A top pillar mining method for converting upward to downward filling mining of soft and broken thin ore veins

Abstract

The present invention provides a method for top pillar mining in the process of transitioning from upward to downward filling mining of soft and broken thin ore veins, which belongs to the field of mining technology. The method first determines the mining sequence, with top pillar mining preceding the downward first layer mining. The top pillar mining is carried out from the middle of the ore body to both ends, with each interval being mined in a mining sequence; then, the approach is excavated, followed by mining support, in the form of anchor net + U-steel bracket combined support; further, a false roof is constructed; and finally, two-stage filling is performed. The method utilizes the self-stabilizing ability of the top pillar ore rock combined with the extrusion and reinforcement arch effect of the support system, and adds strong support from the U-steel bracket to improve the stability of the remaining thin top pillar roof. The method solves the three technical difficulties of soft and broken ore rock, complex loads, and limited support, thereby reducing the adverse effects of upper loose tailings on deep ore mining, improving the secondary stress field of the downward mining field, reducing the overall instability risk of the lower artificial false roof caused by top pillar instability, and ensuring long-term production safety.

Description

Technical Field

[0001] The present invention relates to the field of mining technology, in particular to a method for top pillar mining of soft and broken thin ore veins that switches from upward to downward filling. Background Art

[0002] Steeply inclined, thin veins are one of the main deposit forms of nonferrous metal resources in my country. Influenced by mineralization processes such as tectonic and contact alteration, the ore bodies and surrounding rock are fractured, resulting in poor stability. Furthermore, the thin ore bodies and their steep inclinations make large-scale stopes difficult to form, limiting mining capacity. To achieve safe and efficient mining, the upward approach-and-backfill method is widely used in the mining of these ore bodies due to its high resource recovery rate, low backfilling difficulty, and effective ground pressure control.

[0003] However, as mining depths increase, the stability of the deep ore body deteriorates further. This increases the strength of the roof support in upward-access stopes, increases mining costs, reduces mining efficiency, and makes production safety difficult to ensure. The upward-backfill method can no longer meet the production needs of deep, soft, and fractured ore bodies, prompting a shift in mining methods to the downward-backfill method.

[0004] In the downward filling method, the ore body is mined and filled layer by layer from top to bottom, with stope operations conducted beneath the upper layer filling. Unlike the low-strength tailings filling of the upward filling method, the filling of the downward filling method is mostly high-strength reinforced concrete, thus ensuring the safety of stope operations. When mining transitions from upward to downward filling, a pillar of a certain thickness must be reserved to provide a safe roof for the first downward layer mining. The thickness of the reserved top pillar is related to the stability of the ore rock. When the ore rock is soft and broken, the theoretical calculation shows that the safe thickness of the top pillar varies from 6m to 10m. If the top pillar is not mined, the ore volume of one to three layers will be lost, a huge waste of resources that the mine cannot accept. In addition, with the continuous advancement of deep mining, the bearing capacity of the reserved top pillar gradually deteriorates. The impact of the instability of the top pillar on the artificial false roof below will seriously affect production safety. The mining and filling of the top pillar can not only reduce the loss of ore volume, but also play an extremely important role in reducing the adverse effects of upper loose tailings on deep ore mining, improving the secondary geostress field in the lower mining area, and improving the stability of artificial false roof.

[0005] However, top pillar mining in such soft and thin veins often faces the following three technical difficulties:

[0006] (1) The top pillar rock mass itself is relatively soft and fragile, with poor stability, making top control difficult and construction of soft rock access difficult;

[0007] (2) The loads on the top pillar ore rock are complex. The upper part of the top pillar is a low-strength tailings filling body with extremely poor self-bearing capacity. In addition, the low-concentration tailings slurry dehydrates and seeps downward, the high osmotic pressure environment and water softening effect make the stability of the top pillar ore rock difficult to predict;

[0008] (3) The mining support means are limited. The ore body has a large inclination, the top pillar ore rock is thin and soft, and the upper tailings filling body is loose and water-conductive. As a result, conventional anchor net support is difficult to meet safety requirements, the grouting support slurry leakage problem is difficult to overcome, the long anchor cable support construction period is long and difficult, and the bracket support is difficult to coordinate with the mining of the lower layer ore body.

