Gob area treatment of Fengshan Copper Mine

1 mining conditions
1.1 Geological overview
Poongsan copper deposits produced in the north and south edges of the contact strip Pungsan adjacent rock and rock, formed in South and North ore belt edge margin ore zone, skarn - porphyry complex deposits.
The southern margin belt is located in the contact zone on the southern margin of the Fengshan rock mass, extending northwest and westward. It occurs on the 1st to 20th lines, and the ore belt extends up to 1800m. It is integrated with the northern margin of the 20th line. The ore body tends to Nancy, with an inclination of 50° to 65°. The horizontal width of the ore belt is about 120m, the highest elevation is 150m (1 line), and the mineralization of the 10th to 20th line is 0~-150m. It is the main industrial reserve. The maximum depth of control is -705m (14 lines) and there is still strong copper- molybdenum mineralization.
The southern margin belt is deeper in the 11-15 line, gradually becoming shallower in the west, and the tip is below the 0m elevation. The ore bodies in the ore belt appear in groups, and the ore bodies on the plane are controlled by the northwest westward tectonic line. In space, the ore bodies are arranged in a tile-like shape due to the inter-layer structure control.
The shape and occurrence of the ore body are strictly controlled by the contact zone structure and the surrounding rock layer. The ore bodies of the southern margin belt vary in size, with 96 copper ore bodies with a thickness greater than 3 m and 25 molybdenum ore bodies alone. There are 6 major copper ore bodies extending more than 100m, and their reserves account for 95% of the reserves in the southern margin. The rest are small ore bodies away from the contact zone.
1.2 Rockite stability
Due to the zoning of different mineral components during the two-way metamorphism of the ore-bearing skarn, the rock is not stable at the zoning interface; some ore-bearing rock structures are scattered and fragmented, on the northern margin. Such rock masses are easy to collapse; the wollastonite skarn and diopside skarn in the southern margin are swollen with water and are easy to fall. The shallow part is intrusive into small veins, small faults and joint fissures, cutting ore bodies, and the stability is poor. Some areas of the skarn are later altered minerals, which are softer, and the general joint density is 2-7 strips/m. The integrity of the rock is good and the ore body is relatively stable.
The surface of the granodiorite porphyry group (the lower part of the ore body of the southern margin and the upper part of the ore body of the northern margin) is weathered, and the residual characteristics are remarkable. After the formation of the main rock mass, multiple stages of cryptoexplosion and intrusion occurred, which made the rock near the contact zone strong and unstable. The igneous rock on the upper edge of the contact zone on the north edge is a fragmented structure and a loose structure, which is easy to collapse. The shallow rock mass is broken, the fissure is developed, and the fragments are 5~20cm, the joint density is more than 10/m, f=2~4, 4~6; the deep rock mass is better and the rock mass is stable.
The Daliyan Formation (the upper plate of the ore body in the southern margin and the lower part of the ore body in the northern margin) is a dense block-shaped marble with a relatively hard mass, good integrity and stable rock.
The joints and cracks are relatively developed, and the density is 2 to 4 strips/m. Straight joint surfaces, joint in more or less altered minerals, mineral filler metal. In the upper plate of the ore body in the southern margin of the underground, due to the multi-stage intrusion of the late igneous veins, the triangular joints developed more and the stability was relatively poor. The marble group f=6～8. The rock RQD value is 70% to 90%. The near-contact rock has alterations such as chlorite, serpentine and petrochemical.
2 Mining and engineering status
2.1 Mining overview
The underground mining of Fengshan Copper Mine is two parts of the southern and northern marginal ore belts.
The original design of the southern margin belt adopts the sub-column-free sublevel caving method. Due to the instability of the ore rock, the production cannot be smoothly carried out and the depletion loss index is poor. In 1988, the feasibility study of the mining method in the southern margin was carried out, 1996. The technical transformation of the mining method, the test and the technical reform prove that the cementation filling method is suitable for the mining conditions of the hard-to-mine body in the southern margin of the mine. So far, the main ore body of the southern margin has adopted the segmented gravel cement filling method, and the end and part of the blind The ore body still uses a sub-column-free sublevel caving method.
