A mining method for separately mining and transporting two layers of ore bodies with soft interlayer and gentle inclination

Abstract

This invention discloses a mining method for the separate mining and transportation of two layers of ore body with soft interlayers on a gently dipping slope, relating to the field of underground mining technology for non-metallic minerals. The ore body is vertically divided into a central section, and then further divided into several sub-sections. Each sub-section has horizontally arranged roadways along the floor of the upper ore layer, which are connected to the panel slope and the panel return air incline. Within the panel, the upper and lower ore layers are mined and transported separately. Inter-section mining is carried out at intervals from bottom to top; mining operations are conducted in one sub-section while backfilling is carried out in another. Within a sub-section, mining proceeds from bottom to top, with several access routes operating simultaneously within the same sub-section. The lower ore layer is mined first, and the empty areas are alternately backfilled before the upper ore layer is mined. Along the strike of the ore body, each panel employs a retreating mining method from the flanks towards the center. This invention has advantages such as high ore block production capacity, high labor productivity, low cost, significant economic benefits, strong adaptability and flexibility, and the ability to adapt to changes in ore body morphology.

Description

Technical Field

[0001] This invention relates to the field of underground mining technology for non-metallic minerals, specifically to a mining method for separately mining and transporting two layers of ore bodies with soft interlayers that are gently inclined. Background Technology

[0002] Underground mining methods are classified into three main categories based on ground pressure management: open-cut mining, caving mining, and backfilling mining. Among them, backfilling mining is suitable for mining high-grade, rare, and valuable ores in unstable surrounding rock. It has advantages such as strong adaptability, high ore recovery rate, low dilution rate, relatively safe operation, small amount of mining and cutting work, high flexibility, full utilization of industrial waste, relatively effective maintenance of surrounding rock, reduction of surrounding rock movement and large-scale collapse, and protection of the surface from subsidence.

[0003] Currently, mining gently dipping ore bodies is a recognized global challenge. For gently dipping ore bodies, single-layer backfilling mining or upward horizontal layered backfilling mining is usually adopted. However, when there are weak interlayers between the upper and lower ore layers, the above mining methods are difficult to achieve separate mining and transportation of the ore layer and the interlayer, resulting in high ore loss and dilution, which seriously affects the economic benefits of mining enterprises.

[0004] CN105587318A discloses a backfilling mining method for continuous mining of a gently dipping parallel medium-thick ore body group. The method divides the gently dipping parallel ore body group into a middle section, then divides the middle section into panels along the strike, and further divides each panel into sub-sections. Separate stops and pillars are used for mining, with the stopes arranged perpendicular to the ore body strike. Major preparatory works such as external segmental roadways, layer-by-layer connecting roadways, ore pass connecting roadways, ore passes, and personnel access ventilation shafts are located in the footwall of the ore body. Backfilling return air shafts, lower ore layer return air and backfilling shaft connecting roadways, and filter shaft connecting roadways are located in the upper and lower ore layers, respectively, and connected by cross-cutting roadways at the bottom of the panel. Mining proceeds layer by layer from the bottom up through the uppermost layer of the vein, using a two-mining, two-extraction, one-backfilling work cycle for each layer. The main mining and cutting works are located outside the vein, resulting in large-scale mining and cutting operations and excessive upfront production costs, impacting the company's cash flow.

[0005] CN104179505A discloses an underground mining method for phosphate deposits, specifically for a unique phosphate deposit in the Dianchi Lake area of ​​Yunnan Province that exhibits four characteristics: inclined, thin to medium-thick, fractured roof, and soft interlayers. This method involves excavating an inclined shaft and then a main roadway along the strike of the ore body, dividing the ore body into two layers for separate mining. The interlayer thickness is 4–6 m. The upper layer is mined first, followed by the lower layer. After the roof of the upper layer collapses and stabilizes, the lower layer is mined. The upper mineable layer (average thickness 8.9 m) is mined using a segmented caving method; the lower mineable layer (average thickness 4 m) is mined using a shallow-hole caving method. The end-to-end span between the upper and lower layers is no less than 150 m. However, the method requires mining the two layers separately according to the order of upper layer first, leading to low mining efficiency. The upper part is mined using the segmented ore-caving method, while the lower part is mined using the shallow hole ore-caving method. This results in high mining losses and low mining efficiency, which affects the company's economic benefits. Furthermore, some ore remains unmined, which is not conducive to the comprehensive utilization of mineral resources.

