Method for treating multi-section high and steep goaf by constructing composite isolation layer with waste rock and paste collaborative filling

Abstract

A kind of waste rock-paste cooperative filling construction composite isolation layer multi-section high and steep goaf treatment method belongs to underground mining technical field. At the junction of upper and lower sections, a composite isolation layer of "pillar + high-strength cemented paste" is constructed to realize rigid support and flexible cushioning. Above the isolation layer, a combined filling mode of "waste rock + low-strength paste" is used. Through waste rock dumping and filling to build slope and low-strength paste covering, a cooperative bearing structure is formed. The advantages are that the composite isolation layer not only protects the lower unsampled ore, but also realizes ground pressure control through waste rock paste filling, reduces filling cost, and controls the subsequent ore dilution rate below 8%, reduces the comprehensive filling cost by 25%-35%. It is suitable for complex goaf treatment and sublevel mining scenarios in deep metal mines, coal mines and other underground mines.

Description

Technical Field

[0001] This invention belongs to the field of underground mining technology, specifically providing a method for managing multi-level, steep goaf areas by constructing a composite isolation layer using waste rock and paste co-filling. It is particularly suitable for segmented mining scenarios of underground metal and non-metal mines where the lower ore body and upper multi-level, steep goaf areas coexist. The core focus is on the synergistic technology of goaf safety management, waste rock resource utilization, composite isolation layer construction, and staged mining with reserved pillars. This achieves the dual goals of efficient backfilling of the upper goaf and safe mining of the lower ore body, while also optimizing mining costs and controlling ground pressure stability. It belongs to the interdisciplinary technical field of goaf safety management, waste rock resource utilization, and efficient ore body mining. Background Technology

[0002] In underground metal mining, the typical structure of "upper void + lower ore body to be mined" is often formed due to factors such as the ore body's occurrence morphology and mining sequence. This structure presents both the core contradiction of the void's instability threatening the safety of the lower mining and the pain points of difficult disposal of excavated waste rock and high backfilling costs. Existing technologies are unable to balance safety, economy, and efficient resource utilization.

[0003] If voids are not properly managed, they are prone to collapse due to creep of the surrounding rock and release of ground stress, leading to instability of the roof of the underlying ore body. Meanwhile, with increased mine capacity, the output of excavated waste rock surges. Traditional waste rock disposal methods either occupy hoisting system capacity, affecting ore transportation efficiency, or pile it on the surface, posing environmental and safety risks such as dust and landslides. Furthermore, void remediation requires a large amount of backfill material, resulting in a double waste of "difficult waste rock disposal + material shortage," which contradicts the need for cost reduction and efficiency improvement.

[0004] In summary, there is an urgent need for an integrated mining method to solve the problems of waste rock resource utilization, isolation layer stability, safe pillar recovery, and cost optimization, so as to ensure safe and efficient mining. Summary of the Invention

[0005] The purpose of this invention is to provide a method for managing multi-section high and steep goaf areas by constructing a composite isolation layer using waste rock and paste co-filling. This method addresses the technical pain points in underground metal mines where "multi-section high and steep goaf areas in the upper part + ore body in the lower part" scenarios, such as the instability of the multi-section high and steep goaf areas threatening the safety of lower mining, difficulties in disposing of excavated waste rock, insufficient reliability of the isolation layer, and prominent contradictions between pillar mining and resource recovery. It achieves the synergistic goals of goaf safety management, waste rock resource utilization, backfilling cost optimization, and efficient mining of the lower ore body, and is applicable to various segmented mining scenarios of underground metal and non-metal mines.

