Method for converting underground mining into open-pit mining of metal mine

Abstract

The invention discloses a metal mine underground-to-open-pit mining method, which belongs to the technical field of mine engineering, and comprises the following steps: exploring a goaf and a subsidence area to obtain a spatial three-dimensional model and an ore body geometrical shape model; the ore body is divided into a regular area and a branch area according to the geometric model of the ore body, the regular area refers to the regular part of the geometric shape of the ore body, and the branch area refers to the ore body which extends out of the regular area and is smaller than the ore body of the regular area in size; and the regular area is set as an open-pit mining area, the branch area is set as an underground mining area, and stoping is carried out respectively. By means of the collaborative process of exploration modeling, ore body zoning and stoping in different modes, safety risks are avoided through a model, stoping is conducted in different areas through a zoning matching mining mode, and productivity transition work in the process of converting underground mining into open-pit mining of the metal mine is guaranteed.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of mine engineering, and particularly relates to a method for underground-to-surface mining of a metal mine. BACKGROUND

[0002] In the process of mining ore bodies below the deep and middle stages, due to the influence of geological structure, grade zoning and mining method difference, multiple goaf and local caving area are formed. With the end of underground mining and the change of economic boundary grade, it is often necessary to switch to surface mining to continue mining low-grade ore zones and pillars to improve the comprehensive utilization rate of resources. In this process, there is often a problem of difficulty in connecting production capacity. SUMMARY

[0003] In view of the technical problems in the background art, the present application provides a method for underground-to-surface mining of a metal mine, comprising: exploring the goaf and the caving area to obtain a spatial stereoscopic model and a ore body geometric shape model; filling and treating all goafs that affect the stability of the surface slope and bench to form a bearing arch and an isolation zone to meet the bearing requirements during surface excavation; determining a surface construction plan according to the spatial stereoscopic model and constructing according to the plan; dividing the ore body into a regular area and a branch area according to the ore body geometric model, wherein the regular area refers to a part of the ore body with regular geometric shape, and the branch area refers to a smaller ore body extending from the regular area; setting the regular area as a surface mining area and the branch area as an underground mining area, and separately mining them.

[0004] In some embodiments, in the process of setting the regular area as a surface mining area and the branch area as an underground mining area, and separately mining them, the surface mining area starts to be mined after the end of the surface construction plan, and the underground mining area starts to be mined simultaneously with the filling and treatment.

[0005] In some embodiments, in the process of setting the regular area as a surface mining area and the branch area as an underground mining area, and separately mining them, the underground mining area is divided into multiple stope areas, and the stope area closest to the surface mining area is preferentially mined.

[0006] In some embodiments, in the process of setting the regular area as a surface mining area and the branch area as an underground mining area, and separately mining them, the surface mining area is divided into multiple mining strips, and each strip is surface mined in order from the surface to the underground. The mining of all adjacent open-pit mines within the underground mining area ends before the strip mining of the closest open-pit mine to the underground mining area.

[0007] In some embodiments, the open-pit mining area is divided into multiple mining strips, and each strip is mined in the open-pit order from the surface to the underground. During the process of mining each strip in the open-pit order from the surface to the underground, the underground goaf filling body and surrounding rock within the influence range of the current strip are re-examined and explored.

[0008] In some implementations, during the verification and exploration of the underground goaf filling body and surrounding rock within the current strip's influence range, if there are existing roadways in the open-pit mining area, the roadway projection is formed on the surface of the open-pit mining area, and the roadway is forcibly blasted and filled.

[0009] In some embodiments, steps are provided within the open-pit mining area, and during the sequential open-pit mining of each strip from the surface to the underground, the steps are separated from the goaf areas within the open-pit mining area by surrounding rock.

[0010] In some embodiments, during the sequential open-pit mining of each strip from the surface to the underground, the benches are separated from the underground mining sections by surrounding rock.

[0011] In some implementations, when mining each strip of the open-pit mining area, blasting operations are carried out using micro-delay blasting and double pre-splitting blasting techniques; the blasting operations are staggered from the operations in the underground mining area.

[0012] In some embodiments, the slope angle of the working step in each mining strip of the open-pit mining area is controlled between 30° and 35°.

[0013] This application provides a method for converting underground to open-pit mining in a metal mine, including: Exploration was conducted on the goaf and subsidence areas to obtain spatial three-dimensional models and geometric models of the ore bodies. All mined-out areas affecting the stability of open-pit slopes and steps will be filled and treated to form load-bearing arches and isolation zones to meet the load-bearing requirements during the open-pit excavation period; The outdoor construction plan was determined based on the spatial three-dimensional model, and construction was carried out according to the plan; Based on the geometric model of the ore body, the ore body is divided into regular areas and branch areas. The regular area refers to the part of the ore body with a regular geometric shape, while the branch area refers to the ore body that extends from the regular area and is smaller in volume than the ore body in the regular area. Set the regular area as an open-pit mining area and the branch area as an underground mining area, and mine them separately.

