A method of mining with a downward drift with a reserved roof space

Abstract

The application discloses a downward drift filling mining method with reserved top space, which arranges a stope along the ore body trend, divides the ore body in the middle section from top to bottom into subsections, divides each subsection from top to bottom into layers, divides the ore body in the layer into one-step mining drifts and two-step mining drifts arranged at intervals vertically to the ore body trend, and the one-step mining drifts or two-step mining drifts of the upper and lower layers correspond to each other in position on the plane, the whole adopts the sequence of mining from the upper subsection to the lower subsection and from the upper layer to the lower layer, takes the drift as a production unit to organize production, and reserves the top space by using a ball at the bottom of the drift during the drift filling, thereby improving the blasting free face condition when the next layer drift is mined, and effectively protecting the top filling body. Compared with the prior art, the application can effectively improve the operation efficiency and reduce the labor intensity, the reserved top space can reduce the disturbance and damage of the blasting shock wave to the roof filling body, ensures the overall stability of the roof filling body, and guarantees the safety of the on-site operation.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of mine exploitation, and particularly relates to a downward drift filling mining method with reserved top space. BACKGROUND

[0002] The filling mining method refers to a mining method in which filling materials are filled into the mined-out area while the mining, transportation and other operations are carried out. The purpose of filling is to support the two sides of the mined-out area and to create a stable floor for the upper layer mining. It is suitable for the deposits with unstable ore and surrounding rock, which are not allowed to have a large exposed surface; the deposits whose surface needs to be protected; the deposits with rare noble metals or high-grade ores; the deposits with spontaneous combustion; the deposits with complex occurrence conditions, etc. Since the filling mining method can maximize the recovery of mineral resources and protect the underground and surface environment, especially in recent years, with the continuous progress of filling materials, filling technology, pipeline transportation equipment and technology, the filling mining method has been widely applied in non-ferrous metal mines and precious metal mines. With the continuous reduction of filling cost and the continuous rise of mineral product price, the filling method has an irreplaceable advantage, and the application proportion in mines such as coal mines and iron mines which are not suitable for filling method in the traditional sense is also increasing.

[0003] Among the many filling mining methods, the downward drift filling mining method is a widely used mining method for the mining of ore bodies with extremely broken ore and high economic value in China. This method is a mining method that sequentially mines and fills each layer from bottom to top under the protection of the artificial false roof in the form of roadway access. The downward drift filling mining method is mainly suitable for ore bodies with very unstable ore and surrounding rock and high-grade ore with high economic value. The advantage of this method is that the working place roof is an artificial false roof, which is more safe and reliable, and the ore loss rate and ore dilution rate are low. However, the existing downward drift filling mining method also has the following deficiencies:

[0004] (1) Low mining efficiency and high mining cost. At present, the roadway excavation method is used for blasting and mining in the access, which has great difficulty in blasting, and the once-excavated footage is low, so the mining efficiency is low, which restricts the mining production capacity. At the same time, a large number of blast holes need to be constructed for excavation and blasting, which consumes a lot of labor and explosive materials, and the mining cost is high.

[0005] (2) The blasting of the stope access seriously damages the roof filling body, and the risk of roof filling body collapse is high. The blasting shock wave of the access excavation will cause disturbance and damage to the roof filling body, leading to a decrease in the stability of the roof filling body. In addition, the influence of the quality fluctuation of the filling body leads to an increase in the risk of roof filling body collapse, which threatens the safety of personnel and equipment. SUMMARY

[0006] In view of the problems existing in the above-mentioned existing downward drift filling mining method, the application discloses a downward drift filling mining method with reserved top space, which comprises the following steps:

[0007] Step 1, arranging a stope along the ore body trend, the ore body in the middle section is divided into subsections from top to bottom, each subsection is further divided into layers from top to bottom, the ore body in the layer is divided into one-step mining drifts and two-step mining drifts arranged at intervals and perpendicular to the ore body trend, the one-step mining drifts or the two-step mining drifts of the upper and lower layers correspond to each other in position on the plane, and the drifts are arranged as 3-5° upward slopes from the lower wall to the upper wall of the ore body; the stope is mined in the production unit of the drift, and the whole is mined in the order of from the upper subsection to the lower subsection and from the upper layer to the lower layer;

