Combined method of upward access filling and artificial false roof construction in open-pit boundary pillar recovery

Abstract

The present invention provides a combined method of upward approach filling and artificial false roof construction for recovering open-pit boundary pillars, and relates to the field of mining engineering technology. The method is applicable to the mining conditions of steeply inclined thin to medium-thick open-pit boundary pillars, and includes the following steps: S1, leveling the slope of the open-pit pit bottom; S2, obtaining the construction structure and construction parameters of the artificial false roof through mathematical analysis and numerical simulation technology; S3, first leaving an isolation layer at the bottom of the artificial false roof; then carrying out the construction of the artificial false roof; S4, filling the part of the open-pit pit bottom other than the artificial false roof, and setting a drainage ditch with a predetermined drainage slope and sloping toward the edge of the pit bottom on the surface of the filled pit bottom; S5, recovering the open-pit boundary pillars by the upward approach filling method. The method has a simple process, a clear artificial false roof construction process, and the equipment and materials used are widely used in mines, and has strong applicability to the mining of similar steeply inclined thin to medium-thick open-pit boundary pillars.

Description

Technical Field

[0001] The present application relates to the technical field of mining engineering, and in particular to a combined method of upward access filling and artificial false roof construction for recovering open-pit boundary pillars. Background Art

[0002] For medium-thick to thick steeply inclined ore deposits with deep ore bodies, shallow cover layers, or exposed on the surface, the advantages of open-pit mining in the early stage are remarkable, so it is widely used at home and abroad. When open-pit mining reaches a certain level, it should generally be converted to underground mining for cost, safety and other considerations. The transition method of reserving or artificially constructing boundary pillars is generally adopted at home and abroad, that is, in the final boundary part of the open pit, a boundary pillar of a certain thickness is reserved or constructed to ensure the production safety of the open pit, isolate the space between open pit production and underground production, and avoid mutual interference between the two.

[0003] As underground mining enters deeper areas, it is necessary to recover the reserved boundary pillars. Currently, two mining methods are basically adopted at home and abroad: open-pit decline and push mining and underground mining + construction of artificial false roof. The mining cost of open-pit decline and push mining is relatively high, and the slope needs to be re-stripped, with a long engineering period and economic investment. The underground mining + construction of artificial false roof method mainly depends on the determination of the safe thickness of the isolation layer and the construction parameters of the artificial false roof. Most mines rely on relevant similar experience to design the artificial false roof without considering the influence of the actual geological conditions of the mine. This can easily lead to problems such as lack of basis for construction parameters, unreasonable construction strength, safety risks of the artificial false roof, or excessive cost of artificial false roof construction.

[0004] In view of this, it is necessary to study a combined method of upward access filling and artificial false roof construction for mining open-pit boundary pillars to solve the above technical problems. Summary of the invention

[0005] In view of the technical problems existing in the background technology, the present application provides a combined method of upward route filling and artificial false roof construction for mining open-pit boundary pillars. Based on the mining conditions of steeply inclined thin to medium-thick open-pit boundary pillars, an ideal mathematical model is first used for semi-quantitative research, and then a mechanical model is established to study the safe thickness of the isolation layer, which can not only improve the overall stability of the boundary pillars, but also produce a portion of the ore earlier, ensuring a smooth transition from open-pit to underground mining capacity; the economy and safety of mining open-pit boundary pillars using the upward route filling method are analyzed through mathematical analysis and numerical simulation technology; the bottom stress-bearing parts of the artificial false roof are set on the upper and lower rock masses on both sides of the ore vein, so that the artificial false roof is connected to the upper and lower surrounding rocks through the extension of the artificial false roof, forming an embedded complete boundary pillar, ensuring safe production in underground mining.

[0006] Based on the above technical purpose, the present invention provides a combined method of upward access filling and artificial false roof construction for mining open-pit boundary pillars, which is suitable for mining conditions of steeply inclined thin to medium-thick open-pit boundary pillars, and includes the following steps:

[0007] S1, after the open-pit mining is completed, the bottom of the open-pit pit is leveled;

[0008] S2, first use the ideal mathematical model to conduct semi-quantitative research, then establish a mechanical model to conduct numerical simulation verification, and obtain the construction structure and construction parameters of the artificial false roof;

[0009] S3, first leave an isolation layer at the bottom of the artificial false roof; then carry out the construction of the artificial false roof;

[0010] S4, filling the bottom of the open pit other than the artificial false roof, and setting a drainage ditch with a predetermined drainage slope and sloping toward the edge of the pit bottom on the surface of the filled pit bottom;

[0011] S5, the open-pit boundary pillars are mined using the upward approach filling method.

[0012] As a further improvement of the present invention, in step S2, the ideal mathematical model includes a thickness-span ratio method, a load transfer intersection line method, a collapse filling method, and a Pusch pressure arch method; the mechanical model includes a maximum principal stress model, a settlement displacement model, and a plastic zone model;

[0013] Based on the safe thickness range of the artificial false roof calculated by the ideal mathematical model, a mechanical model was established to simulate and analyze the maximum principal stress, settlement displacement and plastic zone distribution of the mining site and the artificial false roof after mining. The stability parameters of different false roof thicknesses under the mining processes of one-in-one and one-in-five were studied, thereby obtaining the construction structure and construction parameters of the artificial false roof.

[0014] As a further improvement of the present invention, in step S3, the construction structure of the artificial false roof bottom isolation layer is: first leave a 50mm thick powdered rock with a particle size less than 10mm underneath, then lay a 0.5mm thick geomembrane, and finally leave a 100mm plain concrete cushion layer.

[0015] As a further improvement of the present invention, in step S3, the artificial false ceiling is constructed as follows: through theoretical verification of the stress characteristics and boundary conditions of the reinforced concrete artificial false ceiling, and summarizing the construction experience of reinforced concrete artificial false ceiling in metal mines in recent years, it is designed to use reinforced concrete materials to construct the artificial false ceiling, the thickness is set to 1.5m, and C30 concrete is used for pouring, wherein the design value of the concrete compressive strength is not less than 14.3MPa, and the design value of the tensile strength is not less than 1.43MPa; it is arranged along the direction of the ore body and extends 2m to both sides of the ore body.