[0006] This invention is based on Figure 1The example shown is the remediation of four intermediate goaf sections. Section 1 (11) represents the lower, unmined section of the goaf. Sections 2 (12), 3 (13), and 4 (14) represent the three intermediate sections of the goaf from bottom to top, each 50m long. At the junction of the upper and lower sections, a composite isolation layer of "pillar + high-strength cemented paste" is constructed to achieve rigid support and flexible buffering. Above the isolation layer, a combined filling mode of "waste rock + low-strength paste" is adopted, forming a synergistic load-bearing structure through waste rock dumping and slope construction combined with low-strength paste coverage. The process includes the following steps: (1) Three-dimensional modeling of the void area: Based on geological exploration data and 3D laser scanning technology, a three-dimensional model of the void area is constructed to clarify the segmented filling boundary of the void area; (2) Installation of filling facilities: Install paste filling pipelines and belt stone throwing machines using the existing intermediate transport roadway and ore extraction roadway; Install paste filling pipeline 3 and belt stone throwing machine 4 using the existing intermediate transport roadway 1 and ore extraction roadway 2. (3) Blocking of related roadways: Based on the three-dimensional model of the empty area, the middle transport roadway 1 is blocked by retaining wall 7 to prevent the loss of grout or the entry of waste rock into other areas; (4) Construction of composite isolation layer: A composite isolation layer is constructed at the junction of the lower ore body and the upper void. The isolation layer consists of a 10m original stable top plate 5 and 40m~50m high-strength paste. 40m~50m of high-strength paste is poured into the middle section 2 12 through the filling pipeline arranged in the middle section 3 13. The curing time is not less than 28 days and the uniaxial compressive strength is ≥5MPa. (5) Waste rock-paste composite backfilling: After the composite isolation layer reaches the strength standard, the construction is carried out by alternating backfilling of waste rock 8 and low-strength paste 9. The low-strength paste is prepared with a ash-sand ratio of 1:20~1:30, and its 28-day uniaxial compressive strength is controlled at 0.2-0.5MPa. The volume ratio of waste rock to low-strength paste is controlled at 1.5~2:1. After the backfilling of the middle section 3 13 is completed, the paste backfilling pipeline 3 and the belt stone throwing machine 4 are moved to the middle section 4 14 roadway to block the associated roadway of the middle section 3 13. The same method as the middle section 3 13 is used to construct the backfilling section by section until the goaf is filled. (6) Ground pressure monitoring: Stress sensors and displacement monitoring devices are installed at key locations in the isolation layer, pillars and surrounding rock of the goaf to monitor stress and displacement in real time. Based on the monitoring data, the safety of mining the lower ore body is ensured. (7) Lower ore mining: After the upper void area waste rock-paste joint filling is completed and the monitoring data is stable, the lower ore body mining operation will be carried out.

[0007] Furthermore, in step (1), the boundary coordinates, volume, shape, and spatial relationship between the upper empty area and the lower ore body are obtained simultaneously.

[0008] Furthermore, this invention takes the goaf as four sections as an example. Section 1 represents the lower unmined body section, and Sections 2, 3, and 4 represent three goaf sections from bottom to top, each section being 50m long.

[0009] Furthermore, in step (2), the filling pipeline and the belt stone-throwing machine are arranged with multiple inlets, and are first arranged in the associated tunnel of the middle section three; Furthermore, in step (3), the high-strength paste is made from tailings and cementing materials, with a ash-sand ratio of 1:4 to 1:8. The paste concentration meets the yield stress range of 50 to 100 Pa. A 40m to 50m isolation layer is poured into the middle section two through the filling pipeline arranged in the middle section three. The curing time is not less than 28 days and the uniaxial compressive strength is ≥5MPa.

[0010] Furthermore, in step (5), the waste rock is selected from the waste rock generated during underground tunneling and mining, with a particle size controlled at 20-200mm and a loose density ≥1.74t / m³. The waste rock is transported to the empty area by the belt dumper arranged in the middle section and piled up to form a buffer slope with a natural angle of repose of 35°-45°.

[0011] Furthermore, in step (5), the low-strength paste is prepared with tailings as aggregate and cementing material as binder, with a ash-sand ratio of 1:10 to 1:20, and its uniaxial compressive strength is controlled to be 0.2-0.5 MPa. The paste concentration meets the yield stress range of 50-100 Pa.

[0012] Furthermore, in step (5), the low-strength paste is filled into the gaps of the waste rock or covered on the surface of the waste rock by means of pipeline pumping or gravity flow. The volume ratio of waste rock to low-strength paste is controlled at 1.5~2:1, and the middle section is filled. Furthermore, in step (7), the middle section of the ore body is mined back. After the mining is completed, the goaf is filled. The reserved 10m original stable roof is mined back 6m by one mining and one mining method, and a 4m thick permanent pillar is reserved to ensure long-term bearing of the upper filling body load and avoid the collapse of the next middle section goaf.

