Experimental Study On Blasting Fragment-size Of Joints Rock Mass Based On Fractal Theory

The fragment-size from blasting of rock mass is an important index to evaluate the blasting quality quantitatively. It affects the efficiency of each subsequent production processes such as loading,transportation and fragmentation, and the total cost of mining. Therefore, to make a thorough study on the fragment-size in rock mass blasting has a remarkable practical significance. The rock mass has been cut by various kinds of weak planes such as joints and cracks which play an important role in the blasting fragment-size. To solve the problem of blasting fragment-size, a suitable method of describing the distribution of joints and cracks must be found so as to introduce this distribution to the physical process of rock mass blasting, and analyse the blasting mechanism of joints rock mass and the law of forming rock fragments.The joints and cracks of the rock have fractal nature. Using fractal to describe the degree of this defect full is most close to the definition of damage in damage mechanics. According to fractal theory, the damage of rock can be regarded as the reduction of entity's rock dimension, and the mechanics effect of reducing of dimension just like that rock equivalent modulus caused by damage, so with fractal dimension to describe the damage and evolvement can reflect the characteristic of rock damage objectively and comprehensively, and can post out the law of thefragment-size distribution from blasting of rock mass.Proceeding from fractal theory the fractal characteristic of blasting fragment-size of rock mass was studied. According to the fragment-size from blasting with well fractal, the relationship between the fragment-size distribution and the fractal dimension was deduced, and the quadratic equation relationship between explosive specific charge and fractal dimension was deduced and found, and the quadratic equation relationship was better than linear equation in the respect of reflecting the complexity of rock blasting, which was proved theoretically. This article measured various kinds of samples and the fractal dimension D concentrated in the range of 2.10~2.46, which proved that the different damages material's blasting fragment-size is similar under the same explosive specific charge, and fragment-size distribution issimilar too. Fractal geometry offered the quantitative description method for this kind of phenomenon.The article analyzed the influence of joint and crack (damage) to fragment-size on blasting through fractal theory, and has drawn the qualitative relational expression on the basis of analyzing the test data. The experiment proved that fragment-size dimension and damage dimension are inversely proportional.Based on the above mentioned, the coupling relationship between explosive specific charge, damage and fragment-size for blasting has been analyzed. According to which the article explained the process of rock blasting is a strong coupling process by parameters, and the parameters influence and restrict each other.