Extra-thick coal seam layered top coal caving mining method

Abstract

The invention belongs to the field of coal mining, and particularly relates to an extra-thick coal seam layered top coal caving mining method. Aiming at the super-thick coal seam, the super-thick coal seam is divided into a first layer, a second layer and a plurality of top coal caving mining layers from top to bottom, the second layer is firstly mined, a caving zone after the second layer is mined is completely generated by the first layer, and a roof rock stratum is broken into regular large blocks; and mining the lower top coal layer from top to bottom by adopting a top coal mining process, and simultaneously mining the coal bulk generated by the first layer in a layered manner. Due to the fact that the roof strata are regular large blocks, roof strata gangue discrete bodies cannot be generated, the roof strata gangue discrete bodies cannot be discharged, the discharging and mining efficiency is improved, and the coal mining rate is increased. During top coal caving layered mining, the caving-mining ratio is controlled within a proper range, and coal bulk formed by a first layer is caved in a layered and batched mode, so that rotation deformation instability between adjacent blocks is avoided, and safe stoping of a working face is guaranteed.

Description

Technical Field

[0001] This invention belongs to the field of coal mining, specifically relating to a method for layered top coal caving mining of extra-thick coal seams. Background Technology

[0002] Fully mechanized top-coal caving mining technology (generally referred to as top-coal caving mining technology) is a common method for mining thick coal seams in coal mines. For coal seams with a large thickness, they are divided into upper and lower layers according to a certain ratio. The lower layer is mined by a coal mining machine. After the lower layer is mined, the upper layer is broken into loose material under the pressure of the mine and then discharged from the coal discharge port at the rear of the top-coal caving hydraulic support, thus realizing the mining of the thick coal seam. However, the applicable coal seam thickness of this mining technology is limited. When encountering extra-thick coal seams of 20 to 30 meters or more, a single top-coal caving mining operation cannot completely extract such a thick coal seam. For this, existing technologies mostly adopt layered top-coal caving mining technology, that is, dividing the extra-thick coal seam into several layers and mining the top-coal caving layer by layer.

[0003] However, stratified mining presents challenges in roadway maintenance and roof management. Researchers have proposed leveraging the crushing effect of mine pressure on the coal seam to reduce the number of stratification steps. For example, an extra-thick coal seam can be divided into upper, middle, and lower seams. The middle seam can be mined first using the full caving method, where the top coal seam is broken into loose material under mine pressure. Then, the lower seam can be mined using top-coal caving technology, simultaneously releasing the upper coal seam loose material. This reduces the number of stratification steps and improves mining efficiency. However, this method causes the roof strata above the middle seam to also become loose material during mining. This results in the release of roof strata loose material mixed with gangue. Because of the gangue in the upper coal seam loose material, when the proportion of coal released is small and the proportion of gangue is large, the upper coal seam loose material will no longer be released, leading to some upper coal seam loose material remaining unreleased and causing coal resource loss.

[0004] Furthermore, researchers proposed dividing the extra-thick coal seam into several layers, each with an added brittle layer, and then mining it layer by layer from top to bottom using top-coal caving. After each layer is mined using top-coal caving, the coal in the brittle layer breaks into loose material under mine pressure. The increased volume of the brittle layer coal is sufficient to fill the space created by the top-coal caving, thus preventing the roof strata from fracturing. Finally, a coal chute is set up in the floor strata to release all the loose coal from the brittle layer. While this mining method can improve the recovery rate, it requires a significant amount of coal chute excavation work, and the coal chute is prone to blockage during the coal release process. The final release of such a large amount of loose coal from the brittle layer will cause severe fracturing and collapse of the roof strata, easily generating significant impact pressure on the loose material below. This pressure can easily clog and damage the coal chute.

[0005] Therefore, how to improve the extraction rate of extra-thick coal seams and reduce the number of stratified mining operations, while ensuring mine pressure safety, has become an urgent technical challenge to be solved in this field. Summary of the Invention

[0006] To address the shortcomings of the existing technology, this invention proposes a method for layered top-coal caving mining of extra-thick coal seams, comprising the following steps:

[0007] S1: A super-thick coal seam with a total thickness of M is divided from top to bottom into a first layer, a second layer, and n layers of top coal caving layers; wherein the thickness of the first layer is M1, the thickness of the second layer is M2, and the thickness of each top coal caving layer is 2M3, then:

[0008] M1 + M2 + 2nM3 = M (1)

[0009] S2: Let the thicknesses of the first and second layers satisfy the following condition: the caving zone after the second layer is mined is entirely generated by the first layer, and the roof strata only generate water-conducting fracture zones; assuming the caving ratio is a, then

