## ABSTRACT

It is obvious that when initial micro-cracks, defects, or joint fissure in the jointed rock mass become larger, the propagation velocity of ultrasonic waves will decrease. Therefore, it can analyze the degree of damage under the effect of impact loading using a non-metal ultrasonic detector to measure the ultrasonic wave velocity in jointed rock mass after blast. In order to analyze the inner damage degree conveniently, damage variable D is defined based on the concept of ultrasonic wave. The formula is as follows:

D v vn

= −

⎛ ⎝⎜

⎞ ⎠⎟1 0

, (5)

where vr0 denotes the tested ultrasonic wave velocity of jointed rock mass without impact loading and vrn denotes the tested nth ultrasonic wave velocity after blast.