Low-damage mining method for deep metal mine downward drift type stope

Abstract

The application provides a low-damage stoping method for a deep metal mine downward drift type stope, which comprises the following steps: S1, rock mass parameter measurement; S2, calculation of stope peripheral air stress distribution; S3, establishment of a fitting curve of different stresses and blasting crater long-short axis ratio; S4, blasting parameter calculation; and S5, laying of an impact-resistant artificial false floor. The application is designed to jointly act from two aspects of optimization of peripheral hole blasting parameters and change of artificial false floor laying process, so as to cooperatively reduce the damage degree of blasting on peripheral ore rock in the stope stoping process, reduce the explosive consumption, and effectively improve the stability of the artificial false floor and two-side ore rock, and improve the safety of construction.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of mining, in particular to a low-damage stoping method for a downward drift type stope of a deep metal mine. BACKGROUND

[0002] With the gradual depletion of shallow resources, metal mineral resources gradually develop towards deep mining. Deep mining stage faces problems of high ground temperature, high ground stress, high permeation pressure and strong mining disturbance. In the process of deep metal mine mining, in order to improve the ore recovery rate and ensure the safety of personnel and equipment, the downward drift type stoping gradually becomes the preferred mining method of various mines.

[0003] The influence of high stress environment on blasting has gradually been recognized. In the existing process of downward drift type stope stoping, the influence of high stress environment on blasting is rarely considered in the design of blasting parameters, especially in the process of arranging peripheral holes, equal interval single hole is arranged with equal charge quantity, and the unevenness of stress distribution is not considered. The above reasons not only cause the increase of damage of the two sides of the drift stope and the increase of tailings mixed in, but also reduce the safety of stoping and the recovery rate of ore. And it causes serious damage to the artificial false bottom of the upper layer, and increases the risk of overall collapse of the upper layer filling body.

[0004] The invention patent with publication number CN109029177A provides a blasting method for drift type stoping. The method is as follows: the dynamic tensile strength of the rock is lower than the dynamic compressive strength of the filling body, after the peripheral hole is initiated, at the junction of the rock and the filling body, due to the difference in wave impedance between the filling body and the rock, the blasting stress wave will generate reflected tensile wave and transmitted compressive wave at the interface of the two media, by calculating the distance between the peripheral hole and the filling body, the blasting parameters of the working face are determined, so that the stress wave peak value of the transmitted compressive wave generated at the interface of the two media is lower than the dynamic compressive strength of the filling body. However, the blasting method ignores the influence of ground stress on blasting in the process of deep underground engineering construction, and the influence degree of blasting under different stress states is different, and the calculation method used is the traditional theory in the field of dynamics, and the effect of dynamite blasting on rock mass under the action of dynamic and static combination should be fully considered.

[0005] Therefore, it is necessary to design an improved low-damage stoping method for a downward drift type stope of a deep metal mine to solve the above problems. SUMMARY

[0006] The main purpose of the present application is to provide a low-damage stoping method for a downward drift type stope of a deep metal mine, which can effectively reduce the damage degree of the two sides of the rock (or tailings) and the artificial false bottom in the process of blasting stoping, and improve the stability of the artificial false bottom and the two sides of the rock (tailings).

[0007] To achieve the above object, the application provides a low-damage mining method for a deep metal mine downward drift type stope, which comprises the following steps.

[0008] S1, testing of stope peripheral rock mass mechanical parameters;

[0009] S2, calculation of stope peripheral hole stress distribution: ground stress measurement is performed on the region where the project is located to obtain the ground stress distribution of the stope region; a stope numerical model is established and stope peripheral rock mass stress distribution calculation is performed;

[0010] S3, rock blasting crater experiment under different stress ratios under the action of bidirectional load is performed, and a fitting curve of different stresses and blasting crater major axis to minor axis ratio is established;

[0011] S4, peripheral hole blasting parameter design is performed according to the stress distribution of the light blasting layer in step S2 and the construction condition, and blasting is performed;

[0012] S5, impact-resistant artificial false bottom laying: after the blasting and ore drawing are completed, the ore is loaded and transported out of the stope, and an ore buffer layer is reserved at the bottom; during the laying of the artificial false bottom, the ore buffer layer at a predetermined interval from the bottom is reserved.

