A two-step backfill mining method for layerwise extraction of gently inclined ore bodies with interlayers

Abstract

The application discloses a two-step filling mining method for layered recovery of a gently inclined ore body containing interlayer, and belongs to the technical field of mineral exploitation. The method comprises the following steps: vertically dividing the gently inclined ore body containing interlayer into three recovery layers from bottom to top, and arranging a sectional roadway at the position of the interlayer between the two layers; adopting a two-step recovery process, first recovering the second recovery layer containing the interlayer in the middle, protecting the roof, then recovering the triangular ore body in the first recovery layer at the bottom by means of waste rock replacement, and filling the goaf of the first and second recovery layers by once filling with high-strength filling body after the construction of a filling retaining wall; and in the second step, after the strength of the filling body reaches the standard, the third recovery layer at the top is recovered and the roof is protected, and the goaf is filled with low-strength filling body after the construction of a retaining wall. The method can effectively deal with the interlayer, improve the recovery rate and safety, and is suitable for the exploitation of the gently inclined ore body containing interlayer.

Description

Technical Field

[0001] This invention relates to the field of mineral mining technology, and in particular to a two-step backfilling mining method for mining gently dipping ore bodies with interlayers. Background Technology

[0002] Gently dipping ore bodies are a common type of ore body in underground mining, and the choice of mining method directly affects ore recovery rate, mining safety, and economic benefits. Traditional mining of gently dipping ore bodies mainly uses methods such as room-and-pillar method and layered backfilling method. However, when faced with complex geological conditions containing interlayers, these methods often fail to achieve ideal mining results.

[0003] Currently, various technical solutions exist for mining gently dipping ore bodies. Chinese patent CN105587318B discloses a backfilling mining method for continuous mining of gently dipping parallel medium-thick ore body groups. This method divides the gently dipping parallel ore body group into middle sections and adopts a bottom-up, layer-by-layer mining approach, achieving simultaneous mining of multiple ore veins. Chinese patent CN117514175A discloses a mining method suitable for gently dipping medium-thick multi-layer phosphate deposits, improving stope stability through a combination of pseudo-dipping approach backfilling and room-and-pillar mining. Chinese patent CN120592629B discloses an upward horizontal layered backfilling mining method for gently dipping-dipping thick ore bodies, employing a bottom-up, layered mining approach to solve the problem of large preparation workload in traditional methods. Chinese patent CN117386368B discloses an efficient backfilling mining method for the separate mining of gently dipping double-layer ore bodies, avoiding dilution problems caused by ore mixing by mining the upper and lower ore bodies sequentially.

[0004] However, existing technologies still have many shortcomings in mining gently dipping ore bodies with interlayers: First, traditional layered mining methods are difficult to effectively handle interlayer problems, easily causing ore mixing, resulting in low ore recovery rates and high dilution rates; second, existing open-cut mining methods suffer from low mechanization, high labor intensity for workers, and poor safety, and are prone to overlying rock collapse after ore body mining, causing damage to the surrounding safety and ecological environment; third, existing mining methods lack effective backfilling strategies during the layered mining of gently dipping ore bodies, making it difficult to ensure the stability of the goaf; finally, for double-layered ore bodies, especially when the upper and lower ore bodies have different mineral types and the upper ore and rock are unstable, traditional methods cannot effectively solve the problem of the stability of the lower layer's roof and the large number of triangular ore body mining problems, affecting the overall mining efficiency and economic benefits. Summary of the Invention

[0005] To address the challenges of efficient stratified mining in traditional gently dipping orebody mining methods, which result in low ore recovery rates, high dilution rates, and high mining costs, as well as the problems of low recovery rates, low mechanization, high labor intensity, and poor safety in existing open-pit mining methods, this paper proposes a two-step backfilling mining method for stratified mining of gently dipping orebody containing interlayers. This method aims to achieve efficient stratified mining of gently dipping orebody, effectively improve orebody recovery rates, and reduce dilution rates.

