Difference of rock elastic parameters under static and dynamic loading

Rock ultrasonic wave velocity and static deformation were measured simultaneously under triaxial loading to investigate the difference and correlation of rock static/dynamic elastic parameters. The results show that rock dynamic Young's modulus is higher than the static one. The correlation of static/dynamic Young's moduli is good. The ratio of static/dynamic Young's modulus is about 0.6. The static and dynamic Poisson's ratios show some extent of positive dependence but the correlation is more discrete. There is also a difference of static/dynamic Biot's coefficients. The static one is higher than the dynamic one. They are all decrease with confining pressure. The inherent cause of static/dynamic difference is the crack-like pores and the pore fluid in rocks. The external cause is the strain amplitude and its frequency difference under static. And dynamic loading.