Mining method for recovering roof pillars by small entry filling under loose tailings filling

Abstract

The application discloses a mining method for recovering a top pillar by small access filling under loose tailings filling, and relates to the technical field of underground mining methods. The method comprises the following steps: dividing the top pillar into a plurality of layers along a vertical direction, dividing each layer into a plurality of ore blocks along a strike direction, and not arranging a pillar in each ore block; excavating a layer connecting passage to each layer stope, excavating a cutting flat roadway, and excavating a cutting horizontal roadway to connect upper and lower discs from the cutting flat roadway; adopting a top-down layering stoping mode, and adopting a scheme of stoping two ore blocks at the same time; arranging a plurality of small accesses in the ore block, advancing the small access for stoping, and immediately filling the small access with tailings after stoping; immediately filling the cutting horizontal roadway with tailings after stoping and filling of all the small accesses in the ore block are completed; and repeating the above steps until the top pillar in the current stage is completely recovered. The mining method reduces the exposed area of the stope access, and has good stability.

Description

Technical Field

[0001] This invention relates to the field of underground mining methods, specifically to a mining method for recovering the top pillar by small-path backfilling under loose tailings backfill. Background Technology

[0002] Backfilling mining is suitable for mining high-grade, rare, and valuable ores in unstable surrounding rock, as well as ores where surface subsidence is not permitted and mining conditions are complex. Traditional backfilling mining typically divides the ore block into stops and pillars, and mines in two stages. During stope mining, as ore is extracted, the goaf is gradually filled with backfill material. After the stops are mined and filled, the pillars are systematically mined. Backfilling mining is characterized by its high adaptability and low ore dilution rate.

[0003] However, when the top pillar is filled with loose tailings, some technical problems still exist when using the backfill mining method:

[0004] (1) When the mine adopts the backfilling method for mining, the strength of the tailings backfill is low. If it is not handled properly, it may induce the overall collapse of the loose tailings backfill, causing major casualties or property and equipment losses. (2) When the top pillar is a loose tailings backfill, a certain thickness of protective top layer needs to be left to ensure the stability of the mining area, thereby ensuring the safety of personnel and equipment.

[0005] Therefore, how to reduce the exposed area of ​​the mining access road and minimize the thickness of the top support layer while ensuring safety is one of the urgent technical challenges to be solved in recovering the top pillar resources under loose tailings backfill. Summary of the Invention

[0006] The purpose of this invention is to provide a mining method for recovering the top pillar by backfilling with a small access road under a loose tailings backfill body. This method can reduce the exposed area of ​​the stope access road and recover mineral resources as much as possible while ensuring safety.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A mining method for recovering roof pillars by small-entry backfilling under loose tailings backfill, wherein a stage haulage level is arranged in the stage above the roof pillar, including the following steps:

[0009] Step 1: Divide the top pillar into several layers along the vertical direction, and reserve a certain thickness of protective top layer above the uppermost layer; divide each layer into several blocks along the strike direction, and do not leave any pillars in each block;

[0010] Step 2: Using the stage transport roadway level roadway arranged in the previous stage, excavate a layered connecting roadway to each layered stope, and excavate a cutting level roadway along the lower contact zone. From the cutting level roadway, excavate a cutting cross roadway perpendicular to the center of each block to connect the upper and lower sides. When excavating the cutting cross roadway, the roof needs to be supported in time.

[0011] Step 3: Use a bottom-up, layered mining approach, and employ a scheme of mining two blocks simultaneously at intervals.

[0012] Step 4: Arrange several small access roads in the same direction along the strike within the ore block. Proceed mining from the center to the two wings and from the upper plate to the lower plate. Mining each small access road simultaneously within a ore block. After mining is completed, immediately backfill the small access roads with tailings.

[0013] Step 5: After all the small access roads in the ore block have been mined and backfilled, immediately backfill the cutting cross passages with tailings.

[0014] Step 6: Repeat steps 4 and 5 until all the ore blocks in this layer have been mined and filled.

[0015] Step 7: Repeat Step 6 until all layers of ore in the top pillar except for the top protective layer have been mined and filled in this stage.

[0016] The above-mentioned mining method for recovering the top pillar by backfilling with small access roads under a loose tailings backfill body, wherein the width of the ore block is the sum of the lengths of the two small access roads along the strike direction and the length of the cross section of the cutting transverse roadway, and the width of the small access road within the ore block is 3m and the length is 4-6m.