[0006] The technical solution adopted by this invention to solve its technical problem is as follows: This invention provides a two-step backfilling mining method for layered mining of gently dipping ore bodies containing interlayers, including a lower ore layer (1), an interlayer (2), a lower sub-section roadway (3), a lower sub-section pillar (4), a second mining layer (5), a third mining layer (6), a backfilling retaining wall (7), an upper sub-section pillar (8), an upper sub-section roadway (9), an upper sub-section triangular ore body (11), a first mining layer (12), and a lower sub-section triangular ore body (13). The method includes: The first step involves layered mining in the middle of the interlayer and layered mining in the lower part, followed by high-strength backfilling. The second step involves layered mining of the upper section and low-intensity backfilling.

[0007] As a preferred technical solution, the 28-day uniaxial compressive strength of the high-strength filling body is ≥2.5MPa, and the 28-day uniaxial compressive strength of the low-strength filling body is ≥1.2MPa.

[0008] As a preferred technical solution, the first step includes: Step 101: The second mining layer (5) containing the interlayer (2) in the middle of the ore body is mined by the upper segment direction through the lower segment roadway (3) and the top is protected by anchor mesh spraying. The mining is carried out by segmented deep hole blasting. Step 102: Immediately afterwards, the first mining layer (12) is mined. During the mining process, the waste rock replacement method is used to mine the lower triangular ore body (13) and the upper triangular ore body (11) of the first mining layer (12) which are close to the two sections. Step 103: After the first and second layers of the lower part of the ore body have been mined, the goaf of the first and second mining layers is filled in one go after the side walls (7) are built. The filling material is high-strength filling body.

[0009] As a preferred technical solution, the second step includes: Step 201: After the strength of the filling material from the first step reaches the standard, proceed with the second step of backfilling. Step 202: From the upper segment roadway (9) to the lower segment roadway (3), the third mining layer (6) located in the upper part of the ore body is mined. The roof is protected by anchor bolts and shotcrete. One bolt and one shotcrete are used for each excavation cycle (i.e., anchor bolt support and shotcrete are carried out immediately after each excavation cycle). Step 203: After the mining is completed, construct a filling retaining wall (7) on one side of the upper section and fill it with low-strength filling material.

[0010] As a preferred technical solution, the ore body is a gently dipping ore body containing interlayer (2). The interlayer (2) is located between two layers of ore. The vein is developed and prepared, and the segmented roadway is located between the two layers of ore, that is, the segmented roadway exposes the interlayer (2).

[0011] As a preferred technical solution, the vertical direction is divided into three mining layers from bottom to top: the bottom first mining layer (12), the middle second mining layer (5) containing the interlayer (2), and the top third mining layer (6).

[0012] Compared with the prior art, the advantages of the present invention are: 1. Significantly improves ore recovery rate and reduces dilution rate. By dividing the ore body into three mining layers vertically from bottom to top and mining through the lower segment roadway (3) and the upper segment roadway (9), efficient layered mining of the gently inclined ore body is achieved. Compared with traditional mining methods, this effectively solves the problems of low ore recovery rate and high dilution rate, and significantly improves the ore body recovery rate.

[0013] 2. Avoid ore mixing and ensure the independence of mining layers. The method of waste rock replacement and backfilling retaining wall (7) is used for backfilling, which effectively avoids the mixing of mineral materials, ensures the independence of each mining layer, and solves the problem of mineral material mixing and high dilution rate caused by different mineral types and unstable upper layer ore during the mining of double-layer ore bodies.

[0014] 3. Improve the stability of goaf areas and mine safety. The first step uses high-strength filling material, and the second step uses low-strength filling material, which achieves a gradient arrangement of filling materials, effectively supports the stability of the goaf, and improves the overall safety of the mine.

