Pressure-relief mining method with weakening of inner boundary of pillars in thick ore body vertical to the stope strike

Abstract

The application provides a thick and large ore body vertical strike direction stope pillar inner boundary weakening pressure relief mining method, a process roadway is arranged in the pillar, a pressure relief hole is arranged in the process roadway as an operation platform, and a continuous and uniform multi-fracture pressure relief zone is formed through delayed blasting, a double mechanical structure which can efficiently release stress and is self-maintained and stable is accurately and predictably created in the pillar, so that the double disadvantages of "uncontrollable pressure relief" and "strength damage" of the traditional method are completely overcome; and the recovery is performed after a preset stable period; in the whole recovery process, the pillar is overall stable, only a small amount of debris falls off on the surface, and no spalling or rock burst phenomenon occurs, the pillar can still be overall stable after the width of the pillar is reduced, more ore can be recovered on each pillar, and the application has remarkable economic value.

Description

Technical Field

[0001] This invention relates to the field of mining technology, specifically to a method for weakening and decompressing the inner boundary of a vertically trending pillar in a thick ore body. Background Technology

[0002] Deep mineral resource mining has become a major area for ensuring resource supply. When mining thick ore bodies, to achieve large-scale and efficient ore extraction, it is common practice to arrange the stopes perpendicular to the ore body strike, and to leave wide pillars between stopes to maintain stope stability. However, in complex environments with "three highs and one disturbance" (high ground stress, high ground temperature, high well depth, and mining disturbance) at depths of 800m or more, these pillars, due to their open sides (one side adjacent to a mined-out area, and the other side close to the area to be mined), bear extremely high asymmetrical bidirectional loads, leading to a strong stress concentration effect within them, which can easily induce the following problems: (1) Instability of the pillar itself: manifested as severe flaring, internal bulging or even sudden rock bursts, which not only damage engineering facilities, but also seriously threaten personnel safety.

[0003] (2) Mining efficiency constraints: In order to conservatively address the problem of pillar stability, the design phase is often forced to increase the pillar size, resulting in a large amount of high-grade ore being permanently left underground, significantly reducing the resource recovery rate and severely restricting the economic benefits and service life of the mine.

[0004] (3) Limitations of traditional stress relief techniques: Existing stress control techniques have many significant defects: ① Surface support methods (such as shotcrete and grouting) can only improve the surface surrounding rock condition and cannot relieve the high-stress core inside the pillar, which is a passive symptomatic treatment; ② Internal stress relief methods (such as disordered deep-hole blasting) attempt to release stress from the inside, but lack fine design, and the range, degree and form of stress relief are uncontrollable. This method is very likely to cause excessive damage to the key load-bearing structure of the pillar.

[0005] Therefore, the mining engineering field urgently needs a proprietary pillar decompression process that is highly targeted, has a clear mechanism, controllable effects, and does not rely on complex electrical control systems, in order to maximize the release of mineral resources occupied by pillars while ensuring safety. Summary of the Invention

[0006] In view of the technical problems existing in the background art, this application provides a method for weakening and decompressing the inner boundary of the pillar in a vertically trending stope of a thick ore body.

[0007] This application provides a method for weakening and decompressing the inner boundary of a vertically trending pillar in a thick ore body. By using only a standardized and streamlined drilling and blasting process, a dual mechanical structure (i.e., a decompression zone and a core support body) can be precisely and predictably created inside the pillar, which can both efficiently release stress and maintain stability. This completely overcomes the dual drawbacks of traditional methods, namely, "uncontrollable decompression" and "strength damage".

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a method for weakening and decompressing the inner boundary of a vertically trending pillar in a thick ore body, comprising the following steps: S1. Inside the reserved inter-panel pillar, at the horizontal position of the pressure relief height, excavate one or more internal process roadways along the pillar strike that can meet the operation of the rock drilling rig. S2. Using the process roadway in the mine as the working space, use rock drilling equipment to drill multiple rows of pressure relief holes towards the left and right free faces of the pillar. The holes closer to the process roadway are internal holes, and the holes closer to the free faces of the pillar are external holes. S3. The pressure relief borehole is blasted using a sequential delay detonation network. The detonation network is configured such that the inner holes in the same row are detonated first, and after a preset delay, the outer holes in the same row are detonated next. S4. After blasting and ventilation, a continuous and uniform multi-fracture decompression zone is formed on both sides of the pillar. Then, in the next section or adjacent section, the "drilling-blasting" cycle operation of steps S2 to S3 is repeated until the decompression height of the entire pillar is completed. S5. After the depressurization project is completed and a preset stabilization period has passed, the mining of the panel ore body adjacent to the pillar begins.

