A safe recovery method for phosphate rock pillars based on pre-constructed false bottoms

Abstract

This invention belongs to the field of phosphate deposit mining technology, specifically relating to a safe recovery method for phosphate ore pillars based on a pre-constructed false bottom. Addressing the problem of suspended spaces at the bottom of the pillar, posing a risk of localized overall collapse during blasting recovery, this invention divides the pillar into upper and lower layers. The lower layer employs a route mining and backfilling method. Due to the small cross-section of the route and the large spacing between them, and the ability to use a tunneling machine, the disturbance to the pillar is minimal, ensuring both efficiency and safety. Furthermore, the route backfilling fills the suspended spaces at the bottom of the upper pillar, while a portion of the route remains unfilled as drilling and ore extraction roadways for the upper layer. This backfilling of the lower layer provides stable support for the upper layer, allowing for subsequent backfilling of the blasted ore deposit openings in the upper layer using the drilling and ore extraction roadways, improving mining efficiency and ensuring safety. This invention also fully utilizes existing roadways in the middle section, requiring only the construction of two horizontal roadways along the vein, significantly reducing roadway excavation workload.

Description

Technical Field

[0001] This invention belongs to the field of phosphate deposit mining technology, specifically relating to a method for safe recovery of phosphate rock pillars based on pre-constructed false bottoms. Background Technology

[0002] The Datang section of the Wengfu Phosphate Mine is mined using the open-pit backfilling method. The 1130 section has been fully mined. The 1130 section was designed to have a height of 70m, including a 15m pillar height, with an elevation range of 1130-1145m. The mined ore body has a height of 55m, with an elevation range of 1145-1200m. The backfilling method for the mined ore body is: 1:4 backfill at the bottom and 1:6 backfill at the top. The lower section of the 1130 section is the 1060 section, with an elevation range of 1060-1130m. Currently, some areas of the 1060 section have been mined. The mined ore body has a height of 55m, with an elevation range of 1075-1130m. The backfilling method for the mined ore body is: 1:4 backfill at the bottom and 1:10 backfill at the top.

[0003] The 1130 mid-section bottom pillar is located below the lower 1:4 backfill material of the 1030 mid-section and above the top 1:6 backfill material of the 1060 mid-section. Due to water seepage and mining vibrations, the top of the 1:6 backfill material has severely shrunk in some areas, resulting in suspended voids between the 1030 mid-section bottom pillar and the bottom 1:6 backfill material in certain areas. Figure 1 The 1030-level central pillar (section 10) cannot be fully supported by the lower 1:6 backfill, leading to reduced adhesion between the central pillar and the roof and interlayers. If blasting is used for recovery, there is a risk of the entire central pillar collapsing in a localized area. Therefore, how to safely mine the central pillar has become a pressing problem for the mine.

[0004] The Wengfu phosphate mine in the Datang section contains two ore layers, A and B, with a dip angle of 85°. Layer A has an average thickness of 12.5m, and layer B has an average thickness of 18.5m. Between layers A and B is an interlayer (rock) approximately 3m thick. Due to the thinness of the interlayer, it is not mined to ensure ore quality. This further complicates the safe recovery of the 1130 section's bottom pillar; for example, determining the mining sequence and spatial relationship between the two ore layers to ensure mining safety.

[0005] Wengfu Group's Daxin Beidoushan Phosphate Mine proposed a method for recovering the bottom pillar of the phosphate layer under the backfill body when recovering the bottom pillar of the 1080 intermediate section (Authorization Announcement No. CN120061843B). However, the 1080 intermediate section of this mine has a large interlayer thickness of 5m, good stability, and minimal impact on the selection of mining sequence for layers a and b. Furthermore, the backfill body has good roof and floor contact, making it unsuitable for the bottom pillar recovery conditions of the 1030 intermediate section of the Datang mine. For example, the scheme of leaving right-angled triangular or right-angled trapezoidal protective coal pillars, if used for the bottom pillar recovery of the 1030 intermediate section, would fail to provide support to the interlayer due to weak cohesion between the right-angled triangular or right-angled trapezoidal protective coal pillars and even delamination.

