Experimental Study On The Failure Mode Of Material Containing Flaws Under Two-hole Blasting

Because of the significant investment in the modernization construction,many fields of construction are booming,such as underground engineering,infrastructure,transportation,and so on.And the rock blasting technology has been widely used in these fields of construction.But rock mass itself possesses in homogeneity and anisotropy,and it contains different types of structure planes with different attitudes and sizes,this makes the process of rock blasting more complicated and the controlling blasting effect more difficult.In order to improve the blasting quality,obtain satisfactory blasting effect and save construction cost,it is pivotal to understand the role of explosion load in rock mass destruction and the failure mode of jointed crack rock mass.This paper analysis the characteristics of cracks propagation drived by the detonation gas.And the dynamic damage characteristics of rock mass containing joints were obtained by double hole blasting experiments on rock mass containing single and multiple joints.There are some specific conclusions as following:(1)According to the theory of rock explosion,after explosive detonation some radial cracks are formed around the hole under the action of blasting stress wave,then the detonation gas inflates and flows into these radial cracks.This paper established calculation model of fracture propagation driven by gases of explosion and calculated the raw of detonation gas expansion flow within these cracks and cracks propagation driven by detonation gas.(2)By double hole blasting experiments on rock mass containing single and multiple joints with reasonable uncoupling loading coefficient that made cracks longest,this paper found following achievements.(1)The joint cracks had obvious guiding effect on the formation and expansion of the main cracks around the hole from.When multiple large dip join cracks were distributed between the two holes,the guiding effect would be reduced.(2)The position of the joint cracks between the two holes had obvious influence on the velocity of the main crack propagation.(3)Under the experimental condition of two-hole blasting,the prefabricated joint cracks ruptured by reflected and transmitted wave,and the two tips of prefabricated joint cracks extended the derivative cracks out,then derivative cracks extended to the hole.There were some significant regularities in the process of the prefabricated joint cracks propagation.(4)When the intersection of the main cracks,the prefabricated joint cracks and the derivative cracks were near,they would be interrelated by each other to form the fracture zone between the two holes.(3)Because of the prefabricated joint crack,there was a zigzag through plane between the two blast holes.And the through plane deviated from straight lines connecting the two blast holes.The larger angle of the prefabricated crack,the greater degree of deviation.