Through the laboratorial research

the coupling correlation between stress and P wave velocity are studied under uniaxial cyclic loading and unloading ways to create the experimental model based on the characteristic that the velocity gradient is usually high at elastic stage and then begins to level out at plastic stage for burst tendency coal and rock samples from deep coal mine. Also the parameters of the derived model are analyzed. Studies indicate that: ①In the unloading process

the P wave velocity decrease with the drop of stress because of the reopen of closed crack and weakening in the compaction degree between grains; ②The starting P wave velocity of next cyclic is higher than the starting of first cyclic

because that partial crack and pore that closed permanently in the compression phase can not reopen when stress decrease; ③The calculated correlation coefficients to measured value show that the experimental model has the better fitness

and can be well applied to describe the P wave changing sensitivity degree of samples under stress.