[0009] In summary, proposing a reasonable top pillar mining method is not only conducive to maximizing resource recovery, but also the key to ensuring the successful transition of soft and thin vein mining from the top filling method to the bottom filling method. It is the implicit basis for the long-term stability of the bottom filling artificial false roof. Summary of the Invention

[0010] The present invention aims at the technical difficulties of top pillar recovery in the process of upward-to-down filling mining of soft and broken thin veins, and provides a top pillar recovery method in the process of upward-to-down filling mining of soft and broken thin veins, so as to improve the resource recovery rate, reduce the adverse effects of upper loose tailings on deep ore mining, improve the secondary geostress field in the downward mining area, reduce the risk of overall instability of the lower artificial false roof caused by top pillar instability, and ensure long-term production safety.

[0011] In order to solve the above-mentioned purpose of the invention, the technical solution provided by the present invention is as follows:

[0012] A method for top pillar mining in which soft and broken thin ore veins are switched from upward to downward filling mining comprises the following steps:

[0013] S1. Determine the order of mining:

[0014] Top pillar mining precedes downward first layer mining;

[0015] S2. Excavate the approach road:

[0016] The approach section adopts a straight wall 1 / 4 three-center arch shape, with an approach height of 2.5m to 3.5m, an approach width of 3m to 5m, and a remaining top column control thickness of 2.5m to 3m;

[0017] S3. Carry out mining support:

[0018] The approach mining is done with one shot per block, and the support form is a combination of anchor net and U-steel support.

[0019] S4. Build the false roof:

[0020] After the mining support of the approach is completed, the bottom crushed ore is arranged in the stope, and plastic sheeting is laid on the bottom crushed ore and folded up to the two sides of the approach;

[0021] At the same time, two rows of drill holes are arranged perpendicular to the rock wall on both sides of the approach, and resin anchors are arranged in the drill holes;

[0022] Arrange U-shaped transverse reinforcement on the plastic sheet perpendicular to the direction of the route; arrange longitudinal reinforcement on the U-shaped transverse reinforcement along the direction of the route;

[0023] The U-steel bracket arranged in S3 is processed and arranged at the waistline position of the base anti-arch bracket;

[0024] S5. Filling: The filling work is carried out in two stages. The first stage uses high-strength cementitious slurry for filling, and the second stage is top filling to complete the top pillar mining.

[0025] In step S1, top pillar mining is carried out in the order of advancing from the middle of the ore body to both ends, mining every other pillar and mining at intervals.

[0026] In the mining support step S3, resin anchors are arranged on the crown, spandrels and approach waistline in the single row of anchors, and pipe seam anchors are additionally arranged between the crown and spandrels;

[0027] Within the control range of the anchor rod, metal mesh is used to cover the rock wall to form an anchor mesh support system;

[0028] After the anchor net support, U-steel bracket support is carried out. The U-steel bracket has the same shape as the access section, which is a 1 / 4 three-center arch. Tie rod sleeve holes are arranged on the U-steel bracket, and adjacent U-steel brackets are interlocked and fixed through tie rods and tie rod sleeve holes.

[0029] The two rows of drill holes in step S4 include one row of low-position drill holes and one row of high-position drill holes, with the high-position drill holes evenly spaced from the low-position drill holes. The low-position drill holes are 900-1100 mm above the base plate, with a horizontal drilling distance of 800-1000 mm; the high-position drill holes are 1400-1600 mm above the base plate, with a horizontal drilling distance of 1700-1900 mm. One cycle consists of one U-steel bracket, one low-position drill hole, one high-position drill hole, and one low-position drill hole. The spacing between adjacent units is 450 mm.

[0030] In step S4, a certain length of the resin anchor rod is exposed (generally 250mm to 350mm) for welding steel bars, and a metal mesh is used to cover the rock wall within the control range of the resin anchor rod (i.e., the resin anchor rod setting area), and is overlapped and tied with the mining support metal mesh to form a complete approach wall anchor mesh support system.

[0031] In step S4, the U-shaped transverse reinforcement is hooked and welded to the two rows of drilled resin anchor rods along the upper folded sections on both sides of the approach. The welding of the resin anchor rods and the U-shaped transverse reinforcement follows the principle of proximity, and each resin anchor rod is welded with two U-shaped transverse reinforcements.

[0032] In step S4, a metal mesh is laid on the U-shaped transverse reinforcement and the longitudinal reinforcement, and the intersections of the metal mesh, the U-shaped transverse reinforcement and the longitudinal reinforcement are tied and fixed with steel wire.

