Measurement instrument and measurement method for residual crushing and swelling coefficient of caving zone rock mass after coal seam mining

Abstract

The invention discloses a coal seam post-mining caving zone rock residual breaking coefficient measuring instrument which comprises a servo universal testing machine, a first hydraulic system fixed at the top of the inner side of the servo universal testing machine, an upper pressure head fixed at the bottom of the first hydraulic system, a second hydraulic system fixed at the bottom of the inner side of the servo universal testing machine, and a lower pressure head fixed at the bottom of the second hydraulic system. A lower pressing head is fixed to the bottom of the second hydraulic system, a loading system is clamped between the upper pressing head and the lower pressing head, a plurality of rock stratum blocks are installed in the loading system, a sliding system is installed between the bottommost rock stratum block and the lower pressing head, and the first hydraulic system and the second hydraulic system are in common signal connection with an operation instrument. According to the method, the caving form, the component characteristics and the grading characteristics of the caving rock in the goaf are fully considered, the calculation result is more practical, and the problems of high cost, high difficulty and large error in the previous residual fragmentation coefficient obtaining process are solved.

Description

Technical Field

[0001] This invention belongs to the field of coal seam mining technology, and relates to an instrument for measuring the residual fragmentation coefficient of rock blocks in the post-mining caving zone of a coal seam. This invention also relates to a method for measuring the residual fragmentation coefficient of rock blocks in the post-mining caving zone of a coal seam. Background Technology

[0002] During coal mining, the morphology, lithology, and thickness of the collapsed rock mass in the goaf are key factors affecting the subsidence of the overburden. Currently, the measurement of the rock fragmentation coefficient is mostly limited to laboratory settings and experimental equipment to measure rock samples. However, laboratory measurements cannot accurately reflect the collapse morphology, gradation, composition, and contact form of the rock mass in the goaf, resulting in significant errors between the measurement results and the actual situation. These errors will cause huge inaccuracies in the prediction of surface subsidence and delamination grouting. Summary of the Invention

[0003] The purpose of this invention is to provide an instrument for measuring the residual fragmentation coefficient of rock blocks in the post-mining caving zone of coal seams, which solves the problem of large errors in the acquisition of the residual fragmentation coefficient in the existing technology.

[0004] The second objective of this invention is to provide a method for determining the residual fragmentation coefficient of rock blocks in the post-mining caving zone of coal seams.

[0005] The first technical solution adopted in this invention is an instrument for measuring the residual fragmentation coefficient of rock blocks in the post-mining caving zone of a coal seam, including a servo universal testing machine. A first hydraulic system is fixed to the top of the inner side of the servo universal testing machine, and an upper pressure head is fixed to the bottom of the first hydraulic system. A second hydraulic system is fixed to the bottom of the inner side of the servo universal testing machine, and a lower pressure head is fixed to the bottom of the second hydraulic system. A loading system is engaged between the upper pressure head and the lower pressure head. Multiple rock blocks are installed inside the loading system. A sliding system is installed between the bottommost rock block and the lower pressure head. The first hydraulic system and the second hydraulic system are connected to an operating instrument via a common signal.

[0006] The first technical solution of this invention is also characterized by: The servo universal testing machine has a display system on its outside, which is connected to the operator's signal.

[0007] The loading system includes a test cylinder with square openings at both ends. Multiple rock blocks are installed inside the test cylinder, with the top of the top rock block abutting against the upper pressure head. A gap is opened on one side of the test cylinder at the position corresponding to the sliding system. The test cylinder is fixed to the bottom of the servo universal testing machine by several support columns.

[0008] The sliding system includes a sliding plate, which is placed on the lower pressure head and extends from one end through the gap. Several sliders are placed on the top of the sliding plate along the extension direction.

[0009] The second technical solution adopted in this invention is a method for determining the residual fragmentation coefficient of rock blocks in the post-mining caving zone of coal seams, comprising the following steps: Step 1: Calculate the ratio of the caving height, the test cylinder height to the caving height; Step 2: Drill exploration holes into the top plate of the working face. The endpoint of the exploration holes is located at the top boundary of the caving zone. Calculate the thickness of each rock layer corresponding to the rock block in the test cylinder. Step 3: Calculate the composition and gradation characteristics of the rock blocks in the test chamber, and calculate the side length of the rock blocks in the test chamber; Step 4: Calculate the load on the upper part of the caving zone rock block; Step 5: Calculate the residual fragmentation coefficient of the caving zone rock blocks.