[0009] In the technical solution of this application, by opening a process roadway and then drilling multiple rows of pressure relief boreholes, combined with delayed blasting, a continuous and uniform multi-fracture pressure relief zone is formed on both sides of the pillar, thereby completely overcoming the dual drawbacks of "uncontrollable pressure relief" and "strength damage" of the traditional method, avoiding the strong stress concentration effect caused by the pillar bearing extremely high asymmetrical bidirectional load, and thus avoiding the three situations that are easily induced in the background technology.

[0010] As a further improvement of the present invention, the depth L of the pressure relief borehole is determined by the formula L=(WB) / 2-S, where W is the width of the inter-panel pillar, S is the thickness of the free face protection layer reserved according to the rock mass quality, B is the width of the process roadway, and the value of S ranges from 2.5m to 4.0m.

[0011] By calculating the depth of the pressure relief borehole using the formula, it can be ensured that the depth of the borehole matches the width of the pillar, the width of the process roadway, and the thickness of the free-face protection layer. This ensures that blasting can form a continuous and uniform multi-fracture pressure relief zone within the pillar, while preventing the blasting from spreading to the edge of the pillar, thus ensuring the stability of the pillar's core support structure.

[0012] As a further improvement of the present invention, the value of the protective layer thickness S is negatively correlated with the rock mass quality index RQD: when RQD>70%, S is 2.5-3.0m; when RQD is 50%-70%, S is 3.0-3.5m; when RQD<50%, S is 3.5-4.0m.

[0013] By negatively correlated with the rock mass quality index (RQD), i.e., the larger the RQD, the smaller the protective layer thickness, the larger the stress relief zone can be created by blasting while ensuring the stability of a very small load-bearing body, thus further improving the effectiveness of stress release.

[0014] As a further improvement of the present invention, the row spacing of the pressure relief boreholes is 10-14 times the borehole diameter; the hole spacing is 1.1-1.4 times the row spacing, and the first row of holes is located at 1 / 2 to 2 / 3 of the tunnel wall height.

[0015] The pressure relief drilling in this application adopts a "dense row and sparse hole" pattern with small row spacing and large hole spacing, which can enhance the pressure relief strength.

[0016] As a further improvement of the present invention, the preset delay in S3 is 10ms to 25ms.

[0017] During blasting, this application, through a preset delay design, allows the internal holes to detonate before the external holes, thus better forming a continuous and uniform multi-fracture pressure relief zone.

[0018] As a further improvement of the present invention, S3 adopts a radially uncoupled charge structure, and the linear charge density of the outer hole is greater than that of the inner hole.

[0019] As a further improvement of the present invention, the charge density of the outer hole is 1.1-1.3 times that of the inner hole.

[0020] This application employs differentiated charges, with all boreholes using a radially decoupled charge structure. The linear charge density of the outer borehole is 1.1-1.3 times that of the inner borehole. This design ensures that the inner borehole preferentially forms a pre-cracked surface, while the outer borehole provides sufficient energy to propagate the crack to the predetermined range.

[0021] As a further improvement of the present invention, in S5, the preset stabilization period is 7-15 days.

[0022] This application requires waiting for a fixed maintenance and stabilization period before commencing mining operations in the ore body adjacent to the pillar. This period is for the full completion of stress redistribution and the self-stabilization of the stress relief zone.

[0023] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0024] To more clearly illustrate the technical solutions 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.

[0025] Figure 1 This is a schematic diagram of the mine layout and the process tunnel within the mine, according to an embodiment of this application.

[0026] Figure 2 for Figure 1 The AA cross-section diagram shows the decompression structure inside the pillar.

[0027] Figure 3 This is a schematic diagram of a sequential explosive blasting network.

[0028] Figure 4 This is a process flow diagram of a mining method for weakening and decompressing the inner boundary of a vertically trending pillar in a thick ore body.

[0029] The text labels in the diagram represent: 101a, stope a; 101b, stope b; 102, pillar; 201, process roadway; 301, stress relief borehole; 301a, internal hole; 301b, external hole; 401, stress relief zone; 402, reserved natural support zone; 403, core carrier; 501, decoupled charge structure; 502, electronic detonator. Detailed Implementation

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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).