[0016] As a further improvement of the present invention, the artificial ceiling adopts a double-layer steel mesh structure, which is arranged at the top and bottom of the artificial ceiling respectively; HRB400 threaded steel is used, the design value of tensile strength is not less than 360MPa, the thickness of the steel mesh protective layer is set to 100mm, the main reinforcement is perpendicular to the approach direction and a threaded steel bar with a diameter of 20mm is arranged every 20cm, and the secondary reinforcement is arranged along the approach direction and a threaded steel bar with a diameter of 12mm is arranged every 25cm; the top steel mesh is a structural anti-cracking steel bar, and the bottom steel mesh is a stress-bearing steel bar.

[0017] As a further improvement of the present invention, in step S5, the mining field structure of the upward approach filling method is arranged as follows: the mining field is arranged along the strike of the ore body, the height is the height of the isolation pillars, and the width is the horizontal thickness of the ore body; every other ore block is mined, and no intermediate pillars, top pillars, or bottom pillars are left between the ore blocks; the approach width is 3.0m to 3.5m, and the mining height is 3.0m to 3.5m; the mining field approach is arranged along the strike, the approach length is 25m to 30m, and mining is carried out from bottom to top and from the south side to the north side of the ore body.

[0018] As a further improvement of the present invention, the upward approach filling method is in the form of a roadway, each approach is mined, supported, and filled at intervals, and mined layer by layer from bottom to top in a layered manner, including one-step approach mining and two-step approach mining;

[0019] Among them, the one-step approach mining is "mine once every other step", and the two-step approach mining is "fill two and mine once"; after the one-step approach is filled and maintained, the two-step approach is mined; after the approach is mined, it is filled immediately, and after the entire layered approach is mined and filled, the layer transfer is achieved by using the layered connecting road top pressure method, and then the mining of the new layered approach is started.

[0020] As a further improvement of the present invention, in the construction of artificial false roof, the pouring method of C30 concrete adopts layered continuous pouring or push-type continuous pouring. When the interval time between layers exceeds the initial setting time of concrete, the layer is treated as a construction joint; the layer is treated as a construction joint, and thermal insulation and maintenance are carried out in time after each concrete pouring is completed;

[0021] The artificial false roof construction adopts a step-by-step and layered excavation and construction process, and an expansion joint is arranged every 20m, eventually forming an integral open pit artificial false roof.

[0022] As a further improvement of the present invention, the strength of the filling body of the first-step access road is not less than 1.5MPa; the second step is to fill only the goaf; a cemented filling body with a thickness of 0.5m and a strength of 3MPa to 5MPa is poured on the surface of the filling body of each access road;

[0023] After the filling body hardens, the gap between the filling body and the artificial false ceiling is grouted.

[0024] As a further improvement of the present invention, the specific process for leveling the slope in step S1 is: a shallow hole micro-difference blasting method is adopted at the bottom of the open-pit mine to provide a flat slope for the construction of the artificial false roof in the next step, ensuring that the bottom plate is flat, the two bottom corners are straight, and there is no water accumulation.

[0025] The beneficial effects of the present invention are:

[0026] 1. The combined method of upward access filling and artificial false roof construction for mining open-pit boundary pillars provided by the present invention analyzes the economy and safety of mining open-pit boundary pillars using the upward access filling method through mathematical analysis and numerical simulation technology; determines the required materials and structural parameters for constructing the artificial false roof with the help of material mechanics theory and numerical simulation methods, ensuring the reliable and safe construction of the artificial false roof. Therefore, the mining method and its process are scientific, reasonable, economical and safe.

[0027] 2. The combined method of upward access filling and artificial false roof construction for recovering open-pit boundary pillars provided by the present invention has a simple process and a clear artificial false roof construction procedure. The equipment and materials used are widely used in mines and have strong applicability to the mining of similar steeply inclined thin to medium-thick open-pit boundary pillars.

[0028] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings used in the present application. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 A schematic diagram of the combined method of upward access filling and artificial false roof construction for mining open-pit boundary pillars provided by the present invention;

[0031] Figure 2 The plane distribution and cross-sectional view of the artificial false roof at the bottom of the open pit provided by the present invention;

[0032] Figure 3 A schematic diagram of the bottom structure and reinforcement of the artificial false roof provided by the present invention;

[0033] Figure 4 A schematic diagram of the mechanical structure of the artificial false roof provided by the present invention;

[0034] Figure 5A distribution diagram of monitoring point locations in the false roof model provided by the present invention;

[0035] Figure 6 Schematic diagram of the false roof and Z-direction displacement of the mining field under the artificial false roof of 1m thickness provided by the present invention ((a) represents the settlement displacement of the false roof when the ore block adopts the one-for-one mining arrangement; (b) represents the settlement displacement of the mining field when the mining field adopts the one-for-one mining arrangement; (c) represents the settlement displacement of the false roof when the ore block adopts the one-for-five mining arrangement; (d) represents the settlement displacement of the mining field when the mining field adopts the one-for-five mining arrangement);

[0036] Figure 7 Schematic diagram of the false roof and Z-direction displacement of the mining field under the artificial false roof thickness of 1.5m provided by the present invention ((a) represents the settlement displacement of the false roof when the ore block adopts the one-for-one mining arrangement; (b) represents the settlement displacement of the mining field when the mining field adopts the one-for-one mining arrangement; (c) represents the settlement displacement of the false roof when the ore block adopts the one-for-five mining arrangement; (d) represents the settlement displacement of the mining field when the mining field adopts the one-for-five mining arrangement);

[0037] Figure 8 Schematic diagram of the false roof and Z-direction displacement of the mining field under the artificial false roof thickness of 2.0m provided by the present invention ((a) represents the settlement displacement of the false roof when the ore block adopts the one-for-one mining arrangement; (b) represents the settlement displacement of the mining field when the mining field adopts the one-for-one mining arrangement; (c) represents the settlement displacement of the false roof when the ore block adopts the one-for-five mining arrangement; (d) represents the settlement displacement of the mining field when the mining field adopts the one-for-five mining arrangement);