[0006] In summary, how to comprehensively consider the unique occurrence conditions of the a, b and interlayer ore layers and safely mine the bottom pillar of the 1030 middle section has become an urgent problem to be solved by the mine. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention proposes a safe recovery method for a phosphate rock bottom pillar based on a pre-constructed false bottom, applicable to steeply inclined phosphate mines. One side of the interlayer consists of ore layer A and a bottom plate, while the other side consists of ore layer B and a top plate. The bottom pillar is filled with infill material both above and below it, with a suspended space gap between the bottom pillar and the lower infill material. The method includes the following steps: S1: Prepare the upper plate stage transport level, the lower plate stage transport level, and two cross-beam level. The upper plate stage transport level and the lower plate stage transport level extend along the direction, and the two cross-beam level connect the upper plate stage transport level and the lower plate stage transport level. S2: Construct two cross-vein horizontal tunnels on the side of the a and b ore layers away from the interlayers, respectively, to connect the two cross-vein horizontal tunnels along the vein; S3: Divide the bottom pillar into several pillars along the strike, with the height being the height of the entire pillar and the length being the thickness of ore layer a and ore layer b; divide the pillar into upper and lower layers vertically. S4: For each lower layer of a pillar, divide it into 5 dipping passes along the strike and number them sequentially; first mine and fill pass 4, then pass 2, pass 5, and pass 1; finally mine only pass 3 but do not fill it; then connect pass 3, which is opposite to ore layer a and ore layer b on the dip, as the drilling and ore extraction roadway when mining the upper layer of the pillar. S5: For the upper layers of each pillar, the blasting and mining roadways are used to create open spaces for ore extraction, followed by filling. First, the a-layer is mined and filled from the interlayer towards the bottom plate, and then the b-layer is mined and filled from the top plate towards the interlayer. During the filling of the a-layer, the blasting and mining roadways are restored.

[0008] Preferably, in step S1, the bottom plates of the upper stage transport level, the lower stage transport level, and the cross-cut level are at the same elevation as the bottom column bottom plate.

[0009] Preferably, in step S2, in the bottom plate, at the location where the bottom plate is adjacent to ore layer a, a cross-vein tunnel is excavated along the ore layer direction from one cross-vein tunnel to another cross-vein tunnel; in the top plate, at the location where the top plate is adjacent to ore layer b, a cross-vein tunnel is excavated along the ore layer direction from one cross-vein tunnel to another cross-vein tunnel.

[0010] Preferably, in step S3, the length of each pillar along the strike is 15m; the pillar is divided into upper and lower layers vertically in a ratio of 4:1.

[0011] Preferably, in step S4, the width of each access road is 3m; the filling material is 1:2 or 1:3; and finally, the bottom plate of all the No. 3 access road pillars is smoothed.

[0012] Preferably, in step S4, a tunneling machine is used to excavate the lower-level access route.

[0013] Preferably, in step S4, the ore extraction path is as follows: For the sub-layer below the pillar of ore layer a, the ore extracted by the inlet is first transported to the side vein level roadway of ore layer a, and then transported to the footing stage transport roadway via the first cross vein level roadway; For the sub-layer below the pillar of ore layer b, the ore extracted by the inlet is first transported to the side vein level roadway of ore layer b, and then transported to the footing stage transport roadway via the first cross vein level roadway, wherein the first cross vein level roadway is one of two cross vein level roadways.

[0014] Preferably, in step S4, the ventilation path is as follows: fresh air enters the two along-the-vein level from the lower stage transport level, passes through the second through-the-vein level, and then enters the two along-the-vein level. After ventilation, the fresh air is then collected in the second through-the-vein level through the along-the-vein level and discharged through the upper stage transport level. The second through-the-vein level is the other of the two through-the-vein level.

[0015] Preferably, in step S5, the layers on each pillar are mined and filled sequentially along the strike, or the layers on the odd-numbered pillars are mined and filled sequentially first, and then the layers on the even-numbered pillars are mined and filled sequentially.

[0016] Preferably, in step S5, a cutting groove is constructed on the interlayer side of ore layer a, and a cutting groove is constructed on the top plate side of ore layer b.