[0013] The above technical solution has at least the following advantages compared with the existing technology: 1) Significantly improved safety and stability: The composite isolation layer effectively reduces the probability of ground pressure in the upper void and mining disturbance and void instability through the synergistic bearing of the "original stable roof + high-strength paste".

[0014] 2) Win-win situation of waste rock resource utilization and cost optimization: improve the utilization rate of waste rock in underground tunneling, reduce the environmental risks of waste rock on the surface and increase transportation costs; reduce the amount of low-strength paste cementitious material used, and reduce the overall filling cost.

[0015] 3) Significantly improved resource recovery rate: The phased mining design of the pillars increases the resource recovery rate to 80%, and the composite isolation layer effectively prevents waste rock from mixing in, keeping the ore dilution rate below 8%.

[0016] 4) Strong process adaptability: Parameters can be flexibly adjusted according to the shape of the void and the ground stress conditions, without the need for large-scale modification of existing facilities, and it is suitable for various underground mining scenarios with "upper void + lower ore body".

[0017] The advantages of this invention are that it not only protects the unmined ore below with a composite isolation layer, but also controls ground pressure and reduces backfilling costs through waste gypsum backfilling, and controls the dilution rate of subsequent recycled ore to below 8%, reducing the overall backfilling cost by 25%-35%. It is suitable for complex goaf management and segmented mining scenarios in deep underground mines such as metal mines and coal mines. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a longitudinal section view of a single-section waste rock-paste filling.

[0020] Figure 2 Plan view of waste rock-paste filling in the entire middle section.

[0021] Figure 3 Flowchart for waste rock-paste filling.

[0022] Figure 4 This is a cross-sectional view of the specific implementation plan for waste rock-paste production line 95.

[0023] Figure 5 This is a schematic diagram of a specific implementation plan.

[0024] In the diagram: 1. Middle section transport roadway; 2. Ore extraction roadway; 3. Filling pipeline; 4. Belt conveyor rock dumper; 5. Original stabilized roof; 6. High-strength paste; 7. Retaining wall; 8. Waste rock; 9. Low-strength paste; 10. Lower ore body to be mined; 11. Middle section 1; 12. Middle section 2; 13. Middle section 3; 14. Middle section 4; 15. Goaf. Detailed Implementation Plan

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be clearly and completely described below in conjunction with their technical solutions. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0026] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0027] It should be noted that the terms "up", "down", "left", "right", "front", and "back" used in this invention are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0028] The method will be described in detail below with specific implementation steps: The method for co-filling waste rock and paste in multi-level goaf based on composite isolation layers includes the following steps: S1. Three-dimensional modeling of the void area: Based on geological exploration data and 3D laser scanning technology, a three-dimensional model of the void area is constructed to clarify the segmented filling boundaries of the void area; S2. Construction of filling facilities: Utilize the existing intermediate transport roadway 1 and ore extraction roadway 2 to construct paste filling pipeline 3 and belt stone throwing machine 4; S3. Blocking of related roadways: Based on the three-dimensional model of the empty area, the middle transport roadway (1) is blocked by retaining walls (7) to prevent the loss of grout or the entry of waste rock into other areas; S4. Isolation layer construction: A composite isolation layer is constructed at the junction of the lower ore body and the upper void. The isolation layer consists of a 10m original stable top plate 5 and a high-strength paste 6 with a length of not less than 40m. S5. Waste rock-paste composite filling: After the composite isolation layer reaches the strength standard, the construction is carried out by alternating filling of waste rock (8) and low-strength paste 9 to complete the filling of the middle section 3 13. Then, the paste filling pipeline 3 and belt stone throwing machine 4 are moved to the middle section 4 14 roadway to block the associated roadway of the middle section 3 13. The construction is carried out in the same way as the lower middle section until the empty area is filled.

[0029] S6. Ground pressure monitoring: Stress sensors and displacement monitoring devices are installed at key locations in the isolation layer, pillars, and surrounding rock of the goaf to monitor stress and displacement in real time. Based on the monitoring data, the safety of mining the lower ore body is ensured.

[0030] S7. Lower Ore Mining: After the upper void area is filled with waste rock and paste and the monitoring data is stable, the lower ore body 15 mining operation will be carried out.