[0038] Fig. 9 Schematic diagram of the false roof and maximum principal stress of the mining field under the artificial false roof of 1m thickness provided by the present invention ((a) represents the maximum tensile stress of the false roof when the ore block adopts the one-for-one mining arrangement; (b) represents the maximum tensile stress of the mining field when the mining field adopts the one-for-one mining arrangement; (c) represents the maximum tensile stress of the false roof when the ore block adopts the one-for-five mining arrangement; (d) represents the maximum tensile stress of the mining field when the mining field adopts the one-for-five mining arrangement);

[0039] Fig.10 Schematic diagram of the false roof and maximum principal stress of the mining field when mining with an artificial false roof of 1.5m thickness provided by the present invention ((a) represents the maximum tensile stress of the false roof when the ore blocks are mined one by one in an alternate mining arrangement; (b) represents the maximum tensile stress of the mining field when the mining field is mined one by one in an alternate mining arrangement; (c) represents the maximum tensile stress of the false roof when the ore blocks are mined one by one in an alternate mining arrangement; (d) represents the maximum tensile stress of the mining field when the mining field is mined one by one in an alternate mining arrangement);

[0040] Fig.11Schematic diagram of the false roof and maximum principal stress of the mining field when mining with an artificial false roof of 2.0m thickness provided by the present invention ((a) represents the maximum tensile stress of the false roof when the ore block adopts the one-for-one mining arrangement; (b) represents the maximum tensile stress of the mining field when the mining field adopts the one-for-one mining arrangement; (c) represents the maximum tensile stress of the false roof when the ore block adopts the one-for-five mining arrangement; (d) represents the maximum tensile stress of the mining field when the mining field adopts the one-for-five mining arrangement);

[0041] Fig.12 Schematic diagram of false roof and plastic zone of mining field under the artificial false roof thickness of 1m provided by the present invention ((a) represents the plastic zone distribution of false roof when the ore block adopts the one-for-one mining arrangement; (b) represents the plastic zone distribution of mining field when the mining field adopts the one-for-one mining arrangement; (c) represents the plastic zone distribution of false roof when the ore block adopts the one-for-five mining arrangement; (d) represents the plastic zone distribution of mining field when the mining field adopts the one-for-five mining arrangement);

[0042] Fig.13 Schematic diagram of false roof and plastic zone of mining field under the artificial false roof thickness of 1.5m provided by the present invention ((a) represents the plastic zone distribution of false roof when the ore block adopts the one-for-one mining arrangement; (b) represents the plastic zone distribution of mining field when the mining field adopts the one-for-one mining arrangement; (c) represents the plastic zone distribution of false roof when the ore block adopts the one-for-five mining arrangement; (d) represents the plastic zone distribution of mining field when the mining field adopts the one-for-five mining arrangement);

[0043] Fig.14 Schematic diagram of false roof and plastic zone of mining field under the artificial false roof thickness of 2.0m provided by the present invention ((a) represents the plastic zone distribution of false roof when the ore block adopts the one-for-one mining arrangement; (b) represents the plastic zone distribution of mining field when the mining field adopts the one-for-one mining arrangement; (c) represents the plastic zone distribution of false roof when the ore block adopts the one-for-five mining arrangement; (d) represents the plastic zone distribution of mining field when the mining field adopts the one-for-five mining arrangement);

[0044] Fig.15 The Z-direction displacement monitoring diagram of the five monitoring points inside the artificial false roof with a thickness of 1m provided by the present invention ((a) represents the Z-direction displacement of the five monitoring points inside the false roof when the ore block adopts the one-for-one mining arrangement; (b) represents the Z-direction displacement of the five monitoring points inside the false roof when the ore block adopts the one-for-five mining arrangement);

[0045] Fig.16 The Z-direction displacement monitoring diagram of five monitoring points inside the artificial false roof with a thickness of 1.5 m provided by the present invention ((a) represents the Z-direction displacement of five monitoring points inside the false roof when the ore block adopts the one-for-one mining arrangement; (b) represents the Z-direction displacement of five monitoring points inside the false roof when the ore block adopts the five-for-one mining arrangement);

[0046] Fig.17The Z-direction displacement monitoring diagram of the five monitoring points inside the artificial false roof with a thickness of 2.0 m provided by the present invention ((a) represents the Z-direction displacement of the five monitoring points inside the false roof when the ore block adopts the one-for-one mining arrangement; (b) represents the Z-direction displacement of the five monitoring points inside the false roof when the ore block adopts the one-for-five mining arrangement);

[0047] Description of reference numerals:

[0048] 1. Along-vein transport tunnel; 2. Through-vein tunnel; 3. Chute connecting road; 4. Layered connecting road; 5. Segmented tunnel; 6. Ore chute; 7. Filter well; 8. Filling return air shaft; 9. Mining area ramp; 10. One-step mining access road; 11. Two-step mining access road; 12. Return air tunnel; 13. Artificial false roof; 14. C30 concrete; 15. Drainage ditch; 16. Expansion joint; 17. Powdered rock; 18. Geomembrane; 19. Plain concrete cushion; 20. Main reinforcement; 21. Secondary reinforcement. DETAILED DESCRIPTION

[0049] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0051] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0052] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0053] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0054] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0055] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present application.