[0014] Through a collaborative process of exploration modeling, pre-filling of goaf areas, open-pit infrastructure construction, ore body zoning, and mining by different methods, safety risks are first mitigated using models, and slope stability is ensured through filling and treatment. Then, mining methods are matched by zone, and mining is carried out separately in different areas. This achieves the effects of low safety risk, less resource waste, short infrastructure cycle, and smooth production capacity transition during the underground-to-open-pit mining of metal mines. It solves the safety problems such as goaf instability and slope collapse that are prone to occur in traditional underground-to-open-pit mining, and ensures the production capacity transition work during the underground-to-open-pit mining of metal mines.

[0015] To more clearly illustrate the technical solution of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort. Attached Figure Description

[0016] Figure 1 This is a basic schematic diagram illustrating the relationship between the goaf, the collapse zone, and the surface space in a method for converting underground mining to open-pit mining of a metal mine, as provided in the embodiments of this application. Figure 2 This is a schematic diagram of the coordinated layout of the open-pit infrastructure construction period and the underground mining area for a method of converting underground to open-pit mining in a metal mine, provided in the embodiments of this application. Figure 3 This is a schematic diagram of the spatial relationship between the ore body and the underground two-step mining area after the completion of the open-pit infrastructure construction of a metal mine underground to open-pit mining method provided in the embodiments of this application; Figure 4 This is a schematic diagram of the coordinated mining of the first open-pit section and the second underground section in a method for converting underground to open-pit mining of a metal mine, provided in the embodiments of this application. Figure 5 This is a schematic diagram of the open-pit second strip mining space layout of a method for converting underground to open-pit mining in a metal mine, provided in an embodiment of this application. Figure 6 This is a schematic diagram of the final state after the completion of the third open-pit mining of a metal mine from underground to open-pit mining, as provided in the embodiments of this application. Figure 7 This is a schematic diagram illustrating the spatial relationship between the open-pit bench, the goaf, and the surrounding rock in a method for converting underground mining to open-pit mining of a metal mine, as provided in the embodiments of this application. Figure 8 This is a schematic diagram of the higher elevation of the first and second steps of the underground branch area of ​​a metal mine underground-to-open-pit mining method provided in the embodiments of this application; Figure 9This is a horizontal cross-sectional view of the intermediate elevation of the underground branch area stope and connecting roadway in a metal mine underground-to-open-pit mining method provided in the embodiments of this application; Figure 10 This is a schematic diagram of the lower elevation of the two-step mining area in the underground branch zone of a metal mine underground-to-open-pit mining method provided in the embodiments of this application.

[0017] Explanation of reference numerals in the attached diagram: 1. Surface; 2. Ore body; 3. Collapse zone; 4. Third zone boundary slope; 5. Goaf; 6. Construction phase boundary slope; 7. First zone boundary slope; 8. Second zone boundary slope; 9. First-stage underground mining area; 10. Second-stage underground mining area; 11. Roadway; 12. Surrounding rock; 13. Drilling rig; 14. Blasting hole; 15. Bench; 16. Blasted loose material; 17. Excavator. Detailed Implementation

[0018] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0020] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0021] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0022] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0023] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0024] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0025] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0026] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0027] This application provides a method for converting underground to open-pit mining in metal mines, referring to... Figures 1 to 6 ,include: S10. Exploration of the goaf and subsidence areas to obtain spatial three-dimensional models and ore body geometric models. Specifically, the core purpose of this step is to accurately identify the spatial location, size, and hidden risks of the goaf and subsidence areas, while clarifying the spatial relationship between the ore body and the surrounding rock and existing roadways. This provides accurate three-dimensional data support for the subsequent goaf treatment plan, open-pit construction planning, and ore body mining zoning, and avoids safety risks such as goaf instability and slope collapse during open-pit excavation.

[0028] For example, a combined exploration approach using 3D laser scanning on the ground, ground-penetrating radar in underground tunnels, and borehole CT is employed. The ground scan covers the open-pit planning area and a 50m radius around it, with a resolution of 0.1m, to identify surface subsidence pits and cracks. Underground radar is used to detect the walls of existing tunnels at a depth of 3-5m to locate hidden goaf areas around the tunnels. Borehole CT is used on the exploration boreholes to obtain the longitudinal distribution of the ore body and goaf areas.

[0029] Exploration data is imported into Surpac or 3DMine mine modeling software to construct a coupled model of five elements: goaf, subsidence area, ore body, surrounding rock, and roadway. The goaf model is labeled with volume, depth, and roof thickness; the ore body model is divided into grade ranges and thickness gradients; and the roadway model is labeled with support status. Boolean operations are used to analyze the spatial intersection of the ore body and goaf to identify the goaf areas underlying the ore body that require priority treatment. Finally, a dynamically updatable 3D visualization model is output.

