Advanced pressure relief continuous mining method without ore pillar

Abstract

Embodiments of the present application disclose a kind of advanced pressure relief no-pillar continuous mining method, the method comprises the following steps: S1, orebody division: the orebody is divided into multiple middle sections along the height direction;S2, mining preparation engineering arrangement: the upper disc and the lower disc of the orebody are arranged with upper disc along vein roadway and lower disc along vein roadway respectively;S3, advanced pressure relief: before the stoping of panel stope, first form cutting groove through the entire middle section at the boundary of panel stope close to the upper disc;S4, no-pillar continuous stoping;S5, stope filling: after the completion of one-step stope ore stoping, immediately fill it to form a filling body;S6, adjacent stope stoping: after the filling body of one-step stope reaches the predetermined strength, two-step stope adjacent to one-step stope is stoped;S7, continuous ore drawing;S8, filling treatment: after the completion of stope stoping, the goaf is filled by filling system.The advanced pressure relief no-pillar continuous mining method of the embodiments of the present application improves the safety of stoping.

Description

Technical Field

[0001] This invention relates to the field of mining technology, and specifically to a pillarless continuous mining method with advanced pressure relief. Background Technology

[0002] In related technologies, underground mining primarily utilizes the backfilling method, employing either a runway approach or a stope-and-fill process depending on the ore body's occurrence conditions. As mining depth increases, high ground pressure triggers large deformations and rock bursts in the surrounding rock, and effective pressure-relief mining technologies are lacking. Ore extraction relies on loader transport to the pass, electric locomotive transport, and coarse crushing and hoisting, making the process complex. Failure in any link can affect extraction efficiency, and a continuous underground transportation system is lacking. Current stope-and-fill methods require the retention of pillars, leading to significant recovery difficulties and resource losses. Summary of the Invention

[0003] The present invention aims to at least partially solve one of the technical problems in the related art.

[0004] Therefore, embodiments of the present invention propose an advanced pressure relief pillarless continuous mining method that fundamentally alleviates the risk of large deformation and rock bursts in the surrounding rock caused by high ground pressure and improves the safety of mining.

[0005] The pre-decompression pillarless continuous mining method of this invention is applicable to steeply dipping, thick, and large metallic deposits with a dip angle greater than 55° and a thickness greater than 100m. It includes the following steps: S1, Orebody Division: The orebody is divided into multiple intermediate sections along its height, and each intermediate section is further divided into multiple sub-sections. On the intermediate section plane, the orebody is divided into multiple panels along its strike, each panel into multiple mining areas, and each mining area into multiple stopes. The long axis of each stope is perpendicular to the strike of the orebody; S2, Preparatory Engineering Layout: Upper and lower wall-mounted vein roadways are respectively arranged on the upper and lower wall of the orebody. Excavation and... The ore extraction roadway connecting the upper and lower footwall roadways is excavated on one side of the ore extraction roadway, forming a bottom drilling roadway parallel to the ore extraction roadway. Segmented drilling roadways are arranged on each segment plane. Upper and lower footwall segmented roadways are arranged on each segment plane, and connected to the upper and lower footwall segmented roadways via the segmented drilling roadways. S3, Advance pressure relief: Before mining the panel area, a cutting groove is formed at the boundary of the panel area near the upper footwall, penetrating the entire middle section. This cutting groove blocks the deep horizontal high ground stress. The transmission path forms a stress shadow zone in the panel stope; S4, pillarless continuous mining: within the stress shadow zone, the stope in the panel is continuously advanced from the cutting groove towards the hanging wall or footwall according to a predetermined mining sequence, and no pillars are reserved between the panel and the stope. The stope mined first is the first-step stope, and the adjacent stope mined later is the second-step stope; during stope mining, segmented blasting is carried out in the segmented drilling roadway with the cutting groove as the free surface to achieve retreat mining; S5, stope backfilling: after the ore is mined from the first-step stope, it is immediately backfilled to form a backfill body; S6, adjacent stopes S7. Backfilling: After the backfill in the first-stage stope reaches the predetermined strength, the second-stage stope adjacent to the first-stage stope is backfilled. During backfilling, both sides of the second-stage stope are backfilled, and the stope length of the second-stage stope is adjusted in real time according to the stability of the backfill. S8. Continuous ore extraction: After the stope is blasted, the ore is transported out by a loader and unloaded to a mobile crusher. After crushing, it is transferred by a mobile belt conveyor to a belt conveyor arranged in the upper or lower footwall along the vein to achieve continuous ore transportation. S9. Backfilling: After the stope is backfilled, the goaf is backfilled by a backfilling system.

[0006] The pillarless continuous mining method of this invention, through advanced pressure relief via cutting grooves, effectively blocks the propagation of high-level ground stress at depth, forming a stress shadow zone. This fundamentally alleviates the risk of large deformation and rockburst caused by high ground pressure, improving mining safety. The pillarless continuous mining method eliminates the need for pillars between panels and stopes, significantly increasing resource recovery and reducing ore loss. Combining a loader, mobile crusher, and mobile belt conveyor to construct a continuous underground transport system replaces the traditional intermittent process of "loader-pass-electric locomotive-coarse crushing and hoisting," significantly reducing the impact of process failures on ore extraction efficiency and improving overall ore extraction capacity. The "one-step-two-step" operation mode, with mining followed by backfilling and alternating mining and backfilling, utilizes the backfill material to both support the surrounding rock of the goaf and serve as a lateral self-supporting surface for mining adjacent stopes. This allows for parallel and continuous mining and backfilling while ensuring safety, improving mining efficiency. Furthermore, this method is highly adaptable to steeply dipping, thick ore bodies.

[0007] In some embodiments, in step S1, the height of the middle section is 60-80m, each middle section is divided into 2-3 segments with a segment height of 25-30m, the width of the mining area is 15-20m, the width of the panel area is 120-200m, and the length of the stope is 40-60m.