[0056] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0057] In view of the shortcomings of the existing methods for recovering open-pit boundary pillars, the present application provides a combined method of upward route filling and artificial false roof construction for recovering open-pit boundary pillars. Based on the mining conditions of steeply inclined thin to medium-thick open-pit boundary pillars, an ideal mathematical model is first used for semi-quantitative research, and then a mechanical model is established to study the safe thickness of the isolation layer. This can not only improve the overall stability of the boundary pillars, but also produce a portion of the ore earlier, ensuring a smooth transition from open-pit to underground mining capacity; the economy and safety of recovering open-pit boundary pillars using the upward route filling method are analyzed through mathematical analysis and numerical simulation technology; the bottom stress-bearing part of the artificial false roof is set on the upper and lower rock masses on both sides of the ore vein, so that the artificial false roof is connected to the upper and lower surrounding rocks through the extension of the artificial false roof, forming an embedded complete boundary pillar, ensuring safe production in underground mining. It is suitable for the mining conditions of steeply inclined thin to medium-thick open-pit boundary pillars, and includes the following steps:

[0058] S1, after the open-pit mining is completed, the bottom of the open-pit pit is leveled;

[0059] S2, first use the ideal mathematical model to conduct semi-quantitative research, then establish a mechanical model to conduct numerical simulation verification, and obtain the construction structure and construction parameters of the artificial false roof;

[0060] S3, first leave an isolation layer at the bottom of the artificial false roof; then carry out the construction of the artificial false roof;

[0061] S4, filling the bottom of the open pit other than the artificial false roof, and setting a drainage ditch with a predetermined drainage slope and sloping toward the edge of the pit bottom on the surface of the filled pit bottom;

[0062] S5, the open-pit boundary pillars are mined using the upward approach filling method.

[0063] Preferably, in step S2, the ideal mathematical model includes a thickness-span ratio method, a load transfer intersection line method, a collapse filling method, and a Pusch pressure arch method; the mechanical model includes a maximum principal stress model, a settlement displacement model, and a plastic zone model;

[0064] Based on the safe thickness range of the artificial false roof calculated by the ideal mathematical model, a mechanical model was established to simulate and analyze the maximum principal stress, settlement displacement and plastic zone distribution of the mining site and the artificial false roof after mining. The stability parameters of different false roof thicknesses under the mining processes of one-in-one and one-in-five were studied, thereby obtaining the construction structure and construction parameters of the artificial false roof.

[0065] Preferably, in step S3, the construction structure of the artificial false roof bottom isolation layer is: firstly leave powdered rock with a thickness of 50 mm and a particle size less than 10 mm underneath, then lay a 0.5 mm thick geomembrane, and finally leave a 100 mm plain concrete cushion layer.

[0066] Preferably, in step S3, the artificial false roof is constructed as follows: the thickness is set to 1.5m, and C30 concrete is used for pouring, wherein the design value of the concrete compressive strength is not less than 14.3MPa, and the design value of the tensile strength is not less than 1.43MPa; it is arranged along the direction of the ore body and extends 2m to both sides of the ore body.

[0067] Preferably, the artificial ceiling adopts a double-layer steel mesh structure, which is arranged at the top and bottom of the artificial ceiling respectively; HRB400 rebar is used, the design value of tensile strength is not less than 360MPa, the thickness of the steel mesh protective layer is set to 100mm, the main reinforcement is arranged perpendicular to the approach direction with a 20mm diameter rebar every 20cm, and the secondary reinforcement is arranged along the approach direction with a 12mm diameter rebar every 25cm; the top steel mesh is structural anti-cracking steel bar, and the bottom steel mesh is stress-bearing steel bar.

[0068] Preferably, in step S5, the stope structure of the upward approach filling method is arranged as follows: the stope is arranged along the strike of the ore body, the height is the height of the isolation pillars, and the width is the horizontal thickness of the ore body; every other ore block is mined, and no intermediate pillars, top pillars, or bottom pillars are left between the ore blocks; the approach width is 3.0m to 3.5m, and the mining height is 3.0m to 3.5m; the stope approach is arranged along the strike, the approach length is 25m to 30m, and mining is carried out from bottom to top and from the south side to the north side of the ore body.

[0069] Preferably, the upward approach filling method is in the form of a roadway, with each approach being mined, supported, and filled at intervals, and mined layer by layer from bottom to top in a layered manner, including one-step approach mining and two-step approach mining;

[0070] Among them, the one-step approach mining is "mine once every other step", and the two-step approach mining is "fill two and mine once"; after the one-step approach is filled and maintained, the two-step approach is mined; after the approach is mined, it is filled immediately, and after the entire layered approach is mined and filled, the layer transfer is achieved by using the layered connecting road top pressure method, and then the mining of the new layered approach is started.

[0071] Preferably, in the construction of artificial false roof, the pouring method of C30 concrete adopts layered continuous pouring or push-type continuous pouring. When the interval time between layers exceeds the initial setting time of concrete, the layer surface is treated as a construction joint.

[0072] The artificial false roof construction adopts a step-by-step and layered excavation and construction process, and an expansion joint is arranged every 20m, eventually forming an integral open pit artificial false roof.

[0073] Preferably, the strength of the filling body of the first-step access road is not less than 1.5MPa; the second step is to fill only the goaf; a cemented filling body with a thickness of 0.5m and a strength of 3MPa to 5MPa is poured on the surface of the filling body of each access road;

[0074] After the filling body hardens, the gap between the filling body and the artificial false ceiling is grouted.

[0075] Preferably, the specific process for leveling the slope in step S1 is: leveling the slope by shallow hole micro-difference blasting at the bottom of the open pit.

[0076] The present invention is supported and further explained below in conjunction with specific embodiments and drawings, but the following description does not constitute a limitation to the claims of the present invention.

[0077] Example 1

[0078] The isolation layer ore body of a gold mine is a steeply inclined thin to medium-thick ore body with a relatively simple shape and occurrence. It is generally a steeply inclined large vein shape with a high ore grade. According to the occurrence characteristics of this part of the ore body, the mining plan is to use the upward approach filling method + artificial false roof construction to carry out open-pit boundary pillar mining. Figures 1 to 4 As shown. This method requires the construction of a reinforced concrete artificial false roof 13 at the bottom of the open pit in advance. After the artificial false roof 13 is formed, the boundary pillar is recovered by the upward access filling method underground. It mainly includes the following steps:

[0079] Step S1, after the open-pit mining is completed, a shallow hole micro-difference blasting method is adopted at the bottom of the open-pit mine to provide a flat slope surface for the construction of the artificial false roof 13 in the next step.

