| Project/Area Number |
08651116
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
資源開発工学
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| Research Institution | Yatsushiro National College of Technology |
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Principal Investigator |
NAKAMURA Yuichi Yatsushiro National College of Technology, Professor, 土木建築工学科, 教授 (00112392)
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| Project Period (FY) |
1996 – 1997
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| Project Status |
Completed (Fiscal Year 1997)
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| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1997: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1996: ¥1,500,000 (Direct Cost: ¥1,500,000)
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| Keywords | Blast crack control / Guide hole / Stress waves / Visualization / High-speed photography / 可視化観察 / 高速度撮影 / 動ひずみ測定 / き裂進展 / シャドウグラフ法 / 動光弾性法 |
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| Research Abstract |
Fracture control is very important in rock excavation and partial demolition of concrete structures with blasting. In this research, a new method for achieving high degree of fracture control by using bore holes with noches is presented. The effectiveness of the method for blast crack control as a guide hole technique is studied experimentally. Model experiments are carried out to examine the interaction of stress waves with circular hole and to demonstrate the effects of the circular hole with notches using PMMA plates, mortar specimens and electric detonators. The dynamic behavior of cracks along a control fracture plane is observed by means of a high-speed video camera. The following results are obtained.
(1) Shadowgraphs show the behavior of reflected waves, deformations of the circular hole and the generation of converging air shock waves in the hole by interaction with the hole. On the basis of these experimental facts, it might be expected that utilization of the circular hole with notches is effective as a guide hole. It is shown that shadow spots are produced in the vicinity of the apexes of two notches. These are caused by the tensile deformation of the material near the notches.
(2) The images of the high-speed video camera system show that two cracks originating from the apexes of the notches propagate in the direction opposite to each other and the controlled fracture planes are produced. Explosion gases start to expand and penetrate into the cracks after the formation of controlled cracks. These results show that the presented method is a feasible means in controlling the orientation of the fracture planes and in driving the controlled cracks to greater distances.
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