[0015] 4. Increase mechanization and reduce labor intensity By rationally arranging segmented roadways and optimizing the mining sequence, the safety hazards present in traditional open-pit mining methods are avoided, the risk of overlying rock collapse caused after the ore body is mined is effectively reduced, the mechanization level of mining operations is significantly improved, the labor intensity of workers is reduced, and mining efficiency is increased. Attached Figure Description

[0016] Figure 1 This is a structural side view of the mining method of the present invention; Figure 2 This is a flowchart of the mining process of the present invention; Figure 3 This is a schematic diagram of the upper segmented triangular ore body for mining according to the present invention; Figure 4 This is a schematic diagram of the segmented triangular ore body for mining according to the present invention; Figure 5 This is a front view of the filling retaining wall in the mining method of the present invention; Figure 6 This is a side view of the filling retaining wall in the mining method of the present invention; In the diagram: 1-Lower ore layer; 2-Interlayer; 3-Lower section roadway; 4-Lower section pillar; 5-Second mining layer; 6-Third mining layer; 7-Backfilling retaining wall; 8-Upper section pillar; 9-Upper section roadway; 10-Upper section stope connecting roadway; 11-Upper section triangular ore body; 12-First mining layer; 13-Lower section triangular ore body; 14-Lower section stope connecting roadway; 15-Transport path of loader for mining the upper section triangular ore body; 16-Transport path of loader for mining the lower section triangular ore body; 17-Inlaid wall anchor; 18-Groove line; 20-Filter pipe. Detailed Implementation

[0017] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific embodiments.

[0018] Example 1

[0019] I. Mine Overview and Preparation Layout Taking a phosphate mine in Yunnan as an example, such as Figure 1 As shown, the ore body is a gently dipping ore body containing an interlayer (2), which is located between two ore layers. The vein development and preparation method is adopted, and the segmented roadway is located between the two ore layers, that is, the segmented roadway exposes the interlayer (2). Vertically, it is divided into three mining layers from bottom to top, namely the bottom first mining layer (12), the middle second mining layer (5) containing the interlayer (2), and the top third mining layer (6). The segmented roadway (3) is arranged between the two ore layers to expose the interlayer (2), and the lower segmented roadway (3) and the upper segmented roadway (9) are located at the lower boundary and the upper boundary of the ore body, respectively.

[0020] The mining process flow in this embodiment is as follows: Figure 2 As shown, it is divided into two stages: the first step and the second step.

[0021] II. First Step: Mining and High-Intensity Backfilling (a) Second mining layer (5) and roof support The first step involves mining the second mining layer (5) containing the interlayer (2) from the lower segment roadway (3) towards the upper segment roadway (9) and then protecting the roof. A connecting roadway for the second mining layer of the first step is arranged perpendicular to the direction of the lower segment roadway, which is used for mining the layered ore in the direction of the upper segment roadway.

[0022] K41 hydraulic drilling rigs were used to drill horizontal blast holes in the mining interlayer connecting passages and stopes. The blast hole layout parameters were: hole diameter 45 mm, hole depth 3.6 m (interlayer locations controlled within 3.0 m), hole spacing 650 mm, and row spacing 750 mm. A continuous charging structure was used, with 8 sections of explosive loaded per 3 m hole depth, and an explosive consumption of approximately 2.1 kg / m³. 3 The detonation sequence is as follows: first, detonate the cut hole, then detonate sequentially outwards along the auxiliary holes, with the side holes detonating first, and finally the top hole detonating. Medium-deep hole blasting is used for mining. Considering the poor stability of interlayers during drilling, holes in interlayer locations should generally not exceed the required depth, and the charge amount should be appropriately reduced.

[0023] When the second mining layer (5) containing interlayers in the middle of the ore body is completed, anchor mesh shotcrete is used for roof protection. The roof protection parameters are as follows: anchor bolts are φ20 resin anchor bolts with a length of 2m; the row spacing is 1000mm, arranged in a rectangular pattern, with 7 bolts per row; the mesh is made of φ6 steel bars with a spacing of 100×100mm and an overlap of 100mm; the entire cross section is made of C20 shotcrete with a thickness of 100mm.

