相同軸向應變時,加卸載速率比越小,煤樣的變形模量越大.加卸載過程中,煤樣的偏應力、滲透率與應變的關系可分為三個階段:初始壓密與彈性階段、屈服破壞階段和破壞后階段.加卸載速率比越小,煤樣達到峰值應力時,含瓦斯煤的滲透率和體積變形越大.Abstract: Based on the self-made servo-controlled seepage equipment for thermal-hydrological-mechanical coupling of coal and rock, a loading and unloading experimental study was performed by increasing the axial compression and decreasing the confining pressure in consideration of the actual mining method. The mechanical characteristics and permeability evolution rule of coal were analyzed and studied under loading-unloading conditions. The results show that during the process of loading and unloading, the faster the loading rate of axial stress, the longer the platform of the stress-strain curve near the peak, and the larger the peak stress, axial strain and circumferential strain, while the smaller the volume strain. The deformation moduli at different loading and unloading rates exhibit the trend of rapidly decreasing first and then slowly decreasing. When damage occurs, the deformation modulus rapidly decreased and then is nearly constant. Under that condition of the same axial strain, the deformation modulus increases with the decrease of loading and unloading rate. The relations of deviatoric stress and coal permeability with strain can be divided into three stages in the whole test process:initial compaction and elastic stage, yield stage, and post-failure stage. During the process of loading and unloading, the slower the loading and unloading rate is, the larger the coal permeability and volume strain become when the axial stress of coal samples reaches the peak value.
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Key words:
- coal /
- loading and unloading /
- mechanical characteristics /
- permeability
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