Coal mining dense combined filling method

Abstract

This invention discloses a method for dense backfilling in coal mining: Step 1, determine the location of the main critical layer that may exist in the overlying strata; Step 2, determine the low grouting position; Step 3, determine the high grouting position; Step 4, determine the grouting layer position; Step 5, construct grouting boreholes, lay pipelines, and install valves; Step 6, prepare grouting fluid; Step 7, advance the coal face, during which backfilling supports are used for support and gangue is filled into the goaf; Step 8, compact; Step 9, withdraw the supports; Step 10, repeat steps 7-9, during which grouting fills the ex-layer space until the coal seam is mined out; Step 11, if the grouting pressure suddenly increases, proceed to Step 12; Step 12, open all valves. This invention uses a combination of ex-layer grouting and goaf gangue filling technologies to achieve dense backfilling, which can protect the main critical layer from fracture to the greatest extent and play a better role in controlling surface subsidence.

Description

Technical Field

[0001] This invention belongs to the field of coal mine backfilling mining technology, and relates to a method for dense combined backfilling in coal mine mining. Background Technology

[0002] During coal mining, large areas of overlying rock strata are exposed and eventually fracture, with fissures continuously developing upwards, ultimately forming "vertical three-zone" structures. This is detrimental to surface soil and water conservation, contradicts the development concept of ecological environmental protection, and the resulting surface subsidence also causes varying degrees of damage to above-ground structures. Backfilling mining technology involves injecting different materials into the goaf or excavated space to support and protect the overlying rock strata, preventing surface subsidence and effectively addressing the negative impacts of mining activities. Currently, different backfilling mining technologies have been developed, including excavation grouting, gangue backfilling, construction waste backfilling, high-water-content material backfilling, and ultra-high-water-content material backfilling. Among these, high-water-content and ultra-high-water-content materials form backfill bodies with high strength and low compressibility in the later stages, resulting in good surface subsidence control. However, due to the need for coal mine gangue disposal, their overall economic efficiency is poor. Other backfill materials, due to their higher compressibility and the limited variety of backfilling techniques, lead to a decline in surface subsidence reduction after a period of time, resulting in varying degrees of ground depression. With consideration given the issue of gangue disposal, how to achieve more efficient compacted backfill mining is a major challenge faced by many coal mines. Summary of the Invention

[0003] The purpose of this invention is to provide a method for dense combined backfilling in coal mines, in order to solve the problem in the prior art where the surface subsidence reduction effect decreases after a period of backfilling, resulting in varying degrees of ground depression.

[0004] To achieve the above objectives, the present invention employs the following technical solution:

[0005] A method for dense backfilling in coal mining specifically includes the following steps:

[0006] Step 1: Determine the location of the main key layer that may exist in the overlying strata;

[0007] Step 2, determine the grouting low position:

[0008] Step 3: Determine the grouting elevation;

[0009] Step 4, determine the final grouting layer: within the grouting low and grouting high intervals, determine the grouting location based on the key layer identification method and borehole exploration results;

[0010] Step 5: Construct vertical grouting boreholes at the surface locations corresponding to 1 / 4, 1 / 2, and 3 / 4 of the coal seam's strike length to the designated grouting positions. Lay grouting pipes in all grouting boreholes and connect them to the ground filling station. Install the first valve, the second valve, and the third valve on the filling pipes at 3 / 4, 1 / 2, and 1 / 4 of the coal seam's strike length, respectively. The first valve, the second valve, and the third valve are initially closed.

[0011] Step 6: Prepare the grouting fluid;

[0012] Step 7: The coal mining face continues to advance. During this process, the gangue filling hydraulic support is used to support the overlying roof of the goaf from the rear. At the same time, the gangue sorted underground is transported to the goaf for filling through the conveying device of the gangue filling hydraulic support.

[0013] Step 8: When the height of the gangue filling in the goaf reaches the immediate roof or the main roof, stop the gangue filling and compact it; the mass of the gangue filling in this process is m1=ρ1MbL1, where ρ1 is the gangue density, M is the coal seam thickness, b is the coal seam dip length, and L1 is the filling step distance.

[0014] Step 9: After the gangue filling body is compacted, the gangue filling hydraulic support is retracted.

[0015] Step 10: Repeat steps 7-9. During this process, when the coal face has advanced to 1 / 4 of the coal seam's strike length, open the third valve, and the filling station begins to output the grouting fluid prepared in step 6 for grouting. The grout is output from the filling pipe at 1 / 4 of the strike length to fill the resulting separation space. When the face has advanced to 1 / 2 of the coal seam's strike length, close the third valve and open the second valve, and the grout is output from the filling pipe at 1 / 2 of the strike length for grouting. When the face has advanced to 3 / 4 of the coal seam's strike length, close the second valve and open the first valve, and the grout is output from the filling pipe at 3 / 4 of the strike length for grouting, until the coal seam is completely mined.

