Methods for controlling the hazards of rock displacement on open-pit to underground mine slopes without bottom pillars and sloping sides

Abstract

This invention discloses a method for controlling the rock movement hazard of a slope in a subsidence-type mine transitioning from open-pit to underground without a bottom pillar, belonging to the field of mining technology. The control method includes: (1) determining the location of the key subsidence section of the subsidence mine and setting up a delayed mining area on the upper side of the key subsidence section to delay the gradual destruction of the slope; (2) setting up a delayed mining area on the side close to the open-pit pit to form a rock embankment to expand the net volume of the subsidence pit; (3) adopting a downward stepped working face in the normal mining area, and the recovery time of the delayed mining area is controlled by the total ore output. This invention avoids the application of efficient mining methods for subsidence mines that are restricted in the traditional open-pit to underground transition stage in order to ensure slope stability. While achieving efficient mining of the subsidence mine, it can ensure that the slope damage caused by underground mining disturbance will not harm the open-pit mine.

Description

Technical Field

[0001] This invention relates to the field of mining technology, and in particular to a method for controlling rock displacement hazards on the slope of a mine transitioning from open-pit to underground without bottom pillars and in a segmented collapse. Background Technology

[0002] For a large, deep open-pit metal mine transitioning from open-pit to underground mining, in order to achieve simultaneous open-pit and underground mining, it is generally necessary to completely isolate the underground mining area from the open-pit mining area in space. At the same time, in order to reduce the negative impact of underground mining disturbance on slope stability, the choice of underground mining methods is limited to the open-pit method and the backfilling method. This will undoubtedly affect the smooth connection of production capacity during the transition period.

[0003] If efficient mining methods are used in underground mines with attached slopes, they will not disturb the open-pit mine, allowing for simultaneous mining of both. This would effectively improve the production capacity transition between open-pit and underground operations. However, when using the currently efficient pillarless subgrade caving method in attached slope mines, slope damage and instability can occur. The resulting landslides can impact the open-pit mine, making it impossible to safely mine both simultaneously.

[0004] Therefore, there is an urgent need in this field to find a solution to the damage to the lower slope caused by ground disturbance when using the bottomless sublevel caving method in large, deep open-pit mines with sidewalls, so as to achieve safe and efficient open-pit and underground mining without affecting each other, thereby improving the efficiency of mining during the transition period and improving the technical and economic benefits of mining. Summary of the Invention

[0005] The purpose of this invention is to provide a method for controlling the rock displacement hazards of open-pit to underground subsidence slopes in mines with no bottom pillars, in order to solve the above-mentioned problems.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for controlling rock displacement hazards on open-pit to underground mine slopes with segmented collapse and hanging walls, the method comprising:

[0008] (1) Determine the location of the key section of the hanging wall mine and set up a delayed mining area on the upper side of the key section of the hanging wall mine to delay the gradual destruction of the slope; (2) Set up a delayed mining area on the side close to the open pit to form a rock embankment to expand the net volume of the collapse pit; (3) Adopt a downward stepped working face in the normal mining area and control the mining time of the delayed mining area by the total ore output.

[0009] As a preferred technical solution, in step (1), the method for determining the key segment location of the gabion mine is: to determine it using a gabion mine mining-induced slope progressive slip model based on limit equilibrium analysis.

[0010] As a preferred technical solution, in step (3), the total ore output control standard is: ensuring that the thickness of the remaining loose material cushion layer in the collapse pit meets the standard and that the net volume in the collapse pit is greater than the possible volume of the slope slippage body.

[0011] Compared with the prior art, the advantages of the present invention are as follows: The present invention avoids the application of the high-efficiency mining method of the hanging mine in order to ensure slope stability during the transition from open-pit to underground mining. While achieving high-efficiency mining of the hanging mine, it can ensure that slope damage under underground mining disturbance will not harm the open-pit mine. Its mining efficiency can be increased by more than 50% compared with other existing hanging mine mining methods, and its mining cost can be reduced by more than 30% compared with other existing mining methods. Attached Figure Description

[0012] Figure 1 To establish a model for progressive sliding of rock mass in slope induced by side-mounted mining based on limit equilibrium analysis;

[0013] Figure 2 Diagram illustrating the process of controlling slope rock movement hazards in a bottomless, segmented collapse mine.

