Drilling blasting is the main mining mode in open-pit mine. Impact effect induced by blasting will lead to damage and fracture of rock surrounding the blasting area; and then affect the stability of slope. An approach to evaluate equivalent damage field of rock induced by blasting is introduced; and it is named as borehole water seepage field test. Some steps should be taken in this method. Through water seeping in each testing borehole

recording water level and seepage time

drawing water level and seepage time curve

and at last

analyzing it

the damage degree and damage depth are obtained. A relative damage factor is used to represent the damage degree induced by blasting

and the intersection point between sharp decreased stage and gentle changing stage is used to denote damage depth and damage distance. According to field testing; the maximal damage distance of rock induced by blasting is 20 m approximately; and maximal damage depth is about 12 m. The blasting resistance of iron ore is stronger than limestone. At same position

the relative damage factor of iron ore is 7.5% smaller than limestone; the maximal damage depth and maximal damage distance of iron ore is 4-6 m smaller than limestone. Sometimes

water level will decrease to certain elevation rapidly

and then keeps constant. It means a penetrated fractured zone forms; and the electronic peering instrument would be used to observe and check this phenomenon.