[0016] Step 11: Throughout the entire grouting process, monitor the grouting pressure at all times. If the grouting pressure suddenly increases, it indicates that the separation space is basically filled. Proceed to step 12.

[0017] Step 12: Open all valves, slightly slow down the grouting speed, and increase the grouting pressure. When the total mass of grout actually flowing out of the filling station m2 is greater than the mass of grout required to fill the separation space m3, the filling station stops grouting.

[0018] The total mass of the grout actually flowing out of the filling station is m2=ρ2VSt, where ρ2 is the grout density, V is the average grout velocity, S is the cross-sectional area of ​​the grouting pipe, and t is the total grouting time.

[0019] Mass of grout required to fill the delamination space Where L2 is the strike length of the working face, E is the elastic modulus of the rock stratum immediately below the main critical stratum, q is the uniformly distributed load acting on it, h is the thickness of the rock stratum immediately below the main critical stratum, b is the dip length of the coal seam, and q is the deflection of the rock stratum immediately below the main critical stratum. The moment of inertia of the section of the rock layer immediately below the main key layer is

[0020] Furthermore, in step 2, the development height of the water-conducting fracture zone above the working face is determined by on-site drilling observation and ultrasonic imaging, and used as the low point value for grouting.

[0021] Furthermore, in step 2, the grouting elevation value is taken as the larger of the sum of the Quaternary and bedrock weathering zone thicknesses and 0.3 times the coal seam burial depth.

[0022] Furthermore, in step 6, the raw materials for the grouting fluid are fly ash, coal slime or coal gangue, and cement, water glass and suspending agent are used as additives in the preparation of the grout, with a water-to-solid ratio of 1:0.8 to 1:1.3.

[0023] Furthermore, in step 8, the baffle connected to the hydraulic support is compacted by reciprocating movement of the hydraulic jack.

[0024] Furthermore, in step 10, the grouting pressure is 1-5 MPa.

[0025] Furthermore, in step 12, the increase in grouting pressure is 0.5-1 MPa.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] (1) This invention combines two technologies: delamination grouting and goaf gangue backfilling, achieving dense backfilling. Compared to general backfilling schemes, it better utilizes the support and compressibility of gangue, avoiding severe roof collapse and facilitating continuous subsidence of multiple rock strata. Simultaneously, it creates a certain delamination space below the main critical stratum, facilitating subsequent grouting operations. This invention can protect the main critical stratum from fracture to the greatest extent possible, providing better control over surface subsidence.

[0028] (2) This invention provides calculation formulas for the amount of gangue filling required for each filling step goaf and the final amount of grouting in the separation space, effectively controlling the amount of gangue in the well, avoiding gangue accumulation, helping to judge the filling rate of the grout, and better guiding the separation grouting work.

[0029] (3) The present invention connects a hydraulic jack to push the baffle behind the hydraulic support for gangue filling, so as to achieve the purpose of compacting the gangue. Attached Figure Description

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will now be described in detail with reference to the accompanying drawings.

[0031] Figure 1 This is a schematic diagram illustrating the coordinated operation of gangue backfilling and delamination grouting in the goaf.

[0032] Figure 2 This is a magnified view of a portion of the goaf being filled using hydraulic supports.

[0033] Figure 3 This is a schematic diagram for calculating the total amount of grouting for delamination.

[0034] The meanings of the labels in the diagram are as follows:

[0035] 1—Filling pipe at 3 / 4 of the running length; 2—Filling pipe at 1 / 2 of the running length; 3—Filling pipe at 1 / 4 of the running length; 4—First valve; 5—Second valve; 6—Third valve; 7—Filling station; 8—Main key layer; 9—Rock layer immediately below the main key layer; 10—Hydraulic support for gangue filling; 11—Gangue filling body; 12—Hydraulic jack; 13—Baffle. Detailed Implementation

[0036] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0037] The method of this invention achieves dense filling of the overlying strata delamination space and goaf through a combination of surface and underground methods, solving the problem of the overlying strata continuing to subside after a period of time following the completion of filling and mining. This will be beneficial to the protection of the surface ecology and buildings.

[0038] The coal mine compaction combined backfilling method provided by this invention specifically includes the following steps:

[0039] Step 1: Calculate and determine the location of the main key layer that may exist in the overlying strata based on existing geological borehole data.

[0040] Step 2: Determine the grouting low point. The development height of the water-conducting fracture zone above the working face is determined through on-site drilling observations and ultrasonic imaging. This height serves as the grouting low point value. The grouting height must be higher than this value to prevent grout from seeping into the working face and affecting production activities.