[0008] In some embodiments, in step S2, the spacing of the segmented drilling roadways is consistent with the width of the stope, which is 15-20m, and they are arranged in the middle of the stope. The two ends of the segmented drilling roadways are respectively connected to the upper plate segmented vein roadway and the lower plate segmented vein roadway. The ore extraction roadway of the mining area is located in the middle of the peach-shaped structure of the bottom structure. One ore extraction roadway serves two adjacent mining areas. The bottom drilling roadway is connected to the ore extraction access roadway of the stope. The spacing of the segmented drilling roadways is consistent with the width of the stope.

[0009] In some embodiments, in step S3, the width of the cutting groove is 2-3m, and the cutting groove formation process includes the following steps: in the segmented rock drilling roadway of the panel mining area, a cutting roadway is excavated in a direction parallel to the strike of the ore body to connect multiple mining areas; a cutting riser is drilled in the middle of the cutting roadway; using the cutting riser and the cutting roadway as free space, upward vertical blast holes are drilled and blasted in the cutting roadway to form a cutting groove; some or all of the ore produced by the blasting is transported out to reserve compensation space for the next segmented cutting groove blasting.

[0010] In some embodiments, in step S3, the cutting groove is a vertical cutting groove or an inclined cutting groove; when the hanging wall of the ore body is unstable, a vertical cutting groove is used, and a triangular ore body is reserved at the hanging wall to support the hanging wall of the ore body. The triangular ore body is mined after the mining is completed and the hanging wall of the ore body is pre-reinforced; when the hanging wall of the ore body is stable, an inclined cutting groove is used along the interface between the ore and the rock.

[0011] In some embodiments, in step S3, the formation of the cutting groove is carried out synchronously with the mining of the panel stope, and the advancing speed of the cutting groove along the ore body direction is ahead of the mining speed of the stope, so as to ensure that the length of the cutting groove is always greater than 1.5 to 2 times the total width of the stope being mined.

[0012] In some embodiments, in step S4, the mining areas within the panel are advanced in the order from the hanging wall to the footwall, and a mining sequence of three miners mined at a time or one miner mined at a time is adopted, that is, there are 1 to 3 unmined mining areas between mining areas that are mined simultaneously; mining is carried out in the segmented order from top to bottom within the mining area, with the upper segment leading the lower segment by 1 to 2 blasting cycles and the leading distance being 1.5 to 4m.

[0013] In some embodiments, in step S4, the segmented blasting involves drilling upward fan-shaped blast holes in the segmented rock drilling roadway, with a row spacing of 1.5 to 2 m, using the cutting groove as the free surface, and blasting 1 to 2 rows of blast holes each time for retreat mining; in the lower segment of the stope, upward fan-shaped blast holes are arranged in the bottom rock drilling roadway, and 8 to 15 m of triangular pillars are reserved to protect the ore extraction roadway and ore extraction access in the mining area, so that a peach-shaped bottom structure is formed after the mining of two adjacent stops is completed.

[0014] In some embodiments, in step S7, the mobile crusher and the mobile belt conveyor are arranged in the ore outlet roadway near the upper or lower footwall vein roadway; after the shoveler scoops out the ore at the ore outlet of the mining access roadway, it retreats to the ore outlet roadway and unloads it onto the mobile crusher. The crushed ore is then transferred by the mobile belt conveyor to the belt conveyor in the upper or lower footwall vein roadway, and then lifted to the surface by the underground ore bin and the inclined shaft belt conveyor.

[0015] In some embodiments, in step S5 or S8, the filling system relies on the segmented rock drilling roadway located 20-25m above the stope as the filling horizontal roadway. Filling boreholes with a diameter of 250-400mm are drilled downwards from the filling horizontal roadway to the goaf, and filling is carried out through the filling boreholes. During the filling process, borehole photography, borehole three-dimensional laser scanning, or ground penetrating radar are used to detect the cementation and roof connection of the filling slurry, and additional filling boreholes are added according to the detection results to optimize the filling roof connection effect. After the stope and the triangular pillar and peach-shaped bottom structure are all mined out, the filling slurry is used for final filling. Attached Figure Description

[0016] Figure 1 This is a diagram of a mining method according to an embodiment of the present invention.

[0017] Figure 2 This is an embodiment of the present invention. Figure 1 A cross-sectional view at point AA.

[0018] Figure 3 This is an embodiment of the present invention. Figure 2 A cross-sectional view of section BB.

[0019] Figure 4 This is a schematic diagram of an irregularly shaped cross-section tunnel according to an embodiment of the present invention.

[0020] Figure 5 This is a schematic diagram of continuous transportation according to an embodiment of the present invention.

[0021] Figure label: 1. Upper hanging wall along the vein; 2. Lower hanging wall along the vein; 3. Ore body; 4. Filling borehole; 5. Ore exit roadway; 6. Ore exit roadway; 7. Peach-shaped structure; 8. Blasting hole; 9. Triangular ore body; 10. Filling body; 11. Segmented drilling roadway; 12. Belt conveyor; 13. Upper hanging wall segmented along the vein; 14. Lower hanging wall segmented along the vein; 15. Cutting groove; 16. Mobile belt conveyor; 17. Loader; 18. Mobile crusher. Detailed Implementation

