0 Preface
Shandong Grand River Mining Co., Ltd. Zhuo large iron mine located in Laizhou City soil Town Village West big Zhuo about 1 km, is a city of 1.1 million t of iron ore mining and large-scale mining. The ore body is soft and unstable. The mining method is a sub-column-free sublevel caving method, with an upward fan-shaped medium-deep hole falling ore, a section height of 10 m, a mining approach distance of 10 m, and a section of arc arch surface. The main support method is spray anchor net. Joint support.
1 Influence of medium and deep hole damage on production
At first, the deep hole blasting in the mine used the full-length detonating cord, the cohesive granular explosive coupling continuous charging structure in the hole, the detonation method of the plastic detonating tube detonator orifice, and the blasting. The first hole mining area - 240m middle section 156, 157 approach in the deep hole recovery process in the process of blasthole damage is serious. After the blasthole is destroyed, the single hole charge is insufficient, and the blasting has insufficient effect on the rock at the bottom of the hole, resulting in a suspended ceiling and a large block, which brings safety hazards to the mine and also affects the mining efficiency. The ore loss rate increases and wastes resources. In addition, the damage of the blasthole often causes the orifice of the blasthole to be too large or the charge of several blastholes that can be charged is too concentrated, forming an unreasonable structure on the charge; after blasting, the hole is drained and the eyebrow line is destroyed. , causing subsequent deformation and dislocation of the blasthole to form a vicious circle.
After the serious damage to the eyebrow line, the caving ore protrudes too long on the entrance floor, which hinders the subsequent blasting work. Even in order to get out the blasthole, a large amount of waste rock needs to be shoveled, the ore depletion rate and corresponding production As the cost increases, mine production is greatly affected.
2 blasthole damage form and cause
2.1 The shape of the blasthole destruction 1) Collapse. The wall of the blasthole hole collapses or the fragment clomes the blasthole, and the generated part is the full length of the blasthole.
2) Wrong holes. Part of the rock layer produces shear deformation and displacement, causing the blasthole to move and displace in the axial direction. It is only broken in the area within 2~3m from the orifice, and the part above 2~3m is basically intact, and the blasthole can be used after treatment.
3) Shrinkage. The expansion of the hole wall reduces the aperture.
Both the collapsed hole and the wrong hole blasthole appear in the 2 to 3 deep hole rows near the end wall of the mining inlet.
2.2 Causes of blasthole damage 1) Roadway deformation is the root cause of blasthole damage. The Datunhe iron ore body is loose and broken, with low self-supporting capacity and obvious ground pressure. After the roadway into the lane, the roadway continues to have a large amount of deformation and lasts for a long time. The rock mass in the loose ring of the roadway still has a relative displacement, causing damage to the blasthole.
2) Influence of mining blasting on blasthole damage. The stress wave and seismic wave generated by the medium-deep hole blasting affect the integrity of the blasthole. The more frequent impact stress caused by the mining blasting, the greater the effect of the half-wave loss formed at the hole wall on the tensile stress of the rock wall. The more vulnerable it is to destroy. The rock mass vibration caused by the blasting seismic wave further expands the original crack in the rock body, weakens the integrity of the rock mass, and the rock body undergoes multiple vibrations and changes its integrity, and the blasthole is destroyed.
3) The influence of mining pressure and the existence time of the blasthole on the damage of the blasthole. The vertical stress of the rock mass of the blasthole wall changes continuously with time and the demining of the stope. In addition, the half-wave loss tensile stress of the impact blasting impact stress causes the rock mass at the blasthole wall to be subjected to alternating tensile stress. The longer the time, the more the number of actions, the more likely it is to cause damage similar to fatigue. In addition, with the constant transfer of stress, the stress on the rock mass in the pressure-bearing area is constantly increasing. In addition to the erosion of fissure water, the rock mass of the peripheral wall is softened and deformed, which is also likely to cause deformation and damage of the blasthole.
3 Countermeasures
1) Light burst into the roadway. All roadway excavation is carried out by smooth blasting to reduce the damage range of the ore, avoiding stress concentration caused by super and undercut, and reducing damage to the blasthole.
2) Improve the support method and improve the support strength. On the basis of a single spray Gum support the increased spray Bolt and double rib joint support, lots of broken pole in a long long anchor bolt with reinforced support, spray Bolt and metal bracket combined support, more effective The ground changes the stress state of the ore and improves the stability and integrity of the mining route. The ground pressure appears to be controlled to a certain extent, creating conditions for medium-deep hole mining.
3) Through hole, small blast, fill hole. For some collapsed holes, through the use of a charging tube combined with high-pressure air for through-hole treatment before blasting, it is often able to recover. If the hole treatment of some holes has no effect or the hole depth does not meet the design requirements, the hole needs to be filled; the wrong hole blast hole is processed, and the No. 2 rock emulsion explosive (4532 mm) is only required to be misplaced before the deep hole blasting. Inside the blasthole (the fan-shaped medium-deep hole coffee is 65 mm), the misaligned part can be eliminated after blasting, and then the medium-deep hole charge blasting is performed on the intact part of the blasthole; for the crater hole, the hole can be filled. The form is processed (Figures 1-3).