[0033] In step S4, the base inverted arch support and the U-steel support are overlapped by using U-shaped clips.

[0034] In step S4, the arched portion of the base inverted arch support is a 1 / 4 three-center arch, and the inverted arch top is horizontally tangent to the longitudinal reinforcement arrangement.

[0035] In step S4, tie rod sleeve holes are arranged on the base inverted arch bracket, and adjacent base inverted arch brackets are interlocked and fixed through tie rods and tie rod sleeve holes.

[0036] The high-strength cementitious slurry in step S5 refers to a slurry with a strength of ≥1.5 MPa at 3 days, a strength of ≥2.5 MPa at 7 days, and a strength of ≥5.0 MPa at 28 days.

[0037] Compared with the prior art, the above technical solution has at least the following beneficial effects:

[0038] The above scheme utilizes the self-stabilizing ability of the top column ore rock and the extrusion reinforcement arch effect of the support system, and the strong support of the bracket, which can effectively improve the stability of the remaining thin top column top plate and ensure production safety. Anchor rods are used to hang the steel bars at the bottom of the approach. While reinforcing the surrounding rock on both sides, the load on the false roof is transmitted to the deep stable surrounding rock mass, and the friction between the surrounding rock and the filling body is enhanced by the support mesh, thereby increasing the bearing limit of the false roof and alleviating the bearing pressure of the lower false roof. By arranging the base anti-arch bracket on the U-steel bracket, the ballast of the bracket on the bottom ore body is transferred to the inside of the false roof, preventing the excavation of the lower ore body from causing the bracket to fail, causing the top column to become unstable instantly and impact the false roof, causing continuous instability accidents. In addition, the U-steel bracket and the base anti-arch bracket are combined to form a ring arch structure, which uses the arch effect to improve the self-bearing capacity of the false roof and improve the stability of the false roof.

[0039] Use a good bearing false roof to "replace" low-quality ore rock, so as to reduce the adverse effects of upper loose tailings on deep ore mining, improve the secondary ground stress field in the lower mining area, reduce the risk of overall instability of the lower artificial false roof caused by roof column instability, and ensure long-term production safety.

[0040] In summary, the present invention can effectively solve the three technical difficulties faced by top pillar mining in the transition from upward to downward filling mining of soft and broken thin veins, namely soft and broken ore rock, complex loads, and limited support, providing new ideas for such projects. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0042] Figure 1 A schematic diagram of a top pillar mining method for converting upward to downward filling mining of soft and broken thin ore veins according to the present invention;

[0043] Figure 2 for Figure 1 Schematic diagram of the middle BB section;

[0044] Figure 3 for Figure 1 Schematic diagram of the middle CC section;

[0045] Figure 4 for Figure 1 Schematic diagram of the middle DD section.

[0046] Among them: 1-U steel support; 2-pull rod sleeve hole; 3-pull rod; 4-low-position drill hole; 5-high-position drill hole; 6-U-shaped transverse reinforcement; 7-longitudinal reinforcement; 8-resin anchor rod; 9-base anti-arch support; 10-plastic sheeting; 11-bottom crushed ore; 12-metal mesh; 13-pipe seam anchor rod; 14-surrounding rock. DETAILED DESCRIPTION

[0047] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] Unless otherwise defined, technical or scientific terms used in this disclosure shall have the ordinary meanings understood by persons of ordinary skill in the art to which this disclosure pertains. It should be noted that the terms "upper," "lower," "left," "right," "front," and "back" used in this disclosure are intended solely to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0049] The invention provides a top pillar mining method for converting upward to downward filling mining of soft and broken thin ore veins.

[0050] The method comprises the following steps:

[0051] S1. Determine the order of mining:

[0052] In order to coordinate the layout of the downward mining and preparation project, top pillar mining precedes the downward first layer mining; in order to reduce the rock energy accumulation caused by top pillar excavation, and at the same time consider the coordinated mining and preparation work, top pillar mining is carried out from the middle of the ore body to both ends, with every other mining and interval mining sequence.

[0053] S2. Excavate the approach road:

[0054] While improving the recovery rate of top pillars, the cross-sectional dimensions of the access road must meet the requirements of mechanized production. The cross-sectional shape of the access road is a 1 / 4 three-center arch with a straight wall, a height of 2.5m to 3.5m, and a width of 3m to 5m. Smooth blasting is used for construction, and the thickness of the remaining top pillars is 2.5m to 3m.