[0035] 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.

[0036] 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.

[0037] Currently, in the complex environment of "three highs and one disturbance" (high ground stress, high ground temperature, high well depth, and mining disturbance) at depths of 800m and above, the pillars, due to their open sides (one side adjacent to a mined-out area and the other side close to a planned mining area), bear extremely high asymmetrical bidirectional loads, resulting in a strong stress concentration effect inside them, which can easily induce the following problems: (1) Instability of the pillar itself: manifested as severe flaring, internal bulging or even sudden rock bursts, which not only damage engineering facilities, but also seriously threaten personnel safety.

[0038] (2) Mining efficiency constraints: In order to conservatively address the problem of pillar stability, the design phase is often forced to increase the pillar size, resulting in a large amount of high-grade ore being permanently left underground, significantly reducing the resource recovery rate and severely restricting the economic benefits and service life of the mine.

[0039] (3) Limitations of traditional stress relief techniques: Existing stress control techniques have many significant defects: ① Surface support methods (such as shotcrete and grouting) can only improve the surface surrounding rock condition and cannot relieve the high-stress core inside the pillar, which is a passive symptomatic treatment; ② Internal stress relief methods (such as disordered deep-hole blasting) attempt to release stress from the inside, but lack fine design, and the range, degree and form of stress relief are uncontrollable. This method is very likely to cause excessive damage to the key load-bearing structure of the pillar.

[0040] To address the problem of strong stress concentration within ore pillars due to their exposed sides and the resulting high asymmetrical bidirectional loads, this application provides a method for weakening and decompressing the inner boundary of ore pillars in vertically trending stopes of thick ore bodies. By opening process roadways and drilling multiple rows of decompression boreholes, combined with delayed blasting, a continuous and uniform multi-fracture decompression zone is formed on both sides of the ore pillar, thereby completely overcoming the dual drawbacks of traditional methods: "uncontrollable decompression" and "strength damage".

[0041] For ease of explanation, the following embodiments use a method for weakening and decompression mining of the inner boundary of a vertically trending pillar in a thick ore body as an example.

[0042] Please refer to Figures 1-4 , Figure 1 The overall layout of the invention is shown from a top-down perspective. The figure clearly shows the spatial relationship of the stopes (101a, 101b) arranged perpendicular to the ore body strike, the inter-panel pillars (102) between them, and the process roadways (201) excavated inside the pillars. The figure also indicates key design dimensions such as the ore body strike direction, stope length, and pillar width (W), providing a benchmark for subsequent borehole parameter calculations.

[0043] Figure 2This is a cross-sectional view, revealing the core "three-zone" mechanical structure of the invention in three dimensions. The figure clearly shows the pressure relief boreholes (301) drilled from the mine's process roadway (201) to both sides, the multi-fracture pressure relief zone (401) formed after blasting, the reserved natural support zone (402), and the core bearing body (403) protected within it. The figure also illustrates the geometric relationship between the borehole depth (L), the protective layer thickness (S), and the pillar width (W), intuitively demonstrating the practical application of the formula L=(WB) / 2-S.

[0044] Figure 3 The core blasting process is explained in detail. The diagram uses a single row of pressure relief holes as an example to illustrate the division between internal holes (301a) and external holes (301b), the radially decoupled charge structure (501) used (including the explosive cartridge, air gap, and packing material), and the initiation network connection logic implemented through an electronic detonator (502). The diagram uses time sequences (T=0ms, T=15ms) to clearly indicate the sequential initiation process of "internal holes detonating first, external holes detonating after a delay."

[0045] Figure 4 The complete sequence of technological steps and their logical relationships from start to finish in this invention are illustrated in a block diagram. The process begins with the excavation of the process roadway within the mine (S1), followed by drilling pressure relief holes on both sides (S2), sequential controlled blasting (S3), inspection and cyclical operation of the pressure relief zone (S4), and finally, after meeting the conditions for delayed mining (S5), it enters the conventional mining process. The diagram emphasizes the sequential order and cyclical logic of each step (S2-S3-S4 cycle).

[0046] This application provides a method for weakening and decompressing the inner boundary of a pillar in a vertically trending stope of a thick ore body. The process includes the following steps in sequence: S1. Mining process roadway excavation: Inside the reserved inter-panel pillar 102, along its entire length and at the horizontal position of the planned stress relief height, excavate one or more mining process roadways 201. The cross-section of this roadway should be able to meet the operation of a medium-sized rock drilling rig. Its axial position needs to be optimized according to the prediction of the pillar stress distribution. It is usually located on the horizontal centerline of the pillar or slightly biased towards the side of the high stress prediction.

