Near-goaf medium-thick blind ore body mining method based on cooperative utilization of upper prospecting roadways

Abstract

A near-goaf medium-thick blind ore body mining method based on cooperative utilization of an upper prospecting roadway comprises the steps that the prospecting roadway which is tunneled in the upper portion of a blind ore body or in hanging wall surrounding rock in advance is used as a detection work platform, a dense detection drill hole group is constructed, and the boundary of an adjacent goaf and the spatial form of the blind ore body are accurately defined by combining the in-hole detection technology; and active isolation barrier construction and ore body zoning are conducted, a rock stratum reinforcing system composed of anchor rods and anchor cables is constructed downwards, and step-by-step stoping and subsequent filling are conducted. According to the method, single upper prospecting roadway engineering is utilized in multiple stages, the influence of high stress of the goaf on an adjacent engineering structure is blocked from accurate resource and disaster source detection, active isolation of an old goaf and stress zoning to step-by-step stoping, the whole process is safe and controllable, the tunneling amount of a newly-added special engineering roadway is reduced, the construction period is shortened, and the construction cost is reduced. And security pillars which are regarded as necessary sacrifice in a traditional method are converted into safe and controllable recoverable resources, so that dilution and loss of ores are reduced.

Description

Technical Field

[0001] This invention belongs to the field of underground mining technology, and specifically relates to a safe and efficient integrated mining method for medium-thick blind ore bodies that are adjacent to existing goaf areas, have complex geological conditions, and have high mining risks. Background Technology

[0002] Mineral resources are a vital cornerstone of the national economy. With the gradual depletion of easily accessible shallow resources, recovering residual ore bodies and historically inherited blind ore bodies from complex geological environments has become an important method of resource replacement. However, these blind ore bodies are often adjacent to old goaf areas with unclear boundaries and internal conditions, constituting a typical mining challenge of "near-goaf blind ore bodies."

[0003] The three major challenges in mining blind ore bodies near goaf areas are: First, there is stress field disturbance. The goaf area causes a redistribution of stress in the surrounding rock, and the high stress formed around it will be transmitted to the blind ore body, putting it in a state of high static stress. Second, there are many hidden disaster-causing factors and poor self-stabilizing ability of the surrounding rock. Under the superposition of mining stress, it is easy to induce disasters such as rock bursts and water inrush. Third, the risk of mining disturbance is high. Direct mining is easy to break the original stress balance and cause a chain of instability of the rock strata between the goaf area and the newly constructed mining area.

[0004] Traditional mining methods require excavating numerous dedicated tunnels from the surface or safe areas for exploration, remediation, and recovery, resulting in huge engineering investments, long construction periods, and high costs. Moreover, traditional methods passively adapt to the effects of goaf areas or only provide local support to the target ore body, failing to fundamentally block the stress transmission path from goaf areas, leading to extremely high recovery risks and even forcing the abandonment of resource extraction due to safety issues. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies and provide a method for mining medium-thick blind ore bodies in near-goaf areas by systematically and multi-stagely utilizing a single upper exploration roadway, from accurately detecting resources and disaster sources, actively isolating old goaf areas, stress zoning, to step-by-step mining, and ensuring safe and controllable mining throughout the entire process.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A mining method for medium-thick blind ore bodies near the goaf based on the synergistic utilization of the upper exploration roadway includes the following steps: S1. Precise Detection and Boundary Control: Utilizing exploration roadways pre-excavated in the upper part of the blind ore body or the hanging wall as exploration platforms, a dense network of exploration boreholes is constructed. Combined with in-hole detection technology, the boundaries of adjacent goaf areas and the spatial morphology of the blind ore body are accurately defined. Specifically, the upper exploration roadway closest to the target area is used to deploy an upgraded and denser borehole exploration project. A ZYJ-1000 / 200 column-mounted hydraulic rotary drilling rig is used to construct a radial, gridded network of exploration boreholes from within the roadway towards the blind ore body and adjacent goaf areas at the optimal spatial angle. Modern in-hole detection technologies such as borehole cameras or borehole radar are integrated into the boreholes to delineate the actual boundaries of the goaf areas, the height of roof collapse, and the range of fracture development. At the same time, the precise morphology of the blind ore body is identified, including its roof, floor, and surrounding lateral boundaries, providing data support for subsequent isolation engineering and mining plans.

