应力波作用下节理面前后电磁辐射强度的变化

Intensity variation of electromagnetic emission (EME) of the rock masses with joints under stress wave action

从压电体中的压电本构方程出发,得到了含石英等压电介质岩体在应力波作用下产生的电场值的关系表达式.电磁辐射强度随电阻率增大而增大,随传播距离发生衰减.对于电阻率较大导电性能较差的岩石来说,压电电荷的贡献是足够引起重视的.利用所得到的表达式对实际地震电磁信号幅值进行了估算,所得结果与实测结果吻合.依据所得到的电场值的表达式及应力波在节理面处的透射解,获得了垂直入射应力波作用下产生的电磁波在线性变形节理面前后的强度关系.研究了节理参数、岩体电性参数以及入射波频率对节理面前后电磁辐射强度的影响.结果表明,电磁辐射的强度随节理初始刚度增大而增大;对于节理面两侧岩体性质不同的情形,从理论上讲,电磁辐射强度随单个参数的变化是明确的,但在多种参数的综合影响下,电磁辐射强度变化情况相对比较复杂.本文的理论计算结果与其它众多学者得出的实验结果一致.

Based on the piezoelectric constitutive relation in piezoelectric body, the expression of electric field was obtained in piezoelectric rock under stress wave action. The intensity of EME increases with the increase of electric resistivity and decays with the propagation distance. The contribution of the piezoelectric charges is significant for the rock with large resistivity. Using the obtained expression to estimate the EME induced by real earthquakes, the calculated result agrees with the observation. According to the obtained expression and the solution of transmission coefficients of stress wave at the joints, the variation of EME intensity on front and back side of the ioint, when a normally incident stress wave propagates through the linear deformative joint, is derived. The influence of joint parameters, the electric parameters of rock masses and the frequency of incident wave on the variation of EME intensity are investigated. The result shows that the EME intensity increases with the increase of ioint stiffness. When the rock property on the two sides of the joint is different, the EME intensity clearly vary with a single joint parameter. However, the variation of EME intensity becomes complicated under the influence of many parameters. The theoretical derivation of this paper agrees with the experiment results of other researchers.