# Theoretical Study of Large Uncoupling Coefficient Loading for Surface Blasting
## 5 Calculation Examples and Engineering Applications
### Charging Structure and Parameter Selection  
Smooth surface blasting technology was selected based on the slope situation and construction experience. During construction, the blasting parameters are modified in accordance with the flatness of the slope surface and the amount of rock fragmentation after blasting. The interval uncoupled charging structure is used. The volume of explosives is calculated according to the actual length of the blast hole. The explosive sections were evenly tied to a detonation cord. After charging is completed, the blocking is conducted using loess or rock powder. It should be ensured that the blockage does not contain stones. The detonating cord detonation network and electric detonator detonation are adopted.  
(1) Packet production: the explosive roll is bound on a bamboo sheet, each explosive roll is connected with a detonating cable, and one end of the drug pack is tied with a detonating detonator.  
(2) Charging: a segmental charging method is adopted. Under the condition of ensuring the filling length, strengthened charging is used at the bottom of the hole and weakened charging is used in the orifice segment. Normal charging is used on other segments.  
(3) Plugging: To ensure that the high-pressure explosive gas does not leak, effective plugging is required. The plugging length should be 12-20 times the diameter of the blast hole. The blast hole should be tightly plugged with paper balls or bags in the lower part of the plugging section and then plugged solid with rock powder and clay.  
A 90 mm diameter submersible drill is used for construction. Drilling is performed to the design depth twice at one time, and the vertical depth of the borehole \(H\) is 10 m. The blasting distance is taken as 1.2 m. The blasted section of the rock consists of moderately weathered or weakly weathered dolomite. The color of the rock is grayish white. Therefore, the super depth h of the hole is taken as 1.0 m.  
The blast hole length \(L\) is calculated as \(L=(H+h)/\text{sin}\alpha\). The standard value of \(H\) is 10 m, the super depth \(h\) is 1.0 m, and the slope rate is 1:0.75. The standard blast hole length \(L\) is calculated to be 13.8 m. Emulsion explosives of diameter 32 mm meet the requirements of blasting.  
When the radial uncoupling coefficient is \(K_{d}=2.0\) and axial uncoupling coefficient is \(K_{1}=4\), the structure of the charging is as shown in Figure 6a.  
When the radial uncoupling coefficient is \(K_{d}=2.8\) and axial uncoupling coefficient is \(K_{1}=2.22\), the structure of the charging is as shown in Figure 6b.  
Both types of charge structures are applied in field operation and are found to produce satisfactory blasting results. The effect of road rift slope blasting is shown in Figure 7. The light explosion technique performs better, the marking rate of blast hole is 100%, and the newly create free surface does not appear to be overly broken, as shown in Figure 6a. As demonstrated in Figure 6b, the rock crushing effect is improved, and the crushing block size is reduced, making mechanical loading easier and improving slagging efficiency.  
Figure 6: Structure diagram of smooth-face hole charge. (**a**) Radial uncoupling factor 2.0. (**b**) Radial uncoupling factor 2.8.