[0007] S2. Construction of Active Isolation Barrier: Based on the boundary data obtained in step S1, grouting boreholes are constructed from within the exploration roadway towards the key isolation area between the goaf and the blind ore body. Grout is injected under high pressure through these boreholes. Specifically, multiple curtain boreholes are arranged in double rows along the axis of the upper exploration roadway, with a borehole spacing of 800-1200 mm and a borehole direction inclined at 10°-20° towards the goaf side. Layered grouting is employed: first, low-viscosity grout is injected to penetrate and seal micro-fractures; then, high-viscosity grout is injected to form a framework; finally, high-pressure fracturing grouting is performed to connect the grout veins, forming a continuous grouting curtain with high shear and compressive strength. This actively isolates the goaf from the subsequent mining area, reducing the impact of safety hazards in the goaf, improving the overall strength of the rock pillar, and effectively preventing the direct transmission of stress from the goaf to the mining area.

[0008] S3. Ore body zoning: Based on the spatial morphology of the blind ore body obtained in step S1 and the location of the grouting curtain constructed in step S2, combined with the rock mechanics parameters and stress distribution, the blind ore body is divided in three-dimensional space into stress buffer zone I adjacent to the grouting curtain, stress core zone II located in the middle of the ore body, and stress stabilization zone III located on the flank of the ore body. S4. Active pre-reinforcement of the overburden: Using the exploration tunnel as a construction platform, a rock reinforcement system consisting of anchor bolts and anchor cables is constructed downwards to actively pre-reinforce the overburden above the blind ore body; S5. Phased mining and subsequent backfilling: Based on the ore body zoning in step S3, mining is carried out in the following order: first, synchronous mining of stress buffer zone I and stable zone III, followed by mining of stress core zone II. Mining of each zone adopts the medium-deep hole ore extraction method. After the mining of the zone is completed, backfilling slurry is transported to the goaf through backfilling boreholes arranged in the exploration roadway for subsequent backfilling. Specifically, this includes excavating the preparatory roadway, constructing medium-deep holes, blasting ore extraction, and ore extraction within the zone. The existing technology is to use backfilling body to subsequently backfill the goaf after the mining of the zone is completed. Specifically, segmented drilling roadways can be excavated at heights of 5m to 8m. A 2.2m × 2.4m loading roadway is laid out along the ore body strike within the footwall surrounding rock. From the external loading roadway, a 2.2m × 2.4m loading access roadway is excavated along the footwall until the ore collection trench is connected. A bottom-pulling roadway is then excavated at the bottom of the ore body, connecting the loading roadway and the bottom-pulling roadway via the loading access roadway. The main preparatory cutting works include segmented transport roadways, segmented drilling roadways, ramps, cutting roadways, ore exit access roads, and stope connecting roads. Filling boreholes in the stress buffer zone I and stress stability zone III stopes are arranged along the top hanging wall line and the top pillar boundary to optimize the flow path of the filling slurry. Filling boreholes in the stress core zone II stopes are located in the middle of the II stopes.

[0009] Furthermore, the arrangement spacing of the detection borehole group described in this invention is 10-15 meters, and the borehole detection technology includes one or a combination of borehole cameras and borehole radar.

[0010] Furthermore, the grouting holes of the present invention are distributed in at least two rows in a plum blossom or rectangular shape, and the grout material is a cement-based grout with a water-cement ratio ranging from 0.6:1 to 1:1.

[0011] Furthermore, the width L of the stress buffer zone I in this invention is determined according to the formula L = (0.2~0.35)× W, where W is the horizontal width of the blind ore body; the stress core zone II is the area where the maximum principal stress exceeds 1.5 times the original rock stress; and the stress stability zone III is the remaining ore body portion.

