The rocks of parallel bedding and vertical bedding were loaded under uniaxial compression until stable was kept about 95 percent of failure intensty of the specimen. When the specimen were full of water or dry, the variation characteristics of p-wave velocities interior and saturated specimen observed were as follows:
1. Changes of p-wave velocities were quite different in both direction of parallel bedding and that of vertical bedding when the rock would soon become a failure.
2. The amplitude of p-wave and its shape varied with ever-increasing stress.