[0030] S20. All goaf areas affecting the stability of open-pit slopes and benches shall be filled and treated to form a load-bearing arch and isolation zone to meet the load-bearing requirements during the open-pit excavation period. Specifically, the purpose of this step is to reconstruct a load-bearing arch and isolation zone with sufficient load-bearing strength and shear resistance through the filling body, thereby forming a stable load-bearing path for the open-pit slope above the filling body, avoiding the collapse of the goaf roof leading to the instability of the open-pit slope, and preventing the formation of stress concentration zones in untreated goaf areas leading to crack expansion.

[0031] For example, for the goaf on the slope at the end of the open-pit boundary, a high-strength backfill is used. For the goaf on non-end boundary, the strength of the backfill can be lower in order to save costs. The load-bearing arch structure is designed according to the goaf shape: the arch top arc corresponds to the goaf span, the arch foot is embedded in the surrounding rock to a depth of ≥1.5m, and the backfill thickness is not less than 1 / 2 of the goaf height, forming a collaborative protection mode of arch body and side wall isolation zone.

[0032] The backfilling process is carried out in stages and phases. First, the goaf is divided into 2-3m high sections, and each section is equipped with a backfilling pipe and a vent. During backfilling, the flow velocity is controlled to be ≤0.5m / s to avoid erosion of the surrounding rock. After each section is filled, it is left to stand for 24 hours. An ultrasonic detector is used to check the roof contact rate of the backfill body. Sections that do not meet the requirements are refilled. After the backfilling is completed and cured for a period of time, boreholes are drilled in the upper part of the goaf to take samples to verify whether the compressive strength meets the standard, ensuring that it meets the requirement of bearing ≥200kN per square meter (assuming preset value) during open excavation.

[0033] S30. Determine the open-pit construction plan based on the spatial three-dimensional model and carry out construction according to the plan. Specifically, the purpose of this step is to build a basic engineering framework for open-pit mining by planning the open-pit infrastructure content, and at the same time realize the early connection between the open-pit and underground mining systems, shorten the infrastructure cycle, and provide engineering conditions for subsequent separate and coordinated open-pit and underground mining, thereby avoiding the problem of traditional open-pit infrastructure being disconnected from the underground system, which would require additional modifications and extend the infrastructure cycle in the later stages.

[0034] For example, based on the spatial three-dimensional model of S10, the following is planned: Open-pit transport road: arranged along the direction of the ore body, with a slope of ≤8% (avoiding subsidence areas, and the road surface is made of concrete); Spoil dump: selected in a low-potential energy area outside the open-pit boundary, with a capacity designed for 3 years of spoil disposal, and a seepage-proof membrane laid at the bottom to prevent tailings water infiltration; Pass system: utilizing existing underground tunnels to transform the pass, with the pass opening located on the open-pit step platform, and the bottom of the pass connecting to the underground transport tunnel, so that the ore mined in the open-pit can directly enter the underground transport system through the pass, forming a coordinated open-pit and underground mining.

[0035] S40. Based on the ore body geometric model, the ore body is divided into regular areas and branch areas. The regular area refers to the part of the ore body with a regular geometric shape, and the branch area refers to the ore body that extends from the regular area and is smaller in volume than the ore body in the regular area. Specifically, the purpose of this step is to leverage the advantages and avoid the disadvantages of mining methods based on the differences in the geometric shape of the ore body: open-pit mining can take advantage of large scale and high efficiency in the regular area, while underground mining can avoid the waste of resources of small-volume extended ore bodies caused by open-pit excavation. At the same time, the spatial boundaries between open-pit and underground mining are clearly defined by the zoning, which reduces the mutual interference of processes during subsequent mining.

[0036] For example, based on the S10 ore body geometry model, the following zoning criteria are set: Regular zone: ore body thickness ≥ 8m, continuous length ≥ 50m, burial depth ≤ 300m, and the ratio of horizontal projected area to vertical projected area ≤ 1.2; Branch zone: ore body thickness < 5m, continuous length < 30m, extension depth from the regular zone > 300m, or distributed in a branched pattern. A three-dimensional cutting method is used to delineate boundaries. Based on the natural boundaries of the ore body, 2-3m wide isolation pillars are set to physically separate the regular zone and the branch zone. The coordinates of the zoning boundaries are marked in the three-dimensional model to ensure no mining blind spots.

[0037] For the proposed regular zones, calculate the stripping ratio for open-pit mining; for the branch zones, calculate the recovery rate and cost of underground mining (by simulating the resource recovery rates of the two mining methods using FLAC3D software; if open-pit mining in the regular zones recovers ≥10% more resources than underground mining, and underground mining in the branch zones wastes ≥20% less resources than open-pit mining, then the zoning is deemed reasonable).

[0038] For example, irregular branch ore bodies that place ore body 2 outside the standard line of the third boundary slope 4 are defined as branch areas, and ore bodies that are regular in shape and have good integrity placed between the third boundary slope 4 and the infrastructure construction period boundary slope 6 are defined as regular ore bodies.

