(1) Method characteristics
The shallow hole mining ore mining method is characterized by dividing the stage into ore blocks, and the ore blocks are further divided into mining houses and pillars for secondary recovery. The mining room is layered and stratified from top to bottom, and each time the ore that has collapsed is released about one-half, and the rest is stored in the mine room as a workbench to continue mining. After the mining room is finished, it is released, and the mining room is finished. Back to the mining column and processing the gob.
(2) Applicable conditions
The shallow hole ore mining method is mainly used to open ore and stabilized ore bodies. It is generally suitable for medium-thick, thin or still thin ore bodies. The ore body inclination angle is generally required to be not less than 60° in thin veins. Generally, the body is required to be not less than 55°. The smaller the dip angle, the more difficult it is to mine, and the greater the workload of powder mine loss and flat field. Because of the large amount of ore stored in the mine, the ore and surrounding rock cannot be self-igniting, oxidizing and agglomerating.
c) Components
When the thickness of the ore body is less than 15m, the ore blocks are arranged along the strike. When the thickness of the ore body is greater than 15m, the ore blocks are arranged vertically. Divide the nuggets into mines and pillars, and then mine the post-mining pillars. The length of the nugget is 40 to 50 m and the height is 40 to 50 m. The height of the top column is 4m, the height of the bottom column is 6m, the width of the column is 6m, and the spacing between the links is 5.5-6.0m.
(4) Precision cutting
The mining and cutting work mainly includes excavating the middle section of the transportation lane, the patio and the patio connecting road. The bottom pillar is digged into the bottom of the bottom and the funnel neck is digged every 5~7m, and the bottom is cut and the leakage is formed to form the mining free surface.
For the cutting work, the 7565 type pneumatic leg rock drill is used for the roadway excavation, and the YSP45 rock drill is used for the tunnel excavation. The mining roadway is generally unsupported, the local unstable section adopts wooden support, and the extremely unstable zone adopts concrete reinforcement support.
(5) Mining work
1. Mining sequence: The mining work mainly includes rock drilling, blasting, ventilation, partial ore mining, dome flat field, and large amount of mining. Since the mining work is carried out from the bottom level from the bottom to the top, the layer height is generally 2.0 to 2.5 m. In the stope, the 7655-type gas-leg rock drill is used to drill the upward micro-fronting blasting hole. The drilling blasting parameters are: the minimum resistance line is 1.0-1.2m, the blast hole spacing is 0.8-1.0m, and the hole depth is 1.8-2.2m. The front and rear rows of blastholes are staggered, using ammonium nitrate explosives for manual charging, and millisecond non-conducting squibs for detonation. The fresh air flow enters the stop working face from the middle section of the transport roadway through the patio and patio contact road on the side of the mine. The dirty wind passes through the patio contact road on the other side of the mine house and the patio enters the upper middle section transport (return air) roadway. The ore that has collapsed in the stopway relies on gravity to release about one-third of the ore deposit, and then performs the dome, flat field and secondary blasting work. After the recovery of the mining house, a large amount of ore mining work is organized to release all the ore remaining in the mine. The ore is loaded into the mine car through the funnel and discharged through the middle section of the roadway.
2. Rock blasting: The rock in the stope is drilled with a 7655 air leg rock drill. The hole spacing and row spacing are 0.6-0.8m, the hole depth is 2.1m, and the blastholes are staggered. Manually installed No. 2 rock explosives, detonators and non-conducting blasters detonated.
3. Mining and mining: The ore is loaded into the mine by self-weighted manual gates for recovery and mining.
(6) Mining and mining of mined pillars
The pillars are harvested by the caving method. In order to ensure the safety of the mining work of the pillars, before the large amount of ore mining in the mine, the blastholes in the mine room column and the top of the roof are drilled, and all the ore in the mine room is released, and then the column is blasted. Generally, the column is first exploded, and the top and bottom columns are post-explosive.
At the same time as the pillars are harvested, the goaf should be treated in a planned manner by natural or forced collapse of surrounding rock.
(7) Ventilation and dust prevention in the stope
The fresh air flow enters the stop working face from the main ascending well, the stage transporting alley, the side patio and the patio contact road, and the dirty wind passes through the other side patio connecting road, the patio, the return airway road to the return air well. Ventilation in the stope should be supplemented by a local fan.
Wet rock drilling and dust collection in the pit; when the single head working face is excavated, the fan is used to ventilate the dust; when the rock mine is installed, the dust is sprayed on the explosion pile; the sluice gate and the unloading port are installed with a sprayer to reduce the dust; Wall treatment; underground workers wear dust masks.
(8) Mining loss rate and depletion rate
According to the selected shallow hole mining method, combined with the actual situation of small ore bodies in Baotou area, the ore recovery rate is generally about 92%, and the loss rate is about 8%.
Second, the application of shallow hole mining and mining method
(A) small iron ore mine types and morphological occurrence Baotou
The natural type of ore in small iron ore deposits in Baotou area is generally quartz -type magnetite ore, and most of the industrial types are weakly magnetic and iron ore is selected. Most of the ore deposits have ω(mFe)/ω(TFe) between 15% and 85%, which is mixed ore. The genetic type of the deposit is basically the metamorphic ferrosilicon of the sedimentary metamorphic iron deposit to form iron ore.