[0006] Therefore, it is necessary to innovate the existing backfilling mining method and provide a mining method for the separate mining and transportation of weak interlayers between the upper and lower ore layers of a gently dipping ore body to solve the above-mentioned technical problems. This is of great significance for improving the safety conditions and economic benefits of mining. Summary of the Invention

[0007] The purpose of this invention is to provide a mining method for separately mining and transporting two layers of ore bodies with gently inclined soft interlayers, thereby solving the problems of large workload and low efficiency in existing mining methods.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a mining method for separately mining and transporting two layers of ore bodies with gently dipping soft interlayers, characterized by comprising the following steps:

[0009] S1. Divide the ore body into a middle section in vertical height, and then divide it into several sub-sections. Each sub-section is arranged with a sub-section roadway horizontally along the bottom plate of the upper ore layer. The sub-section roadway is connected to the panel slope roadway and the filling return air uphill roadway respectively.

[0010] S2. Within the middle section, panels are divided along the strike of the ore body. Continuous inter-pillars are reserved between two adjacent panels. In the inter-pillars on both sides of the panel, a filling return air incline is arranged along the vein on the floor of the upper ore layer. The filling return air incline is connected to the return air roadway of the upper and middle sections. In the continuous inter-pillars in the center of the panel, a panel ramp is arranged along the vein on the floor of the upper ore layer. The panel ramp is connected to the upper and lower middle sections roadways.

[0011] S3. A conveyor belt roadway is arranged outside the central floor plate of the panel, and it is connected to the middle section conveyor belt roadway through the conveyor belt connecting roadway. Ore chutes are arranged in the floor plates of each section in the central panel, and they are connected to the section roadways through the chute connecting roadways.

[0012] S4. Each panel is symmetrically arranged with ore blocks on both wings. Within each segment, a pass is arranged along the pseudo-dipping direction. The pass is mined twice, with the mining height equal to the thickness of the ore layer. The upper and lower ore layers within the panel are mined and transported separately. Between segments, mining is carried out in an alternating manner from bottom to top. Mining is carried out in one segment while filling is carried out in another segment. Mining is carried out from bottom to top within a segment. Several passes operate simultaneously within the same segment. The lower ore layer is mined first, and the empty area is alternately filled before the upper ore layer is mined. Along the strike of the ore body, each panel adopts a retreating mining method from both wings to the middle. The ore in the stope is loaded and unloaded into the panel ore pass by a loader, then lowered into the panel conveyor belt via the ore pass, and then transported to the surface via the intermediate conveyor belt and the main conveyor belt.

[0013] A further technical solution is that the upper part of the conveyor belt roadway in the panel area is connected to the panel area ramp through a ventilation well; the conveyor belt connecting roadway is arranged in the lower part of the middle panel area, and its two ends are connected to the middle section roadway and the middle section conveyor belt roadway respectively; the segment roadway is provided with a stope connecting roadway on both sides, and the stope connecting roadway is connected to the access road of the upper and lower segments.

[0014] A further technical solution is that the ore pass includes a low-grade ore pass and a high-grade ore pass, and the ore pass connecting roadway arranged in the lower footing of the central ore body of the panel connects the low-grade ore pass, the high-grade ore pass and the segment roadway. The ventilation shaft is arranged at the end of the conveyor belt roadway in the panel and connects with the adjacent ore pass connecting roadway.

[0015] A further technical solution is that if the interlayer can be self-stabilized in each mining cycle, then the ore is mined first, and then the interlayer is removed by blasting or mechanical methods; if the interlayer is not stable, then the top interlayer and some ore are cut off before each mining cycle, and the top of the lower ore layer is first blasted down by blasting, and after separating some ore, the interlayer is transported to the adjacent goaf area for filling by a loader.

[0016] A further technical solution involves fresh air entering the mining area from the middle section roadway through the panel ramp and segment roadways. After washing the working face, the polluted air is discharged to the upper segment return air roadway via local fans, and then discharged to the upper middle section return air roadway through the filling return air uphill. Local fans are installed at the working face to assist ventilation, and the local fans are installed at the connection between the panel ramp and the segment roadways.