[0013] As a further improvement of the application, in step S3, the fitting equation of the fitting curve is the relationship between the blasting crater major axis to minor axis ratio and the stress ratio under different stress ratios;

[0014] The stress ratio is the stress ratio of the rock under the action of bidirectional load, which is the same as the ratio of the stress parallel to the stope contour line to the stress perpendicular to the stope contour line at the stope face hole;

[0015] λ is marked as the ratio of the stress parallel to the stope contour line to the stress perpendicular to the stope contour line at the hole; k is the ratio of the long axis to the short axis of the rock blasting crater under different λ conditions, which is related to the type of rock.

[0016] As a further improvement of the application, in step S4, the peripheral hole blasting parameters include the hole charge amount, and the design process is as follows:

[0017] Q=q0*L / k;

[0018] Wherein: q0 is the linear charge density, unit g / m; Q is the hole charge amount, unit g; L is the hole depth, unit m; k is the ratio of the long axis to the short axis of the rock blasting crater under different λ conditions, which is related to the type of rock, and is the same parameter as k in the above fitting equation.

[0019] As a further improvement of the present application, when the light blast hole diameter is 35-45mm, for the single collapse of the reserved light blast layer, the general linear charge density is 0.1-0.3kg / m, wherein the soft rock is 0.07-0.12kg / m, the medium-hard rock is 0.12-0.15kg / m, and the hard rock is 0.15-0.25kg / m; for the full-face one-time blasting method, the linear charge density is 0.30-0.35kg / m; the rock uniaxial compressive strength is s, when s≤20MPa, it belongs to soft rock; when 20MPa<s≤40MPa, it belongs to medium-hard rock; when s>40MPa, it belongs to hard rock.

[0020] As a further improvement of the present application, in step S4, the peripheral hole blasting parameters include the peripheral hole spacing, which is designed as follows:

[0021] E=(8-18)d;

[0022] Wherein: E is the peripheral hole spacing, unit mm; d is the blast hole diameter, unit mm.

[0023] As a further improvement of the present application, in step S1, the peripheral rock mass mechanical parameters are obtained by carrying out uniaxial compression test, direct shear test, Brazilian splitting test and conventional triaxial test;

[0024] The stope peripheral rock mass includes ore, surrounding rock and filling body near the stope;

[0025] The rock mass mechanical parameters include density, uniaxial compressive strength, shear strength, Poisson's ratio, elastic modulus, cohesion, and internal friction angle.

[0026] As a further improvement of the present application, the calculation process of step S2 is: the stress relief method is used to measure the ground stress of the region where the project is located, and the flac3d software is used to establish a numerical model of the stope; the ground stress distribution includes the horizontal maximum principal stress, the horizontal minimum principal stress and the vertical principal stress.

[0027] As a further improvement of the present application, the numerical model is a stope face actual size model; the stope peripheral rock mass stress distribution calculation includes the stress distribution in the direction parallel to the stope contour line and the direction perpendicular to the contour line, and the stress distribution of the stope reserved light blast layer rock mass;

[0028] The numerical model includes the reserved light blast layer; the light blast layer thickness is calculated as follows:

[0029] W=(10-20)d;

[0030] Wherein: W is the light blast layer thickness, unit mm; d is the blast hole diameter, unit mm.

[0031] As a further improvement of the present application, in step S5, the artificial false floor is composed of vertical main reinforcement and reinforcement; the main reinforcement is fixed in the upper and lower stoping rock along the vertical stope trend, and the reinforcement is arranged along the stope trend; the distance between the artificial false floor and the ore buffer layer is greater than or equal to 100 mm.

[0032] As a further improvement of the present application, in step S5, the damage degree of the artificial false floor under different buffer thickness conditions is calculated by using ls-dyna software, and when the damage degree of the artificial false floor is basically unchanged with the increase of the buffer layer thickness, it is the best.