[0017] The above-mentioned mining method for recovering roof pillars by using a small-entry backfill under a loose tailings backfill body involves using a top protection layer to isolate the stope from the overlying loose tailings backfill body. The thickness of the top protection layer corresponding to the cutting cross passage and the small-entry backfill is calculated using the limit equilibrium theory.

[0018] In the above-mentioned mining method for recovering roof pillars by small-entry backfilling under loose tailings backfill, in step two, immediate support is adopted for the two sides and the roof when the cross tunnel is excavated and cut. The layered connecting tunnels are arranged in an alternating manner. The length of the layered connecting tunnels varies with the height of the layer. When the layer is lower, the length of the layered connecting tunnel is longer and the slope is reduced.

[0019] In the above-mentioned mining method for recovering the top pillar by small-entry backfilling under a loose tailings backfill body, in step two, the layered connecting channels are arranged in an alternating manner, and the length of the layered connecting channels varies with the height of the layers. When the layer is lower, the length of the layered connecting channels is longer and the slope is reduced.

[0020] In the above-mentioned mining method for recovering roof pillars by small-entry backfilling under loose tailings backfill, in step two, during the excavation and cutting of the transverse roadway, the roof is supported by a "metal mesh + anchor bolt" method, and the anchor bolts are prestressed threaded steel anchor bolts.

[0021] In the above-mentioned mining method for recovering the top pillar by small-entry backfilling under loose tailings backfill, in step three, the ore blocks in each layer are numbered sequentially from left to right and divided into two mining steps. The first step mines the ore blocks with odd numbers, and the second step mines the ore blocks with even numbers.

[0022] In the above-mentioned mining method for recovering the top pillar by small-entry backfilling under a loose tailings backfill body, in step four, the backfill material used in the tailings backfill body has a ash-sand ratio of 1:8.

[0023] The above-mentioned mining method for recovering the top pillar by backfilling with a small access road under a loose tailings backfill body, wherein the small access road in the ore block is mined by drilling horizontal holes and blasting to extract the ore.

[0024] In the above-mentioned mining method of small-entry backfilling and recovery of the top pillar under loose tailings backfill, the mined ore is transported to the cutting level through the cutting cross roadway, and then transported to the stage transport level through the layered connecting roadway for outgoing transport.

[0025] Compared with the prior art, the present invention brings the following beneficial technical effects:

[0026] (1) This invention proposes a mining method for recovering the top pillar by small-path filling under loose tailings backfill. The method involves excavating a cutting cross passage perpendicular to the center of each ore block through a cutting horizontal passage to connect the upper and lower plates. The ore block is further divided into several small passages along the strike direction along the cutting cross passage, which reduces the exposed area of ​​the mining access and ensures the safety of the mining area and personnel and equipment.

[0027] (2) The method of the present invention can recover the top pillar. Since the small access road has a small exposed area, it ensures the safe production of the mining area. Therefore, it can reduce the thickness of the top protection layer, reduce the loss and dilution of ore, and provide a practical method for the recovery of the top pillar under the loose tailings backfill.

[0028] In addition, this method has the advantages of simple construction, simple process, flexible mining, safety and high efficiency. Attached Figure Description

[0029] The present invention will be further described below with reference to the accompanying drawings:

[0030] Figure 1 This is a schematic diagram of the layout of the mining method of small-entry backfill recovery of the top pillar under the loose tailings backfill body of the present invention.

[0031] Figure 2 for Figure 1 Schematic diagram of section I-I in the diagram;

[0032] Figure 3 yes Figure 1 Schematic diagram of section II-II in the diagram;

[0033] Figure 4 This is a schematic diagram of the cross-slope support method;

[0034] In the diagram: 1-Loose tailings backfill; 2-Roofing layer; 3-Roof pillar; 4-Stage transport tunnel; 5-Cutting tunnel; 6-Layered connecting road; 7-Small access road; 8-Cutting cross tunnel; 9-Metal mesh; 10-Anchor bolt. Detailed Implementation

[0035] This invention proposes a mining method for recovering the top pillar by small-entry backfilling under loose tailings backfill. To make the advantages and technical solutions of this invention clearer and more explicit, the invention will be further described below with reference to specific embodiments.