[0008] Step 2, mining the one-step mining drift of the first layer of the first subsection, a connecting tunnel is constructed from the subsection gallery to the lower wall boundary of the ore body and perpendicular to the ore body trend direction, then a drift is constructed to the upper wall boundary of the ore body, after the ore is mined in the drift, anchor cables are constructed on the roof of the connecting tunnel and the drift according to the designed grid, drill holes are constructed on the two sides of the wall of the connecting tunnel and the drift at equal intervals, the two sides of the drill holes correspond to each other one by one, and cross support rods are installed in the holes, then balls are laid on the bottom plate of the drift, fine sand is filled in the gaps between the balls, plastic cloth and steel mesh are laid in turn above the balls, hanging rods are uniformly arranged along the direction of the connecting tunnel and the drift, one end of the hanging rod is welded and fixed to the end of the anchor cable on the roof, and the other end is welded and fixed to the steel mesh on the bottom, then a filling retaining wall is built at the intersection of the subsection gallery and the connecting tunnel, and the drift is filled in sections and topped;

[0009] Step 3, after the filling body of the one-step mining drift of the first layer of the first subsection reaches the designed strength, the one-step mining drift of the second layer of the first subsection is mined, a connecting tunnel is constructed from the subsection gallery to the lower wall boundary of the ore body and perpendicular to the ore body trend direction, then a drift is constructed to the upper wall boundary of the ore body, as the working face advances, the upper balls are released to form a top space before each blasting; after the ore is mined in the drift, drill holes are constructed on the two sides of the wall of the connecting tunnel and the drift at equal intervals, the two sides of the drill holes correspond to each other one by one, and cross support rods are installed in the holes, then balls are laid on the bottom plate of the drift, fine sand is filled in the gaps between the balls, plastic cloth and steel mesh are laid in turn above the balls, hanging rods are uniformly arranged along the direction of the connecting tunnel and the drift, one end of the hanging rod is welded and fixed to the steel mesh on the bottom of the previous layer, and the other end is welded to the steel mesh on the bottom, then a filling retaining wall is built at the intersection of the subsection gallery and the connecting tunnel, and the drift is filled in sections and topped; after the filling body of the one-step mining drift of the second layer of the first subsection reaches the designed strength, the one-step mining drift of the third layer of the first subsection is mined, the mining and filling process is the same as that of the one-step mining drift of the second layer of the first subsection, and so on until the one-step mining drifts of all layers of the first subsection are mined;

[0010] Step 4, after the first section all layered one-step mining access recovery is completed, continue to recover the second section of one-step mining access, recovery, filling process with step 3 one-step mining access recovery, filling process, at the same time start to recover the two-step mining access in the first section, two-step mining access recovery, filling process with one-step mining access recovery, filling process is the same, that is, one-step mining access recovery ahead of two-step mining access a section of synchronous production, so the organization until the entire stope recovery is completed.

[0011] Preferably, the borehole diameter on the two sides of the access way wall is 60-80mm, and the borehole depth is 0.5-0.6m.

[0012] Further, the cross brace rod body is welded by two equal length steel pipes, when installing the cross brace rod body, first insert the two steel pipes into the corresponding boreholes on the two sides of the access way, then weld the other side of the two steel pipes, the length of each steel pipe is determined according to the following formula:

[0013] L=1 / 2B+0.8

[0014] In the formula, L is the length of the steel pipe, and B is the width of the access way, in meters.

[0015] Further, the ball is a high-strength plastic hollow ball, the ball radius is 0.1-0.15m, and the compressive strength is greater than the pressure applied to the ball by the upper filling body.

[0016] Further, when laying the ball in the access way, a set of reinforcement mesh is laid every interval along the direction of the access way, the reinforcement mesh is welded and fixed with the steel mesh, and the mesh size of the reinforcement mesh is smaller than the diameter of the ball.

[0017] Further, the width of the plastic cloth is greater than the width of the access way by more than 2m, and the plastic cloth is fixed on the two sides of the access way wall with a height of not less than 1m.

[0018] Further, the mesh size of the steel mesh is smaller than the diameter of the ball, the length of the transverse rib of the steel mesh laid at the bottom of the one-step mining access way in the direction of the width of the access way is longer than the width of the access way by 0.4m, and 0.2m is reserved on both sides, when laying the steel mesh in the one-step mining access way, the 0.2m transverse rib on the two sides of the access way is folded on the wall of the access way, and when laying the steel mesh in the adjacent two-step mining access way, the 0.2m transverse rib on the two sides of the adjacent one-step mining access way is connected and fixed with the steel mesh of the two-step mining access way.