[0010] The second technical solution of the present invention is further characterized by: Step 1 is performed as follows: Step 1.1, calculate the height of the landslide zone using the following formulas: H k =4 M

[0011] H k =K M in, H k The height of the landslide zone is in meters (m). M Where is the coal seam thickness (m); K is the caving ratio, and the maximum value of the caving zone height among the three is taken as the subsequent caving zone height. Step 1.2, Calculate the height of the test cylinder. H k 'and the height of the landslide zone' H k The ratio of .

[0012] Step 2 is performed as follows: Step 2.1: Drill core samples from the working face roadway toward the working face. The final hole location is at the top boundary of the caving zone. Record the lithology and thickness of the core samples during the drilling process. Step 2.2, calculate the thickness of each rock layer in the test chamber:

[0013] in, h n ' The thickness of each rock layer in the test cylinder, h n This represents the thickness of each rock layer in the collapse zone.

[0014] Step 3 is performed as follows: Step 3.1: By calculating the proportions based on the lithology and thickness of the rock strata within the caving zone, the compositional characteristics of the rock blocks within the caving zone (h1:h2:h3...h) are obtained. n ; Step 3.2: Calculate the caving step distance of different lithological strata by testing the mechanical parameters of rock samples of different lithologies.

[0015] in, l k The breakage distance, h k For the first k Thickness of the rock strata, in meters; σ k For the first k Tensile strength of the rock strata, MPa; q k For the first k The load borne by the rock strata, MPa; the gradation characteristics of the collapsed rock blocks in the goaf caving zone are obtained: l1:l2:l3...l n ; Depend on m The load on the bottommost rock beam in the rock beam group formed by layered rock beams is:

[0016] in,( qm 1 represents the load, in MPa; Ei For the first i Elastic modulus of the layered rock beam, MPa; hi For the first i Thickness of the layered rock beam, in meters (m); ri For the first i Unit weight of layered rock beam, N·m⁻³; like Then determine the first i +1 is the critical layer; if the first layer is the key layer; i Layer and first i +2 is the critical layer, the first k The layer is located at the first i Layer and first i Between +2 layers, then the first k The load borne by the layer is: ; Step 3.3, calculate the side length of the rock block inside the test cylinder:

[0017] Among them, l n' is the side length of the rock block inside the test cylinder, l n This represents the caving step distance of the rock blocks within the caving zone.

[0018] The load on the upper part of the caving zone rock block in step 4 is:

[0019] in, q The load on the upper part of the caving zone rock block. m This represents the number of rock layers in the rock block. x This is the key layer closest to the goaf.

[0020] Step 5 is performed as follows: Step 5.1: Record the volume V of the test cylinder; Step 5.2: Process the rock blocks in the caving zone into multiple rock layer blocks that are compatible with the test cylinder, and load the multiple rock layer blocks into the test cylinder in the order of the rock layers in the caving zone. Step 5.3: Start the first hydraulic system via the operating instrument to maintain the initial pressure of the upper pressure head. The initial pressure is:

[0021] in, n This refers to the number of rock layers between the caving zone and the surface. Step 5.4: Pull the sliding plate outward to simulate coal seam mining. After the sliding plate is pulled to the end, let it stand for 20-30 minutes. Step 5.5, adjust the pressure of the upper pressure head to... q After the rock strata collapse, hold them for 20-30 minutes and record the total volume V' of the rock strata at this time. Calculate the residual fragmentation coefficient of the rock strata in the collapse zone.

[0022] in, Kρ The residual fragmentation coefficient of the caving zone rock blocks.

[0023] The beneficial effects of this invention are: This invention first calculates the development height of the collapse zone in the goaf, and obtains the lithology and thickness data of the rock strata within the collapse zone height through core drilling. Rock mechanics testing is used to obtain the compressive, tensile, and unit weight parameters of the rock. Based on this, the compositional and gradation characteristics of the collapsed rock mass in the goaf are calculated. The load above the collapsed rock mass is calculated using key layer theory. Finally, the above data guides the parameter settings of the subsequent servo universal testing machine, ultimately calculating the residual fragmentation coefficient of the collapsed rock blocks in the goaf. This fully considers the collapse morphology, compositional characteristics, and gradation characteristics of the collapsed rock blocks in the goaf, resulting in calculation results that are more realistic and solve the problems of high cost, high difficulty, and large errors in obtaining the residual fragmentation coefficient in the past. Attached Figure Description

[0024] Figure 1 This is a structural diagram of the instrument of the present invention; Figure 2 This is a side view of the instrument of the present invention; Figure 3 This is a flowchart of the present invention; Figure 4 This is a schematic diagram of the rock strata combination of the present invention.