[0024] (II) First mining layer of waste rock replacement mining (12) After the second mining layer (5) is mined and the roof is protected, the first mining layer (12) is mined. During the mining process, the waste rock replacement method is used to mine the lower triangular ore body (13) and the upper triangular ore body (11) of the first mining layer (12) which are close to the two sections.

[0025] The waste rock mainly comes from the nearby external development roadways, exploration roadways, and engineering works. Underground mining trucks (model: UQ-20(C)) and loaders (model: FL105(WJ-4C)) are used to transport the waste rock to the replacement area.

[0026] The replacement steps are as follows: After the upper triangular ore body (11) is mined from the lower segment, the corresponding empty area is backfilled with waste rock until it connects with the upper segment outlet and is leveled and compacted to form a new outlet. Then, the lower triangular ore body (13) is mined from the upper segment, and the ore is extracted from the outlet channel paved with waste rock in the previous step. The mining sequence of the two triangular ore bodies can be temporarily adjusted according to the site conditions.

[0027] like Figure 3As shown, when mining the first mining layer (12) near the upper section roadway triangular ore body, ore is extracted from the lower section roadway. After mining is completed, the muck is used to form a slope that meets the equipment's climbing ability, connecting to the upper mining layer roadway. Figure 4 As shown, when mining the first mining layer (12) near the lower section of the triangular ore body, the ore is extracted from the upper section of the roadway through the channel formed by the previous slag padding.

[0028] The thickness standard of the waste rock layer is controlled by two aspects: first, it must be backfilled to the section opening to ensure that transportation equipment can pass through; second, the slope formed by laying waste rock must not exceed the maximum climbing capacity of the equipment, generally at a slope of 15%, and the surface must be compacted. The acceptance standard after the replacement is completed is mainly to ensure that vehicles can travel and ensure the mining of another triangular ore body, that is, there are certain requirements for the slope and surface travel capacity.

[0029] (iii) Constructing and filling retaining walls with high strength. After the first mining layer (12) and the second mining layer (5) at the bottom of the ore body are mined, the goaf of the first and second mining layers is filled in one go after the side filling retaining walls (7) are built.

[0030] like Figure 5 As shown, the filling retaining wall adopts a brick masonry structure. The lower section uses a 600mm thick brick masonry retaining wall on one side, with a height equal to the stope height, which will eventually seal the stope; the upper section uses a 400mm thick brick masonry retaining wall on one side, with a height that needs to meet the maximum climbing capacity of the equipment entering from the upper section. In principle, it is the height of one mining layer, with appropriate adjustments.

[0031] like Figure 6 As shown, the filter pipes are 100mm in diameter, and the six filter pipes are distributed in two rows near the bottom at equal intervals. The reason for the difference between the two retaining walls is that the gaps in the two layers are relatively large, and the filling must be carried out in stages (steps). The retaining wall on the side closer to the lower layer is for filling after the first layer is mined, while the retaining wall on the side closer to the upper layer is for filling the second layer. The second layer will serve as a base for the third layer.

[0032] The filling material used is a high-strength filler. The mix proportions and performance parameters of the high-strength filler are as follows: ash-sand ratio 1:5 to 1:8; mass concentration 68% to 70%; 28-day uniaxial compressive strength ≥ 2.5 MPa; aggregate is entirely tailings sand, with approximately 91.6% being smaller than 76 μm (-200 mesh), approximately 71.7% being smaller than 37 μm (-400 mesh), and approximately 57.22% being -20 μm; curing time ≥ 14 days. The high-strength filler consists of cemented filler. Curing continues until the uniaxial compressive strength of the filler reaches the design requirements.

