Blasting excavation is a widely used economic and rapid excavation method
Blasting excavation is a widely used economic and rapid excavation method. With the continuous development of blasting technology, the continuous accumulation of experience in tunnel excavation by blasting has allowed people to successfully use blasting methods to carry out tunnels of various cross-section shapes. Excavation can make the excavation effect reach a predetermined level.
Blasting index
• index of blasting action, which is the ratio of the radius of the blasting funnel r to the minimum resistance line W, expressed as n, which can be expressed by the following formula:
n=r/w
• Free surface-the surface of the blasted rock in contact with the air is called the free surface, also called the open surface. The free surface plays a very important role in engineering blasting. With the free surface, the blasted rock can be destroyed and moved to this surface. In order to control the effect of blasting in engineering blasting, people often create free surfaces artificially near the blasting. In the long-term blasting practice, people summed up the next simple experience, that is, there are many free surfaces and the blasting effect is good.
•Minimum resistance line W——the shortest distance from the center of the charge to the free surface, which means the direction of the least resistance of the rock during blasting. Therefore, the minimum resistance line is the dominant direction of blasting action and rock movement.
•Blasting funnel radius r——namely the radius of the bottom circle of the blasting funnel
•Blasting action radius R-also called rupture radius, that is, the distance from the center of the charge to any point on the circumference of the bottom of the blasting funnel.
• Depth of blasting funnel D-the shortest distance from the tip of the blasting funnel to the free surface.
• Visible depth h of the blasting funnel—the shortest distance from the lowest point on the surface of the rock pile in the blasting funnel to the free surface.