[0017] A further technical solution involves the following: the lower ore layer access roadway is filled with a high-strength cemented backfill body. First, the odd-numbered strips within the segment are mined, and the odd-numbered strip goaf is filled with a mixture of crushed stone, tailings, and some cement. After the backfill body reaches a certain strength, the adjacent even-numbered strips are mined in a second step. Then, the goaf is filled with backfill material of the same proportion. Both steps of the backfill body are high-strength, with a strength ≥ 2 MPa. After the lower ore layer backfill body reaches the design strength, the upper ore layer is mined. The upper ore layer is mined in a similar manner to the lower ore layer. After the odd-numbered strips are mined in the first step, high-strength backfill is used. In the second step, the adjacent even-numbered strips are mined, and then low-strength backfill is used. Before the access roadway is filled, the waste rock from the external roadway is transported by truck to the adjacent stope. Then, a retaining wall needs to be installed in the end stope connecting roadway to seal the backfill body. The backfill pipe passes through the upper segment roadway and the return air connecting roadway down to the goaf.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] The panel mining method allows for large-scale ore production, and the use of conveyor belt transportation results in high labor productivity.

[0020] In-vein preparation work is less extensive and less costly. By arranging the mining and cutting work within the vein, mining costs are reduced and economic benefits are improved.

[0021] It is highly adaptable and flexible, with the panel ramps arranged along the bottom plate of the upper ore layer, which can adapt to changes in the ore body shape;

[0022] The mining method provided by this invention can effectively improve the panel area while reducing the ore dilution rate;

[0023] This invention ensures that the ore mining process is safe, efficient, and economical. Attached Figure Description

[0024] Figure 1 This is a front view schematic diagram of the present invention.

[0025] Figure 2 for Figure 1 Section II shown;

[0026] Figure 3 for Figure 2 Section II-II shown;

[0027] Figure 4 for Figure 2 The diagram shown is section III-III.

[0028] Figure 5 for Figure 2 Enlarged view of part A in the middle.

[0029] In the diagram, 1-intermediate roadway, 2-conveyor belt connecting roadway, 3-intermediate conveyor belt roadway, 4-panel conveyor belt roadway, 5-section roadway, 6-return air connecting roadway, 7-stope connecting roadway, 8-section roadway pillar, 9-retaining wall, 10-high-strength cemented backfill, 11-low-strength cemented backfill, 12-blast hole, 13-intercalated rock, 14-ore pass connecting roadway, 15-low-grade ore pass, 16-high-grade ore pass, 17-ventilation shaft, 18-panel ramp, 19-panel pillar, 20-ore pass connecting roadway pillar, 21-backfilled return air incline, 22-backfilled return air incline pillar. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0031] Taking a phosphate mine in Yunnan Province as an example, the ore vein consists of two layers: an upper ore layer and a lower ore layer. The phosphate mine is generally a monoclinic structure gently dipping southeast. The ore layer's occurrence is relatively stable, largely consistent with the overlying strata. The ore layer strikes NE–SW and dips SE, with dip angles ranging from 2° to 31°, averaging 15°. The upper ore layer has a minimum thickness of 2.62m, a maximum thickness of 12.69m, and an average thickness of 6.7m, with a thickness variation coefficient of 33%, classifying it as stable. The average P2O5 content is 22.48%, with a grade variation coefficient of 17%. The lower ore layer has a minimum thickness of 0.34m, a maximum thickness of 12.77m, and an average thickness of 5.67m, with a thickness variation coefficient of 36%, also classifying it as stable. The average P2O5 content is 26.9%, with a grade variation coefficient of 15%. Interlayers of clayey shale are located in the southwest of the mining area, with an average thickness of 1.01m. Both the upper and lower ore layers have industrial value. The clayey shale interlayer between the two ore layers has a lower grade, which is not conducive to mining and beneficiation. Furthermore, the grades of the upper and lower ore layers differ significantly. The rich and poor ore bodies need to be mined and transported separately, and the interbedded rocks should be removed as much as possible.

[0032] The specific mining steps are as follows:

[0033] The ore body has a vertical height of 90m in the middle section, divided into 10m segments, for a total of 9 segments. Each segment has 5 segmental roadways arranged along the floor of the upper ore layer, which are connected to the panel slope roadway 18 and the filling return air incline 21 respectively. Panels are divided along the strike of the ore body, with a spacing of 200m between panels. A continuous column with a width of 19m is reserved between two adjacent panels. In the columns on both sides of the panel, the filling return air incline 21 is arranged along the vein floor of the upper ore layer with a slope of 15%, which is connected to the upper and middle section return air roadways.