The northern margin was originally designed as an upward horizontal layered tailings and cementing filling method, namely, cement column filling and filling, and a two-step mining method for filling the tailings of the mine. Later, due to complicated process, low production capacity of the ore, high cost, etc., 1985 The year is changed to the upward horizontal layering point (bar) column tail sand filling method. This method has a large loss due to ore and has poor safety. After 2006, it was changed to the wall-column type upward stratified tailings filling method.
2.2 The process of forming an empty area
In the southern margin, the mining sections with no sub-pillar sublevel caving method are used for mining and ore mining without the formation of a cover layer in advance. After the end of the mining stop, the surrounding rock and the roof of the stope are not able to fall naturally. The mine has not been forced to ceiling to form or supplement the cover layer, thereby forming an empty area. As the mining progresses, the end of the main ore body adopts the bottomless column caving method to recover multiple sections of the mining area, and the rear empty space is connected to form a large empty field; the blind ore body is used in several sections. The bottom column is subdivided and the upper and lower sections are connected together to form a large-scale empty field. With the new level of mining, the size of the empty area will be further expanded.
2.3 The impact of the existence of empty areas on production
The main impacts of the goaf on the production of the South Rim are:
(1) Long-term storage of a large number of empty areas, the area of ​​the empty area, the height and the stability of the roof change with the mining time of the mine, and various scales of ground pressure activities may occur at any time, so that the personnel, equipment and instruments of the construction operation are always facing Dangerous
(2) There is no overburden in the upper part of the ore body, and the top of the empty area and the surrounding rock of the upper plate may collapse at any time. The collapse of the rock and the shock wave generated seriously threaten the safety of the mining of the segmented ore body;
(3) The collapse of an empty area may cause damage to the transportation or mining project and affect the production of the mine;
(4) The presence of a large number of empty areas affects the mining of surrounding ore bodies, resulting in large areas of ore and loss of ore.
3 empty area processing
3.1-187.5m segment +11 line east main ore body end goaf treatment
3.1.1 Status of occurrence of empty areas
The -187.5m section +11 line east of the main ore body end goaf is 1100, 1013, 1012 stope, and 1010, 1009, 1008, 1007, 1006 stope after the caving method, the roof is not An empty area formed by the natural fall. The main ore body +11 line east of -187.5m will still be recovered by the bottomless column collapse method.
The 1100, 1013, and 1012 stop plates are harvested by segmented gravel cementation filling method, which is a cemented backfill. In the middle of the ore body, a thick stone is formed. In order to reduce the depletion, the stone is retained during the recovery. The lower plate of the stone is recovered by the sublevel caving method without a bottom column, forming a height of 12 m, a width of about 8 to 12 m, and a length of 24 m. Empty area. The top plate of the empty area is -175m segmented filling body, the upper plate of the empty area is the marble of the marble, and the lower plate is 3~6m away from the section road of -187.5m.
The 1010, 1009, 1008, 1007, and 1006 mining sites are all backed by a sub-column-free sublevel caving method to form an empty area with a height of 12 m. The top plate of the empty area is a -175 m segmented gravel cemented backfill. Because the section of the ore body is independent, the 1010, 1009, 1008, 1007, and 1006 stopts are not connected, and the top plate of the empty zone is discontinuous, which is a single independent small empty space, as shown in Figure 1.

3.1.2 empty area treatment plan
The 1100, 1013, 1012 stope will be connected to the empty area east of the +11 line in the -200m section. Therefore, the fan-shaped medium-deep hole is arranged in the -187.5m sub-area. The surrounding rock forms part of the overburden layer, and then the slab-free sublevel caving method is used to recover the -200m section ore body; after the end of the -200m section ore body, the surrounding rock is forced to collapse and further replenish the cover layer. At the same time, the exit to the empty area is closed, and then the mining of the lower ore body is carried out.
1010, 1009, 1008, 1007, 1006 There are pillars between the stope, the top plate of the empty area is discontinuous, and it is a single independent small empty area, which is treated by closed isolation method.
3.1.3 Forced caving and ceiling placement

The -187.5m section +11 line east of the ore body mining end, the next section of the section of the mining ore is no longer used, you can use the 1100, 1013, 1012 stop field to drill the rock approach, in each way The middle and deep holes of 3 to 5 rows are arranged to forcefully collapse the surrounding rock of the lower plate to form a cover layer. If the thickness of the collapsed cover layer is insufficient, after the end of the 1100, 1013, 1012 stope mining corresponding to the -200m segment, the surrounding rock of the lower plate may continue to be collapsed to further replenish the cover layer.
