Filling method in room-and-pillar mined-out area

Abstract

The disclosed method for filling in a room-and-pillar goaf comprises drilling a borehole in a roof stratum of the goaf, identifying a coal seam goaf in the drilling, replacing a directional pressure hole device every 3-5 m to make a high-pressure hole when a coal seam goaf is not encountered, identifying whether a coal seam goaf exists and whether a slurry passage is formed according to the pressure and the extension rate of the pressure rod, and pouring filling slurry after the passage is formed; the borehole is swept and extended after the slurry solidifies to early strength, and the steps of identifying, hole making and grouting are cyclically executed until filling in all the coal seam goafs is completed. The method solves the technical problem of poor filling effect in the prior art that it is difficult to effectively inject filling slurry into a room-and-pillar goaf with an uncollapsed roof.

Description

Technical Field

[0001] This invention belongs to the field of coal seam goaf treatment technology, specifically relating to a filling method for room-and-pillar goaf. Background Technology

[0002] Room-and-pillar mining is a widely used traditional mining technique in the coal mining industry. To ensure the safety of mining operations, large-sized coal pillars are usually left in the mine, resulting in a low coal recovery rate. As the service life of the mine continues to increase, a large number of room-and-pillar goaf areas are exposed to the air for a long time. The long-term load-bearing capacity of the left coal pillars gradually deteriorates, posing a potential risk of instability. This poses a serious safety hazard to subsequent mining of nearby coal seams, layout of floor roadways, and protection of surface buildings and structures.

[0003] Currently, the goaf filling and treatment generally adopts the borehole grouting process, and the relevant technologies are mainly developed and designed for goaf areas of longwall caving. Its core characteristics are: after the coal seam is mined, the roof collapses as the mining continues, the collapsed rock mass is loose and broken, and a large number of natural pores and through fractures are developed inside, providing sufficient channels for grout diffusion. The existing goaf borehole grouting technology is a mature process based on these characteristics.

[0004] Room-and-pillar goaf differs fundamentally from longwall caving goaf in its operating conditions. Room-and-pillar goaf exhibits a discrete, irregular spatial distribution with room-and-pillar intervals, good overall roof integrity, and generally does not experience collapse or only localized, sporadic collapses. It lacks the natural grout channels found in longwall caving goafs, which completely contradicts the premises of existing technologies. Therefore, existing technologies are insufficient to meet the remediation needs of room-and-pillar goafs, presenting the following core technical challenges in practical applications: 1. The accuracy of coal seam goaf identification is insufficient, making it difficult to accurately determine whether there is a coal seam goaf below the drilling hole and the actual size of the coal seam goaf cavity through construction drilling. 2. The roof strata are intact, but there is a lack of natural grouting channels connecting the boreholes and the coal seam goaf. During grouting, the grout cannot be effectively injected into the coal seam goaf and achieve uniform diffusion. 3. It is impossible to achieve dense filling of the coal seam goaf while ensuring the structural stability of the remaining coal pillars and not disturbing their bearing capacity. Summary of the Invention

[0005] The purpose of this invention is to provide a filling method for room-and-pillar goaf, which solves the technical problem in the prior art of effectively injecting filling grout into room-and-pillar goaf where the roof has not collapsed and the filling effect is poor.

[0006] The technical solution adopted in this invention is a method for filling goaf areas in a room-and-pillar type goaf, which includes drilling holes in the roof strata of the goaf area, identifying coal seam goaf areas during drilling, and replacing the directional drilling device every 3m to 5m to perform high-pressure drilling if no coal seam goaf area is encountered; determining the existence of coal seam goaf areas and whether grout channels have been formed based on the pressure and the extension rate of the pressure rod; injecting filling grout after the channels are formed; after the grout has finally set, sweeping and extending the borehole, and repeating the identification, drilling, and grouting steps until the filling of all coal seam goaf areas is completed.