[0039] S50. Designate the regular area as an open-pit mining area and the branch area as an underground mining area, and mine them separately. Specifically, the purpose of this step is to use spatial zoning combined with separate mining to recover the ore body in the branch area through underground mining when open-pit mining fails to achieve large-scale production capacity, thereby avoiding resource waste. Furthermore, by controlling the pace of independent mining, the disturbance of underground operations caused by open-pit blasting and excavation can be avoided, ensuring a smooth transition for stable production capacity.

[0040] For example, an underground-first, open-pit mining sequence is adopted: during the open-pit infrastructure construction, underground mining in the branch area is initiated, using the segmented filling method or the segmented rock drilling stage followed by open-pit filling method. The mined ore is transported out through the existing underground transportation system to make up for the open-pit production capacity gap; after the open-pit infrastructure is completed, the regular area adopts step-type open-pit mining, and the mined ore is transported to the ore dressing plant through transportation roads, or enters the underground system for adjustment and transportation through ore passes; during the parallel operation of the two mining methods, the time interval between open-pit blasting and underground mining is controlled.

[0041] A three-dimensional monitoring system was installed between the open slope and the underground tunnels in the branch area. GNSS displacement monitoring stations were installed on the open slope, and fiber optic strain sensors were installed in the underground tunnels.

[0042] Monthly statistics are compiled on the production capacity of the open-pit regular area and the underground branch area to ensure that the total production capacity meets the mine's production plan. When the open-pit production capacity reaches 90% of the design value, the mining scale of the underground branch area is gradually reduced until the resources in the branch area are exhausted and the underground system is shut down to achieve a smooth transition between underground and open-pit mining.

[0043] In one working condition provided in this example, the layout of the mining area within the underground branch zone is as follows: Figures 8 to 10 ,in, Figures 8 to 10 This is a horizontal cross-sectional view of the underground branch area, cut in order of elevation from high to low. It includes the first-stage underground mining area 9 and the second-stage underground mining area 10. The roadway 11 is arranged as a connecting road between the two mining areas.

[0044] This application provides a method for converting underground to open-pit mining in a metal mine, including: S10. Explore the goaf and subsidence areas to obtain a spatial three-dimensional model and a geometric model of the ore body. S20. All mined-out areas that affect the stability of open-pit slopes and benches shall be filled and treated to form load-bearing arches and isolation zones to meet the load-bearing requirements during the open-pit excavation period. S30. Determine the open-air construction plan based on the spatial three-dimensional model and construct according to the plan; S40. Based on the geometric model of the ore body, the ore body is divided into regular areas and branch areas. The regular area refers to the part of the ore body with a regular geometric shape, and the branch area refers to the ore body that extends from the regular area and is smaller in volume than the ore body in the regular area. S50. Set the regular area as an open-pit mining area and the branch area as an underground mining area, and mine them separately.

[0045] Through a collaborative process of exploration modeling, pre-filling of goaf areas, open-pit infrastructure construction, ore body zoning, and mining by different methods, safety risks are first mitigated using models, and slope stability is ensured through filling and treatment. Then, mining methods are matched by zone, and mining is carried out separately in different areas. This achieves the effects of low safety risk, less resource waste, short infrastructure cycle, and smooth production capacity transition during the underground-to-open-pit mining of metal mines. It solves the safety problems such as goaf instability and slope collapse that are prone to occur in traditional underground-to-open-pit mining, and ensures the production capacity transition work during the underground-to-open-pit mining of metal mines.

[0046] In some implementations, refer to Figure 2 In S50, the regular area is designated as an open-pit mining area, and the branch area as an underground mining area, with separate mining operations underway. Mining in the open-pit mining area begins after the completion of the open-pit construction plan, while mining and backfilling in the underground mining area begin simultaneously. Specifically, this step optimizes the connection between underground and backfilling operations and open-pit infrastructure construction. The objectives are twofold: first, to shorten the underground resource recovery cycle through synchronized operations; and second, to address the issue of insufficient mine capacity during the open-pit infrastructure construction period.

[0047] In the traditional model, during the 6-12 month period of open-pit infrastructure construction, the cessation of underground mining leads to a decrease in the mine's daily production capacity. Simultaneous operations allow the daily production capacity during the infrastructure construction period to originate from branch areas outside the main mining area, thus creating spatial isolation of resources and preventing spatial overlap between underground mining and open-pit infrastructure construction, as well as mining of the main ore body within the main mining area. Branch areas often extend in a branching pattern along the edge of the main mining area and are buried at greater depths, which spatially eliminates mutual interference problems such as underground mining disturbing the foundation of open-pit infrastructure and open-pit excavation damaging the ore body in the branch area, ensuring that the two types of operations can proceed in parallel within independent spaces. The small size and dispersed spatial characteristics of the branch areas are perfectly suited to the process requirements of multiple working faces in parallel underground mining. Three to four branch area mining faces can be started at the same time, quickly forming large-scale production capacity and making up for the production capacity gap during the open-pit infrastructure construction period. The branch areas are mostly located far from the core impact area of ​​the open slope. Even if there is a local backlog in filling during the synchronous operation, it will not directly threaten the safety of the open infrastructure. Spatially, it provides a safe buffer for the synchronous operation to ensure production capacity. The branch areas are widely distributed and small in size, which means that open-pit mining of them requires stripping a large amount of surrounding rock from their tops, resulting in a significant increase in the amount of waste rock stripped.