[0080] Step S2, first use an ideal mathematical model to conduct a semi-quantitative study, then establish a mechanical model to analyze, correct, supplement and verify, and obtain the construction structure and construction parameters of the artificial ceiling 13;

[0081] Specifically: through theoretical verification of the stress characteristics and boundary conditions of the reinforced concrete artificial false ceiling 13, and summarizing the construction experience of reinforced concrete artificial false ceiling in metal mines in recent years, it is designed that the artificial false ceiling 13 is made of C30 concrete 14 material with a thickness of 1.5m. It is arranged along the direction of the ore body and extends 2m to both sides of the ore body to ensure that the artificial false ceiling 13 effectively covers the ore body; the bottom of the open pit outside the artificial false ceiling 13 is filled with C30 concrete 14, and a 2% drainage slope is set on the surface, sloping towards the drainage ditch 15 at the edge of the pit bottom.

[0082] Step S3, in order to prevent the artificial false ceiling 13 from having through cracks, an isolation layer is set at the bottom of the artificial false ceiling 13. The structure of the isolation layer is: firstly, a powdered rock 17 (with a particle size less than 10 mm) of about 50 mm is set at the bottom, then a geomembrane 18 of 0.5 mm thickness is laid, and finally a plain concrete cushion 19 of 100 mm is set.

[0083] The reinforced concrete artificial false ceiling 13 adopts double-layer steel mesh, HRB400 threaded steel, and the tensile strength design value is 360MPa. The steel mesh is arranged at the top and bottom of the artificial false bottom. The top is structural anti-cracking steel, the protective layer thickness is 100mm, the main reinforcement 20 is arranged at every 20cm interval of a threaded steel with a diameter of 20mm, and the secondary reinforcement 21 is arranged at every 25cm interval of a threaded steel with a diameter of 12mm along the approach direction; the bottom is stress-bearing steel, the protective layer thickness is 100mm, the main reinforcement 20 is arranged at every 20cm interval of a threaded steel with a diameter of 20mm, and the secondary reinforcement 21 is arranged at every 25cm interval of a threaded steel with a diameter of 12mm along the approach direction.

[0084] The pouring method of C30 concrete 14 can be layered continuous pouring or push-type continuous pouring. When the interval time between layers exceeds the initial setting time of concrete, the surface layer is treated as a construction joint, and thermal insulation and maintenance are carried out in time after each concrete pouring.

[0085] As the distance to the bottom of the open pit is relatively large, the construction of the artificial false roof 13 adopts a step-by-step and layered excavation and construction process, and an expansion joint 16 is arranged every 20m, finally forming an integral open pit artificial false roof 13.

[0086] Step S4, using the upward approach filling method to recover the open-pit boundary pillars.

[0087] The stope is arranged along the strike of the ore body. The block is 50m long, 28m high as the isolation pillar, and 10.5m wide as the horizontal thickness of the ore body. The block is mined one block at a time, and no pillars, top pillars, or bottom pillars are left between blocks. The access road is 3.0m to 3.5m wide, and the mining height is 3.0m to 3.5m. The cross section of each stope is determined according to the stability of the stope and the thickness of the ore body. The smaller value is taken when it is not stable, and the larger value is taken when it is relatively stable. The stope access road is arranged along the strike, and the access road is 25m to 30m long. Mining is carried out from bottom to top and from the south side of the ore body to the north side.

[0088] The upward approach filling mining method uses the roadway method, with each approach carrying out mining, support and filling at intervals, and mining layer by layer from bottom to top, effectively controlling the exposed area and exposure time of the roof;

[0089] The first-step approach is to mine once every other step, and the second-step approach is to mine once every two steps. After the first-step approach has been filled and maintained for a sufficient period of time, the second-step approach can be mined. After the approach is mined, it is filled immediately. After the entire layered approach is mined and filled, the layer transfer is achieved by using the layered connecting road top pressure method, and the new layered approach is mined.

[0090] The mining between the layered access roads is divided into two steps. In the first step, the strength of the access filling body is not less than 1.5MPa after 28 days, ensuring a certain strength and self-sustaining, and being able to withstand the impact of blasting vibration; in the second step, only the goaf is filled, and the filling body strength requirement is relatively low, which can meet the normal walking of trackless equipment. In order to ensure that the scraper can walk normally on the filling body, reduce the wear of the scraper tires, ore loss and depletion, a cemented filling body with a thickness of 0.5m and a strength of 3MPa to 5MPa is poured on the surface of each access filling body.

[0091] According to the mining process of upward horizontal layered entry filling mining method, there are two mechanical structural states in the non-end entry during layered mining: one is that when the one-step entry is mined, the two sides of the empty entry are the unmined bodies of the two-step, and the reinforced concrete artificial false roof at the empty entry is supported on the ore body, and the span of the artificial false roof is about 3.5m; the other is that when the two-step entry is mined, the two sides of the empty entry are the filling bodies of the one-step entry, and the reinforced concrete artificial false roof at the empty entry is supported on the filling body, and the span of the artificial false roof is about 3.5m. The bearing capacity is verified by material mechanics theory and related numerical simulation tests are carried out to verify the safety and rationality of the reinforced concrete artificial false roof.

[0092] Due to the high water content of the filling body, it shrinks greatly during the hardening process, and it is difficult to connect the filling body with the artificial false ceiling 13, causing the filling body and the artificial false ceiling 13 to be separated. The filling body cannot serve as an effective support end of the artificial false ceiling 13, which increases the span of the artificial false ceiling 13 and cracks the top of the board. In order to ensure that the filling body can form an effective support for the artificial false ceiling 13, the gap between the filling body and the artificial false ceiling 13 needs to be grouted after the filling body hardens.

[0093] The specific calculation process in step S2 is as follows:

[0094] Those skilled in the art know that the artificial false roof 13 can be regarded as the top pillar of the mining area, and its stability calculation is similar to that of the top pillar. There are many factors that affect the stability of the roof of the goaf. The internal factors include the physical and mechanical properties of the rock mass, the chemical properties of the ore rock and its weathering resistance, the occurrence of the rock strata and the joint and fissure conditions, the fault changes of the rock strata and the integrity of the rock mass, the span and shape of the goaf, the geological structure of the ore deposit and the filling of the goaf. The external factors include the impact of earthquakes and blasting vibrations, the water-proof properties of the rock strata and its weakening effect on water, the weathering effect of the natural environment, the size of the load and its number and time of action, temperature, humidity, etc.

