自然及强制饱和煤样的力学特征试验研究

Experimental study on mechanical characteristics of coal samples in natural and forced saturation state

为探讨不同饱水状态下煤的力学变化特征,利用RMT-150B岩石力学系统并自行设计及研制煤样饱和试验装置,对自然饱和与强制饱和的煤样进行单轴、三轴压缩静载试验。结果表明:煤样强制饱和前后波速变化明显,强制吸水后波速增加51.75%;强制饱和煤样单轴抗压强度比自然饱和煤样平均降低了7.61MPa,降幅54.83%;三轴压缩时不同围压下强制饱和煤样峰值强度平均降低了19.5MPa,降幅31.18%;强制饱和煤样吸水量较自然饱和煤样大,K值降低。基于Mohr-Coulomb准则及有效应力原理,推导出孔隙水压与黏聚力、抗压强度呈负相关,表明强制饱和煤样的黏聚力与抗压强度均低于自然饱和煤样,并与试验结果对比验证。

In order to study the mechanical change characteristics of coal samples under different saturation states,an experimental device of coal sample in different saturation state was designed and developed by using the RMT-150 B rock mechanics test system,and the uniaxial and triaxial compression static load tests were conducted on the coal samples in natural and forced saturation stats. The results showed that the wave velocity changed obviously before and after the forced saturation of coal samples,and the wave velocity increased by 51. 75% after the forced saturation. The uniaxial compressive strength of coal samples in forced saturation state decreased by 7. 61 MPa and 54. 83% decreasing amplitude than that of coal samples in natural saturation state on the average. Under the triaxial compression,the peak intensity of coal samples in forced saturation state under different confining pressures decreased by 19. 5 MPa and 31. 18% decreasing amplitude on the average. The water absorption capacity of coal samples in forced saturation state was larger than that of coal samples in natural saturation state,and the K value decreased. Based on the Mohr-Coulomb criterion and the effective stress principle,it was deduced that the pore water pressure has a negative correlation with the cohesive force and compressive strength,which showed that the cohesive force and compressive strength of coal samples in forced saturation state were both lower than those of coal samples in natural saturation state,and the results were verified by comparing with the experimental results.