[0048] For example, refer to Figure 2 Two months before starting open-pit infrastructure construction above surface 1, the boundary of goaf 5 was first checked, the thickness and volume of the roof of goaf 5 were marked, and then filling pipes were laid into goaf 5 through existing roadways. Tailings sand was used for cemented filling until the top surface of the filling body was flush with the roof of goaf 5. After curing for 28 days, the compressive strength was tested.

[0049] The site was leveled starting at surface 1, and the boundary slope 6 for the infrastructure phase was excavated. A chute system was constructed simultaneously, connecting the chute to the existing tunnels. The excavation of the open-field connecting passage was completed in the third month, extending from surface 1 to the existing tunnels. By the end of the sixth month, the boundary slope 6 for the infrastructure phase was stabilized, thus forming… Figure 3 layout; The branch area mining and open-pit infrastructure construction started simultaneously. Figure 2 The first step of the mining preparation project in mining area 9 is carried out. The connecting roadway of the stope is excavated along the inter-pillar. The upward fan-shaped hole is drilled using a medium-deep hole drilling rig. The first blast is started in the second month, and the ore is extracted using a remote-controlled shovel. In the first-step mining area 9, mining is stopped immediately after each segment is completed. Tailings are injected and cemented through the filling pipe, and the filling of the segment is completed within 7 days. Based on the construction period boundary slope 6 within the third boundary slope 4, according to Figure 4 As shown in the diagram, the first mining bench of the first strip boundary slope 7 is excavated, pre-splitting holes are laid, and drilling operations are completed before blasting. Mining will begin after the open-pit infrastructure is accepted.

[0050] In some implementations, refer to Figure 2 In S50, the regular area is designated as an open-pit mining area, and the branch areas are designated as underground mining areas, and mining is carried out separately. The underground mining area is divided into multiple mining areas, with the mining area closest to the open-pit mining area being prioritized for mining. Specifically, by prioritizing the mining area closest to the open-pit mining area, a mining pattern from near to far is formed in the branch areas, thereby avoiding safety hazards on the open-pit slope: if the mining area near the open-pit is delayed, the subsequent excavation of the open-pit bench will cause stress concentration in the rock pillars of the mining area roof, which can easily lead to mining area collapse and thus cause instability of the open-pit slope. In addition, the long transport distance of distant mining areas means that the time taken for a single trip by mining truck is longer than that of nearby mining areas. Mining nearby mining areas first can shorten the transport path, improve the efficiency of capacity utilization during the infrastructure construction period, and avoid excessive capacity gaps during the infrastructure construction period. In addition, if open-pit mining precedes mining in nearby mining areas, the ore body in nearby mining areas may be occupied or damaged due to stripping of the open-pit slope. Prioritizing mining can maximize the recovery of marginal resources.

[0051] For example, taking the area within the open-pit boundary as the regular zone, its outer boundary is the third zone boundary slope 4. Therefore, the stope closest to the open-pit mining area is the first-step stope 9, which is adjacent to the outer side of the third zone boundary slope 4 within the branch area. Taking the open-pit infrastructure period as the time base, the closer stope is prioritized for mining over the farther stope. Based on the layout of the first-step stope 9, the first-step stope 9 begins preparation work before the second-step stope 10, and ultimately forms... Figure 3 The layout after filling is shown.

[0052] In some implementations, refer to Figures 2 to 6 In the process of setting the regular area as an open-pit mining area and the branch area as an underground mining area, and mining them separately, the open-pit mining area is divided into multiple mining strips, and each strip is mined in the open-pit order from the surface to the underground. In underground mining areas, the mining of all adjacent open-pit mines must cease before the strip mining closest to the underground mine in the open-pit area. Specifically, by controlling the mining of adjacent open-pit mines to end at the bottom strip mining, the risk of overlapping operations between the bottom strip and adjacent underground mines is avoided. If the bottom strip mining in the open-pit area does not complete the backfilling work in the adjacent underground mine, the mining activities in the bottom strip of the open-pit area will cause a sharp reduction in the thickness of the roof pillar in the underground mine, leading to roof collapse and subsequently landslides on the open-pit slope. Controlling the mining and backfilling of adjacent underground mines to be completed before the bottom strip mining in the open-pit area can form a backfill support layer in advance, avoiding the risk of roof collapse and preventing open-pit excavation from encroaching on the remaining ore body in the underground mine.

[0053] For example, an open-pit mining area is divided into multiple mining strips, and each strip is mined in an open-pit manner from the surface to the underground, forming a... Figures 2 to 6 The open-pit mines are shown in various stages formed by gradually stripping away the surface 1, the construction phase boundary slope 6, the first zone boundary slope 7, and the second zone boundary slope 8.