[0007] The invention is further characterized by including the following steps: S1, drilling along the predetermined direction within the roof strata of the goaf; S2, If the borehole directly exposes the coal seam goaf formed by the collapse of the roof, then stop drilling and proceed to step S4; if no coal seam goaf is encountered, stop drilling after every 3m to 5m, remove the drill bit and replace the directional drilling device. S3. Using a directional pressure device, high pressure is applied to the borehole wall from the inside out in the drilled section. Based on the pressure stability and the extension rate of the pressure rod of the device, it is determined whether there is a coal seam goaf below and whether a slurry drainage channel has been formed. S4. After determining that the slurry channel has been formed, the directional drilling device is withdrawn, and the filling slurry is injected into the coal seam goaf through the borehole until the slurry fills the corresponding coal seam goaf area. S5. After the filling grout has set, the borehole is swept to connect the solidified section of the hole. The drilling continues to extend forward, and steps S2 to S4 are repeated until the filling operation of all coal seam goaf areas within the design range is completed.

[0008] The normal distance between the borehole and the top plate interface is within 2m.

[0009] The specific rules for determining the coal seam goaf and slurry drainage channel in step S3 are as follows: If the pressure is stable and the extension rate of the pressure rod of the device is lower than the preset threshold, it is determined that there is no coal seam goaf below the position, and the device is withdrawn to continue drilling. If there is no significant pressure reduction but the extension rate of the pressure rod of the device is higher than the preset threshold, it is determined that there is a coal seam goaf below the location but the slurry channel has not been formed. Replace the large-stroke directional drilling device and repeat the drilling operation until a significant pressure relief phenomenon occurs. If obvious pressure relief occurs, it is determined that a slurry drainage channel has been formed between the borehole and the coal seam goaf.

[0010] If it is determined that there is no coal seam goaf below, the directional drilling device will be withdrawn from the bottom of the hole by a fixed distance, and the coal seam goaf and slurry drainage channel will be judged again until the judgment of the current drilled section is completed.

[0011] In step S4, the grouting pressure is maintained at 1.5MPa~2MPa. Grouting is stopped when the pressure at the orifice rises significantly.

[0012] In step S4, the filling grout is a cement-based material or a high-water-rate quick-setting material.

[0013] The hole cleaning operation in step S5 is carried out after the filling material has solidified to a level sufficient to support the hole wall and meet the drilling strength requirements.

[0014] The beneficial effects of this invention are: (1) By establishing a dual-indicator linkage identification system of "pressure change characteristics + pressure rod extension rate", the present invention can verify and accurately identify the hidden room-column goaf under the condition of intact roof in stages during the drilling process. It can simultaneously lock the location and scale of the coal seam goaf cavity, solve the pain point that the existing technology cannot accurately determine the goaf occurrence state below the borehole, and greatly reduce ineffective drilling and ineffective grouting operations.

[0015] (2) The present invention uses a directional pressure hole device to apply high pressure to the rock wall of the hole and actively create holes to connect the goaf below, thus solving the problem that the grout cannot be injected due to the integrity of the roof rock layer.

[0016] (3) The present invention strictly limits the working layer of the entire process of drilling, high-pressure hole making and grouting to within 2m of the roof of the goaf, and keeps it away from the coal pillar below throughout the process. The operation disturbance only acts on the roof rock mass and does not damage the load-bearing structure and integrity of the coal pillar. While achieving dense filling of the goaf, the load-bearing capacity of the coal pillar is preserved to the maximum extent, and the safety risk of coal pillar instability induced during the treatment process is avoided from the source.

[0017] (4) The present invention adopts a closed-loop operation process of "drilling-identification-hole making-grouting-hole sweeping extension". A single hole opening can realize continuous filling treatment of long-distance and multi-section goaf areas without repeated hole opening, greatly simplifying the construction process and improving the operation efficiency. At the same time, through the operation mode of segmented grouting and segmented verification, the design treatment range can be fully covered, avoiding the occurrence of filling blind spots and ensuring the overall filling density of the goaf area. Attached Figure Description

[0018] Figure 1 This is a cross-sectional schematic diagram of the filling method for the goaf in the room-column type of the present invention; Figure 2 This is a schematic diagram of the burring operation state of the directional burring device in this invention.