[0034] Within a 25m continuous column in the center of the panel, a panel ramp 18 (with a 15% slope and a 20m long gentle slope section in the middle) is arranged along the vein of the upper ore layer floor, connecting with the upper and lower middle section roadways 1. A panel conveyor belt roadway is arranged outside the vein in the center floor of the panel, connecting with the middle section conveyor belt roadway 3 via conveyor belt connecting roadway 2. A set of ore chutes is arranged in the second, fifth, and eighth sections of the panel floor, respectively, connecting with the corresponding section roadways 5 via chute connecting roadways 14.

[0035] Each panel is divided into two symmetrically arranged ore blocks. Within each section, an access road is laid out along a pseudo-dipping slope with a gradient of 15%, a length of 48m, a horizontal width of 14m, and a vertical width of 8m. The access road is mined intermittently, with two mining operations per access road. Each mining operation is 7m wide horizontally and the mining height is equal to the thickness of the upper (lower) ore layer. The upper and lower ore layers within the panel are mined and transported separately. To minimize the mutual interference between backfilling and mining, intermittent mining is carried out from bottom to top between sections. Two sections operate in parallel simultaneously (within three sections). Mining is carried out in one section while backfilling is carried out in the other. Within each section, mining proceeds from bottom to top. Within the same section, 5-6 access roads operate simultaneously. The lower ore layer is mined first, and the empty areas are alternately backfilled before the upper ore layer is mined.

[0036] in:

[0037] 1) Preparation Engineering

[0038] The preparation works mainly include panel ramps 18, panel conveyor belt roadways 4, segmented roadways 5, conveyor belt connecting roadways 2, return air connecting roadways 6, stope connecting roadways 7, backfilling return air uphill 21, ore chutes 1516, ore chutes connecting roadways 14, ventilation shafts 17, etc.

[0039] A ramp with a slope of 15% is arranged along the pseudo-inclination of the vein on the floor of the upper ore layer in the center of the panel. It is designed as a three-center arch cross-section, with a net width of 4.5m and a wall height of 2.2m, supported by shotcrete, anchor, and mesh. The excavation section is 16.75m long. 2 .

[0040] A conveyor belt tunnel 4, with a slope of 2°, is arranged at a pseudo-inclined angle outside the central floor slab of the panel. Its lower part connects to the middle section conveyor belt tunnel 3, and its upper part connects to the panel ramp 18 via a ventilation shaft 17. The design features a three-centered arch cross-section with a net width of 4.0m and a wall height of 2.2m, using shotcrete and anchor mesh support. The excavation cross-section is 14.45m. 2 .

[0041] Sectional roadway 5: A horizontal roadway is arranged along the vein on the floor of the upper ore seam in each section, connecting to the panel slope roadway 18 and the backfill return air incline 21 respectively. Continuous pillars, 3m wide, are left on both sides of section roadway 5. Sectional roadway 5 is designed with a three-center arch cross-section, a net width of 4.5m, and a wall height of 2.2m. It uses anchor mesh support; when the rock conditions are poor, shotcrete anchor mesh support is used. The excavation cross-section is 16.60m.2 .

[0042] Belt conveyor roadway 2: Located in the lower part of the panel, it connects to the middle section roadway 1 and the middle section belt conveyor roadway, with a tunneling cross-section of 14.45m. 2 .

[0043] Return air connecting roadway 6 and stope connecting roadway 7: Located on both sides of section roadway 5, connecting with the upper and lower section access roads, they are the main channels for stope recovery, ventilation, and ore extraction. They are unsupported, with a tunneling cross-section of 16.75m. 2 .

[0044] Backfilling and Return Airway 21: Located on the bottom plate of the upper ore layer on both wings of the panel, it is the main return airway. Designed as a three-center arch cross-section, with a net width of 4.5m and a wall height of 2.2m, it adopts anchor mesh support. When the rock conditions are poor, shotcrete and anchor mesh support is used. The excavation section is 16.75m. 2 .

[0045] Ore chute: Three sets of chutes are arranged in one panel, with two chutes in each set (15 for low-grade ore in the upper layer and 16 for high-grade ore in the lower layer), serving all ore blocks in the three adjacent intermediate sections. The net diameter of the chute is 3.0m and it is unsupported.