[0033] III. Second Step: Mining and Low-Intensity Backfilling (a) Third mining layer (6) and roof support After the strength of the first-stage backfill reaches the standard, the second-stage mining will proceed. In the second stage, the third mining layer (6) located in the upper part of the ore body will be mined from the upper section roadway (9) to the lower section roadway (3), with anchor mesh spraying for roof protection, one anchor and one spraying per excavation. A connecting roadway will be built in the upper section roadway (9) to connect the third mining layer. The same blasting technology as the lower layer will be used for blasting. The third mining layer will be mined from the upper section roadway along the direction of the mined ore stopes.

[0034] The parameters for the top protection are the same as in the first step: the anchor bolts are φ20 resin anchor bolts, 2m in length; the row spacing is 1000mm, arranged in a rectangular pattern, with 7 bolts per row; the mesh uses φ6 steel bars, with a spacing of 100×100mm and an overlap of 100mm; the entire cross-section uses C20 shotcrete with a thickness of 100mm.

[0035] (ii) Constructing a retaining wall and filling it with low-strength material. After the mining is completed, a retaining wall (7) is constructed on one side of the upper section. The retaining wall is a brick structure with a thickness of 400mm. Low-strength filling material is used for filling.

[0036] The mix proportions and performance parameters of the low-strength backfill are as follows: ash-sand ratio 1:8; mass concentration 68%–70%; 28-day uniaxial compressive strength ≥1.5MPa; aggregate is all tailings sand, with approximately 91.6% being smaller than 76μm (-200 mesh), approximately 71.7% being smaller than 37μm (-400 mesh), and approximately 57.22% being -20μm; curing time ≥14 days. The backfill pipeline is laid to the highest point of the empty area.

[0037] The term 'strength meets the standard' means that the 28-day uniaxial compressive strength of the filling material meets the design requirements, as tested by on-site core sampling or non-destructive testing methods.

[0038] IV. Implementation Results By adopting the method of this embodiment, the mining problem of gently dipping ore bodies with interlayers is effectively solved, the adverse effects of interlayers on mining operations are avoided, and the ore recovery rate and mining safety are improved.

[0039] Example 2

[0040] The difference between this embodiment and Embodiment 1 lies in the different geological conditions such as the dip angle and thickness of the ore body, and the mining parameters are adjusted accordingly.

[0041] The ore body has a gentle dip angle (approximately 8°–12°) and relatively thick interlayers (approximately 1.5–2.0 m). The total thickness of the ore body is approximately 10–12 m, of which the thickness of the first mining layer is approximately 3.0 m, the thickness of the second mining layer (including interlayers) is approximately 4.0 m, and the thickness of the third mining layer is approximately 3.5 m.

[0042] When mining the second layer in the first step (5), the borehole parameters are adjusted as follows: borehole diameter 45 mm, borehole depth 3.8 m (interlayer position controlled within 3.2 m), borehole spacing 700 mm, and row spacing 800 mm. The charge structure and detonation sequence are the same as in Example 1.

[0043] The waste rock replacement method is the same as in Example 1. The waste rock comes from the development roadways and exploration roadways outside the vein and is transported by mining trucks and loaders. The slope of the slope formed by the waste rock filling is controlled within 15%.

[0044] The parameters for the infill retaining wall are the same as in Example 1. The high-strength infill mix is ​​adjusted to a lime-sand ratio of 1:6, a mass concentration of 69%, and a 28-day uniaxial compressive strength ≥3.0MPa; the low-strength infill mix is ​​a lime-sand ratio of 1:10, a mass concentration of 68%, and a 28-day uniaxial compressive strength ≥1.2MPa. All aggregates are tailings.

[0045] When mining the third layer in the second step (6), the blasting and roof support parameters are the same as in the first step.

[0046] The mining method described in this embodiment also effectively solves the problems of interlayer treatment and recovery of triangular ore bodies in gently dipping ore bodies containing interlayers.

[0047] Finally, it should be noted that the above descriptions are merely preferred embodiments of this application, and this application is not limited to the above embodiments. It is understood that other improvements and variations directly derived or conceived by those skilled in the art without departing from the spirit and concept of this application should be considered to be included within the protection scope of this application.