[0017] Preferably, in step S5, the ore extraction path is the same for ore layer a and ore layer b. The ore extraction roadway passes through the side vein level roadway of ore layer a, and then is transported to the lower stage transport level roadway through the first through vein level roadway. The first through vein level roadway is one of two through vein level roadways.

[0018] Preferably, in step S5, the ventilation path is as follows: the a-seam and the b-seam are the same. Fresh air enters the side vein level of the a-seam from the lower stage transport level through the second cross vein level, then enters the drilling and ore extraction level, washes the stope, and then enters the side vein level of the ore-seam. After that, it is transported through the first cross vein level to the upper stage transport level for discharge. The second cross vein level is the other of the two cross vein level levels.

[0019] The inventive points and beneficial technical effects of this invention are as follows: 1. Addressing the problem of suspended space gaps at the bottom of the foundation pillar, posing a risk of localized overall collapse during blasting and recovery, this invention divides the foundation pillar into upper and lower layers. For the lower layer, a route mining and backfilling method is adopted. Due to the smaller cross-section of the route and the larger spacing between the routes, and the ability to use a tunneling machine for mining, the disturbance to the foundation pillar is minimal, ensuring both efficiency and safety. Furthermore, the route filling method can fill the suspended space gaps at the bottom of the upper foundation pillar, while leaving a portion of the route unfilled as drilling and ore extraction roadways for the upper layer. Thus, the backfilling of the lower layer provides stable support for the upper layer, allowing for subsequent backfilling of the blasted ore extraction voids in the upper layer using the drilling and ore extraction roadways, improving mining efficiency and ensuring safety.

[0020] Furthermore, this invention makes full use of the existing middle section of the roadway. Based on this, only two horizontal run-off roadways along the strike are needed to recover the foundation pillars, thus saving on roadway excavation work. In addition, this invention retains a portion of the access roadway without filling it, serving as the upper-level drilling and ore extraction roadway, and combines the drilling and ore extraction roadways into a single roadway, which can further reduce the amount of roadway construction work.

[0021] 2. Regarding the recovery of the upper layers, this invention fully considers the delamination issues between the A-layer and the interlayer, and between the B-layer and the roof. If the B-layer is mined first, the interlayer will bear greater pressure during mining, which may easily cause the thinner interlayer to break. Since mining the A-layer under the broken interlayer is dangerous, this invention proposes to mine the A-layer first. Based on this, this invention proposes to mine the A-layer from the interlayer towards the floor, and the B-layer from the roof towards the floor. This can fully utilize the delamination between the A-layer and the interlayer, and between the B-layer and the roof, to form cutting grooves, reducing cutting work; and it allows drilling and ore extraction to be carried out under the protection of the drilling and ore extraction tunnels as much as possible, improving the construction environment and ensuring safety of the upper-layer blasting and ore extraction.

[0022] In addition, in order to improve ventilation quality, after the mining of the A ore layer, the drilling and ore extraction roadways are retained, that is, only the ore extraction roadway along the vein side of the A ore layer is used, and only the ore return roadway along the vein side of the ore layer is used. Attached Figure Description

[0023] Figure 1 This is a schematic cross-sectional view of the geological state of the bottom pillar along the dip direction of the ore layer according to the present invention; Figure 2This is a schematic cross-sectional view of the preparation for the bottom pillar recovery method along the dip of the ore layer according to the present invention; Figure 3 This is a schematic diagram of the preparation and route layout for the bottom column recovery method of the present invention; Figure 4 This is a schematic cross-sectional view of the prefabricated false bottom for mining and backfilling along the dip direction of the ore layer according to the present invention; Figure 5 This is a schematic diagram of the pre-constructed false bottom plan for filling the inlet in the bottom column recycling method of the present invention; Figure 6 This is a schematic diagram of the recovery profile of the ore layer along the dip of the upper bottom pillar a of the ore layer according to the present invention; Figure 7 This is a schematic diagram of the cross-section of the filling of the bottom pillar a ore layer along the dip direction of the ore layer according to the present invention; Figure 8 This is a schematic diagram of the cross-section of the recovery of the ore layer along the dip of the upper bottom pillar b of the ore layer according to the present invention; Figure 9 This is a schematic cross-sectional view of the recovery of the upper bottom pillar along the strike of the ore layer according to the present invention; in, Figure 3 and Figure 5 The image only shows four of the eight mines.