[0054] The lowest open-pit strip, namely the third strip boundary slope 4, is the strip closest to the underground mining area within the open-pit mining zone. The adjacent underground open-pit stope is the first-stage stope 9 within the underground mining zone, i.e., the branch area. Spatially, it is located immediately outside the third strip boundary slope 4 and is most susceptible to the impact of open-pit excavation. After confirming that the first-stage stope 9 of the adjacent underground stope has been completely backfilled and passed inspection, mining operations on the third strip boundary slope 4 of the open-pit mining zone will commence, forming... Figure 6 The open-pit mine shown is after complete extraction.

[0055] In some implementations, refer to Figure 2 and Figure 7The open-pit mining area is divided into multiple mining strips, which are mined sequentially from the surface to the underground. During the process of mining each strip sequentially from the surface to the underground, the underground goaf filling and surrounding rock within the influence range of the current strip are re-examined and explored. Specifically, by conducting re-examination and exploration during the project's progress, the project plan can be dynamically revised to avoid potential engineering problems caused by insufficient timeliness of initial data.

[0056] In some implementations, refer to Figures 8 to 10 During the re-examination and exploration of the underground goaf filling and surrounding rock within the current strip influence range, if existing roadways exist in the open-pit mining area, a roadway projection will be formed on the surface of the open-pit mining area, and the roadways will be forcibly blasted and filled. Specifically, the existing underground roadways in the open-pit mining area are mostly remnants from previous underground mining. If they are not treated, as the strip mining depth increases, underground cavities will form in the roadways, leading to stress concentration in the upper slope rock pillars and making them prone to collapse. At the same time, if the medium-deep hole blasting in strip mining encounters untreated roadways, the blasting energy will be reflected due to the cavity effect, causing flyrock overshoot or abnormal blasting vibration.

[0057] For example, the original roadway is an additional roadway built in the transportation roadway or underground branch area left over from the previous underground mining, that is, the existing roadway 11 is specifically distributed within the influence range of the first boundary slope 7 and the second boundary slope 8 of the open-pit mining area.

[0058] When reviewing and investigating the influence range of the first boundary slope 7, the model constructed in step S10 was used to extract the three-dimensional coordinates of the center line of the existing roadway 11, and to clarify the direction and depth distribution of the roadway in the open-pit mining area. The projection coordinates of the tunnel centerline on the ground surface are calculated by the vertical projection method, the tunnel projection outline is marked, and it is marked within the boundary line of the first boundary slope 7 to confirm that the projection is completely located within the open-pit mining area. Forced blasting and backfilling were initiated 15 days before the seventh mining operation on the first strip boundary slope, and were carried out simultaneously with the strip verification and exploration.

[0059] also, In some implementations, refer to Figure 1 and Figure 7In open-pit mining areas, benches are constructed. During the sequential open-pit mining of various sections from the surface to underground, a surrounding rock barrier is maintained between the benches and the goaf areas within the open-pit mining area. Specifically, the excavation of open-pit benches generates vertical stress. If this stress is directly applied to the goaf backfill, it can easily lead to cracking of the backfill and subsequent collapse of the goaf. Furthermore, if the bottom of the bench is directly adjacent to the goaf backfill, it can result in insufficient stability of the bench slope, potentially causing landslides. Additionally, if there are local defects in the goaf backfill, work in the open-pit mining area adjacent to it can cause these defects to expand, creating a chain reaction of risks.

[0060] For example, based on the cross-sectional relationship of goaf 5, surrounding rock 12, and bench 15, the surrounding rock interval parameters are determined by strip mining sequence from the surface to the ground. The core is to ensure that the interval surrounding rock can completely bear the vertical stress of the open-pit bench and avoid directly acting on the filling body of goaf 5.

[0061] In this example, the goaf 5 in the open-pit mining area specifically refers to the goaf below the boundary slope 8 of the second strip. The surrounding rock interval refers to the thickness of the intact surrounding rock 12 between the bottom plate of the open-pit bench 15 and the top surface of the filling body of the goaf 5, and the width of the horizontal surrounding rock from the slope of the bench to the boundary of the filling body of the goaf.

[0062] Based on the three-dimensional model constructed in step S10, a range of 8m vertical intervals and 5m horizontal intervals are marked at the bottom plate of the first mining bench on the second boundary slope 8, forming a restricted mining zone, prohibiting bench excavation from encroaching on this range.

[0063] In some implementations, refer to Figures 2 to 6 During the sequential open-pit mining process from the surface to the underground, a surrounding rock interval is maintained between the bench and the underground mining area. Specifically, the projections of the bench and the filling material in the goaf formed within the underground mining area are separated by surrounding rock in both the vertical and horizontal directions. This can be manifested as the dynamic adjustment of the bench size within the area adjacent to the underground mining area after the formation of the bench surface during open-pit mining. This ensures that, without affecting the slope and functionality of the bench surface, a surrounding rock interval is maintained in both the vertical and horizontal directions between the bench and the filling material in the underground mining area. This provides sufficient length of original surrounding rock to provide bearing capacity between the bench and the filling material, preventing instability of the upper bench due to insufficient bearing capacity of the filling material.