[0022] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0023] like Figures 1-5As shown, the pre-decompression pillarless continuous mining method of this invention is applicable to steeply dipping, thick, and large metal deposits with a dip angle greater than 55° and a thickness greater than 100m. It includes the following steps: S1, dividing the ore body 3: dividing the ore body 3 into multiple middle sections along the height direction, each middle section into multiple sub-sections, and dividing the ore body 3 into multiple panels along the strike of the ore body 3 on the middle section plane, each panel into multiple mining areas, and each mining area into multiple stopes, wherein the long axis of the stopes is perpendicular to the strike of the ore body 3. S2. Preparation Engineering Layout: An upper vein-along roadway 1 and a lower vein-along roadway 2 are respectively arranged on the hanging wall and footwall of ore body 3. An ore extraction roadway 6, communicating with the upper vein-along roadway 1 and the lower vein-along roadway 2, is excavated within the mining area. An ore extraction access roadway 5 is excavated on one side of the ore extraction roadway 6, forming a bottom drilling roadway parallel to the ore extraction roadway 6. Segmented drilling roadways 11 are arranged on each segment plane. Upper segmented vein-along roadways 13 and footwall segmented vein-along roadways 14 are arranged on each segment plane, and the upper segmented vein-along roadways 13 and footwall segmented vein-along roadways 14 are connected by the segmented drilling roadways 11. S3. Pre-decompression: Before mining the panel stope, a cutting groove 15 is formed at the boundary of the panel stope near the hanging wall, running through the entire middle section. The cutting groove 15 blocks the transmission path of deep horizontal high ground stress, forming a stress shadow zone in the panel stope. S4. Pillarless continuous mining: Within the stress shadow zone, the stope in the panel is continuously advanced for mining from the cutting groove 15 towards the hanging wall or footwall according to a predetermined mining sequence. No pillars are reserved between the panel and the stope. The stope mined first is the first-step stope, and the adjacent stope mined later is the second-step stope. During stope mining, segmented blasting is carried out in the segmented drilling roadway 11 with the cutting groove 15 as the free face to achieve retreat mining. S5. Stope backfilling: After the ore in the first-step stope is mined, it is immediately backfilled to form a backfill body 10. S6. Adjacent Stope Reclamation: After the backfill body 10 of the first-stage stope reaches the predetermined strength, the second-stage stope adjacent to the first-stage stope is reclamated. During reclamation, both sides of the second-stage stope are filled with backfill body 10, and the stope length of the second-stage stope is adjusted in real time according to the stability of the backfill body 10. S7. Continuous Ore Extraction: After the stope blasting, the ore is transported out by a loader 17 and unloaded to a mobile crusher 18. After crushing, it is transferred by a mobile belt conveyor 16 to a belt conveyor 12 arranged in the upper wall along the vein 1 or the lower wall along the vein 2 to achieve continuous ore transportation. S8. Backfilling Treatment: After the stope reclamation is completed, the goaf is backfilled by a backfilling system.

[0024] The pre-decompression pillarless continuous mining method of this invention constructs a spatial system perpendicular to the strike of the ore body 3 and advances in layers through the division of the ore body 3. Preparatory work is used to arrange vein-side roadways, ore extraction roadways 6, drilling roadways, and segmented connecting roadways in the hanging and footwalls to form a complete mining channel. Before mining the panel, a cutting groove 15 is pre-dug near the edge of the hanging wall to penetrate the middle section, actively cutting off the transmission path of high ground stress at depth and creating a stress shadow zone within the panel, ensuring a low-stress environment for subsequent mining. Subsequently, using the cutting groove 15 as the free face and the segmented drilling roadways 11 as the working space, retreating blasting mining is carried out in a predetermined sequence within the stress shadow zone. No pillars are placed between mining areas, achieving continuous advancement. The first-step mining area is immediately backfilled after mining. After the backfill body 10 reaches a predetermined strength, the adjacent second-step mining area is then mined. At this time, both sides of the second-step mining area are filled with backfill body 10, and the length of the mining area is adjusted in real time according to the stability of the backfill body 10. In the ore extraction stage, a loader 17 transports the blasted ore to a mobile crusher 18. After crushing, the ore is transferred by a mobile belt conveyor 16 to fixed belt conveyors 12 in the upper and lower footwall roadways 1 and 2, achieving continuous transportation. The post-mining goaf is then promptly filled by a backfilling system, completing the closed loop.

[0025] Compared with related technologies, the pillarless continuous mining method of this invention, through the pre-decompression of the cutting groove 15, effectively blocks the propagation of deep high-level ground stress, forming a stress shadow zone, fundamentally alleviating the risk of large deformation of surrounding rock and rockburst caused by high ground pressure, and improving the safety of mining. The pillarless continuous mining method eliminates the need for pillars between panels and stopes, significantly improving resource recovery and reducing ore loss. The combination of the loader 17, mobile crusher 18, and mobile belt conveyor 16 constructs an underground continuous transportation system, replacing the traditional intermittent process of "loader 17—pass ore—electric locomotive—coarse crushing and hoisting," significantly reducing the impact of process failures on ore extraction efficiency and improving overall ore extraction capacity. The "one-step-two-step" operation mode of mining followed by filling and alternating mining and filling utilizes the filling body 10 to both support the surrounding rock of the goaf and serve as the lateral self-supporting surface for mining in adjacent mining areas. Under the premise of ensuring safety, mining and filling can be carried out in parallel and continuously, improving mining efficiency. At the same time, the method of this invention has strong adaptability to steeply inclined thick ore bodies 3.

[0026] In some embodiments, in step S1, the height of the middle section is 60-80m, each middle section is divided into 2-3 segments with a segment height of 25-30m, the width of the mining area is 15-20m, the width of the panel area is 120-200m, and the length of the stope is 40-60m.

[0027] The pillarless continuous mining method with pre-decompression in this embodiment of the invention has a mid-section height of 60-80m, with each mid-section divided into 2-3 sub-sections, each with a sub-section height of 25-30m. In the planar dimension, the mining area width is 15-20m, the panel width is 120-200m, and the stope length is 40-60m. This standardizes the cutting of the steeply dipping, thick ore body 3 into a five-level spatial unit: mid-section—sub-section—panel—mining area—stope. Vertically, the mid-section and sub-sections form a reasonable stratification, matching the height of the sub-section drilling roadways 11 and sub-section blasting operations. Laterally, a narrow mining area (15-20m) controls the exposed area and reduces the risk of goaf instability, while a wide panel (120-200m) covers the decompression range of the cutting groove 15, ensuring the stress shadow zone completely protects the entire panel. Simultaneously, the stope length of 40-60m facilitates the organization of retreating continuous mining and the operation of supporting ore extraction equipment.