[0019] Further, the access way is filled with high-strength cemented filling body, and the uniaxial compressive strength of the filling body is greater than or equal to 5MPa after 28 days.

[0020] Further, when the access way is filled in several times, the first filling height is not higher than the height of the plastic cloth on the two sides of the access way wall.

[0021] Beneficial effects

[0022] Compared with the prior art, the present application has the following beneficial effects:

[0023] (1) When filling the upper layer access, the space is reserved at the bottom of the access by using a ball, the free surface condition during the next layer access is improved, the full-face blasting technology is changed into lateral blasting and ore collapse technology, the number of drill holes and the consumption of explosives can be greatly reduced, the operation efficiency is improved, and the labor intensity is reduced.

[0024] (2) The top space reservation can reduce the disturbance and damage of the blasting shock wave to the roof filling body, ensure the overall stability of the roof filling body, and ensure the safety of the site operation.

[0025] The technical solutions of the present application will be further described in detail below with the help of the drawings and specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 It is a first layer one-step access recovery schematic diagram of a downward access filling mining method with top space reservation in the embodiment.

[0027] Figure 2 It is a schematic diagram of laying a ball and a steel mesh before one-step access filling of a first layer of a first section of a downward access filling mining method with top space reservation in the embodiment.

[0028] Figure 3 It is an enlarged schematic diagram of A in Figure 2

[0029] Figure 4 It is a first layer one-step access recovery schematic diagram of a downward access filling mining method with top space reservation in the embodiment.

[0030] Figure 5 It is a schematic diagram of laying a ball and a steel mesh before one-step access filling of a second layer of a first section of a downward access filling mining method with top space reservation in the embodiment.

[0031] Reference numerals in the drawing: 1 - section roadway, 2 - connecting way, 3 - ore body, 4 - one-step access, 5 - anchor cable, 6 - hanging reinforcement, 7 - ball, 8 - fine sand, 9 - retaining mesh, 10 - plastic cloth, 11 - steel mesh, 12 - cross brace, 13 - filling body, 14 - top space. DETAILED DESCRIPTION

[0032] ​The technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the drawings. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0033] The present application provides a mining method of reserving top space and downward drift filling, which comprises the following steps:

[0034] Step 1, arranging a stope along the ore body trend, the ore body in the middle section is divided into subsections from top to bottom, and each subsection is further divided into layers from top to bottom, the ore body in the layer is divided into one-step mining drifts and two-step mining drifts arranged at intervals vertically to the ore body trend, the one-step mining drifts or two-step mining drifts of the upper and lower layers correspond to each other in position on the plane, and the drifts are arranged as 3-5° upward slope from the lower wall to the upper wall of the ore body; the stope is recovered in sequence from the upper subsection to the lower subsection and from the upper layer to the lower layer, and the production is organized in the form of drifts as production units;

[0035] Step 2, recovering the one-step mining drifts of the first layer in the first subsection, constructing a connecting tunnel from the subsection gallery vertically to the ore body trend direction to the lower wall boundary of the ore body, then constructing the drift to the upper wall boundary of the ore body, after the recovery of the ore in the drift is completed, constructing anchor cables on the roof of the connecting tunnel and the drift according to the designed grid, constructing drill holes on the two sides of the wall at equal intervals, the drill holes on the two sides correspond to each other one by one, and cross support rods are installed in the holes, then laying balls on the bottom plate of the drift, filling fine sand in the gaps between the balls, laying plastic cloth and steel mesh in turn above the balls, evenly arranging hanging rods along the direction of the connecting tunnel and the drift, one end of the hanging rod is welded and fixed to the end of the anchor cable on the roof, and the other end is welded and fixed to the steel mesh on the bottom, then building a filling retaining wall at the intersection of the subsection gallery and the connecting tunnel, and filling the drift in sections and connecting the roof;