[0025] In the figure, 1. Servo universal testing machine, 2. Operator, 3. First hydraulic system, 4. Upper pressure head, 5. Test cylinder, 6. Rock block, 7. Slider, 8. Sliding plate, 9. Support column, 10. Lower pressure head, 11. Second hydraulic system, 12. Display system. Detailed Implementation

[0026] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0027] Instrument for measuring the residual fragmentation coefficient of rock blocks in the post-mining caving zone of coal seams (see [reference]). Figure 1 , Figure 2 The system includes a servo universal testing machine 1, a first hydraulic system 3 fixed to the top of the inner side of the servo universal testing machine 1, an upper pressure head 4 fixed to the bottom of the first hydraulic system 3, a second hydraulic system 11 fixed to the bottom of the inner side of the servo universal testing machine 1, a lower pressure head 10 fixed to the bottom of the second hydraulic system 11, a loading system connected between the upper pressure head 4 and the lower pressure head 10, multiple rock strata blocks 6 installed inside the loading system, a sliding system installed between the bottommost rock strata block 6 and the lower pressure head 10, the first hydraulic system 3 and the second hydraulic system 11 are connected to an operating instrument 2, and a display system 12 is placed on the outside of the servo universal testing machine 1, the display system 12 is connected to the operating instrument 2, and is used to display the pressure of the first hydraulic system 3 and the second hydraulic system 11.

[0028] The loading system includes a test cylinder 5 with square openings at both ends. Multiple rock blocks 6 are installed inside the test cylinder 5. The top of the top rock block 6 abuts against the upper pressure head 4. A gap is opened on one side of the test cylinder 5 at the position corresponding to the sliding system. The test cylinder 5 is fixed to the bottom of the servo universal testing machine 1 by several support columns 9.

[0029] The sliding system includes a sliding plate 8, which is placed on the pressure head 10 and extends out of the gap at one end. Several sliders 7 are placed on the top of the sliding plate 8 along the extension direction. When the sliding plate 8 is pulled outward, the sliders 7 move downward in sequence. The sliders 7 of different specifications have different end heights to provide different sliding amounts.

[0030] Method for determining the residual fragmentation coefficient of rock blocks in the post-mining caving zone of coal seams, see [link to relevant documentation]. Figure 3 This includes the following steps: Step 1: Calculate the caving zone height using empirical formulas, field measurements, and the "Three-Under Specifications" (specifications for the retention of coal pillars and the mining of coal under pressure in buildings, water bodies, railways, and main shafts). Empirical formula: H k =4 M "Three-level regulations":

[0031] On-site measurement: H k =K M in, H k The height of the landslide zone is in meters (m). M Where is the coal seam thickness (m); K is the caving ratio, and the maximum value of the caving zone height among the three is taken as the subsequent caving zone height. Calculate the height of test cylinder 5 H k 'and the height of the landslide zone' H k The ratio; Step 2: Drill core samples from the working face roadway toward the working face. The final hole location is at the top boundary of the caving zone. Record the lithology and thickness of the core samples during the drilling process. Calculate the thickness of each rock layer inside test cylinder 5:

[0032] in, h n ' The thickness of each rock layer in test cylinder 5, h n The thickness of each rock layer in the collapse zone; Step 3: Calculate the proportions based on the lithology and thickness of the rock strata within the caving zone (see Table 1) to obtain the compositional characteristics of the rock blocks within the caving zone: h1:h2:h3...h n ; Table 1. Overview of Lithology and Thickness within the Collapse Zone

[0033] By testing the mechanical parameters of rock samples of different lithologies, the caving step distance of different lithological layers was calculated:

[0034] in, l k The breakage distance, h k For the first kThickness of the rock strata, in meters; σ k For the first k Tensile strength of the rock strata, MPa; q k For the first k The load borne by the rock strata, MPa; see Table 2, the gradation characteristics of the collapsed rock blocks in the goaf collapse zone are obtained l1:l2:l3...l n ; Table 2. Overview of the gradation characteristics of rock blocks within the caving zone

[0035] Depend on m The load on the bottommost rock beam in the rock beam group formed by layered rock beams is:

[0036] in,( qm 1 represents the load, in MPa; Ei For the first i Elastic modulus of the layered rock beam, MPa; hi For the first i Thickness of the layered rock beam, in meters (m); ri For the first i Unit weight of layered rock beam, N·m⁻³; like Then determine the first i +1 is the critical layer; if the first layer is the key layer; i Layer and first i +2 is the critical layer, the first k The layer is located at the first i Layer and first i Between +2 layers, then the first k The load borne by the layer is: ; Calculate the side length of the rock block inside test cylinder 5:

