单轴加载煤体破坏特征与电荷规律研究及应用

Study and application of failure characteristics and charge law of coal body under uniaxial loading

为了完善电荷感应方法用于冲击地压的预测预报,利用自主研制的电荷监测系统开展了室内单轴压缩条件下煤样破裂电荷监测试验。重点分析了煤样的破坏类型、力学特性以及不同破坏类型下电荷时-频域信号规律,并对试验结果进行了工程验证。研究结果表明:煤样变形破坏特征可分为单剪型、共轭剪切型和破碎型;单剪型煤样电荷时域信号仅在峰后破坏初期,应力跌落至97%σ_c左右时产生,前兆信息难以捕捉,信号具有孤立性,幅值较高,电荷频率分布离散,主频为250 Hz。此特征电荷信号预示着相应工程煤体可能发生局部化破坏,将集聚的能量瞬间释放,冲击危害程度较大;共轭剪切型煤样电荷时域信号在强化损伤后期,应力达到(85%～100%)σ_c时开始产生,信号具有间隔突发性,主频为150Hz。预示着煤体可能发生分区化破裂,能量间断释放,冲击危害程度次之;破碎型煤样电荷时域信号在强化损伤初期,应力达到(70%～85%)σ_c时就开始产生,前兆信息易于捕捉,信号具有群发性,幅值较低,主频为0 Hz。预示着煤体可能发生均匀型破碎,能量缓慢释放,冲击危害程度较小。现场监测结果表明,在工作面煤体破碎区和发生煤炮时监测到的电荷信号特征,与试验室煤样发生均匀型破碎和单剪型破裂而产生的电荷信号特征具有高度相似性,验证了试验室结果的可靠性。

In order to improve the prediction of rock burst with charge induction, the charge monitoring test was carried out on fractured coal samples under uniaxial compression by the self-developed charge monitoring system in the laboratory. The failure types, mechanical properties of coal samples and the law of the charge time-frequency domain signals under different damage types were analyzed emphatically. Moreover, the test results were verified in practice. The results show that the deformation and failure characteristics of coal samples can be divided into single shearing type, conjugated shearing type, and shattered type. The charge time-domain signals of coal samples with single shearing occur only in the early stage of post peak failure, and the stress falls to about 97%σc. Since the signal characterizes a single burst with higher amplitude, discrete charge frequency distribution and the main frequency of 250 Hz, it is difficult to capture the precursory information. Those characteristics of charge signal indicate that the corresponding engineering coal body may occur a localized failure with releasing the accumulated energy instantly, which leads to significant impact hazard. The charge time-domain signals of coal samples with conjugated shearing are produced in the later period of intensified damage, and the stress reaches(85%~100%)σc. The signal has an interval burst, and the main frequency is 150 Hz.This indicates that the partitioned rupture occurs with accumulated energy released gradually, and the impact hazard degree is the second. The charge time-domain signals of shattered coal samples are generated in the early stage of intensified damage, and the stress reaches(70%~85%)σc. The premonitory information is easy to capture because the signals burst continuously with low amplitude and the main frequency of 0 Hz. These results indicate that the coal body may be homogeneously broken with accumulated energy released slowly, and the impact hazard degree is lower. The field monitoring results show that characteristics of charge signals both in crushing area of working face and the occurrence of coal firing gun are highly similar to those charge signals which are produced by coal samples in homogeneous shattered type and single shearing type in the laboratory. These results verify the reliability of the results obtained from the laboratory.