[0033] The present application has the following beneficial effects:

[0034] The deep metal mine downward drift type stope low-damage stoping method provided by the present application is designed to have a combined effect from two aspects of optimizing the blasting parameters of the peripheral holes and changing the artificial false floor laying process, so as to cooperatively reduce the damage degree of the blasting on the peripheral ore rock (tailings, false floor) in the stope stoping process, reduce the explosive consumption, and effectively improve the stability of the artificial false floor and the two-side ore rock (tailings), and improve the safety of construction. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 The present application provides a downward drift type stope light blasting layer rock mass stress distribution diagram;

[0036] Figure 2 The present application provides a fitting curve diagram of the change rule of the long-short axis ratio of the blasting crater under different stress conditions;

[0037] Figure 3 The present application provides a downward drift type stope light blasting layer blast hole layout diagram;

[0038] Figure 4 The present application provides a change curve diagram of the damage range of the artificial false floor under different soft impact layer thicknesses;

[0039] Figure 5 The present application provides a downward drift type stope impact-resistant artificial false floor arrangement structure diagram.

[0040] REFERENCE NUMERALS

[0041] 1-blast hole; 2-light blasting layer; 3-ore buffer layer; 4-main reinforcement; 5-reinforcement. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be described in detail below with reference to the drawings and specific embodiments.

[0043] It should be noted that, in order not to obscure the present application with unnecessary details, only the structures and / or processing steps closely related to the solution of the present application are shown in the drawings, and other details not closely related to the present application are omitted.

[0044] It should also be noted that the terms "comprising", "containing", or any other variant thereof, are intended to cover non-exclusive inclusion, so that a process, method, article or device that includes a series of elements not only includes those elements, but also includes other elements not explicitly listed, or inherent to such a process, method, article or device.

[0045] The present application provides a low-damage mining method for a deep metal mine downward drift type stope, comprising the following steps:

[0046] S1, test the mechanical parameters of the stope surrounding rock mass;

[0047] S2, calculate the stress distribution of the surrounding hole of the stope: measure the ground stress of the region where the project is located to obtain the ground stress distribution of the stope region; establish a numerical model of the stope and calculate the stress distribution of the surrounding rock mass of the stope;

[0048] S3, carry out rock blasting crater experiment under different stress ratios under the action of bidirectional load, and establish a fitting curve of different stress and blasting crater length-to-short-axis ratio;

[0049] S4, according to the stress distribution of the light blasting layer in step S2 and the construction conditions, design the blasting parameters of the surrounding hole, and carry out blasting;

[0050] S5, laying of impact-resistant artificial false bottom: after the blasting and ore drawing are completed, the ore is loaded and transported out of the stope, and an ore buffer layer is reserved at the bottom; during the laying of the artificial false bottom, the ore buffer layer at a predetermined distance from the bottom is reserved.

[0051] Preferably, in step S3, the fitting equation of the fitting curve is the relationship between the length-to-short-axis ratio of the blasting crater and the stress ratio under different stress ratios;

[0052] The stress ratio is the ratio of the stress of the rock under the action of bidirectional load, which is the same as the ratio of the stress parallel to the stope contour line to the stress perpendicular to the stope contour line at the blast hole of the stope face;

[0053] Let λ be the ratio of the stress parallel to the stope contour line to the stress perpendicular to the stope contour line at the blast hole; k is the ratio of the long axis to the short axis of the rock blasting crater under different λ conditions, which is related to the type of rock.

[0054] Preferably, in step S4, the blasting parameters of the surrounding hole include the charge amount of the blast hole, and the design process is as follows:

[0055] Q=q0*L / k;

[0056] Wherein: q0 is the linear charge density, unit g / m; Q is the borehole charge, unit g; L is the borehole depth, unit m; k is the ratio of the long axis and the short axis of the rock blasting crater under different λ conditions, which is related to the type of rock, and the k in the fitting equation above is the same parameter.