[0037] Among them, l n ' is the side length of the rock block inside test cylinder 5, l n This represents the caving step distance of the rock blocks within the caving zone; Step 4: Calculate the load on the upper part of the caving zone rock block:

[0038] in, q The load on the upper part of the caving zone rock block. m This represents the number of rock layers in the rock block. x This is the key layer closest to the goaf. Step 5: Record the volume V of the test cylinder 5. Process the caving zone rock blocks into multiple rock layer blocks 6 that fit the test cylinder 5. Load the multiple rock layer blocks 6 into the test cylinder 5 according to the order of the rock layers in the caving zone. Select appropriate sliders 7 and sliding plates 8 to ensure that the sliding amount of slider 7 is the same as the simulated coal seam thickness. Start the first hydraulic system 3 through the operating instrument 2 to maintain the initial pressure of the upper pressure head 4. The initial pressure is:

[0039] in, n This refers to the number of rock layers between the caving zone and the surface. Pull the sliding plate 8 outward to simulate coal seam mining. After the sliding plate 8 is fully pulled, let it stand for 20-30 minutes, then adjust the pressure of the upper pressure head 4 to... q After the collapse of rock block 6, hold it for 20-30 minutes and record the total volume V' of rock block 6 at this time. Calculate the residual fragmentation coefficient of the rock blocks in the collapse zone.

[0040] in, Kρ The residual fragmentation coefficient of the caving zone rock blocks.

[0041] Example 1: An instrument for measuring the residual fragmentation coefficient of rock blocks in the post-mining caving zone of a coal seam includes a servo universal testing machine 1. A first hydraulic system 3 is fixed to the top of the inner side of the servo universal testing machine 1. An upper pressure head 4 is fixed to the bottom of the first hydraulic system 3. A second hydraulic system 11 is fixed to the bottom of the inner side of the servo universal testing machine 1. A lower pressure head 10 is fixed to the bottom of the second hydraulic system 11. A loading system is engaged between the upper pressure head 4 and the lower pressure head 10. Multiple rock blocks 6 are installed inside the loading system. A sliding system is installed between the bottommost rock block 6 and the lower pressure head 10. The first hydraulic system 3 and the second hydraulic system 11 are connected to an operating instrument 2 via a common signal. A display system 12 is placed on the outside of the servo universal testing machine 1. The display system 12 is connected to the operating instrument 2 via a signal.

[0042] The loading system includes a test cylinder 5 with square openings at both ends. Multiple rock blocks 6 are installed inside the test cylinder 5. The top of the top rock block 6 abuts against the upper pressure head 4. A gap is opened on one side of the test cylinder 5 at the position corresponding to the sliding system. The test cylinder 5 is fixed to the bottom of the servo universal testing machine 1 by several support columns 9.

[0043] Example 2: An instrument for measuring the residual fragmentation coefficient of rock blocks in the post-mining caving zone of a coal seam includes a servo universal testing machine 1. A first hydraulic system 3 is fixed to the top of the inner side of the servo universal testing machine 1. An upper pressure head 4 is fixed to the bottom of the first hydraulic system 3. A second hydraulic system 11 is fixed to the bottom of the inner side of the servo universal testing machine 1. A lower pressure head 10 is fixed to the bottom of the second hydraulic system 11. A loading system is engaged between the upper pressure head 4 and the lower pressure head 10. Multiple rock blocks 6 are installed inside the loading system. A sliding system is installed between the bottommost rock block 6 and the lower pressure head 10. The first hydraulic system 3 and the second hydraulic system 11 are connected to an operating instrument 2 via a common signal.

[0044] The loading system includes a test cylinder 5 with square openings at both ends. Multiple rock blocks 6 are installed inside the test cylinder 5. The top of the top rock block 6 abuts against the upper pressure head 4. A gap is opened on one side of the test cylinder 5 at the position corresponding to the sliding system. The test cylinder 5 is fixed to the bottom of the servo universal testing machine 1 by several support columns 9.

[0045] The sliding system includes a sliding plate 8, which is placed on the lower pressure head 10 and extends out of the gap at one end. Several sliders 7 are placed on the top of the sliding plate 8 along the extension direction.

[0046] Example 3: Method for determining the residual fragmentation coefficient of rock blocks in the post-mining caving zone of coal seams: The stratigraphic and mechanical parameter data of a mine in Inner Mongolia and Shaanxi were selected for modeling and calculation, as shown in Table 3.

