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煤矿井下巷道开挖及采煤是一个卸围压过程,与常规三轴压缩试验相比,煤岩在卸围压时表现出不同的力学性质。通过对常规三轴和卸围压两种应力路径下的试验研究发现,无论是常规三轴还是卸围压试验,高围压均导致煤样更大的应变和更强烈的破坏。在初始围压相同的情况下,与常规三轴试验相比,卸围压试验中峰值点割线模量较小、割线泊松比较大;煤样在卸围压时的破坏更强烈,侧向应变较大,而轴向应变差别不大。通过卸围压效应系数分析发现,初始围压越高和卸围压速率越大,煤样的卸围压效应系数越小,越易失稳破坏,与高围压下割线模量降低相一致。对常规三轴和卸围压试验中无烟煤破坏过程的能量变化分析结果表明,卸围压速率越快,煤样的极限储存能Up越小,煤样越易失稳破坏,验证了卸围压效应系数分析结果。高围压下常规三轴试验和卸围压试验中煤样的破坏需要更多的能量,揭示了高围压下煤样变形破坏强烈的多的原因。
Coal mine tunneling and coal mining is a unloading confining pressure process, compared with the conventional triaxial compression test, coal rock unloading confining pressure showed different mechanical properties. Through the test research under two stress paths of conventional triaxial and unloading confining pressure, it is found that high confining pressure leads to larger strain and more severe destruction of coal sample, no matter the conventional triaxial or unloading confining pressure test. Under the same initial confining pressure, compared with the conventional triaxial test, the peak point secant modulus in the unloading confining pressure test is small and the secant Poisson ratio is relatively large. The destruction of the coal sample during the unloading confining pressure is more intense, Larger lateral strain, while the axial strain difference is not large. Through the analysis of unloading confining pressure effect coefficient, it is found that the higher the initial confining pressure and the larger the unloading confining pressure rate, the smaller the unloading confining pressure effect coefficient of coal sample, the more prone to destabilizing failure, and the lower the secant modulus at high confining pressure Consistent. The results of energy change analysis of anthracite destruction process in conventional triaxial and unloading confining pressure tests show that the faster the unloading confining pressure rate is, the smaller the limit storage energy Up of coal sample is and the more prone to destabilize the coal sample, Effect coefficient analysis results. Under high confining pressure, the destruction of coal sample in conventional triaxial test and unloading confining pressure test requires more energy, which reveals the reason that coal sample deforms strongly under high confining pressure.