Claims

1. A two-step backfilling mining method for mining gently dipping ore bodies containing interlayers, characterized in that, The ore body includes the lower ore layer (1), interlayer (2), lower sub-section roadway (3), lower sub-section pillar (4), second mining layer (5), third mining layer (6), backfill wall (7), upper sub-section pillar (8), upper sub-section roadway (9), upper sub-section stope connecting roadway (10), upper sub-section triangular ore body (11), first mining layer (12), lower sub-section triangular ore body (13), and lower sub-section stope connecting roadway (14). The ore body is a gently dipping ore body containing interlayer (2), which is located between two ore layers. The vein is developed and prepared, and the sub-section roadway is located between two ore layers, that is, the sub-section roadway exposes the interlayer (2). Vertically, it is divided into three mining layers from bottom to top, namely the bottom first mining layer (12), the middle second mining layer (5) containing interlayer (2), and the top third mining layer (6). The three mining layers of the entire ore body are mined according to the following steps: The first step is to mine the second mining layer (5) containing the interlayer (2) from the lower segment roadway (3) to the upper segment roadway (9) and then protect the roof; then, mine all the ore in the first mining layer (12) including the upper segment triangular ore body (11) and the lower segment triangular ore body (13) by means of waste rock replacement; finally, build the filling retaining walls (7) on both sides and fill the goaf of the first and second mining layers in one go; The second step is to mine the third mining layer (6) and support the roof from the upper segment roadway (9) to the lower segment roadway (3) after the filling body strength meets the standard. After constructing a retaining wall on one side (7), fill the goaf of the third mining layer.

2. The mining method according to claim 1, characterized in that: In the first step, a high-strength filler is used for filling; in the second step, a low-strength filler is used for filling; the 28-day uniaxial compressive strength of the high-strength filler is ≥2.5MPa, and the 28-day uniaxial compressive strength of the low-strength filler is ≥1.2MPa.

3. The mining method according to claim 1, characterized in that: In the first step, when mining the second mining layer (5), the segmented deep hole blasting method is used for mining, and the anchor mesh spraying roof is used for protection.

4. The mining method according to claim 1, characterized in that, The waste rock replacement method is as follows: when mining the first mining layer (12), the waste rock replacement method is used to mine the lower triangular ore body (13) and the upper triangular ore body (11) of the first mining layer (12) which are close to the two sections; when mining the first mining layer (12) which is close to the upper triangular ore body of the roadway, the ore is extracted from the lower triangular ore body. After mining is completed, the slag is used to form a slope that meets the climbing ability of the equipment and connects to the upper mining layer roadway; when mining the first mining layer (12) which is close to the lower triangular ore body of the roadway, the ore is extracted from the upper triangular ore body through the channel formed by the slag in the early stage.

5. The mining method according to claim 1, characterized in that: In the second step, the third mining layer (6) is mined from the upper segment roadway (9) to the lower segment roadway (3), and the anchor mesh spraying roof is used for protection, with one anchor and one spraying per excavation.

6. The mining method according to claim 1, characterized in that: In the first step, the first and second mining goaf areas are filled in one go after the two side filling retaining walls (7) are built. In the second step, the third mining goaf area is filled after the filling retaining wall (7) located on one side of the upper section is built.

7. The mining method according to claim 2, characterized in that: The high-strength filler is composed of cemented filler.

8. The mining method according to claim 1, characterized in that: In the second step, during filling, the filling pipeline is laid to the highest point of the empty area.

9. The mining method according to claim 1, characterized in that: In the first step, when mining the second mining layer (5), the connecting roadway of the second mining layer of the first step is arranged vertically downwards along the direction of the segmented roadway, and is used for mining the stratified ore in the direction of the upward segmented roadway (9).

10. The mining method according to claim 1, characterized in that: When the second step of mining the third mining layer (6) is carried out, a connecting road is built in the upper section roadway (9) to connect the third mining layer.

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