[0047] Table 3 Parameter Calculation Table

[0048] Step 1: Calculate the development height of the caving zone: First, collect coal seam thickness data of the working face. The coal seam thickness of a certain working face in Inner Mongolia and Shaanxi is 6m. The empirical formula calculates the caving zone height to be 24m. The "three-under" standard calculates the caving zone height to be 11.3m. The actual measured caving zone height is 30m. The maximum calculated value of 30m is taken as the caving zone height. Calculate the similarity ratio: The height of test cylinder 5 is 0.3m, the height of the collapse zone is 30m, and the similarity ratio is 1:100.

[0049] Step 2: Core drilling is carried out from the working face roadway to the working face. The calculated height of the caving zone is 30m, and the final hole position is 30m above the coal seam roof. During drilling, the lithology and thickness of the core samples were recorded, see Table 4.

[0050] Table 4. Overview of Lithology and Thickness within the Collapse Zone

[0051] Calculate the thickness of the rock layers in test chamber 5: With a similarity ratio of 1:100, the thicknesses of each rock layer in test chamber 5 are 0.05m, 0.05m, 0.06m, 0.06m, and 0.08m, as shown in Table 5. Table 5. Summary of simulated rock layer thicknesses in the model

[0052] Step 3: Calculate the composition and gradation characteristics of the rock strata within the caving zone, and calculate the length and width of the rock block in test cylinder 5. The composition characteristics of the rock strata within the caving zone are: sandy mudstone: medium sandstone: sandy mudstone: coarse sandstone: fine sandstone = 5:5:6:6:8. Gradation characteristics of rock strata within the caving zone: Calculate the breaking moment of each rock stratum (see Table 6). The ratio of sandy mudstone: medium sandstone: sandy mudstone: coarse sandstone: fine sandstone is 30:22:33:22:36. Calculate the length-to-thickness ratio of each rock stratum and use this to calculate the length of the rock strata within the caving zone in the model. The width is the same as the length. Calculate the length and width l of each rock block within test cylinder 5. n '; Table 6 Calculation results of fracture distance

[0053] Step 4: Calculate the upper load of the rock block in the caving zone. The upper load of the rock block in the caving zone is 0.09 MPa. Table 7 Parameter Summary Table

[0054] Step 5: The dimensions of test cylinder 5 are 0.3m. 0.3m If the height is 0.3m, then the volume of the collapsed rock block is V = 0.027m³. 3 Core samples from the roof collapse zone were prepared into multiple rock strata blocks 6 and sequentially filled into the test cylinder 5. The first hydraulic system 3 was activated via the operating instrument 2 to maintain the initial pressure of the upper pressure head 4. The initial pressure was determined based on the density and thickness of the rock strata above the collapse zone, and was 1.135 MPa. The sliding plate 8 was pulled outwards, causing the slider 7 to descend under its own weight and the pressure of the upper rock strata blocks 6. The end height of the sliding plate 8 was 0.6 m to simulate coal seam mining. After the sliding plate 8 reached its end, it was left to stand for 20 minutes. The pressure of the upper pressure head 4 was then adjusted to compress the collapsed rock sample, with a pressure of 0.09 MPa maintained for 20 minutes. Once the upper pressure head 4 stopped moving downwards, the total volume of the rock strata block was recorded as V' = 0.028. The residual fragmentation coefficient of the collapse zone was then determined. Kρ =1.04.

[0055] Example 4: A method for determining the residual fragmentation coefficient of rock blocks in the post-mining caving zone of a coal seam includes the following steps: Step 1: Calculate the height of the landslide zone using the following formulas: H k =4 M

[0056] H k =K M in, H k The height of the landslide zone is in meters (m). M Where is the coal seam thickness (m); K is the caving ratio, and the maximum value of the caving zone height among the three is taken as the subsequent caving zone height. Calculate the height of test cylinder 5 H k 'and the height of the landslide zone' H k The ratio; Step 2: Drill core samples from the working face roadway toward the working face. The final hole location is at the top boundary of the caving zone. Record the lithology and thickness of the core samples during the drilling process. Calculate the thickness of each rock layer inside test cylinder 5:

[0057] in, h n ' The thickness of each rock layer in test cylinder 5, h n The thickness of each rock layer in the collapse zone; Step 3: Calculate the composition and gradation characteristics of the rock block in test cylinder 5, and calculate the side length of the rock block in test cylinder 5; Step 4: Calculate the load on the upper part of the caving zone rock block; Step 5: Calculate the residual fragmentation coefficient of the caving zone rock blocks.