3.1.4 top rock drilling and blasting
Rock drilling adopts YGZ-90 type rock drilling, the hole diameter is Φ65mm, and the hole depth is 12~15m, which is a section height. The minimum resistance line W of the blasthole is 1.4m, the bottom distance of the hole is 2.5-3.0m, and a total of 4 rows are designed, and the rows and rows are staggered. The BQF-100 charger is used to fill the pores with porous granular ammonium explosives, the charge coefficient is 0.6-0.7, and the length of the pores between the adjacent pores is charged. Starting from the boundary of the empty area, the exposed surface of the upper part of the empty area is the free surface, and the coverage is formed by the differential blasting of the non-conductive detonator.
3.1.5 setting of blocking wall
After the cover layer is formed, all the passages leading to the empty area are finally sealed by the sealed isolation method. The sealing wall is located at the intersection of the main transportation lane and the rock-piercing and mining-passing roadway leading to the empty area, and is sealed with a reinforced concrete fully enclosed blocking wall.
-175m segmented reinforced concrete cast-in-wall wave-blocking wall 5, respectively, at the exit of the 1102, 1101, 1100, 1013 and south 1008 stope; 1877.5m section with reinforced concrete cast-in-wall wavewall 2, respectively It is the exit of the 1102 and 1010 stop.
The closed thickness of the reinforced concrete fully enclosed wave-blocking wall is 3m. During construction, the bolt eye of 0.5m deep with a mesh distance of 0.8-1.0m should be inserted around the roadway and inserted into round steel reinforcement. The wall is cast in C18 concrete. Pay attention to the top when pouring, leaving no gaps. The main reinforcement of the steel bar is Φ16mm rebar with a spacing of 400mm and the secondary reinforcement is Φ6.5mm round steel with a spacing of 600mm.
3.2-187.5m segment -12 line ~ -11 line lower blind body empty area treatment
3.2.1 Status of occurrence of empty areas
The main ore body of -12 line to -11 line has a blind ore body. The top of the ore body is at the level of -162.5m, and the bottom extends downward to -200m. The -12 line to the 11th line of the blind ore body has been mined above the level of -187.5m, forming two independent empty areas of the east and west with the +12 line as the boundary. The blind ore body is below -187.5m. The mining method has not been determined (see Figures 2 and 3).

Sections -187.5--175m east of the +12 line have been harvested by segmented gravel cementation filling method, and no empty zone is formed; -175~-162.5m section will be harvested by sub-column sublevel caving method. After mining, an empty area of ​​about 12m high, 14m wide and 46m long will be formed.
The +12 line west is -187.5~-162.5m, and the bottomless column caving method is adopted for mining. Since the roof of the ore body does not fall naturally, a large empty area is formed in the section. The empty zone has an elevation of -187.5~-162.5m, the empty zone is 25m high, the average width is 12m, and the length is about 25m.
The blind ore body of the -12 line to the -11 line is divided into two independent small ore bodies of east and west on the +12 line above -187.5m. The upper part has no connection with each other. The two are on the -187.5m floor plan. A small ore body is connected into a whole. According to the mining status of the ore body and the mining plan of the lower part of the ore body, the empty area treatment divides the ore body into two independent small ore bodies, east and west.
3.2.2+12 line east small ore body empty area treatment
The elevation of the +12 line Dongxiao ore body is about -163m, and the -187.5~-175m section has been harvested by the cement filling method. The empty area has been filled.
Since there is no corresponding project in the upper part of the east small ore body of the +12 line, the -175~-163m section is ready to adopt the caving method, and the east of the +12 line will produce a 12m high area with an empty area of ​​30m and a width of 20m. The empty area is 7200m3.
The empty area has no connection with the surrounding stope and other projects. The lower part has been filled by the filling method, and the height of the empty area is only one segment high.

After the +12 line Dongxiao ore body adopts the caving method for recovery, the formed empty area is treated by the sealing and isolation method. The sealed separation wall is located at the intersection of the empty area leading to the -175m main transportation lane, and the reinforced concrete is used to block the entire block. The wave wall is sealed.