[0012] Furthermore, the rock reinforcement system of the present invention includes long prestressed grouting anchor cables and hollow grouting anchors constructed through the exploration tunnel to form a three-dimensional support network covering the roof and surrounding rock of the blind ore body.

[0013] Furthermore, in the present invention, during the mining of stress buffer zone I and stress stabilization zone III, an arch-shaped top column is formed in the upper part of the mining area by controlling the bottom position of the medium-deep borehole; the goaf in stress buffer zone I and stress stabilization zone III is filled with high-strength backfill material, and after its strength reaches the standard, core zone II is mined, and the goaf in core zone II is filled with low-strength backfill material; the 28-day uniaxial compressive strength of the high-strength backfill material is not less than 2.5 MPa, and the 90-day ultimate uniaxial compressive strength is not less than 3.5 MPa.

[0014] Furthermore, in the core mining zone II, the formation of the cutting groove is carried out simultaneously with the recovery of the top column in the stress buffer zone I; and in the final mining cycle of the stress core mining zone II, the recovery of the top column in the stable zone III is completed simultaneously.

[0015] Furthermore, the present invention employs upward parallel fan-shaped medium-deep holes for micro-differential blasting ore extraction, with a borehole row spacing of 1.2m~1.4m, a hole spacing of 1.0m~1.5m, a hole diameter of 65mm~70mm, a ore extraction step distance of less than 5m, and a millisecond delay time of 25~100ms.

[0016] Compared with the prior art, the significant advantages of the present invention are: 1. This invention utilizes a single upper exploration tunnel project to achieve full-cycle safety management from source disaster prevention to process control, from accurate detection of resources and disaster sources, proactive isolation of old goaf areas, stress zoning to step-by-step mining, and full-process safety control.

[0017] 2. This invention, by actively constructing a grouting curtain and actively reinforcing the overlying rock, blocks the transmission of harmful stress in the goaf and improves the safety of the mining system.

[0018] 3. This invention makes full use of existing exploration tunnels, reduces the amount of excavation required for new dedicated engineering tunnels, shortens the construction period, and reduces production costs.

[0019] 4. By optimizing the stope structure and mining sequence, this invention transforms the safety pillars, which are considered necessary sacrifices in traditional methods, into safe and controllable mineable resources, thereby reducing ore dilution and loss. Attached Figure Description

[0020] Figure 1 This is a schematic diagram illustrating the precise detection and boundary control of thick blind ore bodies near the goaf using the present invention.

[0021] Figure 2 This is the present invention. Figure 4 A schematic diagram of the ore body mining structure along the AA direction; Figure 3 yes Figure 2 Schematic diagram of the orebody mining structure in the BB direction; Figure 4 yes Figure 2 Schematic diagram of the mining structure of the ore body in the CC direction; Figure 5 This is a schematic diagram of the backfilling process after the mining of Zones I and III in the thick blind ore body of this invention is completed; Figure 6 This is a schematic diagram of the mining structure of the II zone mining area in the thick blind ore body of the present invention.

[0022] 1- Goaf; 2- Blind ore body; 3- Hanging exploration roadway; 4- Exploration borehole; 5- Stress buffer zone (Zone I); 6- Stress core zone (Zone II); 7- Stress stable zone (Zone III); 8- Grouting curtain; 9- Grouting borehole; 10- Grouting long anchor cable; 11- Grouting anchor bolt; 12- Interstitial pillar; 13- Collapsed ore; 14- Cutting groove; 15- Top pillar; 16- Segmented drilling roadway; 17- Segmented transport roadway; 18- Ore extraction horizontal roadway; 19- Ore loading access roadway; 20- Fan-shaped medium-deep hole; 21- Filling borehole; 22- Filling body; 23- Stope connection roadway. Detailed Implementation

[0023] To make the present invention clearer, it will be described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments are only used to illustrate the technical solutions of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0024] Taking a certain underground metal mine as an example, there is a medium-thick blind ore body 2 with a dip angle of about 55° and a horizontal thickness of 16 meters in the -300m section of the mine. Preliminary geological exploration has been carried out in the early stage, and the aforementioned upper hanging exploration tunnel 3 has been arranged in the upper hanging rock strata of the ore body. The flank of the ore body is a complex old goaf 1 with unclear boundaries formed by open-field mining. There are a large amount of collapsed rocks and fissure water inside. Preliminary detection shows that there is a risk of water inrush. If traditional mining methods are used, the risk is extremely high.