[0024] In the diagram, a-1130 middle section bottom pillar a ore layer; b-1130 middle section bottom pillar b ore layer; 1-bottom plate, 2-upper filling body; 3-interlayer; 4-roof plate; 5-lower filling body; 6-footing stage transport tunnel; 7-footing stage transport tunnel; 8-vein tunnel; 9-vein tunnel; 10-suspended space gap; 11-access route; 12-prefabricated false bottom; 13-drilling and ore extraction tunnel; 14-blast hole; 15-cutting groove; 16-bottom pillar filling body. Detailed Implementation

[0025] In response to the technical problems pointed out in the background section, the specific implementation method will be based on the bottom pillar of the 1130 section of the Datang section of the Wengfu phosphate mine as an example, combined with the attached... Figure 1-9 The technical solution of the present invention will be further explained below.

[0026] It should be stated that the technical problem described in the background of this invention is illustrated using the Datang section of the Wengfu phosphate mine as an example, particularly its 1130 mid-section bottom pillar. The specific implementation method also uses the 1130 mid-section bottom pillar of the Datang section of the Wengfu phosphate mine as an example to introduce the technical solution of this invention. However, those skilled in the art should be able to conclude from this specific case that ore bottom pillars with the same or similar conditions should also have the same technical problem. That is, the technical problem in this invention is only introduced and explained using a specific example, but it is not limited to this specific example; the specific implementation method is the same.

[0027] like Figure 1As shown, the Wengfu phosphate mine's Datang section contains two ore layers, a and b, with a dip angle of 85°. Between layers a and b is an interlayer 3 approximately 3 meters thick. Ore layer a has an average thickness of 12.5 meters, located on the footwall side, with a base plate 1 at the bottom and interlayer 3 at the top. Ore layer b has an average thickness of 18.5 meters, located on the hanging wall side, with interlayer 3 at the bottom and a top plate 4 at the top. The 1130 section's base pillar is 15 meters high, with the upper part being an upper backfill body 2 formed from ore mined in the 1130 section, a 1:4 backfill body (the lower backfill body has greater strength); the lower part is a lower backfill body 5 formed from ore mined in the 1060 section, a 1:6 backfill body. Due to the effects of seepage and mining vibration, the top of the lower backfill 5 has shrunk significantly in some areas. This means that in some areas, a suspended gap 10 has formed between the bottom pillar of the 1030 middle section and the lower backfill 5, which means that the bottom pillar of the 1030 middle section cannot be fully supported on the lower backfill 5. Consequently, the bonding force between the bottom pillar of the b ore layer and the roof 4, as well as between the bottom pillar of the a ore layer and the interlayer 3, has decreased, and even a separation gap has appeared. If the blasting ore extraction process is used for recovery, there is a risk that the bottom pillar of the 1030 middle section will fall in a local area.

[0028] In order to safely recover the bottom column of section 1130, such as Figures 2-9 As shown, this invention proposes a method for efficient recovery of phosphate rock bottom pillars containing interlayers between upper and lower filling bodies, comprising the following steps: S1: As Figures 2-3 As shown; the original 1130 middle section upper stage transport level 7, lower stage transport level 6, and cross-cut level 9 were repaired. The cross-cut level 9 passes through the entire a ore layer, b ore layer, and interlayer 3, connecting the upper stage transport level 7 and lower stage transport level 6. The bottom plate elevation of the upper stage transport level 7, lower stage transport level 6, and cross-cut level 9 is consistent with the bottom plate elevation of the 1130 middle section pillar, which is 1130m, and the cross-sectional dimensions are 4×4m. The upper stage transport level 7 and lower stage transport level 6 are arranged along the strike of the ore layer, and the cross-cut level 9 is arranged perpendicular to the strike of the ore layer.

[0029] S2: As Figures 2-3 As shown; in the bottom plate 1, at the location where the bottom plate 1 is adjacent to the a ore layer, a cross-vein horizontal tunnel 8 is excavated along the ore layer from one cross-vein horizontal tunnel 9 to another cross-vein horizontal tunnel 9; in the top plate 4, at the location where the top plate 4 is adjacent to the b ore layer, a cross-vein horizontal tunnel 8 is excavated along the ore layer from one cross-vein horizontal tunnel 9 to another cross-vein horizontal tunnel 9; the cross-sectional dimensions of the two parallel cross-vein horizontal tunnels 8 are both 4×4m.