[0041] Step 3: Determine the grouting elevation. The highest grouting position must ensure that the high-pressure grout does not penetrate the upper strata and cause grout leakage. Generally, the grouting elevation depth should be greater than the sum of the thickness of the Quaternary strata and the weathered zone of the bedrock, or greater than 0.3 times the coal seam depth. In this invention, the maximum value of the two is taken as the grouting elevation value.

[0042] Step 4: Determine the final grouting layer. Within the grouting low and high grouting intervals, find a suitable grouting location (i.e., the separation space below the main key layer) based on the key layer identification method and borehole exploration results.

[0043] Step 5: Construct vertical grouting boreholes at the surface locations corresponding to 1 / 4, 1 / 2, and 3 / 4 of the coal seam's strike length, extending to the designated grouting positions. Lay grouting pipes in all boreholes and connect them to the ground filling station 7. Install the first valve 4, the second valve 5, and the third valve 6 on the filling pipes 1 (3 / 4 of the coal seam's strike length), 2 (1 / 2 of the strike length), and 3 (1 / 4 of the strike length), respectively. Figure 1 As shown, this is used for subsequent grouting control. The first valve 4, the second valve 5, and the third valve 6 are initially closed.

[0044] Step 6: Prepare grouting fluid. Preferably, the raw materials for grouting fluid are coal-based solid wastes such as fly ash, coal slime, and coal gangue. For fillers with larger block sizes, they are usually pulverized by ball milling or other methods. In the preparation of grout, cement, water glass, suspending agents, etc. are used as additives to improve the properties of grouting fluid. The water-to-solid ratio is controlled at 1:0.8 to 1:1.3.

[0045] Step 7: The coal mining face continues to advance. During this process, the gangue filling hydraulic support 10 is used to support the overlying roof of the goaf from the rear. At the same time, the gangue sorted underground is transported to the goaf for filling through the conveying device of the gangue filling hydraulic support 10.

[0046] Step 8: When the height of the gangue filling in the goaf reaches the immediate roof or the main roof, stop the gangue filling and compact it by repeatedly pushing the baffle 13 connected to the hydraulic support back and forth using hydraulic jacks 12. Figure 2 As shown. The mass of gangue used for filling in this process is m1 = ρ1MbL1, where ρ1 is the density of gangue, M is the thickness of the coal seam, b is the dip length of the coal seam, and L1 is the filling step distance.

[0047] Step 9: After the gangue backfill 11 is basically compacted, the gangue backfill hydraulic support 10 is withdrawn.

[0048] Step 10: Repeat steps 7-9. During this process, when the coal face is pushed to 1 / 4 of the coal seam's strike length, open the third valve 6, and the filling station 7 begins to output the grouting fluid prepared in step 6 for grouting. The grout is output from the filling pipe 3 at 1 / 4 of the strike length to fill the resulting separation space. The grouting pressure is generally controlled between 1-5 MPa, determined according to the actual situation. When the face is pushed to 1 / 2 of the coal seam's strike length, close the third valve 6 and open the second valve 5. The grout is output from the filling pipe 2 at 1 / 2 of the strike length for grouting. When the face is pushed to 3 / 4 of the coal seam's strike length, close the second valve 5 and open the first valve 4. The grout is output from the filling pipe 1 at 3 / 4 of the strike length for grouting, until the coal seam is completely mined.

[0049] Step 11: Throughout the entire grouting process, continuously monitor the roof subsidence and changes in grouting pressure. Under normal circumstances, as the roof gradually subsides, the grouting pressure will initially decrease slightly and quickly stabilize within a certain range. If the grouting pressure suddenly increases, it indicates that the separation space is essentially filled, and proceed to step 12.

[0050] Step 12: Open all valves (including first valve 4, second valve 5 and third valve 6), slightly slow down the grouting speed, and increase the grouting pressure by 0.5-1 MPa, so that the grout is further compacted and finally fills the crack space inside and outside the delamination space. When the total mass of grout actually flowing out of filling station 7, m2, is greater than the mass of grout required to fill the delamination space, m3, the filling station 7 stops the grouting work.

[0051] The total mass of the grout actually flowing out of filling station 7 is m2=ρ2VSt, where ρ2 is the grout density, V is the average flow velocity of the grout, S is the cross-sectional area of ​​the grouting pipe, and t is the total grouting time.