[0028] The pillarless continuous mining method with pre-decompression in this invention achieves a spatial layout of "vertical stratification and horizontal zoning" through the above parameter combination. This provides a reasonable geometric basis for pre-decompression of the cutting slot 15, pillarless continuous advancement, and alternating mining and filling operations. The height of the intermediate and segmented sections ensures the working height and efficiency of rock drilling and blasting. The width of the mining area and the panel area take into account both the stability control of the surrounding rock and the coverage of the decompression range. The length of the stope is matched with the operating capacity of equipment such as the loader 17 and the mobile crusher 18. Overall, the pillarless continuous mining method with pre-decompression in this invention achieves a balance between surrounding rock stability, decompression effect, recovery efficiency, and resource recovery through dimensional parameters, making this method highly adaptable to steeply dipping, thick, and large metal deposits with dip angles greater than 55° and thicknesses greater than 100m.

[0029] In some embodiments, in step S2, the spacing of the segmented drilling roadways 11 is consistent with the width of the stope, which is 15-20m, and they are arranged in the middle of the stope. The two ends of the segmented drilling roadways 11 are respectively connected to the upper segmented vein roadway 13 and the lower segmented vein roadway 14. The mining area ore extraction roadway 6 is located in the middle of the peach-shaped structure 7 of the bottom structure. One ore extraction roadway 6 serves two adjacent mining areas. The bottom drilling roadway is connected to the stope ore extraction access roadway 5.

[0030] In step S2 of the pre-decompression pillarless continuous mining method of this invention, specific details are provided regarding the layout of the preparatory engineering. The spacing of the segmented drilling roadways 11 is consistent with the width of the stope, ranging from 15 to 20 meters. The segmented drilling roadways 11 are located in the middle of the stope, and their ends connect to the upper segmented vein roadway 13 and the lower segmented vein roadway 14, respectively, forming a drilling operation channel running through the middle of the stope, providing precise operating space for segmented blasting. The ore extraction roadway 6 is located in the middle of the peach-shaped structure 7 at the bottom. One ore extraction roadway 6 serves two adjacent stopes simultaneously, thereby reducing the amount of roadway excavation and improving the utilization rate of the ore extraction roadway 6. The bottom drilling roadway connects to the stope ore extraction access roadway 5, forming a passage for the collection, loading, and transportation of ore after blasting. The spacing between the segmented rock drilling roadways 11 is consistent with the width of the mining area, which is 15-20m, and they are arranged in the middle of the mining area to ensure that each segmented rock drilling roadway 11 can evenly cover the mining area cross section.

[0031] The above-mentioned layout scheme of the pillarless continuous mining method with pre-decompression in this embodiment of the invention ensures a high degree of matching between the preparatory engineering and the ore body 3 division parameters (mining area width 15-20m, stope length 40-60m): the segmented drilling roadways 11 are centrally located with spacing consistent with the stope width, ensuring uniform development of free faces and reasonable explosive consumption during segmented blasting, while avoiding energy waste or under-excavation caused by roadway offset. The shared design of the ore extraction roadway 6 in the mining area significantly reduces the amount of excavation work and lowers the preparatory engineering cost. The bottom drilling roadway is connected to the ore extraction entrance 5, and in conjunction with the peach-shaped structure 7, allows the blasted ore to naturally converge at the ore extraction port, facilitating efficient loading by the loader 17. Overall, the preparatory engineering layout optimizes the number and spatial layout of roadways while ensuring the reliability of drilling and blasting, creating efficient operating conditions for subsequent pillarless continuous mining and continuous ore extraction.

[0032] In some embodiments, in step S3, the width of the cutting groove 15 is 2-3m, and the process of forming the cutting groove 15 includes the following steps: In the segmented drilling roadway 11 of the panel mining area, a cutting roadway is excavated in a direction parallel to the strike of the ore body 3, connecting multiple mining areas. A cutting riser is drilled in the middle of the cutting roadway. Using the cutting riser and the cutting roadway as free space, upward vertical blast holes 8 are drilled and blasted within the cutting roadway to form the cutting groove 15. Part or all of the ore produced by the blasting is transported out to reserve compensation space for the next blasting of the segmented cutting groove 15.

[0033] In step S3 of the pillarless continuous mining method of the present invention, during the formation of the cutting groove 15, the width of the cutting groove 15 is 2-3m. The formation process includes four steps: First, in the segmented drilling roadway 11 of the panel stope, cutting roadways are excavated in a direction parallel to the strike of the ore body 3 to connect multiple stopes. Second, a cutting riser is drilled in the middle of the cutting roadway as the initial blasting free face. Then, using the cutting riser and the cutting roadway as free space, upward vertical blast holes 8 are drilled and blasted in the cutting roadway, advancing upward segment by segment to form the cutting groove 15. Finally, some or all of the ore produced by the blasting is transported out to reserve compensation space for the next segmented cutting groove 15 blasting, ensuring that subsequent blasting has sufficient free face and fragmentation space.

[0034] The core of the cutting trench 15 formation scheme in the pillarless continuous mining method of the present invention lies in the rapid formation of a continuous trench spanning the entire middle section near the boundary of the hanging wall of the panel using a combination of "cutting roadway - cutting raise - upward vertical blast hole 8". The trench is only 2-3 meters wide, requiring minimal engineering work and achieving high formation efficiency. After the cutting trench 15 is formed, it directly blocks the transmission path of deep, high-level ground stress, creating a stress shadow zone within the panel and providing a low-stress environment for subsequent mining. Furthermore, the cutting trench 15 itself provides a continuous free surface for segmented blasting in each stope within the panel, enabling retreat mining to advance segment by segment along the trench boundary, resulting in stable blasting effects and uniform ore crushing. The arrangement of reserved compensation space ensures continuous and reliable blasting operations, avoiding problems such as misfires or trench jams due to insufficient crushing space, laying the foundation for pillarless continuous mining of the entire panel.

[0035] In some embodiments, in step S3, the cutting groove 15 is a vertical cutting groove 15 or an inclined cutting groove 15. When the hanging wall of the ore body 3 is unstable, a vertical cutting groove 15 is used, and a triangular ore body 9 is reserved at the hanging wall to support the hanging wall. The triangular ore body 9 is mined after the stope is completed and the hanging wall is pre-reinforced. When the hanging wall of the ore body 3 is stable, an inclined cutting groove 15 is used along the interface between the ore and the rock.