[0014] Figure 3 This is a schematic diagram of the method for controlling rock movement hazards in open-pit to underground, bottomless, segmented collapse and hanging slope mines according to the present invention.

[0015] Figure 4 and Figure 5 This is an example diagram of slope rock displacement hazard control in a certain mine. Detailed Implementation

[0016] The invention will now be further described with reference to the accompanying drawings.

[0017] Example:

[0018] First, it needs to be clarified that: When the grouting method is used for subgrade caving without pillars, after the underground void breaks through to the surface, forming a goaf, continued mining will cause progressive slope failure. This failure is not continuous, but rather occurs in stages when mining reaches a certain segment; this segment is the "critical segment" described in this invention. The location of the critical segment and the volume of the slope's staged slip can be determined using a progressive slope slip model induced by grouting mining based on limit equilibrium analysis (e.g.,...). Figure 1 (As shown in the figure) to determine. This model assumes that after a sinkhole forms on the surface, as the mine is mined downwards, the surrounding rock of the slope will gradually deteriorate. When mining reaches a certain extreme depth, tensile cracks and shear failure surfaces will form in the slope rock mass due to the influence of rock mass strength.

[0019] Figure 1 and in the following formulas:

[0020] c' - Effective cohesion of the rock mass

[0021] H1 - Mining depth at which damage occurred

[0022] H2 - Mining depth at which subsequent damage occurs

[0023] H c -Thickness of loose material within the collapse pit

[0024] When the S-slope fails, the mining span of the attached mine is...

[0025] The thrust exerted on the fracture surface by T-collapsed ore.

[0026] T c - The thrust exerted by the collapse on the footwall rock mass

[0027] Weight of W-wedge-shaped sliding rock mass

[0028] W c - The quality of the collapsed material

[0029] Z1 - Initial tensile crack depth

[0030] Z2 - Subsequent tension crack depth

[0031] α-slope angle

[0032] γ - The unit weight of the original rock mass before mining

[0033] γ c -Bulk density of loose materials

[0034] θ - Angle between the thrust T and the normal to the failure surface

[0035] Effective internal friction angle of β-rock mass

[0036] β ω - Friction angle between collapsed material and unmined rock mass

[0037] ψ0 - Dip angle of the ore body

[0038] ψ1 - The angle between the edge of the lowest mining area near the pit and the line connecting the edge of the slope collapse pit.

[0039] ψ b - Collapse Angle

[0040] ψ p1 -Initial failure surface inclination angle

[0041] ψ p2 - Subsequent failure surface dip angle

[0042] Based on the above theory, a model for the progressive sliding of rock mass induced by sidewall mining in sluice gates is established (e.g., Figure 1 As shown), and make the following assumptions:

[0043] (1) The initial location of slope failure can be determined by the known geometric parameters H1, H2, ... c Z1, ψ p1 Sure;

[0044] (2) The extent of caving at the new mining depth H2 is determined by the tension fractures that reach the critical depth and are parallel to the ore body;

[0045] (3) The failure of the slope rock mass occurs along a critical shear plane, the location of which can be determined by the rock mass strength and the applied effective stress.

[0046] (4) The slope rock mass has uniform and isotropic mechanical properties. Its shear stress is determined by the effective stress form determined by Coulomb's method;

[0047] (5) In the analysis process, the stress distribution in the collapsed rock mass and the rock mass that is collapsing was simplified;

[0048] (6) The slope environment is in a dry state, and the influence of water is ignored.

[0049] The weight of the progressively collapsing rock mass DBCEFN is:

[0050]

[0051] The area of ​​the base slip surface of the progressively collapsing rock mass DBCEFN, i.e., the area per unit thickness of the EF slip surface, is:

[0052]

[0053] The thrust caused by the collapse of the loose material is:

[0054]

[0055]

[0056] Assuming that the thrust T ultimately transmitted from the granular material to the slip surface EF via the compression slip body DBCEFN is without loss or dissipation during transmission, then the angle between T and the normal to the slip surface EF is:

[0057] θ=ψ p2 +β ω -ψ p1 (5)

[0058] According to the Coulomb criterion, the limiting equilibrium condition can be derived as follows:

[0059] Wcos(ψ p2 -β)+Tsin(θ-β)=c′Acosβ (6)

[0060] Substituting equations (1) to (5) into equation (6), we can derive the quadratic equation for the new mining depth H2 when damage occurs:

[0061]