[0025] The specific steps for mining using the method of this invention are as follows: like Figure 1 As shown, S1. Precise detection and boundary control of goaf 1 and blind ore body 2: Using the existing hanging wall exploration roadway 3 located on the hanging wall of the ore body in the -300m section as a detection platform, a detection drill hole is set every 15 meters along the hanging wall exploration roadway. Radial exploration boreholes 4 are constructed using a tunnel drilling rig. The drilling depth is based on penetrating the old goaf and completely controlling the boundary of the blind ore body. Borehole camera technology is used to confirm the actual boundary of the old goaf, the roof collapse pattern and the partial filling situation. Borehole radar technology is used to accurately delineate the roof and floor boundaries of the blind ore body and detect a water-conducting fracture zone with a width of about 2 to 5 meters extending from below the floor of the goaf to above the blind ore body. S2. Construction of Active Isolation Barrier: Based on the location of the water-conducting fracture zone identified in step S1, a grouting curtain is constructed in the key isolation area between the goaf 1 and the blind ore body 2. In this embodiment, two rows (2.0m apart) of grouting boreholes 9 are arranged in a quincunx pattern within the upper exploration roadway 3, corresponding to the fracture zone location. The borehole spacing is 3.0m. Cement grout with a water-cement ratio of 0.8:1 is used, and segmented downward grouting is employed. The initial pressure is 1~2MPa, and then the pressure is slowly increased at a rate of 0.1~0.15MPa per minute according to the grout intake. When the pressure reaches 5.5MPa and the grout intake remains less than 5 L / min, the grouting is stopped after 10 minutes of pressure stabilization, forming a dense grouting curtain 8 with a thickness of not less than 4.0m to actively isolate the goaf from the subsequent mining operation area. Testing showed that the water blocking rate reached over 92%.

[0026] S3. Ore body zoning: Based on the spatial morphology of the blind ore body obtained in step S1 and the location of the grouting curtain constructed in step S2, combined with the rock mechanics parameters and stress distribution, the blind ore body is divided in three-dimensional space into stress buffer zone I 5 with a width of 8 meters adjacent to the grouting curtain, stress core zone II 6 with a width of 12 meters located in the middle of the ore body, and stress stabilization zone III 7 with a width of 6 meters located on the side of the ore body furthest from the goaf. S4. Active pre-reinforcement of the overburden of the blind ore body: Using the exploration roadway as a construction platform, a rock reinforcement system consisting of anchor bolts and anchor cables is constructed downwards to actively pre-reinforce the overburden above the blind ore body. This is especially important before the high-stress core area of ​​Zone II during mining, where the roof has the largest exposed area and the highest risk, necessitating active reinforcement of the overburden.

[0027] In this embodiment, the upper exploration tunnel 3 is used as the construction platform. Prestressed long grouting anchor cables 10 (20m in length, 2.0m × 2.0m spacing, arranged in a rectangular pattern) are installed downwards to ensure that the anchor ends penetrate at least 5 meters into the stable rock layer. The prestress of a single anchor cable is 200kN, and low-relaxation steel strands are used. Cement grout is used during grouting with a water-cement ratio of 0.8~1 and a grouting pressure of 4~6MPa. A special anchor cable drilling rig is used for construction. At the same time, grouting anchor rods 11 with a length of 5 meters are used between the long anchor cables to reinforce the shallow fractured rock mass. Cement grout / ordinary Portland cement is used during grouting with a water-cement ratio of 0.5~0.8 and a grouting pressure of 3~4MPa, forming a three-dimensional support network composed of anchor rods and anchor cables to actively pre-reinforce the overlying rock.