[0095] This method uses the approach filling method and is mined in two steps. During each step of mining, there are ore bodies or filling bodies on both sides of the approach. The filling body has a certain supporting effect, but its strength is far from that of the ore body. When using mathematical models for quantitative analysis, the model will be more idealized and cannot take into account the influence of multiple factors at the same time. If one approach is taken as the research object, and factors such as the strength of the filling body and the disturbance caused by nearby mining are ignored, the calculated result will be smaller than the actual result; if the entire layer is considered, that is, the supporting effect of the filling body is ignored, the calculated result will be larger than the actual result.

[0096] In view of the above factors, this method first uses an ideal mathematical model for semi-quantitative research, and then studies the safety thickness of the artificial false ceiling 13 by establishing a mechanical model for analysis, correction, supplementation and verification.

[0097] Firstly, a variety of mathematical models are used for research and calculation.

[0098] 1) Thickness-span ratio method

[0099] According to the thickness-to-span ratio theory and calculation method, H / W ≥ 0.5 is obtained from the approximate horizontal projection span W and the thickness H of the thinnest part of the isolation layer. Regardless of the roof shape, load size and nature, the ratio of the thickness of the safety isolation layer to the span of the goaf is required to be greater than or equal to 0.5. Due to the poor stability of rectangular caverns compared to arched caverns, as well as other factors, the approximate horizontal state H / W is used as the minimum ratio for estimating the safety thickness. By introducing the safety factor K, the relationship between the span of the goaf and the thickness of the safety isolation layer under different safety conditions can be obtained, that is, H / (KW) ≥ 0.5 is safe, and the calculation formula is as follows:

[0100]

[0101] Where: H—thickness of safety isolation layer, m;

[0102] W—span of goaf, m;

[0103] K—Safety factor.

[0104] The selection of safety factor is determined by referring to the domestic and foreign roof stability research practices. The safety factor used by domestic and foreign mines is usually K=1.15. The isolation pillar of Dong'an Gold Mine adopts the upward approach filling method for mining. The span of the mining area is 3.0m~3.5m, so the estimated thickness of the safety isolation layer is 1.7m~2.0m.

[0105] 2) Load transfer intersection line method

[0106] Assuming that the load is transferred downward from the center of the roof at a diffusion angle of 30° to 35° with the vertical line, when this transfer line is outside the intersection of the roof and the two sides, it is considered that the goaf directly supports the external load and deadweight on the roof, and the roof is safe. Considering the safety factor, the safe thickness of the roof is:

[0107]

[0108] Where: H—safety thickness of top plate, m;

[0109] b—span of goaf, m;

[0110] β—the angle between the transmission line and the vertical line at the center of the isolation layer;

[0111] K—Safety factor.

[0112] Using the load transfer intersection line method, the relationship between the span of different goafs and the safe artificial false top layer thickness of their roofs is obtained. The calculation results are shown in Table 1 below.

[0113] Table 1 Results of minimum safety thickness calculated by the load transfer intersection line method

[0114]

[0115] 3) Collapse and fill method

[0116] This method believes that after the roof of the goaf collapses, the volume of the collapsed body increases. When it collapses to a certain height, the goaf fills itself up. The collapse height plus an appropriate safety factor is the safe thickness of the roof collapse, which is also the height of the collapse balance arch.

[0117] Assume that the volume of the void is V0, the height is H0, the collapse volume is V, the height is H, and the rock looseness coefficient is K. By assumption, we can get:

[0118] V·K=V0+V, then: V=V0 / (K-1)

[0119] If the cross section of the goaf is a rectangle, the calculation formula can be simplified to:

[0120]

[0121] According to the above formula, the loose coefficient of Dong'an gold mine is K=1.5, H=2H0.

[0122] The goaf's caving height is twice the mining height. After mining using the upward approach filling method, the maximum exposed height is 3.0m to 3.5m. Therefore, an artificial false ceiling of 1.5m to 1.75m should be left when using this mining method.

[0123] 4) Calculation results of the Pugh pressure arch method

[0124] The Pugh pressure arch theory is applicable to the rock formations with weathering and crushing of the roof. When the goaf does not collapse, it is equivalent to the natural arch being in a balanced state. If collapse occurs, a fracture arch is formed, and the fracture arch height H is:

[0125]

[0126] Where: H—safety top plate thickness, m;

[0127] b—width of goaf, m;

[0128] h—height of goaf, m;

[0129] φ—internal friction angle, °;

[0130] f—strength coefficient.

[0131] The weight of the rock mass above the ruptured arch is borne by the arch. Since a certain thickness is required to bear the upper load, the safe thickness of the roof of the goaf is the height of the ruptured arch plus the thickness required for the upper load. Considering the influence of the safety factor, the calculated safe roof thickness is 1.45m.

[0132] The above four methods of establishing mathematical models based on quantitative and semi-quantitative evaluation methods are for analysis and research on single access routes. The influence of factors such as surrounding rock, filling body and mining disturbance is not considered. However, there are many factors that affect the thickness of the isolation layer in different mining methods. The safe thickness of the isolation layer is calculated and shown in Table 2 below.

[0133] Table 2 Summary of mathematical calculations

[0134]

[0135] As shown in Table 2, the safe thickness range of the isolation layer calculated by the quantitative method of the mathematical model is 1.45 to 3.94 m. The calculation formula used above is more suitable for the calculation of the thickness of natural pillars, and the thickness of the reinforced concrete artificial false roof 13 can refer to this calculation result. Since the artificial pillars constructed of reinforced concrete are greater than natural pillars in terms of compressive strength and tensile strength, their required thickness should be less than the above calculation results. Therefore, the pillar thickness obtained based on theoretical calculations is only used as a reference, and the specific thickness is determined according to subsequent simulation results.

[0136] Secondly, a mechanical model is established based on numerical values ​​for simulation research and verification.