[0036] Step 3, after the one-step entry way filling body of the first sublevel of the first section reaches the design strength, the one-step entry way of the second sublevel of the first section is mined, a connecting way is constructed perpendicular to the ore body strike direction from the section roadway, a way is constructed to the ore body upper plate boundary, and with the advance of the mining working face, the upper sphere is discharged to form a top space before each blasting; after the way mining is completed, drill holes are constructed on the two sides of the connecting way and the way at equal intervals, the two sides of the drill holes are one-to-one corresponding, a cross brace is installed in the hole, then a sphere is laid on the way floor, fine sand is filled in the gap between the spheres, plastic cloth and steel mesh are laid in turn above the spheres, hanging reinforcement is uniformly laid along the connecting way and the way, one end of the hanging reinforcement is welded and fixed on the steel mesh at the bottom of the previous sublevel, the other end is welded on the steel mesh at the bottom, then a filling retaining wall is built at the intersection of the section roadway and the connecting way, the way is filled in sections and topped; after the one-step entry way filling body of the second sublevel of the first section reaches the design strength, the one-step entry way of the third sublevel of the first section is mined, the mining and filling process is the same as that of the one-step entry way of the second sublevel of the first section, and so on until the one-step entry way of all sublevels of the first section is mined.

[0037] Step 4, after the one-step entry way of all sublevels of the first section is mined, the one-step entry way of the second section is continued to be mined, the mining and filling process is the same as that of the one-step entry way of the first section in step 3, and the two-step entry way in the first section is started to be mined, the mining and filling process of the two-step entry way is the same as that of the one-step entry way, that is, the one-step entry way mining is ahead of the two-step entry way by one section, and the production is organized in this way until the entire stope is mined.

[0038] Preferably, the diameter of the drill hole on the two sides of the way is 60-80 mm, and the depth of the drill hole is 0.5-0.6 m.

[0039] Further, the cross brace is welded by two equal-length steel pipes, when the cross brace is installed, the two steel pipes are inserted into the corresponding drill holes on the two sides of the way, and then the other sides of the two steel pipes are welded, the length of each steel pipe is determined according to the following formula:

[0040] L = 1 / 2B + 0.8

[0041] In the formula, L is the length of the steel pipe, and B is the width of the way, in meters.

[0042] Further, the sphere is a high-strength plastic hollow sphere, the radius of the sphere is 0.1-0.15 m, and the compressive strength of the sphere is greater than the pressure exerted on the sphere by the upper filling body.

[0043] Further, the steel mesh is welded and fixed with the blocking mesh, and the grid size of the blocking mesh is smaller than the diameter of the spherical body.

[0044] Further, the width of the plastic cloth is greater than the width of the drift by more than 2 m, and the plastic cloth is fixed on the two side walls of the drift with a height of not less than 1 m.

[0045] Further, the grid size of the steel mesh is smaller than the diameter of the spherical body, the length of the transverse rib of the steel mesh laid at the bottom of the one-step drift is 0.4 m longer than the width of the drift, and 0.2 m is reserved on both sides, the 0.2 m long transverse rib on both sides of the one-step drift is bent on the side wall of the drift when the steel mesh is laid in the one-step drift, and the 0.2 m long transverse rib on both sides of the one-step drift is connected and fixed with the steel mesh of the two-step drift when the steel mesh is laid in the two-step drift.

[0046] Further, the drift is filled with high-strength cemented filling body, and the uniaxial compressive strength of the filling body is greater than or equal to 5 MPa after 28 days.

[0047] Further, when the drift is filled in several times, the first filling height is not higher than the height of the plastic cloth on the two side walls of the drift.

[0048] Referring to Figures 1-5 , the downward drift filling mining method with a reserved top space in the figure is the preferred scheme of the present application, and the mining method includes the following steps:

[0049] Step 1, arranging the stope along the trend of the ore body 3, the ore body 3 in the middle section is divided into subsections from top to bottom, and each subsection is further divided into layers from top to bottom, the ore body 3 in the layer is divided into a one-step drift 4 and a two-step drift 5 arranged at intervals perpendicular to the trend of the ore body 3, the one-step drift 4 or the two-step drift 5 of the upper and lower layers correspond to each other in position on the plane, and the drift is arranged as a 3-5° upward slope from the lower disc to the upper disc of the ore body 3; the stope mining is organized as a production unit with the drift, and the whole is mined in sequence from the upper subsection to the lower subsection and from the upper layer to the lower layer;