[0036] The tailings backfill material used in this invention has a ash-to-sand ratio of 1:8.

[0037] Combination Figures 1 to 4 As shown, this invention discloses a mining method for recovering roof pillars using a small-entry backfill method under loose tailings backfill. Its applicable scope is: when the surrounding rock of the hanging wall and footwall of the roof pillar is stable, and a staged haulage roadway is arranged in the previous stage of the roof pillar. The mining method includes the following steps:

[0038] Step 1: Divide the top pillar 3 into several layers along the vertical direction, and reserve a certain thickness of protective layer 2 above the top layer; divide each layer into several blocks along the strike direction, and do not leave any pillars in each block.

[0039] Step 2: Using the stage transport roadway level roadway from the previous stage, excavate a level connecting roadway 6 to each level mining area, and excavate a cutting level roadway 5 along the lower contact zone. From the cutting level roadway, excavate a cutting cross roadway 8 perpendicular to the center of each block to connect the upper and lower plates. When excavating the cutting cross roadway, the roof needs to be supported in time.

[0040] The connecting passages between each layer are arranged in a staggered manner. The length of the connecting passages varies with the elevation of the layer; the lower the layer, the longer the connecting passage and the smaller the slope. During the excavation and cutting of the transverse roadway, the roof is supported by a "metal mesh 9 + anchor bolt 10" method, with prestressed threaded steel anchor bolts used.

[0041] Step 3: Use a bottom-up, layered mining approach, and employ a scheme of mining two blocks simultaneously at intervals.

[0042] Number the blocks in each layer from left to right, such as "1, 2, 3, ...". Divide the mining into two steps. The first step is to mine from left to right the odd-numbered blocks 1, 3, 5, 7, 9, 11, ... The second step is to mine from left to right the even-numbered blocks 2, 4, 6, 8, 10, 12, ...

[0043] Step 4: Arrange several small access roads 7 in the same direction along the strike within the ore block. Advance the small access roads from the center to the two wings and from the upper plate to the lower plate. Simultaneously mine two small access roads opposite each other in the cutting cross roadway within one ore block. After mining is completed, immediately backfill the small access roads with tailings.

[0044] The width of the ore block is the sum of the lengths of the two small access roads along the strike direction and the cross-sectional length of the cutting cross roadway. The width of the small access roads within the ore block is 3m, and the length is 4-6m. The small access roads are advanced by drilling horizontal holes and blasting to extract ore. The extracted ore is transported to the cutting level roadway via the cutting cross roadway, and then to the stage transport level roadway 4 via the layered connecting roadway. Since the top pillar is filled with loose tailings 1, in order to prevent large-scale collapse, the thickness of the top cover corresponding to the cutting cross roadway and the small access roads is calculated using the limit equilibrium theory. When mining the top pillar of the uppermost layer, controlled blasting is adopted to reduce the disturbance of blasting to the stope, including minimizing the amount of explosives used and shortening the blasting advance, in order to minimize the disturbance of blasting vibration to the stope.

[0045] Step 5: After all the small access roads in the ore block have been mined and backfilled, immediately backfill the cutting cross passages with tailings.

[0046] Step 6: Repeat steps 4 and 5 until all the ore blocks in this layer have been mined and filled.

[0047] Step 7: Repeat Step 6 until all layers of ore in the top column, except for the top protective layer, have been mined and filled in this stage.

[0048] The mining method of recovering roof pillars under loose tailings backfill involves excavating a cutting cross passage perpendicular to the strike direction at the center of each ore block during the recovery of roof pillars in loose tailings backfill. This cross passage connects the hanging wall and footwall. The ore block is further divided into several small access passages along the strike direction, reducing the exposed area of ​​the access passages and ensuring the safety of the stope and personnel / equipment. Because of the small exposed area of ​​the small access passages, safe production in the stope is ensured, thus reducing the thickness of the top cover and minimizing ore loss and dilution. This provides a practical method for recovering roof pillars under loose tailings backfill. Furthermore, this method has advantages such as simple construction, straightforward process, flexible mining, and high safety and efficiency.

[0049] Example 1:

[0050] To further illustrate the beneficial technical effects of the loose tailings backfilling and recovery of the top pillar mining method of the present invention, the method of the present invention will be further explained using the 755-855 section of the north wing of a certain mine as an example.