[0036] In step S3 of the pillarless continuous mining method of the present invention, the form of the cutting groove 15 is selected differently according to the stability of the hanging wall: when the hanging wall of ore body 3 is unstable, a vertical cutting groove 15 is used, and a triangular ore body 9 is reserved at the hanging wall. The triangular ore body 9 is used to temporarily support the hanging wall, playing a role in roof protection and stabilizing the hanging wall. After the mining is completed and the hanging wall is pre-reinforced, the triangular ore body 9 is recovered, thereby avoiding ore loss while ensuring safety. When the hanging wall of ore body 3 is stable, an inclined cutting groove 15 formed along the ore-rock interface is directly used. The cutting groove 15 fits the boundary of ore body 3, and there is no need to reserve additional support for ore body 3. The cutting groove 15 requires less engineering work and the ore recovery is more complete.

[0037] The pre-decompression pillarless continuous mining method of this invention embodies the "adaptive to local conditions" design concept of the cutting groove 15, balancing the stability of the surrounding rock and the resource recovery rate. When the hanging wall is unstable, the triangular ore body 9 serves as a temporary support structure, effectively preventing the formation of the cutting groove 15 and the collapse of the hanging wall during mining. It is recovered after pre-reinforcement, ensuring operational safety and achieving secondary recovery of pillar resources. When the hanging wall is stable, the inclined cutting groove 15 is arranged close to the ore-rock interface, and its shape is consistent with the boundary of the ore body 3. This not only reduces the amount of cutting work but also avoids ore loss or excessive exposure of the surrounding rock caused by the cutting groove 15 deviating from the boundary of the ore body 3. Overall, the adaptive cutting groove 15 allows the pre-decompression measures to be flexibly adjusted for different geological conditions, expanding the applicability of the method while ensuring both decompression effect and ore recovery rate.

[0038] In some embodiments, in step S3, the formation of the cutting groove 15 is carried out synchronously with the mining of the panel area, and the advancing speed of the cutting groove 15 along the direction of the ore body 3 is ahead of the mining speed of the mining area, so as to ensure that the length of the cutting groove 15 is always greater than 1.5 to 2 times the total width of the mining area being mined.

[0039] In step S3 of the advanced pressure relief pillarless continuous mining method of this invention, the formation of the cutting groove 15 is not completed in one go, but is advanced synchronously with the mining of the panel stope. The advancing speed of the cutting groove 15 along the direction of the ore body 3 is always ahead of the mining speed of the stope, ensuring that the length of the cutting groove 15 is always greater than 1.5 to 2 times the total width of the stope being mined. This means that the front end of the cutting groove 15 is always ahead of the current working stope, forming a dynamically extended pressure relief barrier, rather than a statically reserved fixed groove.

[0040] This synchronous advancement method allows the advanced advancement of the cutting trench 15 to continuously and dynamically block the transmission path of deep high ground stress, enabling the stress shadow zone to expand synchronously with the mining progress, always covering the current and subsequent mining areas. This avoids the stress recovery transmission caused by insufficient length of the cutting trench 15, which would affect the pressure relief effect. The length of the cutting trench 15 is maintained at 1.5 to 2 times the total width of the mining area, reserving sufficient pressure relief margin. Even if the mining speed fluctuates or the mining conditions change, the cutting trench 15 can still maintain sufficient advance to ensure a safety margin for pressure relief. The formation of the cutting trench 15 and the mining operation are carried out in parallel, avoiding the long period of unsupported roof exposure and additional support costs caused by forming a long cutting trench 15 all at once in advance, thus improving mining efficiency and safety. Overall, this dynamic advance scheme organically integrates the advance pressure relief measures with the continuous mining process, achieving coordinated advancement of pressure relief and mining.

[0041] In some embodiments, in step S4, the mining areas within the panel are advanced in sequence from the hanging wall to the footwall, and a mining sequence of three miners mined every three miners or one miner mined every one miner is adopted, that is, there are 1 to 3 unmined min ...

[0042] Step S4 of the pillarless continuous mining method of the present invention specifies the detailed advance sequence of pillarless continuous mining. On the panel plane, the stope advances sequentially from the hanging wall to the footwall, while adopting a skip-mining sequence of three miners per stope or one miner per stope per stope. That is, there are 1 to 3 unmined stopes between the simultaneously mined stopes, forming a layout of multiple working faces staggered and alternately advancing. Inside the stope, mining is carried out in a segmented sequence from top to bottom. The upper segment advances the lower segment by 1 to 2 blasting cycles, with an advance distance of 1.5 to 4 meters, forming a stepped downward mining structure.

[0043] The advance depressurization pillarless continuous mining method of this invention has multiple functions in setting the mining sequence. In the horizontal plane, it adopts a step-by-step advance, ensuring that a sufficient number of unmined areas are retained between synchronously mined stops as temporary supports. This avoids large-area unsupported roof instability caused by continuous exposure of multiple stops, while also reserving a time window for the backfill body 10 of adjacent stops to reach the predetermined strength, achieving a rhythmic match between mining and backfilling. Inside the stope, the upper section advances the lower section by 1-2 blasting cycles, ensuring continuous free faces and stable blasting effects in the segmented blasting, while also allowing timely backfilling of the upper mined area, forming lateral support of the upper backfill body 10 for the lower mining area, effectively controlling the height of the unexposed area and the deformation of the surrounding rock. Overall, this "horizontal step-by-step, vertical bench" advance mode ensures continuous ore extraction efficiency while taking into account surrounding rock stability, backfill body strength maintenance, and operational safety, fully demonstrating the technological characteristics of pillarless continuous mining.

[0044] In some embodiments, in step S4, the segmented blasting involves drilling upward fan-shaped blast holes 8 in the segmented drilling roadway 11, with a row spacing of 1.5–2 m, using the cutting groove 15 as the free surface. One to two rows of blast holes 8 are blasted each time, followed by retreat mining. In the lower section of the stope, upward fan-shaped blast holes 8 are arranged in the bottom drilling roadway, and triangular pillars of 8–15 m are reserved to protect the ore extraction roadway 6 and ore extraction access roadway 5, so that a peach-shaped bottom structure is formed after the mining of two adjacent stopes is completed.