[0010] M1=aM2 (2)

[0011] S3: For each layer of top coal caving, half the thickness M3 is used as the machine-mined layer, and half the thickness M3 is used as the caving layer; the first layer is divided into n parts in height, and each part is released during the caving of a single layer of top coal caving. Then:

[0012] M1=n(b-1)M3 (3)

[0013] In the formula, b is the top coal release ratio, which is the ratio of the total height of the top coal released to the height of the machine-mined layer;

[0014] S4: Under the condition that formulas (1), (2), and (3) are satisfied at the same time, determine the thickness of the first layer, the second layer, and the nth layer of top coal caving;

[0015] S5: Mining the second layer, the first layer collapsed due to the mining of the second layer, becoming a collapse zone;

[0016] S6: The top coal caving mining process is adopted to mine each top coal caving layer sequentially from top to bottom, and the first layer of coal seam with a thickness of n is released.

[0017] Preferably, in step S2, the cross-mining ratio a = 5 to 7.

[0018] Preferably, in step S2, the second layer is mined using the traditional longwall caving method without venting.

[0019] Preferably, in step S3, the release-to-sampling ratio b = 2.5.

[0020] The inventive points and beneficial technical effects of this invention are as follows: 1. This invention targets extra-thick coal seams, proposing to divide them from top to bottom into a first layer, a second layer, and several top-coal caving mining layers. The second layer is mined first, ensuring that the caving zone after the second layer is entirely generated by the first layer. The roof strata are broken into regular large blocks. Then, a top-coal caving mining process is used to mine the lower top-coal caving layers from top to bottom, while simultaneously / in stages releasing the coal loose material generated by the first layer. Because the roof strata form regular large blocks, no roof rock loose material is generated, and therefore, it cannot be released. This ensures that 100% of the released material is coal, improving both the efficiency of the mining process and the coal recovery rate.

[0021] 2. Furthermore, since the roof strata are formed into regular, large blocks, they are prone to forming beam-plate stress structures during mining. If the thickness of coal released in a single operation is large, it can cause deformation and instability between adjacent blocks, which in turn impacts the hydraulic supports for top coal caving and the working face, hindering coal release operations. To address this, this invention proposes controlling the caving ratio within a suitable range and releasing the coal in batches from the first layer. This avoids reducing the amount of deformation between adjacent blocks, preventing excessive deformation and instability, thus avoiding the risk of rockburst and ensuring safe mining operations. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the layering of an extra-thick coal seam in an embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram of the structure after the second layered mining in an embodiment of the present invention;

[0024] Figure 3 This is a schematic diagram of the structure after the third layer of mining in an embodiment of the present invention;

[0025] In the diagram: First layer 1, collapse zone 11, second layer 2, third layer 3, fourth layer 4, top rock layer 5, water-conducting fracture zone 51; three-layer mining layer 31, three-layer machine-mined layer 32, first mining layer 33; four-layer mining layer 41, four-layer machine-mined layer 42, second mining layer 43. Detailed Implementation

[0026] The specific embodiments of the present invention will now be described in conjunction with the accompanying drawings.

[0027] like Figure 1-3 As shown, this invention proposes a method for layered top-coal caving mining of extra-thick coal seams, comprising the following steps:

[0028] S1: As Figure 1As shown, an extra-thick coal seam with a total thickness of M is divided from top to bottom into a first layer 1, a second layer 2, and n layers of top coal caving layers; wherein the thickness of the first layer 1 is M1, the thickness of the second layer 2 is M2, and the thickness of each top coal caving layer is 2M3, then:

[0029] M1 + M2 + 2nM3 = M (1)

[0030] S2: The thicknesses of the first layer 1 and the second layer 2 shall satisfy the following relationship: the caving zone 11 after the mining of the second layer 2 is entirely generated by the first layer 1, while the roof rock layer 5 only generates the water-conducting fracture zone 51 and does not generate the caving zone; that is, the coal seam in the first layer 1 will generate coal granules under the action of mine pressure, while the roof rock layer 5 will generate regular stratified blocks; it should be noted that only part of the roof rock layer is shown in the accompanying drawings of this invention. Generally speaking, there is also a curved subsidence zone above the water-conducting fracture zone 51; the caving zone, water-conducting fracture zone and completely subsided zone and their internal rock mass characteristics are well known in the art and will not be described in detail here.

[0031] One method in this field for calculating the height of the caving zone is to approximate it by taking several times the mining height. Assuming the caving-to-mining ratio is 'a', then...