[0031] In step S1, the boundary coordinates, volume, shape and spatial relationship with the lower ore body of the upper void are obtained simultaneously. In this invention, the void is taken as four middle sections. Middle section 11 represents the middle section of the lower ore body, and middle section 2 (12), middle section 3 (13) and middle section 4 (14) represent the middle sections of the three voids from bottom to top, each middle section is 50m.

[0032] In step S2, the filling pipeline 3 and the belt stone-throwing machine 4 are arranged with multiple inlets, and are first arranged in the associated tunnel of the middle section 313.

[0033] In step S3, the high-strength paste is made from tailings and cementitious powder, with a ash-to-sand ratio of 1:6, a paste concentration of 74%, and a yield stress of 65Pa. A 40m isolation layer is poured into the middle section 2 12 through the filling pipeline arranged in the middle section 3 13. The curing time is not less than 28 days and the uniaxial compressive strength is ≥5MPa.

[0034] In step S5, the waste rock is selected from the underground tunneling and mining, with a particle size controlled below 200mm and a loose density of 1.74t / m³. The waste rock is transported to the empty area by the belt dumper 4 arranged in the middle section 313, and piled up to form a buffer slope with a natural angle of repose of about 40°.

[0035] In step S5, the low-strength paste is prepared using tailings as aggregate and cementing powder as binder at a ash-sand ratio of 1:20, and its 28-day uniaxial compressive strength is controlled to be no less than 0.5 MPa.

[0036] In step S5, the low-strength paste is filled into the gaps of the waste rock or covered on the surface of the waste rock by means of pipeline pumping or gravity flow. The volume ratio of waste rock to low-strength paste is controlled to be about 2:1, and the middle section 313 is filled.

[0037] In step S7, the ore body of the middle section 11 is mined. After the mining is completed, the goaf 15 is filled. The reserved 10m original stable roof is mined in a 6m interval using the approach method, and a 4m thick permanent pillar is reserved to ensure long-term bearing of the load of the upper filling body and to avoid the collapse of the next middle section goaf.

[0038] The following description, in conjunction with specific embodiments, illustrates this point.

[0039] A lead-zinc mine is located in the southwest region, and its backfilling capacity is estimated at 900 m³. 3 / shift, rock production 200m per day 3The ore body occurs steeply (dipping angle 75°-85°) in a thick, plate-like form. Old goaf areas exist at a horizontal level of 750-900m in the upper part of the mining area, with the goaf at 750m containing 49,203m³. 3 The mid-range airspace volume at 800 m is 78,874 m. 3 The mid-range airspace volume of 850 is 99,852 m. 3 The lower 700-750m level is a mineralized body with a high average ore grade and significant resource value. Due to the risk of instability in the goaf, the lower ore body has not been mined in the past. The following explanation uses the 95 section of a certain ore body as an example.

[0040] The specific technical solution of the multi-section high and steep goaf treatment method for constructing a composite isolation layer using waste rock-paste synergistic backfilling according to the present invention is as follows: 1) 3D modeling of the empty area: A 3D laser scanner is used to scan the horizontal empty area of ​​750-900m to construct a 3D model of the empty area and divide it into three filling segments: 750-800m, 800-850m, and 850-900m.

[0041] 2) Isolation Layer Construction: A 40m section at the 750m to 790m level serves as an isolation zone separating the old and new goaf areas. This requires the pouring of a high-strength paste (cement-sand ratio 1:6, paste concentration 74%, yield stress 65Pa) covering 36204m. 3 It requires curing for more than 28 days and reaching a strength of 5MPa to form a safe isolation, which also provides a safety guarantee for the subsequent combined filling of paste and waste rock in the upper part.

[0042] 3) Blocking of related roadways: After the isolation zone is formed at the 790-850m level, conduct a statistical survey of the roadways in the 800m middle section and the 834m level of the mining area, and seal them with reinforced concrete retaining walls; 4) Waste rock-low-strength paste combined backfilling: After the isolation zone is formed at the 790-850m level, ensure the roadways in the 800m mid-level and the 834m level mining area are properly sealed. Then, waste rock and paste are dumped and injected from the lower roadway at 854m. When using waste rock and paste for combined backfilling, precise measurement is required. The ratio of waste rock to paste is approximately 2:1, and the waste rock backfilling volume is 61248 m³. 3 The low-strength paste filling volume is 30624 m³. 3 .