[0064] For example, following the strip progression from the surface to the underground, the underground mining areas adjacent to each strip are first identified, namely, the first-step mining area 9, which is the core of the underground mining area. Then, the interval requirements are determined based on the state of the mining area filling body and the difference in burial depth, providing a basis for adjusting the bench size.

[0065] Before each strip is mined, the step size is dynamically adjusted based on the interval requirements. Only the platform width and step height are adjusted, and the slope angle is kept constant at 65° and the platform width is ≥20m to meet the passage function of mining trucks before excavation is started.

[0066] In some implementations, when mining each strip in an open-pit mine, micro-delay blasting and double pre-splitting blasting techniques are used for blasting operations; the blasting operations are staggered with the operations in the underground mining area. Specifically, by staggering the blasting operations with the operations in the underground mining area, the timing of the blasting work is staggered, thereby avoiding simultaneous operations and preventing blasting vibrations and shock waves from affecting the mining work in one area.

[0067] In some embodiments, the slope angle of the working step in each mining strip of the open-pit mining area is controlled between 30° and 35°.

[0068] In some implementations, refer to Figures 1 to 10 For example, the mine body dips at approximately 35° and is buried at a depth of 300–600 m; there is an existing underground mining area, with goaf 5 mainly distributed at elevations of +100–+200 m, and small collapse zones 3 forming locally; the surface 1 is stable, and the surrounding rock 12 is moderately stable granite; there are no strong water-rich structures. Follow the procedures in steps one through five.

[0069] Step 1: Use 3D laser + aerial survey point cloud to scan the elevation of all goaf areas, and use transient electromagnetic + drilling engineering to check whether there are hidden goaf areas in the subsidence area. Output the volume, coordinates and range of the goaf area, and propose a treatment plan. For example, if the goaf area is filled with tailings cemented backfill, the equivalent compressive strength target is ≥2.0MPa.

[0070] Forced caving is used to treat goaf-type roadways. The projected boundary of the nearest roadway is marked on each mining bench, along with the roadway name and roof elevation. When the distance to the top of the goaf is more than 5.5m, a Ø110mm down-the-hole drill is used to drill holes above the treatment area, with a hole pattern of (2m~2.5m) × (2m~2.5m). The boundary of the treatment area is determined based on the location of the roadway. After forced caving via deep-hole blasting, the treatment area is filled with loose material. The area near the outer platform is cleared of loose material. After meeting the drilling requirements, normal perforation blasting is performed, and finally, the roadway treatment is completed through unified loading and transportation.

[0071] Step Two: While treating the goaf, open-pit infrastructure construction begins. Planning and mining of underground ore bodies outside the open-pit boundary are carried out to ensure production capacity continuity during the infrastructure transition period. The open-pit boundary is divided into "Infrastructure Construction Period - First Zone - Second Zone - Third Zone (Terminal Boundary)," forming an alternation window with the underground mining areas of Step One and Step Two.

[0072] Recommended parameter ranges for open-pit mines are shown in the table below, and can be calibrated according to geological and equipment conditions.

[0073] The underground mining structure and parameters are determined as follows: The underground ore body is mainly located outside the open-pit boundary, and is mined using staged or segmented open-pit backfilling mining methods. Production is organized by panel as the mining unit. Each panel is 80m long, with pillars arranged between panels, each pillar being 20m wide. Connecting roadways are arranged within the pillars. Each panel has 3-4 stops perpendicular to the strike of the ore body, with alternating stops and pillars. Stopes and pillars are 20m wide, with a maximum width of 100m, and a stage height of 60m. A single-sided access trench bottom structure is adopted. Each stop has a receiving roadway at the bottom. Roadway excavation uses a tunneling trolley, and charging uses a charging trolley. Blasting is used to create a cutting riser, which then forms a slotted area as a free face. Overall, priority is given to mining the stop closest to the open-pit boundary, proceeding from bottom to top. Ore extraction is carried out using a 6m³ remote-controlled loader, which is also used to remove as much residual ore as possible from the stope. A medium-deep hole drilling rig is used to drill upward fan-shaped holes in the drilling chamber at the bottom of the stope, with a row spacing of 2.7-3m and a hole spacing of 4m. The diameter of the blast holes is 120mm. The blast holes in the slotted area are densely arranged, and empty holes are set. The hole network parameters in the slotted area are 0.5m-2m × 0.5m-2m. After the ore is extracted from the stope, the passage leading from the intermediate section to the stope is first sealed (constructing a sealing wall) and corresponding dewatering facilities are installed. Then, the goaf is backfilled. The first-step return pillar is cemented backfill to form an artificial cemented pillar. The second-step return stope is first filled with high-grade cemented backfill, and the second layer is filled with low-grade cemented backfill. The backfilling process of the segmented stope subsequent backfilling mining method is the same as that of the vertical deep hole stage stope subsequent backfilling mining method.