The ore body generally exists in the hornblende slant gneiss , and the output is controlled by the stratum, which is layered, layered, lenticular, and the like. Most of the ore bodies are steeply inclined ore bodies, and the inclination angle is generally 60 to 85°. The thickness of the ore body is medium or very thin ore body, generally 3 to 20 m, mostly around 10 m.
(II) Surrounding rock conditions of the ore body
The surrounding rock of the ore body is mainly mixed igneous hornblende gneiss and black cloud hornblende gneiss. There are generally less stones in the ore body. The boundary between the ore body and the surrounding rock and mezzanine is clear.
(3) Hydrogeological conditions
The aquifers in each mining area of ​​Baotou area are mainly the Quaternary alluvial aquifer and the weak aquifer of the bedrock fissure. The lithology of the Quaternary alluvial aquifer is a gravel layer, and the amount of water inflow is generally small (except for the Laigou iron ore). The lithology of the weak aquifer in the bedrock fissure diving is mostly slanted long-horned flash gneiss, granite , quartz diorite, etc. The weathering fissure is relatively developed, and the water permeability is good, but the water-rich is weak. The topographic conditions of most mining areas are conducive to drainage, and the groundwater ditch directly receives vertical infiltration replenishment of atmospheric precipitation. In short, the small iron ore deposits in Baotou area are mainly filled with fissure water, the second is the void water, the water content is weak, the recharge conditions are poor, the natural drainage conditions are good, and the hydrogeological exploration type of the deposit is the second type first type, ie hydrology. The geological conditions are simple.
(4) Engineering geological conditions
Most of the fault structures in the mining area are extremely undeveloped. The surrounding rock of the top and bottom of the ore body is a semi-hard-hard layered rock stratum. The tensile, compressive and shear strengths are large, and the overall rock stability is strong. There is basically no bad engineering geology. problem. The geological type of deposit exploration engineering belongs to the second type, the first type, which is a mining area with simple engineering geological conditions dominated by hard rock layers. However, the long-term exposure of the rock mass is subject to weathering, and the surface weathering fissure is relatively developed, which causes the integrity of the rock mass to be destroyed, the mechanical strength is reduced, the stability is weakened, and the sliding is easy to occur, which is the main unfavorable factor for the mining.
(5) Environmental geological conditions
According to Figure A1 of "China Earthquake Peak Acceleration Zoning Map" (GB18306-2001), the peak acceleration of Baotou area is 0.15~0.30g, and the contrast intensity is 7.5~8.5 degrees, all of which are seismic fortification areas.
The ecological environment in Baotou is relatively fragile, and mining will change the natural topography of the area, destroying the recharge route and permeability of groundwater. Due to the lack of vegetation in most mining areas, the relative height difference of the topography is large, and the waste rock discharged from the mining is easy to form a small-scale debris flow during rainfall. Therefore, in the mining process, we must pay attention to the unified management and treatment of waste rock, waste residue and wastewater, strengthen the construction and protection of the ecological environment, and avoid pollution and damage to the environment as much as possible.
The stratigraphic lithology of Baotou area is mainly composed of some low gamma value gneiss and magnetite quartzite . The variation of gamma value is relatively stable, and it is the area with low radioactive bottom value.
(6) Adaptability
According to the applicable conditions of the shallow hole mining method, combined with the scale, shape, occurrence and hydrological, engineering and environmental geological conditions of small mines in Baotou, this method is very suitable for most small mines. The mining method is simple in process, easy to grasp, and has good safety. It is recommended to promote the use of mines.
(7) Current status of application
Baotou past two years, many small mines using a shallow hole in the production process shrinkage stoping method, there is a good application Guyang hole No. 1 iron ore silver white, No. 7 iron ore, iron ore No. 12, No. 29 Iron ore, Baotou Steel Guyang Mining Company Public Welfare Mingtie Mine, Guyang County Liuding Account Iron Mine, etc., the annual production scale of these mines is about 150,000 tons.
(8) Problems and suggestions
1. Although many small mines adopt the shallow hole mining and mining method, there are some roads mining methods that are suitable for adopting this method, but adopt the roadway mining method with poor safety, large amount of mining and cutting, and low ore recovery rate. It is recommended that these mines modify the mining method after examining the mines where the method is applied well.
2. In mines where this method has been applied, some applications are not standardized or unscientific and should be improved. For example, some mines are thicker and reach 20m. When the method is applied, no ore outlets are set up in the upper and lower plates of the ore body. The ore in the mine is not clean, resulting in waste of resources. Some mines did not return to the mining column in time after the end of ore mining in the mine, which also resulted in low resource recovery rate.
3. It is necessary to deal with the gobs in time. Most of the mines in the Baotou area that applied the shallow hole mining and mining method did not deal with the goaf in time after the completion of a middle section, resulting in a large safety hazard. It is recommended that the mine should return to the mining column in time and collapse the surrounding rock to treat the goaf. After the collapse of the surrounding rock, the mine should set up fences around the subsidence area in time to prevent people, animals and vehicles from entering the city and causing safety accidents.
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