Digital Analysis Of Stress Distribution And Some Parameters Of Deep Hole Bench Blasting

In this paper, Effective stress field distribution of semi-infinite and bench blasting in rock mass and some design parameters of deep hole bench blasting are analyzed by the method of photo-elastic holography and 3-D dynamic element method.Firstly the digital compute method of 3-dimisional dynamic finite element method of DYNA3D system is introduced The typical question of hourglass control, artificial bulk viscosity, contact-impact algorithm and non-reflecting boundary is explained. In order to use DYNA3D system to simulate deep hole bench blasting, the simulation rule is used. The geometry ratio is 1:10. the geometry simulation , boundary simulation and some dynamic simulation rule is used here. In this paper C,~ =1, C,=10,(7~=1, CE=l, C~=1, C,.=l, C1=C1=10. For the reason that thecharacter of rock under dynamic stress is unknown, the rock mass is considered to be lineal elastic and the Mises stress rule is used to descript the breakage of rock mass.The photo-elasticity holographic test and 3-0 dynamic element method shows that the shape of Mises effective stress field of deep hole blasting in the semi-infinite media is water-like (ignition at the bottom of the hole ) and the angle of the face of stress wave and the axle of the hole is not changed in the process. The shape of stress wave is quasi-ellipsoid and the tip effect appears at both ends. The zero distortion energy field appears at the both ends of the hole in the propagation process of stress field which means that the stress field of the ends of cylinder shaped charge can dense the rock. Theinitial stress field of deep hole blasting is quasi-cylinder with hemisphere atboth ends and the stress field at both ends is attenwted quickly. The effectivestress field of deep hole bench blasting propagation is simulate to that ofsemi-finite rock mass. The zero distortion energy field aPpears both in thetip of the charge of bench blasting and linear charge. The difference is tha thedistribution of zero distortion energy field of linear charge is sytnrnetric andthe distribution of the zero distOrtion energy field of bench blasting isunsyrnmetrical. For the affection of the tip effect at the bottom When blastingwith non-sub-drill, the effeetive stress in the model is one hundred to twohundred percent bigger than tha at the bottom.The digital computation of some design parameters(explosiveconsumption, sub-drill and steedng length) of deep hole bench blastingshows that the change of explosive consumPtion is deeply affect the Misesstress field. When 42% of the consumPtion is increased, the effective stressfield in the direction of the least resistant increase l57 to 3l0 percent. Thechange of the sub-drill affect the bottom stress field greatly and the biggestsub-drill is about 30 Percent of the length of the least resiStan. Thisconclusion is accordan tO the engineering experience. The digitalcomputation also shows the affection of the sternrning length to thefragInentaion of deep hole bench blasting. Although the blasting ofnon-StCmming alinost has no thection to the breakage of the rock mass at thebottom, it heavily affect the Stress field in the uPper rock mass in benchblaning. Under the same condition the stress field of the non-stemrningblasting in the stenuning region decrease 60 Percent, which explains that thenon-Sternrning blasting is not advtuge to the fragmentation of the rock atthe collar. It shows that blasting energy of non-stemming blasting is wasted.The optimal stenuning length is (0.9-l .0) of the least resistant, which is alsoaccordan to the experience.