[0045] Step S4 of the pre-decompression pillarless continuous mining method of this invention provides detailed specifications for the segmented blasting parameters. In the stope recovery blasting, upward fan-shaped blast holes 8 are drilled within the segmented drilling roadway 11, with a row spacing of 1.5–2 m. The cutting groove 15 serves as the free face, and 1–2 rows of blast holes 8 are blasted each time, advancing backward along the stope strike. In the lower section of the stope, blasting operations are changed to arranging upward fan-shaped blast holes 8 within the bottom drilling roadway, and reserving 8–15 m triangular pillars to protect the ore extraction roadway 6 and ore extraction access roadway 5. After the two adjacent stopes are recovered, these reserved pillars form a peach-shaped bottom structure, providing stable space for ore extraction.

[0046] The blasting parameters and structural settings of the pre-decompression pillarless continuous mining method of this invention have the following functions: the upward fan-shaped blast holes 8, combined with a row spacing of 1.5-2m, match the segment height and the working capacity of the rock drilling equipment. During blasting, the cutting groove 15 serves as the free surface, ensuring sufficient development of the free surface and high utilization of explosive energy. Each blast of 1-2 rows of backward blasting can precisely control the blasting scale, avoiding excessive explosive charge in a single blast that could cause impact damage to the surrounding rock and filling body 10. The lower segment reserves 8-15m triangular pillars, effectively protecting the bottom ore extraction roadway 6 and ore extraction entrance 5 during mining, preventing blasting damage and ground pressure compression, and ensuring unobstructed ore extraction channels. The peach-shaped bottom structure formed after the adjacent mining area is completed allows the blasted ore to naturally converge towards the ore outlet, facilitating efficient loading by the loader 17. At the same time, the structure itself has good self-stabilizing ability, reducing the amount of bottom support work and creating favorable conditions for continuous ore extraction. It is designed to be compatible with the aforementioned mining area ore extraction roadway 6, further improving the overall efficiency of the ore extraction system.

[0047] In some embodiments, in step S7, the mobile crusher 18 and the mobile belt conveyor 16 are arranged in the ore outlet roadway 6 near the upper hanging wall seam roadway 1 or the lower hanging wall seam roadway 2. After the loader 17 scoops out the ore at the ore outlet of the ore outlet roadway 5, it retreats to the ore outlet roadway 6 and unloads it onto the mobile crusher 18. The crushed ore is then transferred by the mobile belt conveyor 16 to the belt conveyor 12 in the upper hanging wall seam roadway 1 or the lower hanging wall seam roadway 2, and then lifted to the surface via the underground ore bin and the inclined shaft belt conveyor 12.

[0048] Step S7 of the pre-decompression pillarless continuous mining method of this embodiment of the invention provides a specific arrangement for the equipment layout and operation process of the continuous ore extraction system. The mobile crusher 18 and the mobile belt conveyor 16 are both arranged in the ore extraction roadway 6 near the upper hanging wall seam roadway 1 or the lower hanging wall seam roadway 2. After the loader 17 scoops out the ore at the ore extraction entrance 5 of the stope, it retreats into the ore extraction roadway 6 and directly unloads the ore onto the mobile crusher 18. The crushed ore of suitable block size is transferred by the mobile belt conveyor 16 to the fixed belt conveyor 12 arranged in the upper hanging wall seam roadway 1 or the lower hanging wall seam roadway 2, and then continuously lifted to the surface via the underground ore bin and the inclined shaft belt conveyor 12.

[0049] The above arrangement realizes an integrated process of "short-haulage-crushing-continuous transfer" for underground ore transportation. The loader 17 does not need to transport ore over long distances to the pass, but only operates a short distance between the ore outlet and the crusher in the ore extraction roadway 6, shortening the single transport distance of the loader 17 and significantly improving the ore extraction cycle efficiency. The mobile crusher 18 moves flexibly with the advance of the stope, always close to the working stope, crushing large pieces of ore on-site to a size that can be accepted by the belt conveyor 12, avoiding the strict size restrictions of traditional transportation systems. The mobile belt conveyor 16 directly unloads the crushed ore into the main belt conveyor 12 in the vein roadway, forming a continuous transportation chain from the stope to the surface, replacing the traditional intermittent process of "loader 17-pass-electric locomotive-coarse crushing and hoisting", eliminating the constraints on ore extraction efficiency caused by pass blockage, electric locomotive scheduling, and hoisting failures, and realizing continuous, efficient, and stable operation of underground ore extraction.

[0050] In some embodiments, in step S5 or S8, the backfilling system utilizes the segmented rock drilling roadway 11 located 20-25m above the stope as a backfilling horizontal roadway. Backfilling boreholes 4 with a diameter of 250-400mm are drilled downwards from the backfilling horizontal roadway to the goaf, and backfilling is performed through the backfilling boreholes 4. During the backfilling process, borehole photography, three-dimensional laser scanning of the borehole, or ground-penetrating radar are used to detect the cementation and roof contact of the backfill slurry. Based on the detection results, additional backfilling boreholes 4 are added to optimize the backfilling roof contact effect. After the stope, triangular pillars, and peach-shaped bottom structure are all mined out, final backfilling is performed using backfill slurry.

[0051] Step S5 or S8 of the pre-decompression pillarless continuous mining method of this invention provides a specific scheme for the layout of the backfilling system and the control of backfilling quality. The backfilling system relies on the upper middle section segmented rock drilling roadway 11 located 20-25m above the stope as the backfilling horizontal roadway. Backfilling boreholes 4 with a diameter of 250-400mm are drilled downwards from this horizontal roadway to the goaf. The backfilling slurry is transported to the goaf through the backfilling boreholes 4 to complete the backfilling. During the backfilling process, detection methods such as borehole photography, borehole 3D laser scanning, or ground penetrating radar are used to monitor the cementing strength and roof contact of the backfilling slurry in real time. Based on the detection results, additional backfilling boreholes 4 are added to optimize the roof contact effect of the backfilling. After the stope and the triangular pillars and peach-shaped bottom structure are all mined out, the backfilling slurry is used for final backfilling to ensure that the entire goaf is fully filled.