[0050] Step 2, one-step mining of the first sublevel of the first sublevel in the access 4, the sublevel drift 1 is constructed perpendicular to the strike direction of the ore body 3 to the lower boundary of the ore body 3, and then the access is constructed to the upper boundary of the ore body 3, and after the access mining is completed, the anchor cable 5 is constructed on the roof of the access 2 and the access according to the designed grid, the drill holes are constructed on the two sides of the wall of the access 2 and the access at equal intervals, the diameter of the drill hole is 80mm, the depth of the drill hole is 0.6m, the two sides of the drill hole correspond to each other, and the cross brace rod body 12 is installed in the hole, then the ball 7 is laid on the bottom plate of the access, the ball 7 is a high-strength plastic hollow ball, the radius of the ball 7 is 0.1-0.15m, and the compressive strength of the ball 7 is greater than the pressure applied to the ball 7 by the upper filling body. When the ball 7 is laid, a set of reinforcement mesh 9 is laid at intervals along the strike direction of the access, the reinforcement mesh 9 is welded and fixed with the steel mesh, and the mesh size of the reinforcement mesh 9 is smaller than the diameter of the ball 7. Fine sand 8 is filled in the gap between the balls 7, and plastic cloth 10, steel mesh 11 are laid in turn above the balls 7, the width of the plastic cloth 10 is greater than the width of the access 2m, the plastic cloth 10 is fixed on the two sides of the wall of the access, and the height is not less than 1m; the mesh size of the steel mesh 11 is smaller than the diameter of the ball 7, the length of the transverse reinforcement of the steel mesh 11 laid at the bottom of the one-step mining access 4 in the width direction of the access is 0.4m longer than the width of the access, and 0.2m is reserved on both sides, when the steel mesh 11 is laid in the one-step mining access 4, the 0.2m transverse reinforcement of the access on both sides is bent on the wall of the access, and when the steel mesh 11 is laid in the two-step mining access, the 0.2m transverse reinforcement on both sides of the one-step mining access 4 is connected and fixed with the steel mesh 11 of the two-step mining access. The hanging reinforcement 6 is uniformly arranged along the strike direction of the access 2 and the access, one end of the hanging reinforcement 6 is welded and fixed on the end of the anchor cable 5 on the roof, the other end is welded and fixed on the steel mesh 11 at the bottom, then the filling retaining wall is built at the intersection of the sublevel drift 1 and the access 2, the access is filled and topped in sections, and the first filling height is not higher than the height of the plastic cloth 10 on the two sides of the wall of the access. The access is filled with high-strength cemented filling body, and the 28-day uniaxial compressive strength of the filling body 13 is greater than or equal to 5MPa.

[0051] Step 3, after the first step of the first sublevel one-step mining access road 4 reaches the designed strength, the second step of the first sublevel one-step mining access road 4 is mined, a connecting passage 2 is constructed perpendicular to the strike direction of the ore body 3 to the lower boundary of the ore body 3, then an access road is constructed to the upper boundary of the ore body 3, and as the working face advances, the upper sphere 7 is released to form a top space 14 before each blasting; after the access road is mined, drill holes are constructed on the connecting passage 2 and the two sides of the access road at equal intervals, the diameter of the drill holes is 80 mm, the depth of the drill holes is 0.6 m, the drill holes on the two sides correspond to each other, and a cross strut 12 is installed in the holes, then the sphere 7 is laid on the bottom of the access road, the sphere 7 is a high-strength plastic hollow sphere, the radius of the sphere 7 is 0.1-0.15 m, and the compressive strength of the sphere 7 is greater than the pressure applied to the sphere 7 by the upper filling body. When the sphere 7 is laid, a reinforcement mesh 9 is laid at intervals along the direction of the access road, the reinforcement mesh 9 is welded and fixed with the steel mesh 11, and the mesh size of the reinforcement mesh 9 is smaller than the diameter of the sphere 7. Fine sand 8 is filled in the gaps between the spheres 7, plastic cloth 10 and steel mesh 11 are sequentially laid above the spheres 7, the width of the plastic cloth 10 is greater than the width of the access road by more than 2 m, the plastic cloth 10 is fixed on the two side walls of the access road, and the height is not less than 1 m; the mesh size of the steel mesh 11 is smaller than the diameter of the sphere 7, the length of the transverse reinforcement of the steel mesh 11 laid at the bottom of the one-step mining access road 4 in the width direction of the access road is 0.4 m longer than the width of the access road, and 0.2 m is reserved on each side, and when the steel mesh 11 is laid in the one-step mining access road 4, the 0.2 m transverse reinforcement on the two sides of the access road is bent on the side wall of the access road, and when the steel mesh 11 is laid in the two-step mining access road, the 0.2 m transverse reinforcement on the two sides of the one-step mining access road 4 is connected and fixed with the steel mesh 11 of the two-step mining access road. The hanging reinforcement 6 is uniformly arranged along the direction of the connecting passage 2 and the access road, one end of the hanging reinforcement 6 is welded and fixed on the steel mesh 11 at the bottom of the upper layer, the other end is welded on the steel mesh 11 at the bottom, then a filling retaining wall is built at the intersection of the sublevel roadway 1 and the connecting passage 2, the access road is filled in sections and topped, when the access road is filled in sections, the first filling height is not higher than the height of the plastic cloth 10 on the two side walls of the access road. The access road is filled with high-strength cemented filling body, and the 28-day uniaxial compressive strength of the filling body 13 is greater than or equal to 5 MPa. After the filling body of the second step of the first sublevel one-step mining access road 4 reaches the designed strength, the third step of the first sublevel one-step mining access road 4 is mined, the mining and filling process is the same as that of the second step of the first sublevel one-step mining access road 4, and so on until the first sublevel one-step mining access road 4 of all steps is mined;