[0057] Preferably, when the diameter of the light blast hole is 35-45 mm, for the separate caving of the reserved light blast layer, the general linear charge density is 0.1-0.3 kg / m, wherein the soft rock is 0.07-0.12 kg / m, the medium-hard rock is 0.12-0.15 kg / m, and the hard rock is 0.15-0.25 kg / m; for the full-face one-time blasting method, the linear charge density is 0.30-0.35 kg / m; the uniaxial compressive strength of the rock is s, when s≤20 MPa, it belongs to soft rock; when 20 MPa

[0058] Preferably, in step S4, the blasting parameters of the peripheral holes include the peripheral hole spacing, which is designed as follows:

[0059] E=(8-18)d;

[0060] Wherein: E is the peripheral hole spacing, unit mm; d is the diameter of the borehole, unit mm.

[0061] Preferably, in step S1, the mechanical parameters of the peripheral rock mass are obtained by carrying out uniaxial compression test, direct shear test, Brazilian splitting test and conventional triaxial test;

[0062] The peripheral rock mass of the stope includes ore, surrounding rock and filling body near the stope;

[0063] The mechanical parameters of the rock mass include density, uniaxial compressive strength, shear strength, Poisson's ratio, elastic modulus, cohesion, and internal friction angle.

[0064] Preferably, the calculation process of step S2 is: the stress of the region where the project is located is measured by stress relief method, and the numerical model of the stope is established by using flac3d software; the stress distribution includes the horizontal maximum principal stress, the horizontal minimum principal stress and the vertical principal stress.

[0065] Preferably, the numerical model is a model of the actual size of the stope face; the stress distribution calculation of the rock mass around the stope includes the stress distribution parallel and perpendicular to the contour line of the stope, and the stress distribution of the rock mass of the reserved light blast layer of the stope;

[0066] The numerical model includes the reserved light blast layer; the thickness of the light blast layer is calculated as follows:

[0067] W=(10~20)d;

[0068] Wherein: W is the light blasting layer thickness, unit mm; d is the blast hole diameter, unit mm.

[0069] Preferably, in step S5, the artificial false floor is composed of vertical arrangement of main reinforcement and reinforcement; the main reinforcement is fixed in the upper and lower stoping rock along the vertical trend of the stope, and the reinforcement is arranged along the stope trend; the distance between the artificial false floor and the ore buffer layer is greater than or equal to 100 mm.

[0070] Preferably, in step S5, the damage degree of the artificial false floor under the blasting condition of different buffer thickness is calculated by using ls-dyna software, and when the damage of the artificial false floor is basically unchanged with the increase of the buffer layer thickness, it is the best.

[0071] Example 1

[0072] The embodiment 1 of the present application provides a first sublevel first road stope in the downward horizontal drift mining process, and the embodiment is only used for illustration and does not limit the present application. The specific steps of the stoping method are as follows:

[0073] S1, test the rock mass mechanical parameters of the stope periphery.

[0074] The stope periphery includes ore, surrounding rock and filling body near the stope.

[0075] The rock mass mechanical parameters include density, uniaxial compressive strength, shear strength, Poisson's ratio, elastic modulus, cohesion, internal friction angle and the like.

[0076] The rock mass mechanical parameters of the periphery are obtained by carrying out uniaxial compression test, direct shear test, Brazilian splitting test and conventional triaxial test, wherein the rock mass uniaxial compressive strength is 110 MPa, the density is 2.93 g / cm3, the Poisson's ratio is 0.21, the elastic modulus is 45 GPa, the bulk modulus is 3.5 GPa, the cohesion is 15 MPa, the internal friction angle is 30°, and the tensile strength is 8.5 MPa.

[0077] S2, calculate the stress distribution of the stope periphery hole.

[0078] The ground stress distribution of the stope region is obtained by measuring the ground stress of the region where the project is located. The numerical calculation software is selected to establish the numerical model of the stope and calculate the stress distribution of the surrounding rock mass of the stope.