[0058] Example 5: A method for determining the residual fragmentation coefficient of rock blocks in the post-mining caving zone of a coal seam includes the following steps: Step 1: Calculate the height of the landslide zone using the following formulas: H k =4 M

[0059] H k =K M in, H k The height of the landslide zone is in meters (m). M Where is the coal seam thickness (m); K is the caving ratio, and the maximum value of the caving zone height among the three is taken as the subsequent caving zone height. Calculate the height of test cylinder 5 H k 'and the height of the landslide zone' H k The ratio; Step 2: Drill core samples from the working face roadway toward the working face. The final hole location is at the top boundary of the caving zone. Record the lithology and thickness of the core samples during the drilling process. Calculate the thickness of each rock layer inside test cylinder 5:

[0060] in, h n ' The thickness of each rock layer in test cylinder 5, h n The thickness of each rock layer in the collapse zone; Step 3: By analyzing the lithology and thickness of the rock strata within the caving zone, calculate the proportions to obtain the compositional characteristics of the rock blocks within the caving zone: h1:h2:h3...h n ; By testing the mechanical parameters of rock samples of different lithologies, the caving step distance of different lithological layers was calculated:

[0061] in, l k The breakage distance, h k For the first k Thickness of the rock strata, in meters; σ k For the first k Tensile strength of the rock strata, MPa; q k For the first k The load borne by the rock strata, MPa; the gradation characteristics of the collapsed rock blocks in the goaf caving zone are obtained: l1:l2:l3...l n ; Depend on m The load on the bottommost rock beam in the rock beam group formed by layered rock beams is:

[0062] in,( qm 1 represents the load, in MPa; Ei For the first iElastic modulus of the layered rock beam, MPa; hi For the first i Thickness of the layered rock beam, in meters (m); ri For the first i Unit weight of layered rock beam, N·m⁻³; like Then determine the first i +1 is the critical layer; if the first layer is the key layer; i Layer and first i +2 is the critical layer, the first k The layer is located at the first i Layer and first i Between +2 layers, then the first k The load borne by the layer is: ; Calculate the side length of the rock block inside test cylinder 5:

[0063] Among them, l n ' is the side length of the rock block inside test cylinder 5, l n This represents the caving step distance of the rock blocks within the caving zone; Step 4: Calculate the load on the upper part of the caving zone rock block:

[0064] in, q The load on the upper part of the caving zone rock block. m This represents the number of rock layers in the rock block. x This is the key layer closest to the goaf. Step 5: Record the volume V of the test cylinder 5. Process the landslide rock blocks into multiple rock layer blocks 6 that fit the test cylinder 5. Load the multiple rock layer blocks 6 into the test cylinder 5 according to the order of the rock layers in the landslide rock blocks. Start the first hydraulic system 3 through the operating instrument 2 to maintain the initial pressure of the upper pressure head 4. The initial pressure is:

[0065] in, n This refers to the number of rock layers between the caving zone and the surface. Pull the sliding plate 8 outward to simulate coal seam mining. After the sliding plate 8 is fully pulled, let it stand for 25 minutes, then adjust the pressure of the upper pressure head 4 to... q After the collapse of rock block 6, hold it for 25 minutes and record the total volume V' of rock block 6 at this time. Calculate the residual fragmentation coefficient of the rock blocks in the collapse zone:

[0066] in, Kρ The residual fragmentation coefficient of the caving zone rock blocks.

[0067] Example 6: A method for determining the residual fragmentation coefficient of rock blocks in the post-mining caving zone of a coal seam includes the following steps: Step 1: Calculate the height of the landslide zone using the following formulas: H k =4 M

[0068] H k =K M in, H k The height of the landslide zone is in meters (m). M Where is the coal seam thickness (m); K is the caving ratio, and the maximum value of the caving zone height among the three is taken as the subsequent caving zone height. Calculate the height of test cylinder 5 H k 'and the height of the landslide zone' H k The ratio; Step 2: Drill core samples from the working face roadway toward the working face. The final hole location is at the top boundary of the caving zone. Record the lithology and thickness of the core samples during the drilling process. Calculate the thickness of each rock layer inside test cylinder 5:

[0069] in, h n ' The thickness of each rock layer in test cylinder 5, h n The thickness of each rock layer in the collapse zone; Step 3: By analyzing the lithology and thickness of the rock strata within the caving zone, calculate the proportions to obtain the compositional characteristics of the rock blocks within the caving zone: h1:h2:h3...h n ; By testing the mechanical parameters of rock samples of different lithologies, the caving step distance of different lithological layers was calculated:

