Abstract
Experimental and numerical analyses were conducted to investigate the effect of an eccentric loaded contour hole on a rock mass. In the concrete blocks used for the analyses, detonating cords were placed at the centre of the blast hole and eccentrically against the wall of the blast hole. PFC2D and AUTODYN were used for the numerical analyses, and the results of these software showed that an eccentric decoupled charge can result in the directional development of fractures, thereby enabling the control of cracks in the opposite direction. Even though both types of blasting have identical decoupling indexes, the crack and fracture patterns were affected by the location of the explosive, tamping, and other conditions. The results showed that an eccentric charge holder can be applicable to control the fracture direction and the damaged zone. For an eccentric charge, the initial crack was generated at 0.01 ms and expanded in the intended direction. For the eccentric charge, the maximum pressure at the area in contact with the blast hole wall exceeded that for the central decoupled charge by a factor of 5.5. Furthermore, the pressure in the intended direction was twice of that in the opposite direction.
Highlights
Several experimental studies have been conducted to analyze the dynamic mechanical behavior of materials and structures
A semi-disc dynamic three-point bending test involving impact loading was conducted in a previous study; the results showed that the dynamic loading rate has a significant influence on the fracture toughness and arrest toughness of materials [1, 2]
PFC2D and AUTODYN2D analyses were conducted for these models to verify the controlled decoupling effects
Summary
Several experimental studies have been conducted to analyze the dynamic mechanical behavior of materials and structures. The use of eccentric charges is an ideal method to reduce the damage caused to the final wall and to concentrate the energy toward the free face, for a well fracture [3e5]. Better knowledge of bench geology and structure will allow a better evaluation of zones’ blastability and a timely blast design modification, and will facilitate production and processing processes and reduce the operation cost [12]. They discussed on blast fragmented with assume the rock properties. An eccentric charge was used to maximize the decoupling effect to the final wall and to concentrate the blasting energy toward the free face. Previous studies have focused on crack/ fracture evolution and the distinction between the mechanical and flow EDZ to establish the extent to which a coupled model is required [16e19]
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