[0079] The ground stress distribution includes the horizontal maximum principal stress, the horizontal minimum principal stress and the vertical principal stress.

[0080] The numerical model is a stope face actual size model, and the model includes a reserved light blasting layer. The thickness of the light blasting layer is calculated as follows:

[0081] W = (10~20) d (1)

[0082] Wherein: W is the light blasting layer thickness, mm; d is the blast hole diameter, mm.

[0083] The specific measurement results are as follows:

[0084] The in-situ stress of the engineering area is measured by stress relief method, the horizontal maximum principal stress is 34 MPa, the horizontal minimum principal stress is 28 MPa, and the vertical principal stress is 19 MPa. The model of the stope is established by flac3d.

[0085] The numerical model is the actual size model of the stope face, the stope width is 7 m, and the height is 6.5 m. The drilling equipment used in the field is a blast hole diameter of 38 mm. The blasting layer thickness is 570 mm, which is calculated as follows:

[0086] W = 15 * 38 = 570;

[0087] The stress distribution calculation of the rock mass around the stope includes the stress distribution in the direction parallel to the stope contour line and the direction perpendicular to the contour line. Especially the stress distribution of the light blasting layer rock mass reserved in the stope, as shown in Figure 1

[0088] S3, under the action of bidirectional load, the rock blasting crater experiment under different stress ratios is carried out, and the fitting curve of different stress and blasting crater length-short axis ratio is established; the fitting equation of the fitting curve is the relationship between the blasting crater length-short axis ratio and the stress ratio under different stress ratios.

[0089] The stress ratio is the ratio of the stress of the rock under the action of bidirectional load, which is the same as the ratio of the stress parallel to the stope contour line to the stress perpendicular to the stope contour line at the blast hole of the stope face.

[0090] Specifically, based on the above parameter setting, the stress ratio under the action of bidirectional load and the corresponding blasting crater length-short axis ratio are calculated by using lsdyna software, and the fitting curve is obtained as shown in Figure 2 Based on the data in the fitting curve, the corresponding fitting equation is further obtained as follows:

[0091]

[0092] Wherein: λ is the ratio of the stress parallel to the stope contour line to the stress perpendicular to the stope contour line at the blast hole; k is the ratio of the long axis to the short axis of the rock blasting crater under different λ conditions, which is related to the type of rock.

[0093] S4, according to the stress distribution of the light blasting layer in step S2 and the construction conditions, the peripheral hole blasting parameter design is carried out. The blast hole depth is 3.0 m. ​

[0094] Q = q0*L / k (2)

[0095] Wherein: q0 is the linear charge density, kg / m; Q is the borehole charge, kg; L is the borehole depth, m; when the light hole diameter is 35-45 mm, for the single caving of the reserved light blasting layer, the linear charge density is generally 0.1-0.3 kg / m, wherein the soft rock is 0.07-0.12 kg / m, the medium-hard rock is 0.12-0.15 kg / m, and the hard rock is 0.15-0.25 kg / m; for the full-face one-time blasting method, the linear charge density is 0.30-0.35 kg / m. The uniaxial compressive strength of the rock is s, when s≤20 MPa, it belongs to soft rock; when 20 MPa

[0096] Table 1 is the design of the borehole charge of the peripheral hole blasting parameters in Example 1

[0097]

[0098] In step S4, the peripheral hole blasting parameters further include a peripheral hole spacing, which is designed as follows:

[0099] E = (8-18) d;

[0100] Wherein: E is the peripheral hole spacing, unit mm; d is the borehole diameter, unit mm.

[0101] Specifically to this embodiment, the peripheral hole blasting parameters include a peripheral hole spacing, which is designed as follows:

[0102] E = (8-18) d = 12*38 = 456 mm (3)

[0103] Wherein: E is the peripheral hole spacing, mm; d is the borehole diameter, mm; the calculated peripheral hole arrangement is as shown in Figure 3 .