[0070] in, l k The breakage distance, h k For the first k Thickness of the rock strata, in meters; σ k For the first k Tensile strength of the rock strata, MPa; qk For the first k The load borne by the rock strata, MPa; the gradation characteristics of the collapsed rock blocks in the goaf caving zone are obtained: l1:l2:l3...l n ; Depend on m The load on the bottommost rock beam in the rock beam group formed by layered rock beams is:

[0071] in,( qm 1 represents the load, in MPa; Ei For the first i Elastic modulus of the layered rock beam, MPa; hi For the first i Thickness of the layered rock beam, in meters (m); ri For the first i Unit weight of layered rock beam, N·m⁻³; like Then determine the first i +1 is the critical layer; if the first layer is the key layer; i Layer and first i +2 is the critical layer, the first k The layer is located at the first i Layer and first i Between +2 layers, then the first k The load borne by the layer is: ; Calculate the side length of the rock block inside test cylinder 5:

[0072] Among them, l n ' is the side length of the rock block inside test cylinder 5, l n This represents the caving step distance of the rock blocks within the caving zone; Step 4: Calculate the load on the upper part of the caving zone rock block:

[0073] in, q The load on the upper part of the caving zone rock block. m This represents the number of rock layers in the rock block. x This is the key layer closest to the goaf. Step 5: Record the volume V of the test cylinder 5. Process the landslide rock blocks into multiple rock layer blocks 6 that fit the test cylinder 5. Load the multiple rock layer blocks 6 into the test cylinder 5 according to the order of the rock layers in the landslide rock blocks. Start the first hydraulic system 3 through the operating instrument 2 to maintain the initial pressure of the upper pressure head 4. The initial pressure is:

[0074] in, nThis refers to the number of rock layers between the caving zone and the surface. Pull the sliding plate 8 outward to simulate coal seam mining. After the sliding plate 8 is fully pulled, let it stand for 30 minutes, then adjust the pressure of the upper pressure head 4 to... q After the collapse of rock block 6, hold it for 30 minutes and record the total volume V' of rock block 6 at this time. Calculate the residual fragmentation coefficient of the rock blocks in the collapse zone:

[0075] in, Kρ The residual fragmentation coefficient of the caving zone rock blocks.

Claims

1. An instrument for measuring the residual fragmentation coefficient of rock blocks in the post-mining caving zone of a coal seam, characterized in that, The servo universal testing machine (1) includes a first hydraulic system (3) fixed on the top of the inner side of the servo universal testing machine (1), an upper pressure head (4) fixed at the bottom of the first hydraulic system (3), a second hydraulic system (11) fixed at the bottom of the inner side of the servo universal testing machine (1), a lower pressure head (10) fixed at the bottom of the second hydraulic system (11), a loading system is connected between the upper pressure head (4) and the lower pressure head (10), a plurality of rock blocks (6) are installed inside the loading system, and a sliding system is installed between the bottommost rock block (6) and the lower pressure head (10). The first hydraulic system (3) and the second hydraulic system (11) are connected to an operator (2) via a common signal.

2. The instrument for determining the residual fragmentation coefficient of rock blocks in the post-mining caving zone of a coal seam according to claim 1, characterized in that, A display system (12) is placed on the outside of the servo universal testing machine (1), and the display system (12) is connected to the operator (2) via signal.

3. The instrument for determining the residual fragmentation coefficient of rock blocks in the post-mining caving zone of a coal seam according to claim 1 or 2, characterized in that, The loading system includes a test cylinder (5), which has square openings at both ends. Multiple rock blocks (6) are installed inside the test cylinder (5). The top of the top rock block (6) abuts against the upper pressure head (4). A gap is opened on one side of the test cylinder (5) at the position corresponding to the sliding system. The test cylinder (5) is fixed to the bottom of the servo universal testing machine (1) by several support columns (9).

4. The instrument for determining the residual fragmentation coefficient of rock blocks in the post-mining caving zone of a coal seam according to claim 3, characterized in that, The sliding system includes a sliding plate (8), which is placed on the lower pressure head (10) and one end extends out of the gap. Several sliders (7) are placed on the top of the sliding plate (8) along the extension direction.

5. A method for determining the residual fragmentation coefficient of rock blocks in the post-mining caving zone of a coal seam, characterized in that, Using the instrument for determining the residual fragmentation coefficient of rock blocks in the post-mining caving zone of coal seams as described in claim 4, the following steps are included: Step 1: Calculate the ratio of the caving zone height and the height of the test cylinder (5) to the caving zone height; Step 2: Construct exploration holes in the top plate of the working face. The endpoint of the exploration holes is located at the top boundary of the collapse zone. Calculate the thickness of each rock layer corresponding to the rock block in the test cylinder (5). Step 3: Calculate the composition and gradation characteristics of the rock blocks in the test cylinder (5), and calculate the side length of the rock blocks in the test cylinder (5); Step 4: Calculate the load on the upper part of the caving zone rock block; Step 5: Calculate the residual fragmentation coefficient of the caving zone rock blocks.