[0055] S3. Carry out mining support:

[0056] In order to give full play to the self-stabilizing ability of rock, the approach mining is carried out with one shot per block, and the support form is a combination of anchor net + U steel support;

[0057] S4. Build the false roof:

[0058] In order to cushion the blasting impact of lower-layer mining on the false roof and improve the false roof formation rate, after the mining support of the approach is completed, a bottom layer of crushed ore is laid in the stope, and plastic sheeting is laid on the bottom layer of crushed ore and folded upwards on both sides of the approach.

[0059] At the same time, two rows of drill holes are arranged perpendicular to the rock wall on both sides of the approach, and resin anchors are arranged in the drill holes;

[0060] Arrange U-shaped transverse reinforcement on the plastic sheet perpendicular to the direction of the route; arrange longitudinal reinforcement on the U-shaped transverse reinforcement along the direction of the route;

[0061] Process and arrange the base anti-arch bracket at the waistline position of the U-steel bracket;

[0062] S5. Filling: The filling work is carried out in two stages. The first stage uses high-strength cementitious slurry for filling, and the second stage is top filling to complete the top pillar mining.

[0063] In the mining support step S3, resin anchors are arranged on the crown, spandrels and approach waistline in the single row of anchors, and pipe seam anchors are additionally arranged between the crown and spandrels;

[0064] Within the control range of the anchor rod, metal mesh is used to cover the rock wall to form an anchor mesh support system;

[0065] After the anchor net support, U-steel bracket support is carried out. The U-steel bracket has the same shape as the access section, which is a 1 / 4 three-center arch. Tie rod sleeve holes are arranged on the U-steel bracket, and adjacent U-steel brackets are interlocked and fixed through tie rods and tie rod sleeve holes.

[0066] The two rows of drill holes in step S4 include a row of low-position drill holes and a row of high-position drill holes, and the high-position drill holes and the low-position drill holes are evenly spaced.

[0067] In step S4, a certain length of the resin anchor rod is exposed for welding steel bars, and a metal mesh is used to cover the rock wall within the control range of the resin anchor rod, and is overlapped and tied with the mining support metal mesh to form a complete approach wall anchor mesh support system.

[0068] In step S4, the U-shaped transverse reinforcement is hooked and welded to the two rows of drilled resin anchor rods along the upper folded sections on both sides of the approach. The welding of the resin anchor rods and the U-shaped transverse reinforcement follows the principle of proximity, and each resin anchor rod is welded with two U-shaped transverse reinforcements.

[0069] In step S4, a metal mesh is laid on the U-shaped transverse reinforcement and the longitudinal reinforcement, and the intersections of the metal mesh, the U-shaped transverse reinforcement and the longitudinal reinforcement are tied and fixed with steel wire.

[0070] In step S4, the base inverted arch support and the U-steel support are overlapped by using U-shaped clips.

[0071] In step S4, the arched portion of the base inverted arch support is a 1 / 4 three-center arch, and the inverted arch top is horizontally tangent to the longitudinal reinforcement arrangement.

[0072] In step S4, tie rod sleeve holes are arranged on the base inverted arch bracket, and adjacent base inverted arch brackets are interlocked and fixed through tie rods and tie rod sleeve holes.

[0073] like Figure 1 In the specific implementation process, follow the steps below:

[0074] S1) Mining sequence: Top pillar mining precedes the first layer mining in the downward direction. The mining length of a single stope is 50m. Top pillar mining is carried out from the middle of the ore body to both ends, with every other mining interval.

[0075] S2) Approach Excavation: The approach section will be a 1 / 4 straight wall three-center arch, with an approach height of 2.5m to 3.5m and an approach width of 3m to 5m. Smooth blasting will be used, with the remaining top column controlling the top thickness being 2.5m to 3m.

[0076] S3) Mining support: The approach mining support is one shot at a time. The support form is a combination of anchor net and U-steel support.

[0077] In the anchor net support single row anchor rod, resin anchor rods 8 are arranged in the arch crown, arch span and approach waistline, and pipe seam anchor rods 13 are arranged between the arch crown and arch span. The anchor rods are perpendicular to the tangent line of the cross section arrangement point, the distance between the bottom of adjacent anchor rod holes is about 1m, and the anchor rod row spacing is 1.5m to 1.8m. The anchor rods are fully supported. Within the control range of the anchor rods, metal mesh 12 is used to cover the surrounding rock 14 rock wall to form an anchor net support system. Figure 3 shown.