[0052] The backfilling scheme of the pre-decompression pillarless continuous mining method of this invention relies on the existing segmented rock drilling roadway 11 in the previous section as the backfilling horizontal roadway, eliminating the need for additional dedicated backfilling roadways. This fully utilizes existing preparatory works and reduces the construction cost of the backfilling system. The backfilling borehole 4 has a diameter of 250-400mm, ensuring both the flow rate and pressure of the backfilling slurry while avoiding damage to the surrounding rock caused by excessively large boreholes. The backfilling borehole 4 is located directly above the stope, allowing the slurry to flow by gravity, resulting in high backfilling efficiency. By detecting the backfilling effect through borehole imaging, 3D laser scanning, or ground-penetrating radar, problems such as non-connection to the roof and poor cementation can be detected in a timely manner. These issues can be corrected by adding additional boreholes, effectively ensuring the integrity and bearing capacity of the backfill body 10 and providing reliable lateral support for the mining of adjacent stopes. After the triangular pillars and peach-shaped bottom structures have been completely mined, final backfilling is carried out to ensure that all goaf areas are filled with backfill slurry, completely eliminating goaf hazards and providing a guarantee for goaf management and post-mining safety under the pillarless continuous mining mode.

[0053] In some specific embodiments, a deep, thick iron ore deposit in China has an ore body 3 with a strike length of approximately 1000m, a thickness of approximately 200m, and a dip angle of approximately 70°. The direction of the maximum principal stress in the mining area is perpendicular to the strike of the ore body 3, classifying it as a deep, extra-thick, steeply dipping metallic deposit. The pillarless continuous mining method with pre-decompression depressurization proposed in this invention has been applied to this deposit and has achieved good results. The panel and stope layout are as follows... Figure 1 As shown, the specific implementation method is as follows: (1) The panel is 160m long and has 8 mining areas, each 20m wide. The panel length and mining area length are both the thickness of ore body 3, approximately 200m. (2) The middle section height is 80m, that is, the panel mining area height is 80m, which is divided into 3 sections with heights of (25m, 25m, 30m; from bottom to top); (3) A cutting groove 15 with a width of 2.5m is formed at the boundary of the panel near the hanging wall. The cutting groove 15 has a height of 80m and a length of 160m, which is the length of the panel. Two mining areas are mined simultaneously in the panel, with one mining area mined and one mining area mined at a time. (4) The mining in the panel area is carried out from the cutting groove 15 towards the footing, and the length of the first mining step is about 60m; (5) In the first step of the mining area, the ore is discharged by an electric loader 17. The loader 17 enters the mining area ore discharge roadway 6 from the lower plate along the vein roadway 2, shovels out the ore from the ore discharge entrance 5 and then retreats to the ore discharge roadway 6. The ore is then unloaded into a mobile crusher 18 arranged near the upper plate. The mobile crusher 18 is connected to a mobile belt conveyor and then transported out by a belt conveyor in the upper plate along the vein roadway 1. (6) After the ore in the first step of the mining area is exhausted, the filling pipeline and filling borehole 4 arranged in the upper middle section of the segmented rock drilling roadway 11 are used to fill the mining area void. (7) After the empty area of ​​the first-step stope is filled and cemented, the second-step stope between the first-step stopes is mined; during the mining process of the second-step stope, both sides of the stope are filled with 10. In order to ensure the safety of the stope, the length of the second-step stope is adjusted to 40m. (8) As mining progresses, it continues to advance towards both sides of the ore body 3 and the footwall mining area.

[0054] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0055] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0056] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0057] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0058] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0059] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A pillarless continuous mining method with advanced pressure relief, characterized in that, This method is applicable to steeply dipping, thick, and large metallic deposits with a dip angle greater than 55° and a thickness greater than 100m, and includes the following steps: S1. Ore body (3) division: The ore body (3) is divided into multiple middle sections along the height direction. Each middle section is divided into multiple sub-sections. On the middle section plane, the ore body (3) is divided into multiple panels along the strike of the ore body (3). Each panel is divided into multiple mining areas. Each mining area is divided into multiple mining fields. The long axis of the mining fields is perpendicular to the strike of the ore body (3). S2. Layout of the mining preparation project: The upper wall along the vein roadway (1) and the lower wall along the vein roadway (2) are arranged on the upper wall and the lower wall respectively. The mining area ore extraction roadway (6) is excavated in the mining area and is connected to the upper wall along the vein roadway (1) and the lower wall along the vein roadway (2). The mining area ore extraction roadway (5) is excavated on one side of the mining area ore extraction roadway (6) and a bottom drilling roadway is formed parallel to the ore extraction roadway (6). The segmented drilling roadway (11) is arranged on each segment plane. The upper wall segmented vein roadway (13) and the lower wall segmented vein roadway (14) are arranged on each segment plane and connected to the upper wall segmented vein roadway (13) and the lower wall segmented vein roadway (14) through the segmented drilling roadway (11). S3, Pre-decompression: Before mining in the panel area, a cutting groove (15) is formed at the boundary of the panel area near the upper plate, which runs through the entire middle section. The cutting groove (15) blocks the transmission path of deep horizontal high ground stress and forms a stress shadow area in the panel area. S4. Pillarless continuous mining: The mining area within the panel is continuously advanced from the cutting groove (15) towards the hanging wall or footwall in the predetermined mining sequence within the stress shadow zone. No pillars are reserved between the panel and the mining area. The mining area mined first is a first-step mining area, and the adjacent mining area mined later is a second-step mining area. During mining, the cutting groove (15) is used as the free surface in the segmented rock drilling roadway (11) for segmented blasting to achieve retreat mining. S5. Mining backfill: After the ore is mined out in the first step, it is immediately backfilled to form a backfill body (10). S6. Re-mining of adjacent mining areas: After the filling body (10) of the first-step mining area reaches the predetermined strength, the second-step mining area adjacent to the first-step mining area is re-mined. During the re-mining, both sides of the second-step mining area are filled bodies (10), and the mining length of the second-step mining area is adjusted in real time according to the stability of the filling body (10). S7. Continuous mining: After the mining area is blasted, the ore is transported out by a loader (17) and unloaded to a mobile crusher (18). After crushing, it is transferred by a mobile belt conveyor (16) to a belt conveyor (12) arranged in the upper wall along the vein roadway (1) or the lower wall along the vein roadway (2) to realize continuous transportation of ore. S8. Backfilling treatment: After the mining is completed, the goaf is backfilled through the backfilling system.