[0052] Step 4, after the first sublevel all layered one-step mining entry 4 is mined, continue to mine the second sublevel one-step mining entry 4, the mining and filling process is the same as the one-step mining entry 4 mining and filling process in step 3, at the same time, start to mine the two-step mining entry in the first sublevel, the two-step mining entry mining and filling process is the same as the one-step mining entry 4 mining and filling process, that is, the one-step mining entry 4 mining is ahead of the two-step mining entry one sublevel, the production is organized until the whole stope is mined.

[0053] The cross brace 12 is welded by two equal length steel pipes. When installing the cross brace 12, first, the two steel pipes are inserted into the corresponding drill holes of the two sides of the entry, and then the other sides of the two steel pipes are welded. The length of each steel pipe is determined according to the following formula:

[0054] L = 1 / 2B + 0.8

[0055] In the formula, L is the length of the steel pipe, and B is the width of the entry, in meters.

[0056] The above is only the preferred specific embodiment of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art, according to the technical solution and the inventive concept of the present application, can make equivalent replacement or change within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A top space reserving, underhand drift fill mining method, characterized in that, The method comprises the following steps: Step 1, arranging the stope along the ore body trend, the ore body in the middle section is divided into sub-sections from top to bottom, each sub-section is further divided into layers from top to bottom, the ore body in the layer is divided into one-step and two-step mining entries arranged in intervals vertically to the ore body trend, the one-step or two-step mining entries of the upper and lower layers correspond to each other in the plane, and the entries are arranged as 3-5° upward slope from the lower wall to the upper wall of the ore body; the stope is organized in production units of entries, and the whole is sequentially mined from the upper sub-section to the lower sub-section and from the upper layer to the lower layer; Step 2, mining the one-step mining entry of the first layer in the first sub-section, a connecting tunnel is constructed from the sub-section drift vertically to the ore body trend direction to the lower wall boundary of the ore body, then the entry is constructed to the upper wall boundary of the ore body, after the entry is mined out, anchor cables are constructed on the roof of the connecting tunnel and the entry according to the designed grid, drill holes are constructed on the two sides of the wall of the connecting tunnel and the entry at equal intervals, the two sides of the drill holes correspond to each other, and cross brace rods are installed in the holes, then balls are laid on the bottom plate of the entry, fine sand is filled in the gaps between the balls, plastic cloth and steel mesh are sequentially laid above the balls, hanging rods are uniformly arranged along the direction of the connecting tunnel and the entry, one end of the hanging rod is welded and fixed to the end of the anchor cable on the roof, and the other end is welded and fixed to the steel mesh on the bottom, then a filling retaining wall is built at the intersection of the sub-section drift and the connecting tunnel, and the entry is filled and topped in sections; Step 3, after the filling body of the one-step mining entry of the first layer in the first sub-section reaches the designed strength, the one-step mining entry of the second layer in the first sub-section is mined, a connecting tunnel is constructed from the sub-section drift vertically to the ore body trend direction to the lower wall boundary of the ore body, then the entry is constructed to the upper wall boundary of the ore body, as the working face advances, the upper ball is released to form a top space before each blasting; after the entry is mined out, drill holes are constructed on the two sides of the wall of the connecting tunnel and the entry at equal intervals, the two sides of the drill holes correspond to each other, and cross brace rods are installed in the holes, then balls are laid on the bottom plate of the entry, fine sand is filled in the gaps between the balls, plastic cloth and steel mesh are sequentially laid above the balls, hanging rods are uniformly arranged along the direction of the connecting tunnel and the entry, one end of the hanging rod is welded and fixed to the steel mesh on the bottom of the upper layer, and the other end is welded and fixed to the steel mesh on the bottom, then a filling retaining wall is built at the intersection of the sub-section drift and the connecting tunnel, and the entry is filled and topped in sections, after the filling body of the one-step mining entry of the second layer in the first sub-section reaches the designed strength, the one-step mining entry of the third layer in the first sub-section is mined, the mining and filling process is the same as that of the one-step mining entry of the second layer in the first sub-section, and so on until the one-step mining entry of all layers in the first sub-section is mined out; Step 4, after the one-step mining entry of all layers in the first sub-section is mined out, the one-step mining entry of the second sub-section is continuously mined downward, the mining and filling process is the same as that of the one-step mining entry in step 3, and the two-step mining entry in the first sub-section is started to be mined at the same time, the mining and filling process of the two-step mining entry is the same as that of the one-step mining entry, that is, the one-step mining entry is mined ahead of the two-step mining entry by one sub-section, and the production is organized in this way until the whole stope is mined out.