1 ~ mining approach; 2 a good blasthole; 3 a wrong hole blasthole;
4 a shrinkage hole or a collapsed hole; 5 a hole-shaped fan hole; 6 a caving ore Figure 1 Schematic diagram of the treatment of the destruction gun L
Fig. 1 Section sketch map of destroyed blastholes
1 together with the detonator line; 2 to 2 rock emulsion explosives Figure 2 handles the misplaced L gun hole schematic
Fig. 2 Sketch map of staggered blastholes
Figure 3 Schematic diagram of the fan-shaped deep hole in the hole
Fig. 3 Sketch map 0f fan-shaped middle-deep blastholes
4) Adopting hole-by-hole detonation technology to reduce blasting seismic effect China's Blasting Safety Regulations (GB6722-2003) stipulates that the particle vibration velocity is used as the standard for the degree of damage to buildings in blasting. Sadowski's empirical formula:
Where: V-rock mass vibration velocity, cm/s; Q-explosive amount, uniform blasting is the total dose, time blasting is the maximum dose, kg; R-blasting distance, m; K- and medium Constant associated with the blasting method; attenuation index of the α-seismic wave.
It can be known from the above formula that the particle vibration velocity is related to the charge amount, the blasting distance, and the geological conditions. When the other parameters are unchanged, the vertical vibration velocity of the particle is directly affected by the maximum dose of the same segment. Under the premise of not reducing the total amount of blasting, reducing the maximum dose of the same section of detonation is the most direct and effective way to reduce the blasting seismic effect. At first, in order to reduce the blasting vibration, the mine uses the domestic millisecond plastic detonating tube detonator to perform the staged delay blasting in the row. Each row of blastholes is divided into 1, 3, and 5 sections, and the blasting vibration is reduced compared with the same row. 30%, to a certain extent, reduced the damage of the blasting vibration to the rear blasthole, and the serious damage of the blasthole was significantly reduced. However, new problems have emerged: (1) With the method of orifice initiation, the blasting energy is attenuated too fast in the hole, the effect on the rock at the bottom of the hole is insufficient, the bulk rate is increased, and the overhang is easily generated; and the energy of the orifice is concentrated. It has a strong squeezing effect on the rear blasthole, which is easy to cause damage to the rear blasthole and severely damage the eyebrow line, thus affecting the blasting of the deep hole in the rear row. (2) The accuracy of domestic non-electrical millisecond detonators is not enough to meet the needs of further segmentation and differential vibration reduction. In this regard, in 2008, the mine adopted the high-precision millisecond detonating tube detonator produced by Oricai (Weihai) Blasting Equipment Co., Ltd., and conducted a hole-by-hole bottom detonation test in the middle section of the middle section of the 240-meter mid-section 1411. Figures 4 to 5. The test effect is remarkable, and any blasthole in the explosion zone is realized, and the blasting is performed separately in a certain detonation sequence in space and time, thereby achieving the purpose of reducing blasting vibration and improving blasting effect. The eyebrow line is protected and the blasthole integrity rate increases. At the same time, the large block rate is reduced, the secondary blasting cost is saved, the mining efficiency is improved, and the secondary support cost of the mining route is reduced.
5) Shorten the existence time of the blasthole and control the number of blastholes. The mining technical department carefully prepares the production technology plan to ensure that the production tasks are highly consistent with the consumption of the medium and deep hole mining. The construction workshop organizes the construction according to the plan reasonably, increases the number of rock drilling equipment, improves the rock drilling efficiency, and makes the close connection between the mining and the preparation blasthole. The deep hole of the construction is neither owed nor over-planned. The existence time of the blasthole is strictly controlled within 2 months from the original 5-6 months. The “three-concentration†measures are adopted for the areas where the extremely fractured Yuan Earth stress is particularly large: concentrated chiseling, concentrated mining, and concentrated mining. Minimize the existence of the blasthole and eliminate various forms of damage to the blasthole.
Fig. 4 Schematic diagram of the detonation segment and charge distribution of the high-precision detonator L bottom. 4 Sketch map 0f detonation one by one from
Hole bottom with high-precision detonator
And charging distribution
Figure 5 is a schematic diagram of the structure of the sub-hole detonation charge
Fi faint 5 Sketch map of charging structure 0f
Detonation one by one from hole bottom
4 Conclusion
references
[1] Hu Xingbao. Research on rock drilling and blasting technology of Yangjiaba Iron Mine [J]. Metal Mine, 1993.10:10-11.
[2] China Blasting Network. GB6722-2003 blasting safety regulations [OL[//www. Cbsw. Cn.
[3] Wu Weicheng, Pang Bin. Application of medium and deep hole row cannon pulling groove in gently inclined broken ore body [J]. Non-ferrous metals (mining parts), 2009, 61 (4): 51-58.
[4] Ren Xiang, Guo Xuebin, Guo Fang. Experimental study on hole-by-hole initiation technology of karst-developed limestone mine [J]. Metal Mine, 2008, 11:12.
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