2. The pillarless continuous mining method with pre-decompression as described in claim 1, characterized in that, In step S1, the height of the middle section is 60-80m, each middle section is divided into 2-3 segments with a segment height of 25-30m, the width of the mining area is 15-20m, the width of the panel area is 120-200m, and the length of the stope is 40-60m.

3. The pillarless continuous mining method with pre-decompression as described in claim 1, characterized in that, In step S2, the spacing of the segmented rock drilling roadways (11) is consistent with the width of the stope, which is 15-20m, and they are arranged in the middle of the stope. The two ends of the segmented rock drilling roadways (11) are connected to the upper plate segmented vein roadway (13) and the lower plate segmented vein roadway (14), respectively. The mining area ore extraction roadway (6) is located in the middle of the peach-shaped structure (7) of the bottom structure. One ore extraction roadway (6) serves two adjacent mining areas. The bottom rock drilling roadway is connected to the mining area ore extraction access road (5).

4. The pillarless continuous mining method with pre-decompression as described in claim 1, characterized in that, In step S3, the width of the cutting groove (15) is 2-3m, and the process of forming the cutting groove (15) includes the following steps: In the segmented rock drilling roadway (11) of the panel mining area, cutting roadways that connect multiple mining areas are excavated in a direction parallel to the strike of the ore body (3); Drill a cutting well in the middle of the cutting tunnel; Using the cutting well and cutting tunnel as free space, drill upward vertical blast holes (8) in the cutting tunnel and blast them to form a cutting groove (15). Some or all of the ore produced by the blasting is transported out to reserve compensation space for the next blasting of the segmented cutting groove (15).

5. The pillarless continuous mining method with pre-decompression as described in claim 1, characterized in that, In step S3, the cutting groove (15) is a vertical cutting groove (15) or an inclined cutting groove (15); when the hanging wall of the ore body (3) is unstable, a vertical cutting groove (15) is used, and a triangular ore body (9) is reserved at the hanging wall to support the hanging wall. The triangular ore body (9) is mined after the mining is completed and the hanging wall is pre-reinforced; when the hanging wall of the ore body (3) is stable, an inclined cutting groove (15) is used along the interface between the ore and the rock.

6. The pillarless continuous mining method with pre-decompression as described in claim 1, characterized in that, In step S3, the formation of the cutting groove (15) is carried out synchronously with the mining of the panel area, and the advancing speed of the cutting groove (15) along the direction of the ore body (3) is ahead of the mining speed of the mining area, so as to ensure that the length of the cutting groove (15) is always greater than 1.5 to 2 times the total width of the mining area being mined.

7. The pillarless continuous mining method with pre-decompression as described in claim 1, characterized in that, In step S4, the mining area within the panel is advanced in the order from the hanging wall to the footwall, and a mining sequence of three miners mined at a time or one miner mined at a time is adopted, that is, there are 1 to 3 unmined mining areas between mining areas that are mined simultaneously; mining is carried out in the segmented order from top to bottom within the mining area, with the upper segment leading the lower segment by 1 to 2 blasting cycles and the leading distance being 1.5 to 4m.

8. The pillarless continuous mining method with pre-decompression as described in claim 1, characterized in that, In step S4, the segmented blasting involves drilling upward fan-shaped blast holes (8) in the segmented rock drilling roadway (11), with a row spacing of 1.5 to 2m. The cutting groove (15) is used as the free surface, and 1 to 2 rows of blast holes (8) are blasted each time for retreat mining. In the lower section of the mining area, upward fan-shaped blast holes (8) are arranged in the bottom rock drilling roadway, and 8 to 15m of triangular ore pillars are reserved to protect the mining area ore extraction roadway (6) and ore extraction access roadway (5) so that a peach-shaped bottom structure is formed after the mining of two adjacent mining areas is completed.

9. The pillarless continuous mining method with pre-decompression as described in claim 1, characterized in that, In step S7, the mobile crusher (18) and the mobile belt conveyor (16) are arranged in the ore outlet roadway (6) near the upper plate vein roadway (1) or the lower plate vein roadway (2); after the shoveler (17) shovels the ore at the ore outlet of the ore outlet roadway (5) in the mining area, it retreats to the ore outlet roadway (6) and unloads it to the mobile crusher (18). The crushed ore is transferred by the mobile belt conveyor (16) to the belt conveyor (12) in the upper plate vein roadway (1) or the lower plate vein roadway (2), and then lifted to the surface by the underground ore bin and the inclined shaft belt conveyor (12).

10. The pillarless continuous mining method with pre-decompression as described in claim 1, characterized in that, In step S5 or S8, the filling system relies on the segmented rock drilling roadway (11) located 20-25m above the mining area as the filling horizontal roadway. Filling boreholes (4) with a diameter of 250-400mm are drilled downward from the filling horizontal roadway to the goaf, and filling is carried out through the filling boreholes (4). During the filling process, borehole photography, borehole three-dimensional laser scanning or ground penetrating radar are used to detect the cementation and roof connection of the filling slurry, and additional filling boreholes (4) are added according to the detection results to optimize the filling roof connection effect. After the mining area and the triangular pillar and peach-shaped bottom structure are all mined out, the filling slurry is used for final filling.

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