[0078] Furthermore, after the anchor net support, the U-steel bracket 1 is supported. The U-steel bracket 1 is consistent with the cross-section shape of the access road, which is a 1 / 4 three-center arch, and the spacing between the U-steel brackets 1 is 1.8m to 2.0m. Preferably, the U-steel bracket 1 is provided with a tie rod sleeve hole 2, and adjacent U-steel brackets 1 are interlocked and fixed through the tie rod 3 and the tie rod sleeve hole 2. Figure 1 shown.

[0079] S4) False roof construction: After the mining support of the approach is completed, a bottom crushed ore 11 of about 300mm is laid in the stope, and a plastic sheet 10 is laid on the bottom crushed ore 11 and folded up on both sides of the approach. Figure 3 shown.

[0080] Furthermore, two rows of drill holes are arranged perpendicular to the rock wall on both sides of the access road. The two rows of drill holes include a row of low-position drill holes 4 and a row of high-position drill holes 5, with a drilling depth of 1900mm. The low-position drill holes 4 are 1000mm away from the bottom plate, and the horizontal distance between the drill holes is 900mm. The high-position drill holes are 1500mm away from the bottom plate, and the horizontal distance between the drill holes is 1800mm. The high-position drill holes and the low-position drill holes are evenly spaced, with a horizontal distance of 450mm. As shown in the attached figure Figure 1 shown.

[0081] Furthermore, resin anchors 8, each 2200 mm long and 300 mm exposed, were placed in the low-level borehole 4 and high-level borehole 5. Metal mesh 12 was used to cover the rock wall within the anchor control range and was overlapped and tied to the mining support metal mesh 12 to form a complete approach wall anchor mesh support system.

[0082] Furthermore, U-shaped transverse reinforcements 6 are arranged 100mm above the plastic sheet 10 and perpendicular to the direction of the access route, with a spacing of 300mm between the U-shaped transverse reinforcements 6. The U-shaped transverse reinforcements 6 are hooked and welded to the anchor rods of the low-position drill hole 4 and the high-position drill hole 5 along the upper folded sections on both sides of the access route, with a welding length of ≥100mm. The welding of the anchor rods and the U-shaped transverse reinforcements 6 follows the principle of proximity, with two U-shaped transverse reinforcements 6 welded to each anchor rod. Figure 1 and attached Figure 3 shown.

[0083] Furthermore, longitudinal reinforcements 7 are arranged on the U-shaped transverse reinforcements 6 along the route, with a spacing of 600 mm between the longitudinal reinforcements 7. Figure 4 shown.

[0084] Preferably, a metal mesh 12 is laid on the U-shaped transverse reinforcement 6 and the longitudinal reinforcement 7, and the intersections of the metal mesh 12, the U-shaped transverse reinforcement 6 and the longitudinal reinforcement 7 are tied and fixed with steel wire.

[0085] Furthermore, a base inverted arch support 9 is processed and arranged at the waistline position of the U-steel support 1, and the base inverted arch support 9 and the U-steel support 1 are overlapped by a U-shaped clip, and the overlap length is ≥300mm. The arched part of the base inverted arch support 9 is a 1 / 4 three-center arch, and the inverted arch top is horizontally tangent to the longitudinal reinforcement 7. Preferably, a tie rod sleeve hole 2 is arranged on the base inverted arch support 9, and adjacent base inverted arch supports 9 are interlocked and fixed by tie rods 3 and tie rod sleeve holes 2. As shown in the attached figure Figure 2 shown.

[0086] S5) Filling: The filling work is carried out in two stages. The first stage uses high-strength cementitious slurry for filling (strength ≥1.5MPa at 3 days old, ≥2.5MPa at 7 days old, and ≥5.0MPa at 28 days old). The second stage is top filling to complete the top pillar mining.

[0087] The above is only a technical solution of an embodiment of a method for recovering top pillars in the process of converting from upward to downward filling mining in soft and broken thin veins proposed by the present invention. This technical solution can effectively solve the technical difficulties of recovering top pillars in the process of converting from upward to downward filling mining in soft and broken thin veins, and use a good bearing false roof to "replace" inferior ore rock, thereby reducing the adverse effects of upper loose tailings on deep ore mining, improving the secondary geostress field in the downward stope, reducing the risk of overall instability of the lower artificial false roof due to top pillar instability, and ensuring long-term production safety.