[0019] In the diagram, 1. Coal seam goaf, 2. Roof strata, 3. Directional pressure drilling device, 4. Borehole, 5. Slurry drainage channel, 6. Pressure application area, 7. Coal seam. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] Example 1 This invention relates to a method for filling goaf areas in a column-type housing, combined with attached... Figure 1 As the construction structure reveals, the core operation involves drilling directional boreholes 4 within the roof strata 2 of the room-and-pillar goaf. Through an integrated process of drilling identification, high-pressure borehole creation, grouting and filling, and cyclic extension, efficient treatment of goafs with intact roofs is achieved. This method can precisely construct grout delivery channels and complete dense filling while protecting the integrity of the remaining coal pillars. The specific implementation steps are as follows: Includes the following steps: S1, In the roof rock layer 2 of the goaf, drill hole 4 is drilled along the extension direction of the coal seam goaf 1. The normal distance between drill hole 4 and the roof interface is strictly controlled within 2m. This layer setting can avoid disturbing the coal pillar below, and at the same time ensure the stability of the drilling. S2, during the drilling process, the coal seam goaf 1 is identified in real time. If the borehole 4 directly exposes the coal seam goaf 1 formed by the roof collapse, the drilling is stopped immediately and the grouting process is started. If the coal seam goaf 1 is not detected, the drilling is stopped every 3m to 5m, the conventional drilling tool is removed and replaced with a special directional pressure hole device 3. S3, using the directional pressure device 3 (its basic structure is similar to a scissor jack, using threads to control the height of the pressure rod), directional high pressure is applied from the inside out to the borehole wall of the completed drilling section. Combined with pressure stability data and pressure rod extension rate, it accurately determines whether a coal seam goaf 1 exists below the borehole section, and whether the slurry drainage channel 5 has been successfully constructed; combined with the attached... Figure 2 It can be seen that the directional pressure hole device 3 is equipped with multiple pressure application areas 6, which can expand the detection and hole-making range and effectively avoid the problem of missed detection of goaf areas; S4. After confirming that the slurry channel 5 is fully formed, quickly withdraw the directional drilling device 3 and continuously inject filling slurry into the coal seam goaf 1 through the borehole 4 until the slurry completely fills the corresponding area of ​​the coal seam goaf 1 to eliminate the cavity hazard. S5. After the filling grout has set, the borehole 4 is swept to penetrate the section of the hole that has been solidified by the filling material. The drilling continues to extend forward, and steps S2 to S4 are repeated until the filling operation of all coal seam goaf 1 within the design range is completed.

[0022] This invention adopts a closed-loop cycle operation process of "drilling-identification-hole making-grouting-hole sweeping extension". A single hole opening can achieve continuous filling and treatment of long-distance, multi-section goaf areas without the need for repeated hole opening, which greatly simplifies the construction process and improves the operation efficiency. At the same time, through the operation mode of segmented grouting and segment-by-segment verification, it can fully cover the designed treatment range, avoid filling blind spots, and ensure the overall filling density of the goaf area.

[0023] Example 2 Based on Example 1 above, the specific rules for determining the coal seam goaf 1 and the slurry drainage channel 5 in step S3 of this example are as follows: If the pressure is stable and the extension rate of the pressure rod of the device is lower than the preset threshold, it is determined that there is no coal seam goaf 1 below this position, and the device is withdrawn to continue drilling; If there is no significant pressure reduction but the extension rate of the pressure rod of the device is higher than the preset threshold, it is determined that there is a coal seam goaf 1 below the location but the slurry channel 5 has not been formed. Replace the large stroke directional pressing device 3 and repeat the pressing operation until a significant pressure relief phenomenon occurs. The large-stroke directional drilling device 3 has a larger load and size. The parameters of the directional drilling device 3 used in this embodiment are: standard load 1.5t, length 36cm, width 9cm, height 10cm; the parameters of the large-stroke directional drilling device 3 are: standard load 3t, length 47cm, width 11cm, height 10cm, which is suitable for directional drilling in the borehole 4.