[0043] 5) When the filling of the paste + waste rock is close to the 850m level (<5m), stop filling and simultaneously construct a void at the 850m level to seal it. Then, simultaneously fill the waste rock and paste from the 900m level, with a waste rock filling volume of 50738m³. 3 The low-strength paste filling volume is 49123 m³. 3The ratio of waste rock to paste is approximately 2:1, and this process continues until the waste rock and empty areas are completely filled.

[0044] 6) Ground pressure monitoring: 20 monitoring points were set up. The monitoring data showed that the maximum vertical displacement was 0.18 mm and the maximum first principal stress was 3.8 MPa, both of which were within the safe range.

[0045] 7) Lower ore mining: The next intermediate section 700-740 level adopts the upward horizontal layered filling mining method to mine the ore volume. A 6m pillar is reserved for the 740-746 level and the approach method is used for step mining. A 4m permanent roof is left at the 746-750 level to stabilize and bear the upper load.

[0046] Implementation results: By using this method, the mine achieved a waste rock utilization rate of 75%, a 28% reduction in backfilling costs, a ore dilution rate of 7.5%, and a resource recovery rate of 88%. At the same time, it eliminated the risk of instability in the upper void area and ensured the safe mining of the lower ore body.

[0047] The specific filling plan for each layer is shown in Table 1.

[0048] Table 1 Filling Plan for Each Layer level Layered volume Waste rock filling volume Paste filling volume Filling type Filling plan Remark 840-900 34040 15379 18669.5 Waste rock + low strength 77d waste rock + 20 class paste No maintenance required, filled with 5 days of waste rock / paste per shift 865-840 30525 16262 14262 Waste rock + low strength 81d waste rock + 16 class paste No maintenance required, fills with 5 days of waste rock / per shift of paste 850-865 35287 19096 16191 Waste rock + low strength 96d waste rock + 18 class paste No maintenance required. Fill with 5 days' worth of waste rock per shift. 840-850 23616 15744 7872 Waste rock + low strength 79d waste rock + 9 class paste No maintenance required. Fill with 9 days' worth of waste rock / per shift of paste. 825-840 24591 16394 8197 Waste rock + low strength 82d waste rock + 9 class paste No maintenance required. Fill with 9 days' worth of waste rock / per shift of paste. 815-825 10779 7186 3593 Waste rock + low strength 36d waste rock + 4 class paste No maintenance required, fills with 9 days of waste rock / per shift of paste 800-815 19885 13257 6628 Waste rock + low strength 66d waste rock + 8 class paste No maintenance required, fills with 9 days of waste rock / per shift of paste 790-800 12999 8666 4333 Waste rock + low strength 44d+ Waste Rock Class 5 Paste No maintenance required, fills with 9 days of waste rock / per shift of paste 750-790 36204 - 36204 High strength 41-day cream + 28-day maintenance It requires 28 days of curing until the strength reaches 5MPa. total 227929 111978 115951 The following points need to be explained: (1) The equipment involved in the embodiments of the present invention (such as three-dimensional laser scanner, loader, ground stress monitoring equipment, etc.) can be selected according to the actual conditions of the mine, as long as the corresponding functions can be realized.

[0049] (2) Where there is no conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other to obtain new embodiments, all of which are within the protection scope of the present invention.

Claims

1. A method for treating multi-section steep goaf areas by constructing a composite isolation layer using waste rock and paste co-filling, wherein the goaf area consists of four intermediate goaf sections, each 50m long; characterized in that, Includes the following steps: 1) Three-dimensional modeling of the void area: Based on geological exploration data and 3D laser scanning technology, a three-dimensional model of the void area is constructed to clarify the segmented filling boundaries of the void area; 2) Construction of filling facilities: Using the existing intermediate transport roadway (1) and ore extraction roadway (2), a paste filling pipeline (3) and a belt stone throwing machine (4) are constructed. 3) Blocking of related roadways: Based on the three-dimensional model of the empty area, the middle transport roadway (1) is blocked by retaining walls (7) to prevent the loss of grout or the entry of waste rock into other areas; 4) Construction of composite isolation layer: A composite isolation layer is constructed at the junction of the lower ore body and the upper void. The isolation layer consists of a 10m original stable top plate (5) and 40m~50m high-strength paste. The high-strength paste is poured into the middle section two (12) through the filling pipeline arranged in the middle section three (13). The curing time is not less than 28 days and the uniaxial compressive strength is ≥5MPa. 5) Waste rock-paste composite filling: After the strength of the paste reaches the standard, the construction is carried out by alternating filling of waste rock (8) and low strength paste (9). The low strength paste is prepared with a ash-sand ratio of 1:20~1:30 and its 28-day uniaxial compressive strength is controlled at 0.2-0.5MPa. The volume ratio of waste rock to low strength paste is controlled at 1.5~2:

