岩体稳定性的声发射监测研究

【作者】 李争荣；

【导师】 余贤斌；

【作者基本信息】 昆明理工大学 ， 采矿工程， 2011， 硕士

【摘要】 对大红山铜矿岩样进行了单轴压缩和劈裂实验,研究岩样在加载过程中的声发射特征。同时,对该矿2个盘区进行了采场顶板的声发射监测,探索岩体的破坏机理和预测破坏的方法。从室内单轴压缩和劈裂实验中得知,多数岩样于加载初期的声发射相当活跃,随着荷载的增加,声发射率有所下降；当加载达到极限应力的80%-90%时,声发射活动剧烈,事件率和能率等参数数值猛烈增大,并在岩样破坏时声发射参数值达到最大。现场声发射监测数据发现,在监测开始后的4个多月中,660中段50Ⅱ盘区声发射活动一直相对平静；3月6日至4月上旬声发射活动表现得极为活跃。现场观察发现,该盘区顶板西侧岩体已发生冒落,并于3月底垮通至上中段巷道。由此推断岩体稳定性状态与声发射参数密切相关。声发射率和能率等参数值前后变化不太明显的盘区顶板相对稳定；声发射能率突然增大,是前期的数十倍甚至上百倍,且持续时间长,具有这种声发射参数值变化特征的盘区顶板稳定性相对较差。现场声发射监测信号的波谱分析发现,随着监测时间的推进,声发射信号主频有增大-降低-增大-降低(岩体局部冒落破坏)的变化过程。主频第二次降低后岩体有冒落的现象发生,且在岩体发生冒落期间接收到较多幅值较大以致削顶失真的声发射信号。通过声发射监测可以推测岩体冒落发生的情况。声发射活动从平静到剧增且维持较长时间的变化,大量大幅值削顶失真声发射信号的长期出现,和声发射信号主频的第二次降低可视为岩体失稳的前兆信息。更多还原

【Abstract】 In this paper, both compressive and Brazilian tests were performed with rock samples from Dahongshan copper mine, and investigation was conducted on the characteristics of acoustic emission (AE) during the loading process. In situ AE monitoring was also performed at some panels of the mine to explore both the failure mechanism of rock mass and the way of failure prediction.The results showed from the uniaxial compressive and Brazilian tests that AE activities occur at the beginning of loading in most samples. As the load increases, the rate of AE events of the rock samples declined. Later AE activities appear frequently when the loading stress reaches 80% to 90% of the failure stress. At the moment of failure, the AE parameters reach maximum values.AE activities from in situ monitoring data were relatively quiet at the first four months at panel 5011, level 660, while AE activities turned abrupt starts from 6th March and continued until beginning of April. Meanwhile, roof falling happened at the end of March at west part of the panel. It could be concluded from both the in situ monitoring data and the observation results that the rock mass stability is closely related with the AE activities. The stope roof without obvious changes of AE rate and energy rate is relatively stable. The increase of AE energy rate which reaches decade times even hundreds times sudently to that in before and holds a long time is less stable.The spectrum analysis of AE signals obtained from in situ monitoring results was also investigated. With the conducting of the in situ monitoring, there is a rule that the main frequency of the AE signals increases at first, then decreases, increases again and decreases eventually. The second decrease of the main frequency shows that rock mass was damaged possibly and plenty of overflowing signals were received during failing of rock mass.AE monitoring is a feasible way to predict failure of rock mass. The changes of AE activity from quiet state to long-term abrupt one, appearance of overflowing signals over a long period of time, and the second reduction of the main frequency of AE signals could be regarded as the forewarning for the failure of rock mass.更多还原