[0137] In order to study the thickness of false roof that can ensure safe production in mines, according to the requirements of the thickness of safety roof pillars for underground boundary after the end of open-pit mining in Chapter 10.2.3 of Code for Design of Nonferrous Metal Mining (GB50771-2012): when approach mining is adopted and the approach width is not more than 4m, the thickness of reinforced concrete false roof should not be less than 1m; this simulation is modeled according to the false roof thickness of 1m, 1.5m and 2m respectively, and the most economical and safe false roof thickness is selected for mining by analyzing the stress, strain and plastic zone of the stope, artificial false roof13 and open-pit slope.

[0138] In order to facilitate the analysis of the false ceiling under each scheme, 5 monitoring points are arranged in the model false ceiling. The locations of the monitoring points are as follows: Figure 5 The coordinates of the monitoring points are shown in Table 3 below.

[0139] Table 3 Monitoring point coordinates

[0140]

[0141] This study mainly analyzes the maximum principal stress, settlement displacement and plastic zone of the mining area and false roof after mining, and studies the stability of different artificial false roof thicknesses under one-on-one mining and one-on-five mining.

[0142] The false roof and Z-direction displacement of the mining area under three artificial false roof thicknesses are shown as follows Figure 6-8As shown in the figure, it can be seen that when the mining field adopts the arrangement of mining every other one, the settlement displacement of the artificial false roof 13 at the thickness of 1m, 1.5m and 2m are 11.184mm, 9.908mm and 9.022mm respectively. When the ore block adopts the arrangement of mining every other five, the settlement displacement of the false roof at the thickness of 1m, 1.5m and 2m are 10.165mm, 9.145mm and 8.638mm respectively. The overall settlement values ​​are small, and the maximum settlement value is 11.184mm.

[0143] The maximum principal stress of the false roof and the mining area under the three artificial false roof thicknesses is shown as follows Figure 9-11 As shown in the figure, it can be seen that the tensile stress is the largest when the false roof is 1m thick. The stress values ​​when mining once every one and mining once every five are 1.122MPa and 1.295MPa respectively, both of which are less than the tensile strength of 1.43MPa of the artificial false roof 13. The maximum tensile stress in the mining area is 2.226MPa, which is less than the tensile strength of the ore body 2.419MPa. From the perspective of stress, the three thicknesses of artificial false roof 13 can ensure safe mining in the mining area.

[0144] The numerical simulation results are shown in Table 4 below.

[0145] Table 4 Statistics of simulation results

[0146]

[0147] From the simulation results, it can be seen that the displacement and stress values ​​of the three artificial false ceilings at a thickness of 13 are small. The maximum settlement value of the false ceiling is 11.184mm, and the maximum tensile stress is 1.295MPa, which is less than the tensile strength of the false ceiling 1.43MPa. From the perspective of stress and strain, the false ceiling is in a stable state.

[0148] Clouds in the plastic zone Figure 12-14 In the figure, the green area represents tension-p, which indicates that tensile plastic deformation has occurred during mining, and the red area represents shear-p&tension-p, which indicates that tensile and shear plastic deformation have occurred during mining. The plastic zone distribution is dense when the false roof is arranged with a thickness of 1m. The volume of the plastic zone in every other mining and every fifth mining is 2181.57m³ and 1857.01m³, respectively, accounting for 12.30% and 10.47% of the volume of the artificial false roof. The overall plastic zone has not been penetrated, but the plastic zone has been penetrated in some local areas.

[0149] The distribution of the plastic zone when the false roof is arranged with a thickness of 1.5m and 2m is relatively scattered. According to statistical data, when the thickness of the artificial false roof 13 is 2m, the volume of the plastic zone under the mining method of every other mining and every other mining is 1140.65m³ and 904.40m³ respectively, accounting for only 3.14% and 2.49% of the volume of the artificial false roof 13. The distribution area is very small and no plastic zone is formed through it. The artificial false roof 13 is in a stable state.

[0150] The displacement of the five monitoring points inside the artificial ceiling 13 is as follows: Figure 15-17 As shown in the figure, it can be seen that during the overall mining process, the displacement change trend of each monitoring point is the same, among which the No. 3 and No. 1 monitoring points located at the bottom of the pit and the north of the bottom of the pit have the largest displacements, mainly because the ore body thickness in this area is the largest, resulting in the largest settlement in this area.

[0151] By analyzing the vertical displacement, maximum principal stress and plastic zone distribution of the artificial false ceiling 13, it is found that the settlement displacement, maximum tensile stress and plastic zone distribution range of the false ceiling decrease with the increase of the false ceiling thickness. The settlement values ​​under the three thicknesses of artificial false ceiling 13 are all small. From the strain perspective, the three thicknesses of artificial false ceiling 13 can ensure safe mining in the mine. However, when the artificial false ceiling 13 is arranged at 1m, the plastic zone is distributed more densely and has been penetrated locally. The false ceiling is in an unstable state during the mining process.

[0152] When the artificial false ceiling 13 is arranged with a thickness of 1.5m and 2m, the distribution of the plastic zone is relatively scattered, and no penetration is formed. The mining process is relatively stable. In order to ensure the safe production of the mine and reduce the construction period and cost of the artificial false ceiling 13, it is recommended that the thickness of the artificial false ceiling 13 be arranged to be 1.5m. When the thickness of the artificial false ceiling 13 remains unchanged, the use of every five mining is more stable than the every one mining, and the settlement value and plastic zone are smaller, but the impact is not significant. From the analysis of the plastic zone cloud map, it can be seen that the ore body recovery method is not enough to change the stability of the artificial false ceiling 13, so the ore body recovery method is no longer studied in depth. Considering that the ore body is long along the strike, multiple ore blocks can be arranged. In order to ensure the production capacity of the mine, it is recommended to adopt the every five mining scheme for recovery.

