An Experimental Study: Variation Law of Magnetic Field around Concrete during Loading

Abstract

In order to reveal the magnetic field response law and mechanism of concrete under load, the variation law of magnetic field intensity (MFI) of concrete samples under uniaxial loading, graded loading and cyclic loading was tested, and the field application scenarios of magnetic field monitoring technology are proposed. The results showed that a magnetic field signal would be generated during the loading failure process of the concrete sample, which was accompanied by the whole loading process. In the uniaxial compression process, MFI showed a steady increase trend, but it would increase rapidly when the load drop occurred in the sample. The stronger the rupture, the more significant the change of MFI. MFI was not linearly proportional to the amount of change in the load drop. MFI around the concrete sample was positively correlated with the load. When the concrete was in the constant load stage, MFI around the concrete remained basically stable. When the main rupture of the concrete sample occurred, MFI reached a peak value, it did not keep at a high level all the time, but decreased rapidly. There are two mechanisms for the generation of the magnetic field in the process of concrete failure under load, namely the piezomagnetic effect and the friction effect, which correspond to the action of the load and the excitation of the fracture, respectively. The former causes the stable increase of MFI, and the effect is related to the influence of the content of the piezoelectric magnetic material in the material composition; the latter leads to a sudden increase of MFI, and the effect is related to the triboelectric effect of the micro-particles of the material. The research results are conducive to the accurate prediction of the concrete magnetic field monitoring, and help promote the development of mine dynamic disaster monitoring and early warning technology.