[0046] Ore pass connecting roadway 14: Located in the footwall of the central ore body of the panel, connecting section roadway 5 and the ore pass, unsupported, with a tunneling cross-section of 16.75m. 2 .

[0047] Ventilation shaft 17: Located at the end of conveyor belt roadway 4 in the panel area, it connects with the adjacent chute connecting roadway 14. It is the main return air shaft and safety passage of the conveyor belt in the panel area, with a net diameter of 2m and no support.

[0048] Interlayer removal: There are two methods for interlayer removal based on the stability of the interlayer. If the interlayer is self-stabilizing within each mining cycle, the ore is mined first, and then the interlayer is removed by blasting or mechanical methods. If the interlayer is poorly stable, the top interlayer and part of the ore are cut off before each mining cycle. First, the top of the lower ore layer (about 2m thick, including the total thickness of the ore and interlayer) is blasted down using blasting. After separating part of the ore, the interlayer is transported to the adjacent goaf by a loader for backfilling.

[0049] Mining sequence: Each panel is divided into two symmetrically arranged ore blocks on both wings. The access road is arranged along the pseudo-inclination within the section. Mining is carried out twice within the access road, with the mining height being the thickness of the ore layer. The upper and lower ore layers within the panel are mined and transported separately. Mining is carried out in intervals from bottom to top between sections. Mining is carried out in one section while backfilling is carried out in another section. Mining is carried out from bottom to top within a section. Several access roads operate simultaneously within the same section. The lower ore layer is mined first. During the mining of the lower ore layer, mining is carried out in two steps. In the first step, the odd-numbered strips within the section are mined. The odd-numbered strip goaf is filled with a mixture of crushed stone and tailings with some cement. After the backfill reaches a certain strength, the second step is carried out to mine the adjacent even-numbered strips. Then, the goaf is filled with backfill material with the same mix ratio. The backfill in both steps is high-strength, with a strength ≥2MPa. The upper ore layer is mined only after the lower ore layer's backfill reaches its designed strength. The mining method for the upper ore layer is similar to that of the lower ore layer. In the first step, the odd-numbered ore strips are mined and then backfilled with high-strength backfill. In the second step, the adjacent even-numbered strips are mined and then backfilled with low-strength backfill. The upper ore layer is mined only after the empty areas are alternately backfilled. Along the strike of the ore body, each panel is mined using a retreating mining method from both wings towards the middle. The ore in the stope is loaded and unloaded into the panel ore pass by a loader, then lowered into the panel conveyor belt via the ore pass, and finally transported to the surface via the intermediate conveyor belt and the main conveyor belt.

[0050] 3) For stope ventilation, fresh air enters the stope from the middle section roadway, through the panel ramp and sub-section roadways, and washes the working face. After that, the polluted air is discharged to the upper sub-section return air roadway via local fans, and then discharged to the upper-middle section return air roadway through the filling return air uphill. Local fans are installed at the working face for auxiliary ventilation, and are installed at the connection between the panel ramp and the sub-section roadways.

[0051] 4) Stope backfilling: High-strength cemented backfill is used for the lower ore seam access roadway. High-strength cemented backfill is used for the first-stage mining access roadway of the upper ore seam, and low-strength cemented backfill is used for the second-stage mining access roadway. Before backfilling, waste rock from the external roadways of the excavated vein is transported by truck to the adjacent stope. Then, retaining walls are installed in the end stope connecting roadway to seal the backfill. The backfill pipe goes down to the goaf through the upper section roadway and the return air connecting roadway.

[0052] Although the invention has been described herein with reference to several illustrative embodiments, it should be understood that many other modifications and implementations can be devised by those skilled in the art, which will fall within the scope and spirit of the principles disclosed herein. More specifically, various modifications and improvements can be made to the components or layout of the subject matter arrangement within the scope of the disclosure, drawings, and claims. Besides modifications and improvements to the components or layout, other uses will be apparent to those skilled in the art.