[0024] If a significant pressure relief occurs and the extension rate of the device pressure rod is higher than the preset threshold, it is determined that the slurry drainage channel 5 between borehole 4 and the coal seam goaf 1 has been formed.

[0025] Example 3 This embodiment optimizes the detection process when there is no goaf by improving the judgment rules of Embodiment 2. It achieves full-section identification without blind spots by segmented retesting, completely eliminating the problem of missed detection of hidden goaf areas. The specific optimizations are as follows: If it is determined that there is no coal seam goaf 1 below the current hole bottom position, drilling will not continue directly. Instead, the directional drilling device 3 will be withdrawn from the bottom of the hole by 0.3m to 0.7m (this distance is adapted to the length of the drilling device), and high pressure detection and coal seam goaf 1 identification operations will be carried out again. The above method is used to retest each section upwards until all drilled sections have been identified as coal seam goaf 1 and slurry drainage channel 5, ensuring that the hidden coal seam goaf 1 under the condition of intact roof is fully detected, providing a reliable basis for subsequent accurate filling.

[0026] Example 4 Based on the segmented identification technology of Example 3, this embodiment optimizes the grouting process parameters and filling material selection in step S4. While ensuring the filling density, it adapts to the needs of rapid downhole construction. The specific optimizations are as follows: In step S4, the grouting pressure is maintained at 1.5MPa~2MPa. This pressure range can ensure that the filling grout is fully diffused in the coal seam goaf 1, while avoiding excessive pressure that could damage the roof rock structure. When the orifice pressure rises significantly, it is determined that the coal seam goaf 1 is full and grouting is stopped immediately. The filling grout selected in step S4 is a cement-based material or a high-water-rate-setting material. The high-water-rate-setting material used in underground mines is selected based on the mine's hydrogeological conditions and the strength requirements of the filling body. This type of material has the characteristics of early strength, density, and moderate fluidity, and can quickly solidify and meet the support requirements of the coal seam goaf.

[0027] In this embodiment, the cement-based material is WF series mining composite cement-based filling cementitious material, which uses cement as the base material and is mixed with industrial solid waste and additives. It has early strength and high flowability characteristics, has obtained mining safety certification, and can be used directly.

[0028] The high-water-rate quick-setting material uses XC-Ⅲ type high-water-rate coagulant, a publicly procured model for mining, and is used for high-water-rate quick-setting filling of coal seam goaf 1. Its performance meets the requirements for underground construction.

[0029] Example 5 This embodiment discloses a method for filling goaf areas with room-and-pillar structures. Specifically, it includes drilling holes 4 in the roof rock strata 2 of the goaf area; identifying coal seam goaf areas 1 during drilling; if no coal seam goaf area 1 is encountered, replacing the directional drilling device 3 every 3m to 5m to perform high-pressure drilling; identifying coal seam goaf areas 1 and grouting channels 5 based on pressure and pressure rod extension rate; injecting filling grout after the channels are formed; after the grout has set, cleaning and extending the borehole; and repeating the identification, drilling, and grouting steps until all goaf areas are filled.

[0030] Specifically, the following steps are included: S1, Drill hole 4 in the roof rock layer 2 of the goaf along the predetermined direction; S2, if borehole 4 directly exposes the coal seam goaf 1 formed by the collapse of the roof, then stop drilling and proceed to step S4; if the coal seam goaf 1 is not encountered, then stop drilling after every 3m to 5m, remove the drill bit and replace the directional drilling device 3. S3, using the directional pressure device 3 to apply high pressure to the borehole wall from the inside to the outside of the drilled section, and judging whether there is a coal seam goaf 1 and whether the slurry channel 5 is formed below based on the pressure stability and the extension rate of the pressure rod of the device. S4. After determining that the slurry channel 5 has been formed, the pressure hole device is removed, and the filling slurry is injected into the coal seam goaf 1 through the borehole 4 until the slurry fills the corresponding area of ​​the coal seam goaf 1. S5. After the filling grout has set, the borehole 4 is swept to penetrate the section of the hole that has been solidified by the filling material. The drilling continues to extend forward, and steps S2 to S4 are repeated until the filling operation of all coal seam goaf 1 within the design range is completed.

