自由面爆破におけるCorner Fractureの生成条件について
1969 年 85 巻 969 号 p. 1-7
詳細
1969 年 85 巻 969 号 p. 1-7
The stresses in the various assumed materials caused by the blasting with two free faces were analysed by using equations derived from the theory of elasticity to present necessary conditions which are required to produce the corner fracture and the data for the stress computation were determined on the basis of those used in our former study with Tako-Sandstone.
The results of the present stress analysis showed that the pattern of the stress distribution in the material was affected with both the physical properties of the material and the blasting condition.
The results obtained in connection with the development of the corner fracture can be summarized as follows;
(1) The stress concentration which is considered to give rise to the corner fracture is chiefly affected with both the Poisson's ratio of the material and the length of the stress wave produced in the material by an explosion.
(2) The development of the corner fracture can not be expected in the material of which Poisson's ratio is less than about 2.5.
(3) When the value of the Poisson's ratio of the material is larger than about 2.5, the development of the corner fracture in the material is controlled by the value of Cf, and there is a possibility of producing the corner fracture for the case of Cf<1.0, but no _possibility for the case of Cf>1.0, where Cf=tr·CL/W, and tris the rise time of the stress wave, CL is the velocity of the longitudinal wave and W is the length of the burden.