[0030] S3: As Figures 3-5As shown; the 1030 middle section bottom pillar is divided into 8 pillars along the strike, each pillar is 15m long along the strike; the height is the height of the entire pillar, and the length is the thickness of the a and b ore layers; that is, in this embodiment, the distance between the two cross-cut horizontal roadways 9 selected in step S1 along the strike is 120m; the pillar is divided into upper and lower layers in a 4:1 ratio in vertical height, where the upper layer is 12m and the lower layer is 3m; S4: As Figures 3-5 As shown; the lower layer is mined using a backfilling method, with a mining elevation of 1030-1033m. A single, unfilled access road 11 is reserved at the bottom of each pillar as a drilling and ore-exit roadway 13 for the upper layer mining. Specifically: for each pillar's lower layer, it is divided into 5 dip-extending access roads 11 along the strike and numbered sequentially, each access road being 3m wide. First, access road 4 of all pillars is mined, backfilled after mining; then access road 2 of all pillars is mined, backfilled after mining; then access road 5 of all pillars is mined, backfilled after mining; then access road 11 of all pillars is mined, backfilled after mining; finally, access road 3 of all pillars is mined but not backfilled. The backfill material uses a ratio of 1:2, 1:3, or 1:4, with 1:2 or 1:3 being preferred. Then, the No. 3 access road, which is opposite to the A and B ore layers, is connected to serve as the drilling and ore extraction roadway 13 for layered mining of the pillar. Since the cross-sectional size of the access road is only 3×3m and the access roads 11 being mined at the same time are far apart, even if there are suspended gaps 10 in some areas of the pillar, it can still be safely mined back. When the access road 11 is filled after mining, the suspended gaps 10 can be eliminated (filled) at the same time. Finally, the bottom plate of the No. 3 access road of all pillars is smoothed. Through access road mining and filling, a solid false bottom is formed under the pillar in the middle section of 1130, so that even if the upper layer is blasted to extract ore, it can still be carried out safely without worrying about the pillar shifting down a lot.

[0031] Among them, the lower-level access road mining is preferably carried out by tunneling machines, and the number of access roads to be mined simultaneously can be set according to the number of tunneling machines.

[0032] Ore extraction path: For the sub-layer below the pillar of ore layer A, the ore extracted by the inlet is first transported to the side vein level 8 of ore layer A, and then transported to the footing stage level 6 via the first cross vein level 9; For the sub-layer below the pillar of ore layer B, the ore extracted by the inlet is first transported to the side vein level 8 of ore layer B, and then transported to the footing stage level 6 via the first cross vein level 9.

[0033] Ventilation path: Fresh air enters from the lower stage transport level 6 through the second through-vein level 9, and then enters two along-vein level 8 to ventilate the intake 11. After passing through the along-vein level 8, it is collected in the second through-vein level 9, and then discharged through the upper stage transport level 7.

[0034] In this embodiment, Figure 3 For example, the cross-vein tunnel near the reference numeral 3 in the attached diagram is defined as the first cross-vein tunnel, and the other is defined as the second cross-vein tunnel.