[0031] In step S5, the drilling operation must be carried out under strict timing control. It must be carried out only after the filling material has solidified to the early structural strength that can independently support the borehole wall. This can effectively resist the surrounding rock stress, prevent the borehole wall from collapsing and falling off, and ensure the stability of the borehole formation. At the same time, it must be strictly controlled to be carried out within the window period when the filling material has not fully hardened and has not reached the final design strength.

[0032] This precise timing selection not only relies on the early consolidation strength of the filling material to build a solid safety barrier for the borehole wall, completely avoiding the risks of borehole collapse, diameter reduction, and borehole scrapping caused by borehole sweeping disturbance, but also utilizes the low hardness and low cutting resistance characteristics of the filling material before it reaches its final strength, which greatly reduces the difficulty of borehole sweeping operations, reduces wear, impact, and energy consumption of drilling rigs and tools, and extends the service life of downhole construction equipment.

[0033] Meanwhile, this optimized scheme effectively avoids problems such as excessive strength after the filling material has fully hardened, a sharp increase in hole-sweeping resistance, frequent drill jams and blockages, and obstructed hole extension. It ensures that the hole-sweeping operation can quickly penetrate the hole section that has been solidified by the filling material, and smoothly extend the hole forward. This allows the cyclic filling process of "drilling identification - active hole making - high-pressure grouting - hole-sweeping extension" to maintain continuous and efficient operation, significantly improving the construction efficiency and smoothness of long-distance, large-scale room-and-pillar goaf filling, and providing stable process support for the overall dense filling of the goaf.

[0034] Example 6 A certain mine has a large-scale room-and-pillar goaf. The roof stratum 2 is fine sandstone with good integrity, but the remaining coal pillars are quite wide. The method of this invention is used for backfilling, and the specific operation is as follows: Equipment preparation: Prepare a fully hydraulic tunnel drilling rig, 3 directional drilling devices (with pressure display and pressure rod displacement display functions), a high-concentration filling pump station and a slurry preparation system.

[0035] Step 1: Based on the geological exploration data of the mine, drill hole 4 is opened in the stable fine sandstone layer 1.5m above the coal seam 7 in the coal seam goaf 1. The drilling diameter is 150mm and the drilling direction is oriented. This hole diameter and the layer position can ensure the hole quality and at the same time meet the grouting flow requirements. Step 2: After drilling to 5m without detecting coal seam goaf 1, drilling is paused and the drill rod is withdrawn. The directional drilling device 3 is lowered to the bottom of the hole. When the pressure is initially increased to 12MPa, the pressure is stable, and the extension rate of the pressure rod is only 60% (below the preset threshold of 80%), indicating that there is no coal seam goaf 1 below. The device is withdrawn 0.5m from the bottom of the hole and the pressure is increased to 10MPa again. The extension rate of the pressure rod reaches 90%, but the pressure does not decrease, indicating that there is a cavity but the slurry drainage channel 5 has not been formed. The directional drilling device 3 with a large stroke is replaced and the pressure is increased to 12MPa again. The extension rate of the pressure rod reaches 90% and the pressure drops sharply to below 1MPa, confirming that the slurry drainage channel 5 has been constructed. Step 3: Quickly withdraw the directional drilling device 3 and connect the grouting pipeline. Inject high-concentration filling grout into the coal seam goaf 1 through the borehole 4. Maintain the grouting pressure at 1.5MPa. Stop grouting when the borehole pressure rises significantly to ensure that the coal seam goaf 1 is densely filled. Step 4: After the filling grout has set, use a drilling rig to clean the original borehole, drill through the consolidated filling body and continue to extend the borehole. Repeat the identification, drilling and grouting process to complete the treatment of the entire coal seam goaf 1.