[0051] The mine employs a segmented open-cut backfilling method for mining the 755-855m section of the north wing. Currently, the goaf in the 755m section (No. 1 ore body) has been largely treated. In the 805m section, some goaf areas are being backfilled with 1:10 graded tailings, and no false bottom has been constructed. The plan is to fully recover the roof pillars in the 755m section. These pillars are 70m long, have an average thickness of 15m, and a height of 10m, with a uniformly distributed overburden load of 0.28MPa. The mining method of this invention, using a small-path backfilling method to recover the roof pillars, is employed. Each layer is 3m high, divided into three layers (the uppermost layer is 4m high). Each layer is further divided into several blocks along the strike direction, with each block being 14m long. Ten small paths, each 3m wide and 5.5m long, are divided along the strike by a cutting crossroads.

[0052] To compare with the reserved top layer thickness in the upward layered approach backfilling mining method, the required top layer thickness was calculated based on the limit equilibrium theory:

[0053]

[0054] Where: h—safety thickness of the top protective layer, m;

[0055] σ t —Tensile strength of the ore body, MPa;

[0056] a—Route length, in meters;

[0057] b—Road width, m.

[0058] The thickness of the top support is mainly affected by its access dimensions and the tensile strength of the ore body. Using the Hoek-Brown strength criterion, the rock mechanical parameters are reduced, resulting in a tensile strength of 1.4 MPa for the top support. When using the upward-slicing layered access mining method, with an exposed area of ​​15m × 5m for one access, the calculated thickness of the top support is approximately 0.7498m; considering practical engineering needs, it is set at 0.8m. When using the small-access upward-slicing layered access mining method, with an exposed area of ​​14m × 3m for one ore block, the calculated thickness of the top support is approximately 0.4084m; considering practical engineering needs, it is set at 0.5m.

[0059] Compared to the thickness of the protective top layer left by the original mining method, an additional 0.3m of pillar ore can be extracted. Based on an ore body density of 3.6t / m³... 3 Calculations show that one stope can extract an additional ore quantity of 14m × 15m × 0.3m × 3.6t / m.3 ×5=1134t. Based on a grade of 3.7g / t, an additional 4195.8g of gold can be recovered. Based on the market price of gold of 410 yuan / g, a single mine can generate a profit of 1.7203 million yuan.

[0060] The following calculation outlines the costs of prestressed anchor bolts and metal mesh support required for the small-entry backfill mining method, where the dimensions of the roof of the cutting cross passage are 3m × 15m. Based on a spacing of 1m × 1m, 28 anchor bolts are needed for one cutting cross passage, costing 28,000 yuan per bolt at 1000 yuan. The cost of the metal mesh for the roof is calculated at 30 yuan / m. 2 Calculations show that a cutting cross passage requires 45m. 2 ×30=1350 yuan; Considering the costs of water, electricity, ventilation, pipeline laying, transportation, and equipment wear and tear, the installation cost is approximately 40 yuan / m. 3 The topmost layer consists of a single cross passageway measuring 3m × 3.5m × 15m = 157.5m. 3 The calculation is 6300 yuan. Other sections are divided into layers, with each section consisting of a 3m × 3m × 15m = 135m section. 3 The calculated cost is 5400 yuan. The total support cost for one mining area is approximately 10.515 × 5 = 52.58 million yuan.

[0061] For any excess ore extracted, the goaf needs to be backfilled using the tailings cemented backfill method, thus requiring calculation of additional backfilling costs. The cementing material is 425# ordinary Portland cement, the backfill aggregate consists of tailings from the mine's tailings dam and crushed stone transported from underground, and the backfill water is mine wastewater. A 1:8 cement-sand ratio is used, meaning a cement content of 100 kg / m³. 3 Based on a price of 300 yuan per ton, and considering the costs of tailings, gravel, and water, the cost is approximately 50 yuan per cubic meter. 3 The filling process includes factors such as ventilation, slurry preparation, transportation, equipment wear and tear, power supply, water supply, and drainage, with an estimated cost of 30 yuan / m³. 3 Total: 80 yuan / m 3 According to the formula: 15m × 14m × 0.3m × 5 = 315m 3 Based on spatial calculations, the cost of filling materials required for one mining area is 25,200 yuan.