[0047] S2. Symmetrical drilling of pressure relief holes on both sides: Using the process roadway 201 in the mine as a fixed working platform, a series of pressure relief holes 301 are drilled simultaneously towards the left and right free faces of the pillar 102 using a rock drilling rig.

[0048] Its core process parameters are as follows: Hole depth control: The drilling depth is precisely calculated using the formula L=(WB) / 2-S, where W is the designed width of the pillar, B is the width of the process roadway, and S is the thickness of the protective layer reserved to ensure the stability of the free face, determined according to the rock mass quality index (RQD): when RQD>70%, S is 2.5-3.0m; when RQD is 50%-70%, S is 3-3.5m; when RQD<50%, S is 3.5-4.0m.

[0049] Hole layout: Multiple rows of parallel holes are arranged, with the row spacing strictly controlled at 10-14 times the drilling diameter; the hole spacing is 1.1-1.4 times the row spacing. For the high-stress side, a "dense row and sparse hole" pattern with small row spacing and large hole spacing is adopted to enhance the pressure relief strength.

[0050] S3. Sequential Controllable Blasting Decompression: Employing a core technology combining "sequential delayed initiation through internal and external holes" with "differentiated charges": Sequential detonation: The pressure relief holes in the same row are clearly divided into internal holes 301a (near the process roadway) and external holes 301b (near the pillar boundary). Electronic detonators 502 are used, and the detonation sequence is strictly followed: internal holes 301a detonate first (0ms) and external holes 301b detonate after a delay (10-25ms).

[0051] Differentiated Charges: All boreholes utilize a radially decoupled charge structure 501. The charge coefficient (charge length / hole depth) is differentiated based on the rock mass stability coefficient f: the charge coefficient for internal holes is 0.5-0.55; the charge coefficient for external holes is 0.55-0.75, and the linear charge density is 1.1-1.3 times that of internal holes. This design ensures that internal holes preferentially form pre-fracture surfaces, while external holes provide sufficient energy to propagate and penetrate the fracture to the predetermined range. Specifically... Figure 3 As shown.

[0052] S4. Formation and Cyclic Operation of Decompression Zone: After blasting and ventilation, through visual observation and simple measurement, it is confirmed that a continuous and uniform multi-fracture decompression zone 401 has been formed on both sides of the pillar. Subsequently, in the next segment or adjacent section, the "drilling-blasting" cyclic operation of steps S2 to S3 is strictly repeated until the designed decompression height of the entire pillar is completed.

[0053] S5. Delayed Mining: As a key technological requirement, after all decompression works are completed, a fixed stabilization period (usually 7-15 days) must be waited before mining operations can begin in the ore body adjacent to the pillar. This period is used for the full completion of stress redistribution and the self-stabilization of the decompression zone.

[0054] Specific embodiments are listed below. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific technologies or conditions are not specified in the embodiments, they shall be performed in accordance with the technologies or conditions described in the literature in this field or in accordance with the product manual.

[0055] Example 1 This embodiment provides a method for weakening and decompressing the inner boundary of a vertically trending pillar in a thick ore body.

[0056] The mining technical conditions in this embodiment are as follows: Underground mining in a copper mine in southwestern Sichuan Province, at a depth of H=950m, involves a thick skarn-type ore body with an average true thickness of 38m. The stopes are arranged perpendicular to the strike of the ore body, with a mid-section height of 60m. The designed width of the pillars between blocks is W=22m. The pillar lithology is mainly skarnified marble, with a uniaxial compressive strength of [missing information]. =126MPa, rock mass firmness coefficient f=12, rock mass quality index RQD=75%, the original rock stress field is dominated by tectonic stress, and the pillar bears a high horizontal stress.

[0057] Specific steps of this embodiment S1 Mine Internal Process Roadway Excavation Tunnel positioning: Inside the 22m wide inter-panel pillar, along its entire length, at a height of 15m above the bottom plate of this middle section (i.e., to provide a free face for the next section of drilling), excavate an internal mine process tunnel 201; Tunnel parameters: To meet the needs of rock drilling rig operations, the tunnel cross-section is a three-centered arch with a width × height of 4.0m × 3.5m, and the tunnel axis is located on the center line of the pillar width; Support method: The support adopts a combination of "anchor bolts + shotcrete". Φ20mm×2400mm full-length bonded resin anchor bolts are installed, with a row spacing of 1.2m×1.2m and a quincunx arrangement. C20 concrete with a thickness of 100mm is shotcreted.