[0104] S5, an impact-resistant artificial false bottom is laid, as shown in Figures 4-5 After the blasting and ore drawing are completed, the ore is shovelled and transported out of the stope, but a certain thickness of ore buffer layer 3 is reserved at the bottom. During the laying process of the artificial false bottom, the distance from the bottom to the ore buffer layer 3 is a certain spacing.

[0105] The thickness of the ore buffer layer 3 is related to the artificial false bottom filling material, and the degree of damage of the artificial false bottom under different buffer thickness conditions is calculated by using ls-dyna software, and when the damage of the artificial false bottom basically remains unchanged with the increase of the buffer thickness, it is the best.

[0106] The thickness of the ore buffer layer 3 is not less than 400 mm, which acts as a buffer layer during the next sublevel mining, and plays a role of blasting the filling body of the previous sublevel.

[0107] The artificial false floor is composed of vertical main reinforcement 4 and reinforcement 5, wherein the main reinforcement 4 is fixed in the upper and lower stoping rock along the vertical stope trend, and the reinforcement 5 is arranged along the stope trend.

[0108] The artificial false floor is not less than 100 mm away from the ore buffer layer, and the filling body can effectively wrap the false floor during the filling process.

[0109] Specific to the embodiment, the design is as follows:

[0110] The filling material selected in the embodiment 1 is 1:4 full tailings cemented filling material, and the lsdyna software is used to calculate the filling body damage thickness under different buffer layer thickness conditions, as shown in the table. Figure 4 When the soft alluvium thickness reaches 400 mm, the damage range of the artificial false floor tends to be stable. Therefore, in this embodiment, the ore is excavated and transported out of the stope after blasting and mining is completed, and a 400 mm thick ore buffer layer 3 is reserved at the bottom.

[0111] During the laying process of the artificial false floor, a 100 mm spacing is kept from the bottom ore buffer layer 1 to ensure that the main reinforcement 4 and the reinforcement 5 can completely wrap the false floor. The main reinforcement 4 is φ15 mm threaded steel with a horizontal spacing of 0.3 m, and the reinforcement 5 is φ6 mm threaded steel arranged vertically with the main reinforcement 4 with an interval of 0.3 m.

[0112] Based on the mutual cooperation of the above steps S1 to S5, the low-damage stoping of the downward drift stope of the deep metal mine is realized.

[0113] In summary, the application provides a low-damage stoping method for a downward drift stope of a deep metal mine. It includes the following steps: S1, determination of rock mass parameters; S2, calculation of stope peripheral stress distribution; S3, establishment of fitting curve; S4, calculation of blasting parameters; and S5, laying of impact-resistant artificial false floor. The application is designed to work together from two aspects of optimizing the peripheral hole blasting parameters and changing the artificial false floor laying process, to cooperatively reduce the damage degree of blasting to the peripheral rock during the stope stoping process, and effectively improve the stability of the artificial false floor and the two side rocks, and improve the safety of construction.

[0114] The above embodiments are only used to illustrate the technical solutions of the application and not to limit it. Although the application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the application can be modified or replaced equivalently without departing from the spirit and scope of the technical solutions of the application.

Claims

1. A low-damage mining method for down-entry stopes in deep metal mines, characterized in that: Includes the following steps: S1, Test of rock mechanics parameters of the ore mass surrounding the mining area; S2, Calculation of stress distribution around the mining area: Conduct geostress measurements in the area where the project is located to obtain the geostress distribution in the mining area; establish a numerical model of the mining area and calculate the stress distribution of the rock mass around the mining area; S3. Conduct rock blasting funnel experiments under bidirectional loads and different stress ratios to establish fitting curves for different stresses and the ratio of the major and minor axes of the blasting funnel; the fitting equation of the fitting curve is the relationship between the ratio of the major and minor axes of the blasting funnel and the stress ratio under different stress ratios. The stress ratio is the ratio of rock stresses under bidirectional loading, which is the same as the ratio of stress in the direction parallel to the stope contour line to stress perpendicular to the stope contour line at the blast hole of the working face, and is denoted as... ; S4. Based on the stress distribution of the light blasting layer in step S2 and the construction conditions, design the blasting parameters for the surrounding holes and carry out the blasting. The peripheral hole blasting parameters include the amount of explosive charge in the blast hole, and the design process is as follows: ； in: q 0 represents the density of the linear charge, in units of... g / m Q represents the charge amount in the borehole, in units of... g ; L For borehole depth, in units m ; k For different The ratio of the major axis to the minor axis of the rock blasting funnel is related to the type of rock. S5, Impact-resistant artificial false bottom laying: After the blasting and ore extraction is completed, the ore is shoveled out of the mining area and a buffer layer of ore is reserved at the bottom; during the artificial false bottom laying process, the distance from the bottom ore buffer layer is predetermined.