[0028] S5. Phased mining and subsequent backfilling: Based on the ore body zoning in step S3, mining is carried out in the order of first synchronously mining Zone I and Zone III, and then mining Zone II. like Figures 2-4As shown, firstly, the ore-exit horizontal roadway 18 is excavated at the bottom of Zones I and III, and the drilling chamber is constructed. A pillar 12 is left in the ore block of Zone I, and different mining rooms are divided along the strike of the ore body using this pillar as the boundary. Sectional drilling roadways 16 are excavated at 8m intervals. Within the footwall of the ore body, a 2.2m × 2.4m cross-section loading roadway 19 is arranged along the strike of the ore body until it connects to the ore-gathering trench. A stope connecting roadway 23 is arranged to connect the sectional drilling roadways and the sectional transport roadways 17 within the ore body. The bottom-excavation of the bottom-pull roadway is achieved, and the loading roadway is connected to the bottom-pull roadway through the loading access roadway. Using a rock drilling rig or a YGZ-90 type drilling rig / ZYJ-1000 / 200 column-mounted hydraulic rotary drilling rig, 20 upward parallel fan-shaped medium-deep holes are drilled row by row in a backward manner in the segmented rock drilling roadway. The row spacing is 1.2mm, the hole spacing is 1.5m, the hole diameter is 70mm, and the blasting step distance is less than 5m. The millisecond delay time of the segmented micro-differential blasting is 25~100ms.

[0029] In Zones I and III, the upper section is mined two caving steps ahead of the lower section. In Zone I, the bottom of the medium-deep borehole in the uppermost section is lowered gradually along the length of the stope strike, the borehole spacing, and the designed elevation difference line at the bottom of the borehole, with the location of the top pillar 15 as the apex. In Zone III, the bottom of the medium-deep borehole in the uppermost section is raised gradually along the designed elevation difference line at the bottom of the borehole, with the location of the cutting groove as the apex, to the top of the stope, the upper hanging wall line, and the top pillar boundary. During the blasting of Zones I and III, an arch-shaped top pillar is formed in the upper part.

[0030] After the mining in Zones I and III is completed, three filling boreholes 21 with a diameter of 200 mm are immediately drilled in the upper exploration roadway 3 using a drilling rig. The borehole ends are located at the highest point of the roof of the mining area in Zones I and III.

[0031] Backfilling: Tailings cemented with a concentration of 70%~75% is used for backfilling. The backfill slurry is prepared through the surface backfilling station, transported to the -300m middle section through the main backfilling pipe, introduced into the upper exploration roadway through the branch pipe, and finally flowed into the empty area of ​​the I and III mining areas through the backfilling borehole 21. The 28-day design uniaxial compressive strength of the backfill body 22 is 2MPa.

[0032] After the filling strength of Zones I and III reaches the design index, Zone II will be mined. The cutting groove formation operation in Zone II will be carried out simultaneously with the recovery of the roof pillar in Zone I. Similarly, in the final mining cycle of Zone II, the recovery of the roof pillar in Zone III will also be completed simultaneously. All the above-mentioned roof pillar recovery operations adopt small-step, alternating sequential mining, and use shallow hole drilling and controlled blasting.

[0033] In Zone II, the upper section was advanced by three caving steps in the lower section during mining. All mining sections employed a stepped, retreating mining method, with the upper section advancing the lower section. The caving ore (13 tons) fell to the bottom of the stope by its own weight and was transported out via a loader through the ore extraction roadway. After the mining of Zone II was completed, low-strength backfill was used to fill the goaf.