6. The method for determining the residual fragmentation coefficient of rock blocks in the post-mining caving zone of a coal seam according to claim 5, characterized in that, Step 1 is performed as follows: Step 1.1, calculate the height of the landslide zone using the following formulas: H k =4 M H k =K M in, H k The height of the landslide zone is in meters (m). M Where is the coal seam thickness (m); K is the caving ratio, and the maximum value of the caving zone height among the three is taken as the subsequent caving zone height. Step 1.2, calculate the height of the test cylinder (5). H k 'and the height of the landslide zone' H k The ratio of .

7. The method for determining the residual fragmentation coefficient of rock blocks in the post-mining caving zone of a coal seam according to claim 6, characterized in that, Step 2 is performed as follows: Step 2.1: Drill core samples from the working face roadway toward the working face. The final hole location is at the top boundary of the caving zone. Record the lithology and thickness of the core samples during the drilling process. Step 2.2, calculate the thickness of each rock layer in the test cylinder (5): in, h n ' The thickness of each rock layer in the test cylinder (5) h n This represents the thickness of each rock layer in the collapse zone.

8. The method for determining the residual fragmentation coefficient of rock blocks in the post-mining caving zone of a coal seam according to claim 7, characterized in that, Step 3 is performed as follows: Step 3.1: By calculating the proportions based on the lithology and thickness of the rock strata within the caving zone, the compositional characteristics of the rock blocks within the caving zone (h1:h2:h3...h) are obtained. n ; Step 3.2: Calculate the caving step distance of different lithological strata by testing the mechanical parameters of rock samples of different lithologies. in, l k The breakage distance, h k For the first k Thickness of the rock strata, in meters; σ k For the first k Tensile strength of the rock strata, MPa; q k For the first k The load borne by the rock strata, MPa; the gradation characteristics of the collapsed rock blocks in the goaf caving zone are obtained: l1:l2:l3...l n ; Depend on m The load on the bottommost rock beam in the rock beam group formed by layered rock beams is: in,( qm 1 represents the load, in MPa; Ei For the first i Elastic modulus of the layered rock beam, MPa; hi For the first i Thickness of the layered rock beam, in meters (m); ri For the first i Unit weight of layered rock beam, N·m⁻³; like Then determine the first i +1 is the critical layer; if the first layer is the key layer; i Layer and first i +2 is the critical layer, the first k The layer is located at the first i Layer and first i Between +2 layers, then the first k The load borne by the layer is: ； Step 3.3, calculate the side length of the rock block inside the test cylinder (5): Among them, l n ' is the side length of the rock block inside the test cylinder (5), l n This represents the caving step distance of the rock blocks within the caving zone.

9. The method for determining the residual fragmentation coefficient of rock blocks in the post-mining caving zone of a coal seam according to claim 8, characterized in that, The load on the upper part of the caving zone rock block in step 4 is: in, q The load on the upper part of the caving zone rock block. m This represents the number of rock layers in the rock block. x This is the key layer closest to the goaf.

10. The method for determining the residual fragmentation coefficient of rock blocks in the post-mining caving zone of a coal seam according to claim 9, characterized in that, Step 5 is performed as follows: Step 5.1, record the volume V of the test cylinder (5); Step 5.2: Process the rock blocks in the caving zone into multiple rock layer blocks (6) that are compatible with the test cylinder (5), and load the multiple rock layer blocks (6) into the test cylinder (5) in the order of the rock layers in the caving zone. Step 5.3: Start the first hydraulic system (3) using the operating instrument (2) to maintain the initial pressure of the upper pressure head (4). The initial pressure is: in, n This refers to the number of rock layers between the caving zone and the surface. Step 5.4: Pull the sliding plate (8) outward to simulate the coal seam mining situation. After the sliding plate (8) is pulled to the end, let it stand for 20-30 minutes. Step 5.5, adjust the pressure of the upper pressure head (4) to... q After the rock stratum (6) is crushed, it is held for 20-30 minutes. The total volume V' of the rock stratum (6) is recorded at this time. The residual fragmentation coefficient of the rock block in the collapse zone is calculated: in, Kρ The residual fragmentation coefficient of the caving zone rock blocks.

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