3.2.3+12 line west small ore body empty area treatment
In the west of the +12 line, the small ore body is distributed in the range of -162.5 to -200 m and below, and the upper part of the -162.5 m is mine-free. The mine originally used the sub-column sublevel caving method in the two sections of -175m and -187.5m. Since the roof did not collapse naturally, the empty zone was formed at the elevation of -162.5~-187.5m, and the empty zone was 30m long. It is 13.5m wide and 25m high. Between -187.5 and -200m and below, ore needs to be recovered. The east of the 12th line has been treated with gravel cementation filling method, and the west of the -12 line has been recovered by the sub-column sublevel caving method.
The treatment of the empty area of ​​the +12 line west small ore body is treated by forced separation and surrounding rock isolation method. The scheme is as follows:
In the southern edge of the 175m section-12 line, the lower sluice mine is connected to the roadway. The liaison lane is about 10~15m away from the empty area, and the roadway section is 3.0m×3.0m, separated by 15~18m. Two sections of 3.0m×3.0m rock drilling roadway are arranged along the direction of the empty area.
In the rock drilling alley, the empty area is used as the blasting free surface. The YGZ-90 rail type rock drill is used to drill the upper fan-shaped medium-deep hole. Three rows of blastholes are arranged in each rock-rocking lane, and the fan-shaped hole row spacing is 1.8~ 2.2m, hole depth 8 ~ 15m, aperture 65mm. The BQF-100 type charge device is equipped with a porous granular ammonium explosive, and the charge coefficient is 0.6-0.7. The length of the interval between adjacent holes of the orifice is charged. Taking the exposed surface of the goaf of the goaf as a free surface, the non-electrical thunder blasting row is slightly detonated, and the surrounding rock is collapsed to form a covering layer at a time.
After the cover protective layer is formed, the sub-column sub-cavity method or the filling mining method may be used to recover the ore of the section -187.5--200m and below. When the -187.5m or less is crushed by the crushed stone cementing method, the -187.5~-200m section is used as the isolation layer, and the mining body is returned from the bottom to the top. After the completion of the filling below -200m, the caving method is used to recover the -200m segmentation layer ore under the caving cover. When all the -187.5m or less is adopted by the caving method, the ore in the stope and the surrounding rock in the caving face should retain a covering layer of at least 20m thick to ensure the safety of the lower part.
After the ore is completely recovered in the independent empty area, the empty area is treated by the sealed isolation method, and all the passages leading to the empty area are sealed and sealed. The sealed partition wall is made of reinforced concrete and fully enclosed blocking wall.
After the empty area is processed, the surface above the empty area should be observed frequently, and vigilance and other preventive measures should be done in time.
3.3+15 line to -15 line empty area processing
3.3.1 Status of occurrence of empty areas
The +15 line to the -15 line empty area has been thoroughly immersed in the surface above -175m, and the empty area has been filled with waste rock. Yellow mud can be seen in the empty field and in the section roadway.
3.3.2 Empty area treatment plan
As the empty area has penetrated the surface, surface waste rock and yellow mud can be seen in the -175 section empty space and roadway. It is easy to form mudslide during the rainy season, which poses great harm to underground personnel, equipment and engineering. For the +15 line ~ -15 line empty area, the prevention and control of underground debris flow should be done.
(1) Closed +15 line to -15 line empty area -162.5m section, -175m section and -187.5m section stopway, segregate stope.
(2) When mining the ore body below -187.5m, the surrounding rock of the upper and lower plates should be collapsed, the cover layer should be replenished continuously, the mud content of the cover layer should be improved, and the passage of the upper mud flow fluid and the normal mining area should be cut off.
(3) During the rainy or heavy rain season, the management personnel of the stope shall pay attention to observe the mining situation. Once the yellow mud is found, the mining will stop immediately. For the abnormal water seepage of individual face, it is necessary to check the situation before deciding whether to stop the mining of the face, such as the seepage of the face in the entire mining area.
Abnormal, the mining area must be stopped immediately.
4 Conclusion
The goaf will form a major safety hazard to the normal production of the mine, restricting normal production, and timely carrying out comprehensive airspace investigation and treatment is of great significance to the safe and efficient recovery of mineral resources. The Fengshan Copper Mine has achieved good results by investigating the goafs in the southern margin and selecting different schemes to control the empty areas according to the mining technical conditions and mining status.
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