[0153] In summary, the present invention provides a combined method of upward access filling and artificial false roof construction for mining open-pit boundary pillars, which relates to the field of mining engineering technology. The method is suitable for mining conditions of steeply inclined thin to medium-thick open-pit boundary pillars, and includes the following steps: S1, after the open-pit mining is completed, the slope of the open-pit pit bottom is leveled; S2, first use an ideal mathematical model to conduct semi-quantitative research, and then establish a mechanical model to conduct numerical simulation verification to obtain the construction structure and construction parameters of the artificial false roof; S3, first leave an isolation layer at the bottom of the artificial false roof; then construct the artificial false roof; S4, fill the bottom of the open-pit pit other than the artificial false roof, and set a drainage ditch with a predetermined drainage slope and sloped toward the edge of the pit bottom on the surface of the filled pit bottom; S5, use the upward access filling method to mine the open-pit boundary pillars. Through mathematical analysis and numerical simulation technology, the economy and safety of mining open-pit boundary pillars using the upward approach filling method are analyzed; with the help of material mechanics theory and numerical simulation methods, the required materials and their structural parameters for constructing an artificial false roof are determined to ensure the reliability and safety of the construction of the artificial false roof. Therefore, this mining method and its process are scientific, reasonable, economical and safe.

[0154] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A combined method of upward access filling and artificial false roof construction for mining open-pit boundary pillars, characterized in that: Applicable to mining conditions of steeply inclined thin to medium thick open pit boundary pillars, including the following steps: S1, after the open-pit mining is completed, the bottom of the open-pit pit is leveled; S2, first use the ideal mathematical model to conduct semi-quantitative research, then establish a mechanical model to conduct numerical simulation verification, and obtain the construction structure and construction parameters of the artificial false roof; S3, first leave an isolation layer at the bottom of the artificial false roof; then carry out the construction of the artificial false roof; S4, filling the bottom of the open pit other than the artificial false roof, and setting a drainage ditch with a predetermined drainage slope and sloping toward the edge of the pit bottom on the surface of the filled pit bottom; S5, using the upward approach filling method to recover the open-pit boundary pillars; In step S2, the ideal mathematical model includes a thickness-span ratio method, a load transfer intersection line method, a collapse filling method, and a Pusch pressure arch method; the mechanical model includes a maximum principal stress model, a settlement displacement model, and a plastic zone model; Based on the safe thickness range of artificial false roof calculated by ideal mathematical model, the maximum principal stress, settlement displacement and plastic zone distribution of the mining field and artificial false roof after mining were simulated and analyzed by establishing a mechanical model, and the stability parameters of different false roof thicknesses under the mining process of one-on-one and one-on-five mining were studied, thereby obtaining the construction structure and construction parameters of the artificial false roof. The artificial ceiling adopts a double-layer steel mesh structure, which is arranged at the top and bottom of the artificial ceiling respectively; The upward approach filling method adopts the roadway mode, each approach is mined, supported and filled at intervals, and is mined layer by layer from bottom to top, including one-step approach mining and two-step approach mining; Among them, the one-step approach mining is "mining one after another", and the two-step approach mining is "filling two and mining one"; after the one-step approach is filled and maintained, the two-step approach is mined; after the approach is mined, it is filled immediately. After the entire layered approach is mined and filled, the layer transfer is achieved by using the layered connecting road top pressure method, and then the mining of the new layered approach is started.

2. The combined method of upward access filling and artificial false roof construction for recovering open-pit boundary pillars according to claim 1 is characterized in that: In step S3, the construction structure of the isolation layer at the bottom of the artificial false roof is as follows: firstly, a powdered rock with a thickness of 50 mm and a particle size less than 10 mm is left underneath, then a geomembrane with a thickness of 0.5 mm is laid, and finally a plain concrete cushion layer with a thickness of 100 mm is left.

3. The combined method of upward access filling and artificial false roof construction for recovering open-pit boundary pillars according to claim 1 is characterized in that: In step S3, the artificial false roof is constructed as follows: the thickness is set to 1.5m, and concrete is used for pouring, wherein the design value of the concrete compressive strength is not less than 14.3MPa, and the design value of the tensile strength is not less than 1.43MPa; it is arranged along the direction of the ore body and extends 2m to both sides of the ore body.

4. The combined method of upward access filling and artificial false roof construction for recovering open-pit boundary pillars according to claim 3 is characterized in that: The artificial false ceiling adopts HRB400 threaded steel bar with a designed tensile strength of not less than 360MPa. The thickness of the steel mesh protective layer is set to 100mm. The main reinforcement is arranged perpendicular to the approach direction with a threaded steel bar with a diameter of 20mm every 20cm, and the secondary reinforcement is arranged along the approach direction with a threaded steel bar with a diameter of 12mm every 25cm. The top steel mesh is structural anti-cracking steel bar, and the bottom steel mesh is stress-bearing steel bar.

5. The combined method of upward access filling and artificial false roof construction for recovering open-pit boundary pillars according to claim 1 is characterized in that: In step S5, the stope structure of the upward approach filling method is arranged as follows: the stope is arranged along the strike of the ore body, the height is the height of the isolation pillars, and the width is the horizontal thickness of the ore body; every other ore block is mined, and no intermediate pillars, top pillars, or bottom pillars are left between the ore blocks; the approach width is 3.0m to 3.5m, and the mining height is 3.0m to 3.5m; the stope approach is arranged along the strike, the approach length is 25m to 30m, and mining is carried out from bottom to top and from the south side to the north side of the ore body.

6. The combined method of upward access filling and artificial false roof construction for recovering open-pit boundary pillars according to claim 3 is characterized in that: In the construction of artificial false roof, the pouring method of concrete is layered continuous pouring or push-type continuous pouring. When the interval time between layers exceeds the initial setting time of concrete, the layer surface is treated as a construction joint; The artificial false roof construction adopts a step-by-step and layered excavation and construction process, and an expansion joint is arranged every 20m, eventually forming an integral open pit artificial false roof.

7. The combined method of upward access filling and artificial false roof construction for recovering open-pit boundary pillars according to claim 1 is characterized in that: The strength of the filling body of the first-step approach is not less than 1.5MPa; the second step is to fill only the goaf; a cemented filling body with a thickness of 0.5m and a strength of 3MPa to 5MPa is poured on the surface of the filling body of each approach; After the filling body hardens, the gap between the filling body and the artificial false ceiling is grouted.

8. The combined method of upward access filling and artificial false roof construction for recovering open-pit boundary pillars according to claim 1 is characterized in that: The specific process for leveling the slope in step S1 is: leveling the slope by shallow hole micro-difference blasting at the bottom of the open pit.

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