Claims

1. A mining method for separately mining and transporting two layers of ore bodies with soft interlayers on a gently dipping slope, characterized in that... Includes the following steps: S1. Divide the ore body into middle sections in vertical height, and then divide it into several subsections. Each subsection is arranged with a subsection roadway (5) horizontally along the bottom plate of the upper ore layer. The subsection roadway (5) is connected to the panel slope roadway (18) and the filling return air uphill roadway (21) respectively. S2. The middle section is divided into panels along the strike of the ore body. A continuous inter-pillar is reserved between two adjacent panels. A filling return air incline (21) is arranged along the vein in the upper ore bottom plate of the inter-pillar on both sides of the panel. The filling return air incline (21) is connected to the upper and middle section return air roadway. A panel ramp (18) is arranged along the vein in the continuous inter-pillar in the center of the panel and the upper ore bottom plate. The panel ramp (18) is connected to the upper and lower middle section roadways (1). S3. A conveyor belt roadway (4) is arranged outside the central bottom plate of the panel area, and is connected to the middle section conveyor belt roadway (3) through the conveyor belt connecting roadway (2). Ore chutes are arranged in each section of the central bottom plate of the panel area, and are connected to the section roadway (5) through the chute connecting roadway (14). S4. Each panel is divided into two symmetrically arranged ore blocks on both wings. The approach is arranged along the pseudo-inclination within the section. The approach is mined twice, with the mining height being the thickness of the ore layer. The upper and lower ore layers within each panel are mined and transported separately. The sections are mined from bottom to top at intervals. Mining is carried out in one section, and backfilling is carried out in the other section. Mining proceeds from bottom to top within each section, with multiple access routes operating simultaneously within the same section. The lower ore layer is mined first, and the empty areas are alternately filled before the upper ore layer is mined. Along the strike of the ore body, each panel adopts a retreating mining method from both wings to the middle. Ore in the stope is loaded and unloaded into the panel ore pass by a loader, then lowered into the panel conveyor belt via the ore pass, and finally transported to the surface via the intermediate conveyor belt and the main conveyor belt. If the interlayer is self-stabilizing within each mining cycle, the ore is mined first, and then the interlayer is removed by blasting or mechanical methods. If the interlayer is not stable, the top interlayer and some ore are cut off before each mining cycle. First, the top of the lower ore layer is blasted down by blasting. After separating some ore, the interlayer is transported to the adjacent goaf area for filling by a loader.

2. A mining method for the selective mining and haulage of gently inclined two-layer ore bodies with soft interlayers according to claim 1, characterized in that: The upper part of the panel belt roadway (4) is connected to the panel ramp (18) through the ventilation well (17); the belt connecting roadway (2) is arranged in the lower part of the middle panel, and its two ends are connected to the middle section roadway (1) and the middle section belt roadway (3) respectively; the segment roadway (5) is provided with the mining area connecting roadway (7) on both sides, and the mining area connecting roadway (7) is connected to the upper and lower segment access roads.

3. A mining method for the selective mining and haulage of gently inclined two-layer ore bodies with soft interlayers according to claim 1, characterized in that: The ore chute includes a low-grade ore chute (15) and a high-grade ore chute (16). A chute connecting roadway (14) located in the lower footing of the central ore body of the panel connects the low-grade ore chute (15) and the high-grade ore chute (16) with the segment roadway (5). A ventilation shaft (17) is located at the end of the conveyor belt roadway in the panel and connects with the adjacent chute connecting roadway (14).

4. The mining method of claim 1, wherein: Fresh air enters the mining area from the middle section roadway (1), through the panel slope roadway (18) and the segment roadway (5). After washing the working face, the polluted air is discharged to the upper segment return air roadway through the local fan, and then discharged to the upper middle section return air roadway through the filling return air uphill (21). Local fans are arranged at the working face for auxiliary ventilation. The local fans are installed at the connection between the panel slope roadway (18) and the segment roadway (5).

5. A mining method for the selective mining and haulage of gently inclined two-layer ore bodies with soft interlayers according to claim 1, characterized in that: Specifically, the backfilling involves using high-strength cemented backfill for the lower ore layer access roadway, and high-strength cemented backfill for the upper ore layer after the first step of mining the odd-numbered strips, and low-strength cemented backfill for the second step of mining the adjacent even-numbered strips. Before backfilling the access roadway, the waste rock from the external roadway is transported by truck to the adjacent stope. Then, a retaining wall needs to be installed in the end stope connecting roadway to seal the backfill. The backfill pipe goes down to the goaf through the upper section roadway and the return air connecting roadway.

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