[0036] On-site testing showed that this method achieved full-section dense filling of the goaf area with hidden room pillars. The strength of the filling body fully met the design standards. The entire construction process did not disturb the surrounding residual coal pillars 3. There were no problems such as coal pillar spalling or abnormal stress, effectively eliminating the safety hazards of goaf instability.

[0037] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0038] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for filling goaf areas in a room-and-column type goaf, characterized in that, The process includes drilling holes (4) in the roof rock strata (2) of the goaf, identifying the goaf (1) during drilling, and replacing the directional pressure hole device (3) every 3m to 5m to create a high-pressure hole if no goaf (1) is encountered. The existence of the goaf (1) and whether the slurry channel (5) is formed are determined based on the pressure and the extension rate of the pressure rod. When the channel is formed, the slurry is injected and filled. After the slurry has set, the hole is swept and the drilling is extended. The identification, hole creation and grouting steps are repeated until all the goaf (1) of the coal seam is filled.

2. The method for filling goaf areas with pillars according to claim 1, characterized in that, Includes the following steps: S1, Drill holes (4) in the roof rock layer (2) of the goaf along the predetermined direction. S2, if the borehole (4) directly exposes the coal seam goaf (1) formed by the collapse of the roof, then stop drilling and proceed to step S4; if the coal seam goaf (1) is not encountered, then stop drilling after drilling for 3m to 5m, remove the drill bit and replace the directional drilling device (3). S3, using the directional pressure device (3) to apply high pressure to the borehole wall from the inside to the outside of the drilled section, and judging whether there is a coal seam goaf and whether the slurry channel (5) is formed based on the pressure stability and the extension rate of the pressure rod of the device. S4. After the formation of the slurry channel (5), the directional drilling device (3) is removed, and the filling slurry is injected into the coal seam goaf (1) through the borehole (4) until the slurry fills the corresponding coal seam goaf (1). S5. After the filling grout has set, the borehole (4) is swept to penetrate the section of the hole that has been solidified by the filling body. The drilling continues to extend forward, and steps S2 to S4 are repeated until the filling operation of all coal seam goaf areas (1) within the design range is completed.

3. The method for filling goaf areas with pillars according to claim 2, characterized in that, The normal distance between the borehole (4) and the top plate interface is within 2m.

4. The method for filling goaf areas with pillars according to claim 2, characterized in that, The specific rules for determining the coal seam goaf and slurry drainage channel in step S3 are as follows: If the pressure is stable and the extension rate of the pressure rod of the device is lower than the preset threshold, it is determined that there is no coal seam goaf below the position (1), and the device is withdrawn to continue drilling; If there is no significant pressure drop but the extension rate of the pressure rod of the device is higher than the preset threshold, it is determined that there is a coal seam goaf area (1) below the location but the slurry channel (5) has not been formed. Replace the large stroke directional pressing device (3) and repeat the pressing operation until a significant pressure drop occurs. If obvious pressure relief occurs, it is determined that the slurry channel (5) between the borehole (4) and the coal seam goaf (1) has been formed.

5. The method for filling goaf areas with pillars according to claim 4, characterized in that, If it is determined that there is no coal seam goaf (1) below, the directional drilling device (3) will be withdrawn from the bottom of the hole by a fixed distance, and the coal seam goaf (1) and slurry channel (5) will be judged again until all the drilled sections have been judged.

6. The method for filling goaf areas according to claim 2, characterized in that, In step S4, the grouting pressure is maintained at 1.5MPa~2MPa, and grouting is stopped when the orifice pressure rises significantly.

7. The method for filling goaf areas with pillars according to claim 2, characterized in that, In step S4, the filling grout is a cement-based material or a high-water-rate quick-setting material.

8. The method for filling goaf areas with pillars according to claim 2, characterized in that, The hole-sweeping operation in step S5 is carried out when the filling material has solidified to a level sufficient to support the hole wall and meet the drilling strength requirements.

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