[0058] S2 Double-sided pressure relief hole drilling Equipment selection: The above-mentioned rock drilling rig is adopted, equipped with a Φ89mm drill bit.

[0059] Hole depth calculation: Since RQD=75%>70%, the reserved protective layer thickness S is taken as 2.8m. Substitute into the formula to calculate the drilling depth: L=(WB) / 2-S=(22-4) / 2-2.8=6.2m.

[0060] Hole parameters: Number of rows: 3 rows of pressure relief holes are arranged on each side.

[0061] Row spacing: Take 12 times the borehole diameter, that is, 0.089m×12≈1.07m, rounded to 1.1m.

[0062] Hole spacing: Take 1.2 times the row spacing, that is, 1.1m × 1.2 ≈ 1.3m.

[0063] Drilling direction: All drill holes are parallel to the pillar strike and perpendicular to the left and right free faces of the pillar.

[0064] Work Flow: After the trolley is in place, drill three rows of holes on one side first, then turn around and drill three rows of holes on the other side, ensuring a symmetrical arrangement of the holes. It is important to note that the height of the first row of holes is not an arbitrary value, but a key engineering parameter determined through a comprehensive design process based on pressure relief requirements, equipment capacity, tunnel dimensions, and geological conditions. Generally, it is located at 1 / 2 to 2 / 3 of the tunnel wall height. In this implementation case, the center height of the first row of pressure relief holes is located 1.2m above the tunnel floor.

[0065] S3 Sequential Chemical Detonation Explosive selection: Use emulsion explosive rolls with a diameter of Φ35mm (each roll is 400mm long and weighs 0.5kg), with a wave impedance of approximately 4.5×10⁻⁶. 6 kg / (m²·s).

[0066] Explosive loading structure: Radially decoupled continuous explosive loading is adopted, with a radial decoupling coefficient K=89 / 35=2.54.

[0067] The charging coefficient for internal hole 301a (the first row of holes near the process tunnel) is 0.52. The charging length per hole is 6.2m × 0.52 ≈ 3.22m, which requires approximately 8.06 rolls of explosives, rounded up to 8 rolls (4kg).

[0068] The charge coefficient for the outer hole 301b (second and third row holes) is 0.6. The charge length per hole is 6.2m × 0.6 = 3.72m, which requires approximately 9.3 rolls of charge. Rounded up to 9 rolls (4.5kg), the charge density is approximately 1.14 times that of the inner hole.

[0069] Detonation network: Digital electronic detonator 502 is used, with all internal holes 301a using 0ms delay detonators and all external holes 301b using +15ms delay detonators.

[0070] S4 pressure relief belt inspection and circulation Effect inspection: After blasting and ventilation, personnel entered the process tunnel for inspection and found that obvious fractures were developed at the borehole openings on both sides. Rock powder was thrown out. When illuminated with a flashlight, it could be observed that a network of interconnected fractures had been formed inside. The measured depth of fracture development was about 1.5-1.8m, indicating that the multi-fracture pressure relief zone 401 had been successfully formed.

[0071] Cyclic operation: Move the rock drilling rig to the next section, repeat steps S2 and S3 until the decompression work of the entire pillar of this section is completed, then descend to the next section and continue construction until the entire designed decompression height is completed.

[0072] S5 delayed recovery After all decompression works are completed, mining operations in the panel adjacent to the pillar are suspended. Based on the rock mass conditions (f=12, high RQD), a 10-day stress release and creep stabilization period is selected. After the period expires, conventional medium-deep hole mining technology is used to start mining the ore in panel 101b on the right side.

[0073] Safety of Example 1: Throughout the entire mining process, the pillar remained stable overall, with only a small amount of debris falling off the surface, and no spalling or rock bursting occurred.

[0074] Because the stability of the pillars was ensured, the pillar width was optimized from 22m to 18m in subsequent designs, which is Example 2. Compared to Example 1, Example 2 optimizes the pillar width from 22m to 18m. The drilling depth changes from L = (WB) / 2 - S = (22 - 4) / 2 - 2.8 = 6.2m to L = (WB) / 2 - S = (18 - 4) / 2 - 2.8 = 4.2m; The internal hole 301a has a charge coefficient of 0.52. The charge length per hole is 4.2m × 0.52 ≈ 2.22m, which requires about 5.55 rolls of charge. Rounded up, this is 5 rolls (2.5kg).