2. The low-damage mining method for down-entry stopes in deep metal mines according to claim 1, characterized in that: When the diameter of the smooth blasting holes is 35 - 45 mm, for the separate caving of the reserved smooth blasting layer, the linear charge density is generally 0.1 - 0.3 kg / m , among which, for soft rock it is 0.07 - 0.12 kg / m , for medium-hard rock it is 0.12 - 0.15 kg / m , for hard rock it is 0.15 - 0.25 kg / m ; for the full-face one-shot blasting method, the linear charge density is 0.30 - 0.35 kg / m ; the uniaxial compressive strength of the rock is s. When s ≤ 20 MPa, it belongs to soft rock; when 20 MPa < s ≤ 40 MPa, it belongs to medium-hard rock; when s > 40 MPa, it belongs to hard rock.

3. The low-damage mining method for down-entry stopes in deep metal mines according to claim 1, characterized in that: In step S4, the peripheral hole blasting parameters include the peripheral hole spacing, which is designed as follows: ； in: E The distance between the peripheral holes, in units of mm ; d The borehole diameter is expressed in units of... mm .

4. The low-damage mining method for down-entry stopes in deep metal mines according to claim 1, characterized in that: In step S1, the mechanical parameters of the surrounding ore rock mass are obtained by conducting uniaxial compression tests, direct shear tests, Brazilian splitting tests, and conventional triaxial tests. The surrounding ore and rock of the mining area includes the ore, surrounding rock and backfill near the mining area; The rock mass mechanical parameters include density, uniaxial compressive strength, shear strength, Poisson's ratio, elastic modulus, cohesion, and internal friction angle.

5. The method for low-damage mining in a down-entry stope of deep metal mines according to claim 1, characterized in that: The calculation process of step S2 is as follows: the geostress in the area where the project is located is measured by stress relief method, and the numerical model of the mining area is established by flac3d software; the geostress distribution includes the horizontal maximum principal stress, the horizontal minimum principal stress and the vertical principal stress.

6. The low-damage mining method for down-entry stopes in deep metal mines according to claim 5, characterized in that: The numerical model is the actual size model of the mining face; the stress distribution calculation of the rock mass around the mining area includes the stress distribution in the direction parallel to and perpendicular to the mining outline, as well as the stress distribution of the rock mass in the reserved blasting layer of the mining area. The numerical model includes retaining the light burst layer; the thickness of the light burst layer is calculated as follows: ； in: W The thickness of the light burst layer, in units of mm ; d The borehole diameter is expressed in units of... mm .

7. The low-damage mining method for down-entry stopes in deep metal mines according to claim 1, characterized in that: In step S5, the artificial false bottom is composed of vertically arranged main reinforcement and auxiliary reinforcement; the main reinforcement is fixed in the upper and lower hanging walls of the ore perpendicular to the direction of the stope, and the auxiliary reinforcement is arranged along the direction of the stope; the distance between the artificial false bottom and the ore buffer layer is greater than or equal to 100mm.

8. The low-damage mining method for down-entry stopes in deep metal mines according to claim 7, characterized in that: In step S5, the degree of damage to the artificial false bottom caused by blasting under different buffer thickness conditions is calculated using ls-dyna software. The optimal result is when the damage to the artificial false bottom remains basically unchanged as the buffer layer thickness increases.

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