[0088] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. The protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A method for top pillar mining in soft and thin ore veins by turning from upward to downward filling, characterized in that: The steps are as follows: S1. Determine the order of mining: Top pillar mining precedes downward first layer mining; S2. Excavate the approach road: The approach section adopts a straight wall 1 / 4 three-center arch shape, with an approach height of 2.5m~3.5m, an approach width of 3m~5m, and a remaining top column control thickness of 2.5m~3m; S3. Carry out mining support: The approach mining is done with one shot per block, and the support form is a combination of anchor net and U-steel support. S4. Build the false roof: After the mining support of the approach is completed, the bottom crushed ore is arranged in the stope, and plastic sheeting is laid on the bottom crushed ore and folded up to the two sides of the approach; At the same time, two rows of drill holes are arranged perpendicular to the rock wall on both sides of the approach, and resin anchors are arranged in the drill holes; Arrange U-shaped transverse reinforcement on the plastic sheet perpendicular to the direction of the route; arrange longitudinal reinforcement on the U-shaped transverse reinforcement along the direction of the route; The U-steel bracket arranged in S3 is processed and arranged at the waistline position of the base anti-arch bracket; S5. Filling: The filling work is divided into two stages. The first stage uses high-strength cementing slurry for filling, and the second stage is top filling to complete the top pillar mining; In the mining support step S3, resin anchors are arranged on the crown, spandrels and approach waistline in the single row of anchors, and pipe seam anchors are additionally arranged between the crown and spandrels; Within the control range of the anchor rod, metal mesh is used to cover the rock wall to form an anchor mesh support system; After the anchor net support, the U-steel bracket is supported. The U-steel bracket has the same shape as the access road section, which is a 1 / 4 three-center arch. The U-steel bracket is provided with tie rod sleeve holes. Adjacent U-steel brackets are interlocked and fixed through tie rods and tie rod sleeve holes. The two rows of drill holes in step S4 include a row of low-position drill holes and a row of high-position drill holes, the high-position drill holes and the low-position drill holes are evenly spaced, the low-position drill holes are 900-1100 mm high from the bottom plate, and the horizontal drilling distance is 800-1000 mm; the high-position drill holes are 1400-1600 mm high from the bottom plate, and the horizontal drilling distance is 1700-1900 mm; In step S4, the exposed length of the resin anchor is 250mm to 350mm, which is used for welding steel bars. Metal mesh is used to cover the rock wall within the control range of the resin anchor, and is overlapped and tied with the metal mesh used for mining support to form a complete approach wall anchor mesh support system; In step S4, the U-shaped transverse reinforcement is hooked and welded to the two rows of drilled resin anchor rods along the upper folded sections on both sides of the approach. The welding of the resin anchor rods and the U-shaped transverse reinforcement follows the principle of proximity, and each resin anchor rod is welded with two U-shaped transverse reinforcements. In step S4, a metal mesh is laid on the U-shaped transverse reinforcement and the longitudinal reinforcement, and the intersections of the metal mesh, the U-shaped transverse reinforcement and the longitudinal reinforcement are tied and fixed with steel wire.

2. The method for top pillar mining in the process of converting upward to downward filling mining of soft and broken thin ore veins according to claim 1 is characterized in that: In step S1, top pillar mining is carried out in the order of advancing from the middle of the ore body to both ends, mining every other pillar and mining at intervals.

3. The method for top pillar mining in the process of converting upward to downward filling mining of soft and broken thin ore veins according to claim 1 is characterized in that: In step S4, the base inverted arch support and the U-steel support are overlapped by using U-shaped clips.

4. The method for top pillar mining in the process of converting upward to downward filling mining of soft and broken thin ore veins according to claim 1 is characterized in that: In step S4, the arched portion of the base inverted arch support is a 1 / 4 three-center arch, and the inverted arch top is horizontally tangent to the longitudinal reinforcement arrangement.

5. The method for top pillar mining in the process of converting upward to downward filling mining of soft and broken thin ore veins according to claim 1 is characterized in that: In step S4, tie rod sleeve holes are arranged on the base inverted arch bracket, and adjacent base inverted arch brackets are interlocked and fixed through tie rods and tie rod sleeve holes.

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