[0075] The charge coefficient for the outer hole 301b (second and third row holes) is 0.6. The charge length per hole is 4.2m × 0.6 = 2.52m, which requires approximately 6.3 rolls of charge. Rounded up to 6 rolls (3kg), the charge density is 1.2 times that of the inner hole.

[0076] The steps and procedures are the same as in Example 1.

[0077] Safety of Example 2: Throughout the entire mining process, the pillar remained stable overall, with only a small amount of debris falling off the surface, and no spalling or rock bursting occurred.

[0078] Comparing Examples 1 and 2, both ensure pillar stability. Compared to Example 1, the pillar width in Example 2 is optimized from 22m to 18m. This alone allows for the recovery of an additional ore from each pillar: (22-18)m (width) × 38m (thickness) × 60m (height) × 3.4 (t / m³) ≈ 31,000t, resulting in significant economic benefits. This application's method for weakening and decompressing the inner boundary of pillars in vertically trending stopes of thick ore bodies can significantly improve economic efficiency while ensuring pillar stability.

[0079] 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 weakening and decompressing the inner boundary of pillars in vertically strike stopes of thick ore bodies, characterized in that: Includes the following steps: S1. Inside the reserved inter-panel pillar, at the horizontal position of the pressure relief height, excavate one or more internal process roadways along the pillar strike that can meet the operation of the rock drilling rig. S2. Using the process roadway in the mine as the working space, use rock drilling equipment to drill multiple rows of pressure relief holes towards the left and right free faces of the pillar. The holes closer to the process roadway are internal holes, and the holes closer to the free faces of the pillar are external holes. S3. The pressure relief borehole is blasted using a sequential delay detonation network. The detonation network is configured such that the inner holes in the same row are detonated first, and after a preset delay, the outer holes in the same row are detonated next. S4. After blasting and ventilation, a continuous and uniform multi-fracture decompression zone is formed on both sides of the pillar. Then, in the next section or adjacent section, the "drilling-blasting" cycle operation of steps S2 to S3 is repeated until the decompression height of the entire pillar is completed. S5. After the depressurization project is completed and a preset stabilization period has passed, the mining of the panel ore body adjacent to the pillar begins.

2. The method for weakening and decompressing the inner boundary of the vertically strike pillar in a thick ore body according to claim 1, characterized in that, The depth L of the pressure relief borehole is determined by the formula L=(WB) / 2-S, where W is the width of the inter-panel pillar, S is the thickness of the free face protection layer reserved according to the rock mass quality, B is the width of the process roadway, and the value of S ranges from 2.5m to 4.0m.

3. The method for weakening and decompressing the inner boundary of the pillar in a vertically trending stope of a thick ore body according to claim 2, characterized in that, The thickness S of the protective layer is negatively correlated with the rock mass quality index RQD: when RQD > 70%, S is 2.5-3.0m; when RQD is 50%-70%, S is 3.0-3.5m; when RQD < 50%, S is 3.5-4.0m.

4. The method for weakening and decompressing the inner boundary of the pillar in a vertically trending stope of a thick ore body according to claim 1, characterized in that, The row spacing of the pressure relief boreholes is 10-14 times the borehole diameter; the hole spacing is 1.1-1.4 times the row spacing, and the first row of holes is located at 1 / 2 to 2 / 3 of the tunnel wall height.

5. The method for weakening and decompressing the inner boundary of the pillar in a vertically trending stope of a thick ore body according to claim 1, characterized in that, The default delay in S3 is 10ms to 25ms.

6. The method for weakening and decompressing the inner boundary of the pillar in a vertically trending stope of a thick ore body according to claim 1, characterized in that, S3 employs a radially uncoupled charge structure, and the linear charge density of the outer hole is greater than that of the inner hole.

7. The method for weakening and decompressing the inner boundary of a vertically striking pillar in a thick ore body according to claim 6, characterized in that, The charge density of the outer hole is 1.1-1.3 times that of the inner hole.

8. The method for weakening and decompressing the inner boundary of the pillar in a vertically trending stope of a thick ore body according to claim 1, characterized in that, In S5, the preset stabilization period is 7-15 days.

Images