[0035] S5: As Figure 6-9 As shown; for the upper layers of each pillar; the pillars are sequentially mined and filled along the strike using drilling and ore-exit roadways 13, or the odd-numbered pillars are first mined and filled sequentially along the strike, and then the even-numbered pillars are mined and filled sequentially; for the upper layers of each pillar, the specific mining and filling methods are as follows: The ore pillar is layered, and the a-layer is mined first from the interlayer 3 towards the bottom plate 1 (if the b-layer is mined first, the interlayer will be under greater pressure during mining, which will easily cause the thinner interlayer to break. Since mining the a-layer under the broken interlayer is dangerous, this invention proposes to mine the a-layer first). Since the adhesion between the a-layer and the interlayer 3 is small and there is delamination in some areas, it is convenient to construct the cutting groove 15 on the side of the a-layer close to the interlayer 3; then, fan-shaped blast holes 14 are constructed upward in rows in the rock drilling and ore extraction roadway 13, with rows diagonally separated. The ore is blasted sequentially from interlayer 3 towards the bottom plate 1 to the drilling and ore extraction roadway 13. The ore is then extracted from the drilling and ore extraction roadway 13 to the horizontal roadway 8 along the vein near the bottom plate and transported out. After that, backfilling is carried out. During backfilling, the drilling and ore extraction roadway 13 is restored at the original location. For example, a door-shaped template with a cross-sectional dimension of 3×3m is set at the original location of the drilling and ore extraction roadway 13. During backfilling, the drilling and ore extraction roadway 13 can be formed under the door-shaped template (the backfilling material does not enter the door-shaped template). Then, the b ore layer is mined from the top plate 4 towards the interlayer 3. Since the adhesion between the b ore layer and the top plate 4 is small and there is delamination in some areas, it is convenient to construct the cutting groove 15 on the side of the b ore layer near the top plate 4. After that, fan-shaped blast holes 14 are constructed in rows upward in the drilling and ore extraction roadway 13, with the rows distributed at intervals along the dip. The ore is blasted from the top plate 4 towards the interlayer 3 to the drilling and ore extraction roadway 13, and the ore is extracted from the drilling and ore extraction roadway 13 to the vein level roadway 8 on the side near the top plate and then transported out. Then, backfilling is carried out, and the drilling and ore extraction roadway 13 in the entire pillar is filled together.

[0036] Ore extraction path: Ore layer a and ore layer b are the same. The ore is extracted from the rock and the ore extraction roadway 13 passes through the side vein horizontal roadway 8 of ore layer a, and then through the first cross vein horizontal roadway 9 to the lower stage transport horizontal roadway 6. Ventilation path: The same for ore layers A and B. Fresh air enters the side vein level 8 of ore layer A from the lower stage transport level 6 through the second cross vein level 9, then enters the drilling and ore extraction level 13, washes the stope, and then enters the side vein level 8 of ore layer B. After that, it is transported through the first cross vein level 9 to the upper stage transport level 7 for discharge.

[0037] To improve the working environment and ensure safety during the upper-layer blasting and ore extraction, this invention involves mining both the A and B ore layers from the top to the bottom, allowing drilling and ore extraction to be carried out under the protection of the drilling and ore extraction roadway 13 as much as possible. At the same time, to improve ventilation quality, the drilling and ore extraction roadway 13 is retained after the A ore layer is mined, and only the A ore layer side-mounted horizontal roadway 8 is used for ore extraction, while only the B ore layer side-mounted horizontal roadway 8 is used for return air.

[0038] This invention is not limited to the preferred embodiments described above. Anyone can derive other methods in various forms under the guidance of this invention. Any technical solution that is the same as or similar to this application falls within the protection scope of this invention.

Claims

1. A method for safe recovery of phosphate rock bottom pillars based on pre-constructed false bottoms, used in steeply inclined phosphate mines, wherein one side of the interlayer consists of ore layer A and a bottom plate, and the other side consists of ore layer B and a top plate, with the bottom pillar consisting of filling bodies both above and below it, and a suspended space gap existing between the bottom pillar and the lower filling body, characterized in that... Includes the following steps: S1: Prepare the upper plate stage transport level, the lower plate stage transport level, and two cross-beam level. The upper plate stage transport level and the lower plate stage transport level extend along the direction, and the two cross-beam level connect the upper plate stage transport level and the lower plate stage transport level. S2: Construct two cross-vein horizontal tunnels adjacent to the ore layers on the side of ore layer a and ore layer b away from the interlayer, respectively; S3: Divide the bottom pillar into several pillars along the strike, with the height being the height of the entire pillar and the length being the thickness of ore layer a and ore layer b; divide the pillar into upper and lower layers vertically. S4: For each lower layer of a pillar, divide it into 5 dipping passes along the strike and number them sequentially; first mine and fill pass 4, then pass 2, pass 5, and pass 1; finally mine only pass 3 but do not fill it; then connect pass 3, which is opposite to ore layer a and ore layer b on the dip, as the drilling and ore extraction roadway when mining the upper layer of the pillar. S5: For the upper layers of each pillar, the blasting and mining roadways are used to create open spaces for ore extraction, followed by filling. First, the a-layer is mined and filled from the interlayer towards the bottom plate, and then the b-layer is mined and filled from the top plate towards the interlayer. During the filling of the a-layer, the blasting and mining roadways are restored.