[0062] Differentiate the Z2 term in equation (8) while keeping ψ p2 Since is a constant, setting its result to zero, we can obtain the critical tensile fracture depth as:

[0063]

[0064] Simplifying equation (8), we get:

[0065]

[0066] in:

[0067]

[0068]

[0069] Keeping Z2 constant, for ψ in equation (9) p2 Differential, let After rearranging, the expression for the critical failure surface dip angle is obtained as follows:

[0070]

[0071] In the formula:

[0072]

[0073]

[0074] The volume of the newly induced slope slip is:

[0075]

[0076] Based on the above formula, the volume of the slope slippage induced by the mining of the attached mine is obtained through the following calculation steps:

[0077] (1) Calculate K according to equation (4),

[0078] (2) Assumption

[0079] (3) Calculate Z2 according to equation (8).

[0080] (4) Calculate H2 according to equation (9).

[0081] (5) Calculate the inclination angle ψ of the slip surface according to equation (12). p2 The estimated value,

[0082] (6) Perform iterative calculations, and calculate ψ from step (5). p2 The estimated value and ψ in step (2) p2e Compare, if ψ p2 ≠ψ p2e , using ψ p2 Instead of ψ p2e Repeat calculations (3) and (4) until the difference between the two is less than 0.1%.

[0083] (7) Calculate the volume of the induced slope slip body according to formula (15).

[0084] Please see Figure 4 and Figure 5 The following example, using the open-pit to underground caving transition of a certain mine as an example, further illustrates the method of this invention: The open-pit mining boundary of a certain mine is designed at a level of -190m. During the transition from open-pit to underground, the eastern caving section is mined using a pillarless subgrade caving method. The first mining section is the -69m section. By pulling the bottom to form a goaf, the roof collapse is induced to form a cover layer. Subsequent sections are arranged at -87m, -105m, -123m, -141m, -159m, -177m, and -195m. Calculations show that after the initial subsidence pit is formed on the surface, when the mining of the -87m section of the caving section ends, the surrounding rock on the hanging wall of the slope may slip and fail. The slip surface dip angle is 74°, and the volume of the slip body calculated based on the slope slip surface is approximately 707,000 m³. 3 .

[0085] A delayed mining zone I was established on the east side of the -87m section. The sliding of the upper slope rock mass was delayed by retaining the triangular ore through delayed mining of the No. 1 access road. By setting up a delayed mining zone II on the west side (with access roads No. 6 and No. 7) and using stepped mining faces in the normal mining areas (with access roads No. 2, No. 3 and No. 4), the volume of the subsidence pit that can support the loose material was expanded as quickly as possible.

[0086] By adjusting the mining intensity to regulate the volume of loose material within the subsidence pit, the lower limit of the mined ore volume must ensure sufficient space within the subsidence pit to accommodate the loose landslide mass; the upper limit of the mined ore volume must ensure that the remaining loose material within the subsidence pit meets the requirements of the overburden layer. Calculations show that before mining the I# delayed mining area, a minimum mined ore volume of 615,000 m³ is required. 3 The maximum amount cannot exceed 1.223 million m³. 3 This is to meet the requirements for overburden thickness and to accommodate the landslide body. After the I# delayed mining area is fully mined, the slope will be damaged by landslide, and the landslide body will be completely contained by the collapse pit. Then, the II# delayed mining area will be mined in conjunction with the mining plan. This avoids the slope damage caused by the pillarless subgrade caving method in the hanging-side mine, which could affect the safety of the open-pit mine.

[0087] This invention is particularly applicable to large metal deposits that are converted from open-pit to underground mining. While the caving method is used for mining in the hanging mine, mining can also be carried out in the open-pit mine, enabling efficient and safe coordinated mining of open-pit and underground mines.