[0062] In summary, when the roof pillar of the mining area is recovered using this invention, an additional revenue of 172.03 - 52.58 - 2.52 = 116.93 million yuan can be obtained from a single mining area. It can be seen that, under the premise of ensuring safe production, the method of this invention improves the efficiency of the mine.

[0063] For any parts not mentioned in this invention, existing technologies can be used or referenced.

[0064] Although this document frequently uses terms such as loose tailings backfill 1, top cover 2, and top column 3, the possibility of using other terms is not excluded. These terms are used merely for the convenience of describing and explaining the essence of the invention; interpreting them as any additional limitation would be contrary to the spirit of the invention.

[0065] It should be further noted that the specific embodiments described herein are merely illustrative examples to illustrate the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A mining method for recovering roof pillars by small-entry backfilling under loose tailings backfill, characterized in that a stage haulage level is arranged in the stage above the roof pillar, wherein... Includes the following steps: Step 1: Divide the top pillar into several layers along the vertical direction, and reserve a protective layer of a certain thickness on the top layer; divide each layer into several blocks along the strike direction, and do not leave any pillars in each block; Step 2: Using the stage transport roadway level roadway arranged in the previous stage, excavate a layered connecting roadway to each layered stope, and excavate a cutting level roadway along the lower contact zone. From the cutting level roadway, excavate a cutting cross roadway perpendicular to the center of each block to connect the upper and lower sides. When excavating the cutting cross roadway, the roof needs to be supported in time. Step 3: Use a bottom-up, layered mining approach, and employ a scheme of mining two blocks simultaneously at intervals. Step 4: Arrange several small access roads in the same direction along the strike within the ore block. Proceed mining from the center to the two wings and from the upper plate to the lower plate. Mining each small access road simultaneously within a ore block. After mining is completed, immediately backfill the small access roads with tailings. Step 5: After all the small access roads in the ore block have been mined and backfilled, immediately backfill the cutting cross passages with tailings. Step 6: Repeat steps 4 and 5 until all the ore blocks in this layer have been mined and filled. Step 7: Repeat Step 6 until all layers of ore in the top column, except for the top layer, have been mined and filled in this stage. The width of the ore block is the sum of the lengths of the two small access routes along the strike direction and the length of the cross section of the cutting transverse roadway. The width of the small access routes within the ore block is 3m, and the length is 4-6m.

2. The mining method for recovering the top pillar by small-entry backfilling under a loose tailings backfill body according to claim 1, characterized in that: The aforementioned top cover isolates the stope from the overlying loose tailings backfill. The thickness of the top cover corresponding to the cutting cross passage and the small access road is calculated using the limit equilibrium theory.

3. The mining method for recovering the top pillar by small-entry backfilling under a loose tailings backfill body according to claim 1, characterized in that: In step two, the layered connecting channels are arranged in an alternating manner, and the length of the layered connecting channels varies with the height of the layers. When the layer is lower, the length of the layered connecting channels is longer and the slope is smaller.

4. The mining method for recovering the top pillar by small-entry backfilling under a loose tailings backfill body according to claim 1, characterized in that: In step two, during the excavation and cutting of the transverse tunnel, the roof is supported by a "metal mesh + anchor bolt" method, with prestressed threaded steel anchor bolts used.

5. The mining method for recovering the top pillar by small-entry backfilling under a loose tailings backfill body according to claim 1, characterized in that: In step three, the ore blocks within each layer are numbered sequentially from left to right, and the mining is divided into two steps. In the first step, the ore blocks with odd numbers are mined, and in the second step, the ore blocks with even numbers are mined.

6. The mining method for recovering the top pillar by small-entry backfilling under a loose tailings backfill body according to claim 1, characterized in that: In step four, the backfill material used for the tailings backfill has a ash-sand ratio of 1:

8.

7. The mining method for recovering the top pillar by small-entry backfilling under a loose tailings backfill body according to claim 1, characterized in that: The small access routes within the ore block are mined by drilling horizontal holes and blasting.

8. The mining method for recovering the top pillar by small-entry backfilling under a loose tailings backfill body according to claim 1, characterized in that: After mining, the ore is transported through the cutting cross tunnel to the cutting level tunnel, and then through the layered connecting tunnel to the stage transport level tunnel for disposal.

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