Performance Assessment of the Circular-Cut Blasting by Numerical Analysis

• Published in: Geosystem engineering Vol. 7; no. 3; pp. 75 - 82
• Main Authors: Jong, Yonghun, Lee, Chung-In, Jeon, Seokwon, Cho, Young-Dong, Shim, Dong-Soo
• Format: Journal Article
• Language: Korean
• Published: 2004
• Subjects: Tunnel blasting; Circular-Cut; Blast vibration; Particle flow code (PFC2D)
• ISSN: 1226-9328; 2166-3394

The most important operation in the tunnel blasting procedure is to create an opening in the face in order to develop more free surface in the rock mass. This operation is highly dependent on the cut holes. In general, the bum-cut or V-cut is commonly adopted to blast the cut section. But, these traditional methods often raise problems. There are instances (a) that the actual advance is considerably less than the designed advance depending on the rock mass, (b) that they cannot sometimes enlarge the free surface efficiently and (c) that the blast vibration resulted from the cut blast exceeds the allowable vibration level. In order to resolve the problems, many different kinds of the cut blast can be considered. The objectives of this study are to suggest a new cut blast (named as 'circular-cut') using pre-splitting technique with an array of large empty holes and blast holes and to investigate the efficiency of the circular-cut. The distinct element computer program, particle flow code (PFC2D), was used to investigate the effect of the cut blast. By using the program, we could identify (a) the optimal spacing between the large empty holes and blast holes surrounding a central hole and (b) the optimal amount of explosive charge for the central hole. We could also evaluate the vibration attenuation rate of the cut blast obtained by pre-splitting. The optimal values of the above parameters favorably agreed with the field-measured data. In addition, a series of numerical simulations using the optimal values showed that the suggested method could reduce the blast vibration caused by the cut blast in comparison with the traditional methods.