1. After the middle section three (13) is filled, the paste filling pipeline (3) and belt stone throwing machine (4) are moved to the middle section four (14) roadway to block the associated roadway of the middle section three (13). The same method as the middle section three (13) is used to fill the section upwards until the goaf is filled. 6) Ground pressure monitoring safety measures: Stress sensors and displacement monitoring devices are installed at key locations in the isolation layer, pillars and surrounding rock of the goaf to monitor stress and displacement in real time. Based on the monitoring data, the safety of mining the lower ore body is ensured. 7) Lower ore mining: After the upper void area waste rock-paste joint filling is completed and the monitoring data is stable, the lower ore body (15) mining operation can be carried out.

2. The method for treating multi-section high and steep goaf areas by constructing a composite isolation layer using waste rock and paste synergistic backfilling according to claim 1, characterized in that, In step 1), the boundary coordinates, volume, shape, and spatial relationship with the lower ore body of the upper void area are obtained simultaneously.

3. The method for treating multi-section high and steep goaf areas by constructing a composite isolation layer using waste rock and paste synergistic backfilling according to claim 1, characterized in that, In step 2), the filling pipeline (3) and the belt stone-throwing machine (4) are arranged with multiple inlets, and are first arranged in the associated tunnel of the middle section 3 (12).

4. The method for treating multi-section high and steep goaf areas by constructing a composite isolation layer using waste rock and paste synergistic backfilling according to claim 1, characterized in that, Step 3) The high-strength paste is made from tailings and cementing materials with a ash-sand ratio of 1:4 to 1:

8. The paste concentration meets the yield stress range of 50 to 100 Pa. A 40m to 50m isolation layer is poured into the middle section 2 (12) through the filling pipeline arranged in the middle section 3 (13). The curing time is not less than 28 days and the uniaxial compressive strength is ≥5MPa.

5. The method for treating multi-section high and steep goaf areas by constructing a composite isolation layer using waste rock and paste synergistic backfilling according to claim 1, characterized in that, In step 5), the waste rock is selected from the underground development and preparation. The particle size is controlled between 20mm and 200mm, and the loose density is ≥1.74t / m³. The waste rock is transported to the empty area by the belt dumper (4) arranged in the middle section (13) and piled up to form a buffer slope with a natural angle of repose of 35°-45°.

6. The method for treating multi-section high and steep goaf areas by constructing a composite isolation layer using waste rock and paste synergistic backfilling according to claim 1, characterized in that, Step 5) The low-strength paste is prepared using tailings as aggregate and cementing material as binder at a ash-sand ratio of 1:20~1:

30. Its 28-day uniaxial compressive strength is controlled at 0.2-0.5MPa, and the paste concentration meets the yield stress range of 50~100Pa.

7. The method for treating multi-section high and steep goaf areas by constructing a composite isolation layer using waste rock and paste synergistic backfilling according to claim 5, characterized in that, The low-strength paste is pumped through a pipeline or by gravity flow to fill the gaps between waste rocks or cover the surface of waste rocks. The volume ratio of waste rocks to low-strength paste is controlled at 1.5~2:1, and the middle section (13) is filled.

8. The method for treating multi-section high and steep goaf areas by constructing a composite isolation layer using waste rock and paste synergistic backfilling according to claim 1, characterized in that, In step 7), the middle section (11) ore body is mined back. After the mining is completed, the goaf (15) is filled. The reserved 10m original stable roof is mined back 6m by the approach method, and a 4m thick permanent pillar is reserved to ensure long-term bearing of the upper filling body load and avoid the collapse of the next middle section goaf.

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