[0088] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for controlling rock displacement hazards on open-pit to underground mine slopes with segmented collapse and hanging walls, characterized in that, The control method includes: (1) Determine the location of the key section of the hanging wall mine and set up a delayed mining area on the upper side of the key section of the hanging wall mine to delay the gradual destruction of the slope; (2) Set up a delayed mining area on the side close to the open pit to form a rock embankment to expand the net volume of the collapse pit; (3) Adopt a downward stepped working face in the normal mining area. The mining time of the delayed mining area is controlled by the total ore output. The standard for controlling the total ore output is: to ensure that the thickness of the remaining loose cushion layer in the collapse pit meets the standard and that the net volume in the collapse pit is greater than the possible volume of the slope sliding body; The key segment is as follows: When the suspended ore is mined using the sublevel caving method without pillars, after the underground void breaks through to the surface, forming a goaf, continued mining of the suspended ore will cause progressive slope damage. This damage does not occur continuously, but rather in stages when mining reaches a certain segment; this segment is the key segment. The method for determining the key segment location of the attached-side mine is as follows: A progressive slope slip model induced by attached-side mine mining based on limit equilibrium analysis is used. This progressive slope slip model assumes that after a subsidence pit forms on the surface, the surrounding rock of the slope will progressively fail as the attached-side mine is mined downwards. When mining reaches a certain limit depth, tensile cracks and shear failure surfaces will form in the slope rock mass due to the influence of rock mass strength. Based on the above theory, a progressive slope slip model induced by attached-side mine mining based on limit equilibrium analysis is established, and the following assumptions are made: (1) The initial location of slope failure is determined by the known geometric parameters H1, Hc, Z1, and ψ. p1 Sure; (2) The extent of caving at the new mining depth H2 is determined by the tension fractures that reach the critical depth and are parallel to the ore body; (3) The failure of the slope rock mass occurs along a critical shear plane, the location of which can be determined by the rock mass strength and the applied effective stress. (4) The slope rock mass has uniform and isotropic mechanical properties; its shear stress is determined by the effective stress form determined by Coulomb. (5) In the analysis process, the stress distribution in the collapsed rock mass and the rock mass that is collapsing was simplified; (6) The slope environment is in a dry state, and the influence of water is ignored; The weight of the progressively collapsing rock mass DBCEFN is: (1)， The area of ​​the base slip surface of the progressively collapsing rock mass DBCEFN, i.e., the area per unit thickness of the EF slip surface, is: （2）， The thrust caused by the collapse of the loose material is: （3）， （4）， Assuming that the thrust T ultimately transmitted from the granular material to the slip surface EF via the compression slip body DBCEFN is without loss or dissipation during transmission, then the angle between T and the normal to the slip surface EF is: (5)， Based on the Coulomb criterion, the limiting equilibrium condition is derived as follows: (6)， Substituting equations (1) to (5) into equation (6), we can derive the quadratic equation for the new mining depth H2 when damage occurs: （7）， Differentiate the Z2 term in equation (8) while keeping ψ p2 Since is a constant, setting its result to zero, we can obtain the critical tensile fracture depth as: （8）， Simplifying equation (8), we get: （9）， in: （10）， （11）， Keeping Z2 constant, for ψ in equation (9) p2 Differential, let After rearranging, the expression for the critical failure surface dip angle is obtained as follows: （12）， In the formula: （13）， （14）， The volume of the newly induced slope slip is: （15）， In the above formula, Effective cohesion of the rock mass; : The depth at which initial damage occurs; : The depth at which subsequent damage occurs; Thickness of loose material within the collapse pit; The mining span of the attached mine when the slope fails; The thrust exerted by collapsed rock on the damaged surface; The thrust exerted on the footwall rock by the collapsed loose material; The weight of the wedge-shaped sliding rock mass; The quality of the collapsed material; Initial tensile crack depth; Subsequent tensile crack depth; : Slope angle; : The unit weight of the unexcavated original rock mass; : The bulk density of loose materials; The angle between the thrust T and the normal to the failure surface; Effective internal friction angle of the rock mass; : The friction angle between the collapsed material and the unmined rock mass; : Dip angle of the ore body; : The angle between the edge of the lowest mining area near the pit and the line connecting the edge of the slope collapse pit; : Collapse angle; Initial failure surface dip angle; Subsequent failure surface dip angle; Based on the above formula, the volume of the slope slippage induced by the mining of the attached mine is obtained through the following calculation steps: (1) Calculate K according to equation (4), (2) Assumption , (3) Calculate Z2 according to equation (8). (4) Calculate H2 according to equation (9). (5) Calculate the inclination angle ψ of the slip surface according to equation (12). p2 The estimated value, (6) Perform iterative calculations, and calculate ψ from step (5). p2 The estimated value and ψ in step (2) p2e Compare, if ψ p2 ≠ψ p2e , using ψ p2 Instead of ψ p2e Repeat calculations (3) and (4) until the difference between the two is less than 0.1%. (7) Calculate the volume of the induced slope slip body according to formula (15).

Images