[0034] The above embodiments are merely examples, used only to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the embodiments of the present invention or to some technical features without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for mining medium-thick blind ore bodies near goaf based on the synergistic utilization of upper exploration roadways, characterized in that, Includes the following steps: S1. Precise Detection and Boundary Control: Using the exploration tunnels pre-excavated in the upper part of the blind ore body or the hanging wall as the exploration operation platform, construct a dense group of exploration boreholes, and combine in-hole detection technology to accurately define the boundaries of adjacent goaf areas and the spatial morphology of the blind ore body. S2. Construction of active isolation barrier: Based on the boundary data obtained in step S1, grouting boreholes are constructed from the exploration roadway toward the key isolation area between the goaf and the blind ore body. Grout is injected under high pressure through the grouting boreholes to form a continuous grouting curtain to actively isolate the goaf from the subsequent mining operation area. S3. Ore body zoning: Based on the spatial morphology of the blind ore body obtained in step S1 and the location of the grouting curtain constructed in step S2, combined with the rock mechanics parameters and stress distribution, the blind ore body is divided in three-dimensional space into a stress buffer zone (zone I) adjacent to the grouting curtain, a stress core zone (zone II) located in the middle of the ore body, and a stress stabilization zone (zone III) located on the flank of the ore body. S4. Active pre-reinforcement of the overburden: Using the exploration tunnel as a construction platform, a rock reinforcement system consisting of anchor bolts and anchor cables is constructed downwards to actively pre-reinforce the overburden above the blind ore body; S5. Step-by-step mining and subsequent backfilling: Based on the ore body zoning in step S3, mining is carried out in the following order: first, synchronous mining of the stress buffer zone (Zone I) and stress stabilization zone (Zone III), and then mining of the stress core zone (Zone II). Mining of each zone adopts the medium-deep hole mining method. After the mining of the zone is completed, backfilling slurry is transported to the goaf through backfilling boreholes arranged in the exploration roadway for subsequent backfilling.

2. The mining method according to claim 1, characterized in that, In step S1, the spacing between the detection boreholes is 10-15 meters, and the borehole detection technology includes one or a combination of borehole cameras and borehole radar.

3. The mining method according to claim 1, characterized in that, In step S2, the grouting holes are arranged in at least two rows in a quincunx or rectangular pattern, and the grout material is a cement-based grout with a water-cement ratio ranging from 0.6:1 to 1:

1.

4. The mining method according to claim 1, characterized in that, In step S3, the width L of the stress buffer zone (zone I) is determined according to the formula L = (0.2~0.35)× W, where W is the horizontal width of the blind ore body; the stress core zone (zone II) is the area where the maximum principal stress exceeds 1.5 times the original rock stress; and the stress stabilization zone (zone III) is the remaining ore body portion.

5. The mining method according to claim 1, characterized in that, In step S4, the rock strata reinforcement system includes long prestressed grouting anchor cables and hollow grouting anchors constructed through the exploration tunnel to form a three-dimensional support network covering the surrounding rock of the blind ore body roof.

6. The mining method according to claim 1, characterized in that, In step S5, when mining the stress buffer zone (zone I) and the stress stabilization zone (zone III), an arch-shaped roof column is formed in the upper part of the stope by controlling the position of the bottom of the medium-deep hole; the goaf of the stress buffer zone (zone I) and the stress stabilization zone (zone III) is filled with high-strength filling material. After the strength reaches the standard, the stress core zone (zone II) is mined, and the goaf of the stress core zone (zone II) is filled with low-strength filling material; the 28-day uniaxial compressive strength of the high-strength filling material is not less than 2.5 MPa, and the 90-day ultimate uniaxial compressive strength is not less than 3.5 MPa.

7. The mining method according to claim 6, characterized in that, When mining the stress core zone (zone II), the formation of its cutting groove is carried out simultaneously with the recovery of the roof column in the stress buffer zone (zone I); and in the final mining cycle of the stress core zone (zone II), the recovery of the roof column in the stress stabilization zone (zone III) is completed simultaneously.

8. The mining method according to claim 1, characterized in that, In step S5, micro-differential blasting is used to cut ore using upward parallel fan-shaped deep holes. The spacing between rows of blast holes is 1.2m to 1.4m, the hole spacing is 1.0m to 1.5m, the hole diameter is 65mm to 70mm, the ore-cutting step distance is less than 5m, and the millisecond delay time is 25 to 100ms.

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