[0074] Step 3: The first strip mining begins in the open-pit mine, entering the open-pit and underground co-mining stage. The thickness of the isolation layer between the open-pit and underground mines is >50m. Combined with the backfill body to block the transmission of disasters in vertical and horizontal space, the open-pit and underground co-mining area is divided into relatively independent units for parallel open-pit and underground mining to ensure safety during the open-pit and underground co-mining process. At the same time, the open-pit and underground adopt a staggered weekly plan, with open-pit blasting and key underground operations (hoisting, support, backfilling) arranged alternately. When the strip advances across the underground operation area, a temporary safety window (such as 24-48 hours) is set to complete underground evacuation and inspection. Before the start of the second strip mining, all ore bodies outside the underground final boundary are recovered, ending the open-pit and underground co-mining state and achieving a smooth connection between the open-pit and underground.

[0075] Steps 3 and 4: After the completion of open-pit and underground co-mining, the mine officially enters open-pit mining. Mining and stripping operations are carried out normally according to the open-pit mining bench parameters. The bench height is set to a dynamic height to match the underground segment height. Through real-time data interaction and collaborative optimization, the process of deepening of the open-pit mining area and the process of forming underground voids are highly matched in time and space, forming a coordinated and mutually adaptive mining system. At the same time, before each strip advances, the affected area should be re-examined and reinforced with filling material.

[0076] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

[0077] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for converting underground to open-pit mining in a metal mine, characterized in that, include: Exploration was conducted on the goaf and subsidence areas to obtain spatial three-dimensional models and geometric models of the ore bodies. All mined-out areas affecting the stability of open-pit slopes and steps will be filled and treated to form load-bearing arches and isolation zones to meet the load-bearing requirements during the open-pit excavation period; The outdoor construction plan was determined based on the spatial three-dimensional model, and construction was carried out according to the plan; Based on the geometric model of the ore body, the ore body is divided into regular areas and branch areas. The regular area refers to the part of the ore body with a regular geometric shape, while the branch area refers to the ore body that extends from the regular area and is smaller in volume than the ore body in the regular area. Set the regular area as an open-pit mining area and the branch area as an underground mining area, and mine them separately.

2. The method for converting underground to open-pit mining in a metal mine according to claim 1, characterized in that, In the process of setting the regular area as an open-pit mining area and the branch area as an underground mining area, and carrying out separate mining, the mining of the open-pit mining area begins after the completion of the open-pit construction plan, and the mining of the underground mining area begins simultaneously with the backfilling and remediation.

3. The method for converting underground to open-pit mining in a metal mine according to claim 2, characterized in that, In the process of setting the regular area as an open-pit mining area and the branch area as an underground mining area, and mining them separately, the underground mining area is divided into multiple mining areas, among which the mining area closest to the open-pit mining area is mined first.

4. A method for converting underground to open-pit mining in a metal mine according to claim 3, characterized in that, In the process of setting the regular area as an open-pit mining area and the branch area as an underground mining area, and mining them separately, the open-pit mining area is divided into multiple mining strips, and each strip is mined in the open-pit order from the surface to the underground. The mining of all adjacent open-pit mines within the underground mining area ends before the strip mining of the closest open-pit mine to the underground mining area.

5. A method for converting underground to open-pit mining in a metal mine according to claim 1, characterized in that, The open-pit mining area is divided into multiple mining strips, and each strip is mined in the order from the surface to the underground. During the process of mining each strip in the order from the surface to the underground, the filling body and surrounding rock of the underground goaf within the influence range of the current strip are re-examined and explored.

6. A method for converting underground to open-pit mining in a metal mine according to claim 5, characterized in that, During the verification and exploration of the underground goaf filling body and surrounding rock within the current strip influence range, if there are existing roadways in the open-pit mining area, the roadway projection is formed on the surface of the open-pit mining area, and the roadway is forcibly blasted and filled.

7. A method for converting underground to open-pit mining in a metal mine according to claim 5, characterized in that, The open-pit mining area is equipped with steps, and during the sequential open-pit mining of each strip from the surface to the underground, the steps are separated from the goaf areas within the open-pit mining area by surrounding rock.

8. A method for converting underground to open-pit mining in a metal mine according to claim 7, characterized in that, During the process of sequential open-pit mining of each strip from the surface to the underground, the benches are separated from the underground mining sections by surrounding rock.

9. A method for converting underground to open-pit mining in a metal mine according to claim 1, characterized in that, When mining each strip in the open-pit mining area, blasting operations are carried out using micro-delay blasting and double pre-splitting blasting techniques; the blasting operations are staggered from the operations in the underground mining area.

10. A method for converting underground to open-pit mining in a metal mine according to claim 1, characterized in that, In each mining strip of the open-pit mining area, the slope angle of the working bench in each strip is controlled between 30° and 35°.

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