2. A top-sliced, downward-sloping drift fill mining method according to claim 1, characterized in that: The diameter of the drilling hole on the two side walls of the access is 60-80 mm, and the drilling depth is 0.5-0.6 m.

3. A top-slicing, downward fill mining method reserving a roof space according to claim 1, characterized in that: The cross support rod body is welded by two equal-length steel pipes, when the cross support rod body is installed, the two steel pipes are inserted into the corresponding drilling holes on the two sides of the access respectively, and then the other sides of the two steel pipes are welded, the length of each steel pipe is determined according to the following formula: L =1 / 2 B +0.8 wherein L is the length of the steel pipe, B is the width of the pass, in meters.

4. A top-slicing, downward advance mining method reserving roof space as claimed in claim 1, characterized in that: The sphere is a high-strength plastic hollow sphere, the sphere radius is 0.1-0.15 m, and the compressive strength is greater than the pressure applied to the sphere by the upper filling body.

5. A top-slicing, downward fill mining method reserving a roof space according to claim 1, characterized in that: When the sphere is laid in the access, a set of retaining mesh is laid every interval along the direction of the access, the retaining mesh is welded and fixed with the steel mesh, and the mesh size of the retaining mesh is smaller than the diameter of the sphere.

6. A top-slicing, downward advance mining method reserving roof space as claimed in claim 1, characterized in that: The width of the plastic cloth is greater than the width of the access by more than 2 m, the plastic cloth is fixed on the two side walls of the access, and the height is not less than 1 m.

7. A top-slicing, downward advance mining method reserving roof space as claimed in claim 1, characterized in that: The mesh size of the steel mesh is smaller than the diameter of the sphere, the length of the transverse rib of the steel mesh laid at the bottom of the one-step access in the direction of the width of the access is longer than the width of the access by 0.4 m, and the length of the transverse rib on the two sides is reserved by 0.2 m, the 0.2 m transverse rib on the two sides of the one-step access is bent on the side wall of the access when the steel mesh is laid in the one-step access, and the 0.2 m transverse rib on the two sides of the one-step access is connected and fixed with the steel mesh of the two-step access when the steel mesh is laid in the two-step access.

8. A top-slicing, downward advance mining method reserving roof space as claimed in claim 1, characterized in that: The access filling is filled with high-strength cemented filling body, and the uniaxial compressive strength of the filling body is greater than or equal to 5 MPa after 28 days.

9. A top-slicing, downward advance mining method reserving roof space as claimed in claim 1, characterized in that: When the access is filled in several times, the first filling height is not higher than the height of the plastic cloth on the two side walls of the access.

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