[0052] Mass of grout required to fill the delamination space Where L2 is the strike length of the working face, E is the elastic modulus of the rock stratum 9 immediately below the main key stratum, q is the uniformly distributed load acting on it, h is the thickness of the rock stratum 9 immediately below the main key stratum, and b is the dip length of the coal seam. Figure 3 The deflection of the rock layer 9 immediately below the main key layer in the established rectangular coordinate system shown. The moment of inertia of the section of the rock layer 9 immediately below the main key layer is:

Claims

1. A method for dense backfilling in coal mining, characterized in that, Specifically, the following steps are included: Step 1: Determine the location of the main key layer that may exist in the overlying strata; Step 2, determine the grouting low position: Step 3: Determine the grouting elevation; Step 4, determine the final grouting layer: within the grouting low and grouting high intervals, determine the grouting location based on the key layer identification method and borehole exploration results; Step 5: Construct vertical grouting boreholes at the ground locations corresponding to 1 / 4, 1 / 2, and 3 / 4 of the coal seam strike length to the designated grouting positions. Lay grouting pipes in all grouting boreholes and connect them to the ground filling station (7). Install the first valve (4), the second valve (5), and the third valve (6) on the filling pipe (1) at 3 / 4 of the coal seam strike length, the filling pipe (2) at 1 / 2 of the strike length, and the filling pipe (3) at 1 / 4 of the strike length, respectively. The first valve (4), the second valve (5), and the third valve (6) are initially closed. Step 6: Prepare the grouting fluid; Step 7: The coal mining face continues to advance. During this process, the gangue filling hydraulic support (10) is used to support the overlying roof of the goaf in the rear. At the same time, the gangue sorted underground is transported to the goaf for filling through the conveying device of the gangue filling hydraulic support (10). Step 8: When the height of the gangue filling in the goaf reaches the immediate roof or the main roof, stop the gangue filling and compact it. Step 9: After the gangue filling body (11) is compacted, the gangue filling hydraulic support (10) is retracted; Step 10: Repeat steps 7-9. During this process, when the coal face is pushed to 1 / 4 of the coal seam's strike length, open the third valve (6), and the filling station (7) starts to output the grouting fluid prepared in step 6 for grouting. The grout is output from the filling pipe (3) at 1 / 4 of the strike length to fill the resulting separation space. When the face is pushed to 1 / 2 of the coal seam's strike length, close the third valve (6) and open the second valve (5). The grout is output from the filling pipe (2) at 1 / 2 of the strike length for grouting. When the face is pushed to 3 / 4 of the coal seam's strike length, close the second valve (5) and open the first valve (4). The grout is output from the filling pipe (1) at 3 / 4 of the strike length for grouting until the coal seam is mined out. Step 11: Throughout the entire grouting process, monitor the grouting pressure at all times. If the grouting pressure suddenly increases, it indicates that the separation space is basically filled. Proceed to step 12. Step 12, open all valves, slightly slow down the grouting speed, and increase the grouting pressure. When the total mass of the grout actually flowing out of the filling station (7) is... > Mass of grout required to fill the delamination space At that time, the filling station (7) stopped grouting work; The total mass of slurry actually flowing out of filling station (7) is ,in, For the density of the slurry, V The average flow velocity of the slurry. S The cross-sectional area of ​​the grouting pipe is... t Total grouting time; Mass of grout required to fill the delamination space ,in, L 2 represents the length of the working face. E The elastic modulus of the rock layer immediately below the main key layer (9) is... q The uniformly distributed load acting on it. h The thickness of the rock layer immediately adjacent to the main key layer (9), b The deflection of the rock strata immediately below the main key stratum (9) is the length of the coal seam dip. The moment of inertia of the section of the rock layer (9) immediately below the main key layer is: .

2. The coal mine compaction combined backfilling method as described in claim 1, characterized in that, In step 2, the development height of the water-conducting fracture zone above the working face is determined by on-site drilling observation and ultrasonic imaging, and is used as the low point value for grouting.

3. The coal mine compaction combined backfilling method as described in claim 1, characterized in that, In step 2, the grouting elevation value is taken as the larger of the sum of the thickness of the Quaternary strata and the bedrock weathering zone and 0.3 times the coal seam burial depth.

4. The coal mine compaction combined backfilling method as described in claim 1, characterized in that, In step 6, the raw materials for the grouting fluid are fly ash, coal slime or coal gangue. Cement, water glass and suspending agent are used as additives in the preparation of the grout, and the water-to-solid ratio is 1:0.8 to 1:1.

3.

5. The coal mine compaction combined backfilling method as described in claim 1, characterized in that, In step 8, the baffle (13) connected to the hydraulic support is compacted by the hydraulic jack (12) pushing back and forth.

6. The coal mine compaction combined backfilling method as described in claim 1, characterized in that, In step 10, the grouting pressure is 1-5 MPa.

7. The coal mine compaction combined backfilling method as described in claim 1, characterized in that, In step 12, the grouting pressure is increased by 0.5-1 MPa.

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