Research On Stress-Magnetic Strength Expetiment Of Compression Process For Brittle Rock

To study mechanical property of rock under stress, know the regularity of the fracture evolution procedure is important for the safety of project. It showed that all natural rocks is magnetic, which would activate variational magnetic field under stress. Meanwhile, magnetic field will also been aroused in the space around and vary with the fracture inside. The magnetic induction from the magnetism field is introduced to the research of extrusion rupture procedure of the rock in this paper.Brittle granite was chosen as the sample with the magnetic core been planted into the cylinder. The magnetic field of the rock itself is magnified. The sample is put into the magnetic filed simulated by the magnetic core. The axially loading procedure of the rock is monitored with the loading system、bidirectional magnetic induction strength testing system and triple tunnel data collecting system. Rock mechanics parameter is linked together with magnetic induction. The correspondence between stress, strain, and magnetic induction is obtained. Finally, a magnetic testing method of detecting the fracture change is built in the progress of rock extruding.According to the test of magnetic field distribution around the magnetic core granite specimen, the distribution regularity of the magnetic field in the medium of air and rock is as follows:The farer the specimen from the low-intensity magnetic detect sensor, the lower the magnetic field strength. Moreover, a district of magnetic sensitively is existed, in which magnetic strength changes apparently with the distance. Perfect test results are got from the district in the bidirectional magnetic induction strength test. It is very important to find the district in the experiment.Experiment results show that:elastic energy is generated from work of external force in internal rock in the elasticity loading phase. Microcosmic complex variation of rock internal failure is occurred which influenced distribution of magnetic lines of force of magnetic core. Magnetic induction is little increased by0-5μT. When it is reached to the maximum elastic internal energy, the surface energy of crack is appeared and the dissipation is done. The increase by leaps of magnetic induction and the point mutations is generated on the curves of magnetic induction-strain. The anomalous magnetic characteristics are inducted during critical destruction of extrusion rupture of the rock. In the process of plastic flow softening phase, the rock is broken for the inner extrusion. The way of magnetic flow is changed by the magnetic line of force in magnetic core. It is expanded from inner to outside in the rock. The magnetic strength is expanded rapidly. The magnetic induction is increased to10～130μT in the whole destruction process. The magnetic core of some specimen is moved and the magnetic strength is reduced for the rock fraction.