Fankou lead zinc ore body mainly occur in several major faults, fissures ore poor structural stability. After years of mining, the mining site of the ore body above the middle of the -320m area is decreasing, and there are more mines and corners. The roof of the stope is difficult to control, the safety is poor, and the roof is often thrown off. It is difficult to safely recover. According to statistics, between 2000 and 2004, it is difficult to recover and the residual mining yard accounts for about 20% of the construction stope. The annual cost of safe treatment and support for the roof of the stope is up to one million yuan, leaving more than 15,000 tons of minerals per year due to the left of the safe pillars and the mining and mining losses caused by the roof. Therefore, how to effectively control the safety of the roof of the stope is an urgent problem to be solved.
First, smooth blasting control technology
The main feature of smooth blasting is to take a denser hole at the boundary of the blasting control, and do not couple the interval charge. After the main blasthole rings, the blast hole is detonated, so that the crack develops along the hole line to form a smooth surface to control and Protect the blasting boundary and reduce the impact and damage of the blast on the boundary, thus reducing the cost of handling and supporting the control boundary.
The main mining method currently used in Fankou lead-zinc mine is the mechanized upward stratified filling mining method. The stope is arranged vertically or along the ore body. The width is generally controlled at 6~9m, and the stratified filling height is 3.0~3.5m. After filling, the working space is kept at 3.0m, and the height of the mining top is 3.0~3.5m. The ore and surrounding rock are relatively stable, f=8~14.
(1) Smooth blasting parameters
Determine the smooth blast hole spacing according to the thickness of the smooth layer, ie:
La≥(0.6~0.8) Wa
Where: La-light face spacing, m; Wa-gloss layer thickness, m.
Gunhole line charge: Q= qLaWa
In the formula:
Q-charge, kg·m -1 ; q-unit explosive consumption, kg·m -3 .
According to the experience of Fankou Mine, generally, Wa is taken from 0.6 to 0.8 m, La is not more than 0.6 m, and Q = (0.3 to 0.18) kg·m -1 .
(2) Determination of the shape of the top of the stope
Firstly, according to the span of the stope, the roof structure and the stability conditions, the shape of the roof is pre-controlled. Generally, the roof of the stope with large span and poor structure should be made into a three-heart arch with a high height. The arch height is 1/5~1/4 of the span, and the roof structure is particularly poor, and it is arc arch; the span of the stope The small, well-knotted roof of the stope is arched into a small three-heart arch with an arch height less than 1/5 of the span.
(3) Cloth hole charge
The top of the stope is generally propelled from the outside to the inside from the stopway of the stope, and horizontal drilling is arranged. The rock drilling equipment uses YT24~YT27 drilling rig , the drill diameter is 38mm, and the hole depth is 1.8~3.0m. The arrangement of the top blasthole is shown in Figure 1. The parameters of the main blasthole mesh are (1.0~1.2) m×(1.0～1.2) m, generally using plum-shaped cloth holes. The light face is arranged on the control line of the pre-control top plate and the side gang, and the light column face is arranged only on the top plate, and the two gangs are 0.4-0.6 m away from the filling body. The light face hole distance is 0.6m, the light surface layer thickness is 0.8m, and each hole is charged 3~5 according to the hole depth. Explosives mainly use rock floatation fry, specifications: φ = 35mm; L = 200mm; 0.2kg / strip. The uncoupled charge is used, the middle is separated by a bamboo tube, and the hole end is blocked by the gun mud. The structure of the charge in the hole is shown in Fig. 2. The light face is detonated after the main blasthole and the auxiliary hole are detonated, and all the light faces are detonated by the same or two detonators.
Fig.1 Grating blasthole arrangement of stope
Figure 2 Schematic diagram of light-face charge structure
Second, the application effect of smooth blasting top control technology
The application of smooth blasting to control the safety of the roof is demonstrated by relevant technical experts. It was promoted to the underground difficult mining and mining field in June 2001, and was fully promoted and applied in the Fankou mine mining site in June 2002. At present, in the mining of difficult mining and mining, all use of smooth blasting is required for roof control, and the application rate of other houses and columns is more than 70%. Using this technology, the blasting has little damage to the new rock wall, the hole marks are clearly visible, the forming is regular, not over and undercut, so that the shape and size of the roof of the stope are controllable, and the excavated roof of the stop is arched. Smooth surface, less turquoise, good stability, safe and reliable, providing operators with better working conditions. Especially in the difficult mining and roof mining, after the smooth blasting treatment, the roof of the stope is stable and easy to operate. In the three years from 2001 to 2003, due to the promotion and application of smooth blasting roof control technology, the mines in mines and mines returned to the mining 630124t safely and smoothly, and the probability of roof collapse was 70% lower than the original. The mining provides a guarantee of safety, greatly improving the recovery capacity of the difficult mining and recovering a large amount of mine damage every year.
Stope smooth blasting control top example
Stope name | Stope nature | Rock Coefficient | Section height × width (m×m) | Smooth layer Thickness / mm | Light face distance / mm | Hole depth /m | Line charge density / (kg · m -1 ) | Blasting effect |
Sh-240mS3-4# | Column Hard to pick | f=8~10 | 3.0×(3～8) | 700～800 | 600～700 | 2.0 | 0.3 | Clear hole marks, complete rock face |
Shd-80m27a# | Room mining | f=10~12 | 3.5×(4～10) | 700～800 | 600～700 | 2.0 | 0.3 | The rock face is flat and there is no pumice |
Jb-240m4-5# | Column Hard to pick | f=10～14 | 3.0×(5～7) | 600～700 | 500～600 | 2.0 | 0.3 | Clear hole marks, smooth surface |
Sh-320N2# | Room mining | f=8~10 | 3.5×8 | 700～800 | 600～700 | 2.0 | 0.4 | The rock face is flat and the hole marks are left. |
Sh-240m209# | Room mining | f=10~12 | 3.5×(4~12) | 700～800 | 600～700 | 2.0 | 0.4 | The rock face is flat and the hole marks are left. |
Third, the application should pay attention to the problem
(1) In the process of popularization and application, it is necessary to strengthen the quality education of the blasting workers, and improve the theoretical understanding level and practical operation ability of the operators. Glossy blasting technology is a kind of controlled blasting with high technical content. It must be adapted to local conditions in use. It can flexibly use traditional smooth blasting technology. It depends on the safety conditions of the mining site in terms of cloth eye, charge and detonation sequence. According to the actual situation of the rock and rock structure, reasonable design and construction can ensure the quality of smooth blasting and achieve the desired results.
(2) Adopt certain mandatory or incentive measures to ensure the comprehensive promotion and application of the technology. Smooth blasting requires dense cloth holes, intermittent charging, and the amount of blastholes per metre is reduced, and the charging structure in the holes is more cumbersome. The use of bamboo tubes brings inconvenience to the blasting workers, so some blasters are greedy. Saving things, pursuing production, unwilling to adopt smooth blasting control, or arranging light faces, but the net degree can not meet the technical requirements. The pre-control top plate is greatly damaged after blasting, resulting in poor safety conditions in the stope operation, and even the roof Losing control has brought great disadvantages to the next step.
Fourth, the conclusion
In the underground mining process, the smooth blasting technology is applied to control the roof of the stope, which greatly reduces the safe treatment and support workload of the stope, reduces the mine damage, speeds up the mining speed, improves the mining efficiency, and has obvious economic benefits. It has the value of promotion and application in similar mines.
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