Investigating the new physical response law of rock failure process will advance rock mass monitoring and early warning technology. This study conducted magnetic field monitoring experiments on sandstone deformation and failure under uniaxial loading and cyclic loading and unloading using fluxgate weak magnetic detection technology. The magnetic field signals during sandstone deformation and failure were tested

and the relationships between the magnetic field

load and acoustic emission were analyzed. The results indicate that sandstone generates magnetic field signals during deformation and failure. During uniaxial loading

as the load increases

the magnetic field signal in the compaction stage fluctuates and rises

with a high fluctuation coefficient. In the elastic stage

the magnetic field signal increases steadily while the fluctuation coefficient decreases. In the plastic stage

the magnetic field signal increases significantly

and the fluctuation coefficient increases in the late plastic stage. In the failure stage

the magnetic field signal rapidly increases

and the fluctuation coefficient changes significantly

corresponding to the load drop and the main failure. Compared to the fluctuation coefficient

the variance of the magnetic field signal remains relatively stable during the first three loading stages

but the variance gradually increases during the failure stage

showing a significant mutation. During cyclic loading and unloading

the magnetic field signal gradually increases with increasing load and decreases with reducing load. Near instability and failure

the magnetic field signal increases rapidly

which is significantly higher than the previous cyclic loading and unloading process. There is a strong correlation between the magnetic field signal and the acoustic emission count

indicating that the generation of the magnetic field is closely related to the deformation and failure of the sample. Under stress

micro-damage continuously forms inside sandstone

leading to non-uniform deformation between adjacent particles. This disrupts the electrical balance at the interface

resulting in the generation and migration of free charges that alter the current. The movement of charges and changes in current produce magnetic field signals. Evaluating rock mass stability using magnetic field signals is expected to be a new non-destructive

non-contact and continuous monitoring method.