2. The method for safe recovery of phosphate rock pillars based on pre-constructed false bottoms according to claim 1, characterized in that, In step S1, the floor slabs of the upper stage transport level, the lower stage transport level, and the cross-cut level are at the same elevation as the floor slabs of the bottom pillars.

3. The method for safe recovery of phosphate rock pillars based on pre-constructed false bottoms according to claim 2, characterized in that, In step S2, in the bottom plate, at the location where the bottom plate is adjacent to ore layer a, a cross-vein tunnel is excavated along the ore layer direction from one cross-vein tunnel to another cross-vein tunnel; in the top plate, at the location where the top plate is adjacent to ore layer b, a cross-vein tunnel is excavated along the ore layer direction from one cross-vein tunnel to another cross-vein tunnel.

4. The method for safe recovery of phosphate rock pillars based on pre-constructed false bottoms according to claim 1, characterized in that, In step S3, each pillar is 15m long along the strike; the pillar is divided into upper and lower layers vertically in a ratio of 4:

1.

5. The method for safe recovery of phosphate rock pillars based on pre-constructed false bottoms according to claim 4, characterized in that, In step S4, each access road is 3m wide; and / or, the filling material is 1:2 or 1:3; and / or, the bottom plate of access road No. 3 is leveled for all pillars; and / or, the lower layer access road is excavated using a tunneling machine.

6. The method for safe recovery of phosphate rock pillars based on pre-constructed false bottoms according to claim 1 or 5, characterized in that, In step S4, the ore extraction path is as follows: For the sub-layer below the pillar of ore layer a, the ore extracted by the inlet is first transported to the side vein level roadway of ore layer a, and then transported to the footing stage transport roadway through the first cross vein level roadway; For the sub-layer below the pillar of ore layer b, the ore extracted by the inlet is first transported to the side vein level roadway of ore layer b, and then transported to the footing stage transport roadway through the first cross vein level roadway, where the first cross vein level roadway is one of two cross vein level roadways.

7. The method for safe recovery of phosphate rock pillars based on pre-constructed false bottoms according to claim 6, characterized in that, In step S4, the ventilation path is as follows: fresh air enters the two along-the-vein level from the lower plate stage transport level through the second through-the-vein level, ventilates the incoming path, and then gathers in the second through-the-vein level through the along-the-vein level, and is then discharged through the upper plate stage transport level. The second through-the-vein level is the other of the two through-the-vein level.

8. The method for safe recovery of phosphate rock pillars based on pre-constructed false bottoms according to claim 1, characterized in that, In step S5, the layers on each pillar are mined and filled sequentially along the strike, or the layers on the odd-numbered pillars are mined and filled sequentially first, and then the layers on the even-numbered pillars are mined and filled sequentially. And / or, cut grooves are constructed on the interlayer side of ore layer a, and cut grooves are constructed on the top plate side of ore layer b.

9. The method for safe recovery of phosphate rock pillars based on pre-constructed false bottoms according to claim 1 or 8, characterized in that, In step S5, the ore extraction path is the same for ore layer a and ore layer b. The ore is extracted from the rock and the ore extraction roadway passes through the side vein level roadway of ore layer a, and then is transported to the lower stage transport level roadway through the first through vein level roadway. The first through vein level roadway is one of the two through vein level roadways.

10. The method for safe recovery of phosphate rock pillars based on pre-constructed false bottoms according to claim 1 or 8, characterized in that, In step S5, the ventilation path is the same for ore layers a and b. Fresh air enters the side vein level of ore layer a from the lower stage transport level through the second cross vein level, then enters the drilling and ore extraction level, washes the stope, and then enters the side vein level of the ore layer. After that, it is transported through the first cross vein level to the upper stage transport level for discharge. The second cross vein level is the other of the two cross vein level levels.

Images