[0032] M1=aM2 (2)

[0033] In the formula, the caving ratio a is the height of the caving zone produced by mining a coal seam with a thickness of M2. Generally, the caving ratio a = 5 to 7, that is, M1 = (5 to 7)M2. The appropriate multiple can be determined according to the specific geological conditions. In this example, 5 times the mining height is used for this calculation, that is, M1 = 5M2.

[0034] The second layer 2 can be mined using the top coal caving mining process or the traditional longwall caving method (i.e., without coal caving); in this implementation, the traditional longwall caving method is used, meaning that there is no coal caving step when mining the second layer 2.

[0035] S3: The thickness of each top coal caving layer is 2m3. It is divided into upper and lower parts based on the thickness and mined using the top coal caving mining process. The height of the caving layer does not exceed the height of the machine-mined layer. Half the thickness can be used as the machine-mined layer and half as the caving layer. For example, when the thickness of the top coal caving layer is 10m, the lower 5m can be used as the machine-mined layer and the upper 5m as the caving layer, or the lower 6m can be used as the machine-mined layer and the upper 4m as the caving layer. In this embodiment, for each top coal caving layer, half the thickness M3 is used as the machine-mined layer and half the thickness M3 is used as the caving layer.

[0036] Corresponding to the number n of top coal caving layers, the first layer 1 is divided into n parts in height, preferably equally divided into n parts. Each part is released during the top coal caving layer mining. That is, the coal bulk material generated by the first layer 1 under the mine pressure after the second layer 2 is mined is released in n stages.

[0037] M1=n(bM3-M3)=n(b-1)M3 (3)

[0038] In the formula, b is the top coal release ratio, which is the ratio of the total height of the top coal released to the height of the machine-mined layer. It is generally taken as 1:1 to 2.8, and does not exceed 1:3. In this embodiment, the height of the machine-mined layer is M3, the height of the top coal release layer in each top coal release layer is M3, and the total height of the top coal released is bM3. Then the height of the first layer released in each top coal release layer is bM3-M3. In this embodiment, b is taken as 2.5.

[0039] S4: Under the condition that formulas (1), (2), and (3) are satisfied at the same time, determine the thickness of the first layer 1, the second layer 2, and the nth layer of top coal caving; In this embodiment, the total thickness of the coal seam is 38m, the thickness of the first layer M1 is determined to be 15m, the thickness of the second layer M2 is determined to be 3m, and n=2 layers of top coal caving are arranged below the second layer 2, with thicknesses 2M3 both being 10m, which are the third layer 3 and the fourth layer 4 respectively, and the thicknesses of the machine-mined layer and the caving layer are both 5m;

[0040] S5: Mining the second layer 2, the first layer 1 collapses due to the mining of the second layer, forming a collapse zone 11, and the top rock layer 5 breaks and displaces, forming a water-conducting fracture zone 51.

[0041] S6: As Figure 2 As shown, the third layer 3 is mined using the top coal caving mining process, and the third layer machine mining layer 32 is mined using a coal mining machine. The third layer release mining layer 31 and the first layer release mining layer 33 are released through the coal discharge port of the top coal caving hydraulic support. The first layer release mining layer 33 is one-nth of the thickness of the caving zone 11 formed by the first layer 1. In this embodiment, it is 1 / 2, which corresponds to the thickness of the caving zone formed by the 7.5m thick coal seam in the lower part of the first layer 1.

[0042] S7: As Figure 3 As shown, the fourth layer 4 is mined using the top coal caving mining process, and the fourth layer 42 is mined using a coal mining machine. The fourth layer 41 and the first layer 2 caving layer 43 are released through the coal discharge port of the top coal caving hydraulic support. The first layer 2 caving layer 43 is one-nth of the thickness of the caving zone 11 formed by the first layer 1. In this embodiment, it is 1 / 2, which corresponds to the thickness of the caving zone formed by the upper 7.5m thick coal seam in the first layer 1.

[0043] This invention is not limited to the preferred embodiments described above. Anyone can derive other methods in various forms under the guidance of this invention. Any technical solution that is the same as or similar to this application falls within the protection scope of this invention.

Claims

1. A method for layered top-coal caving mining of extra-thick coal seams, characterized in that, Includes the following steps: S1: A super-thick coal seam with a total thickness of M is divided from top to bottom into a first layer, a second layer, and n layers of top coal caving layers; wherein the thickness of the first layer is M1, the thickness of the second layer is M2, and the thickness of each top coal caving layer is 2M3, then: M1 + M2 + 2nM3 = M (1) S2: Let the thicknesses of the first and second layers satisfy the following condition: the caving zone after the second layer is mined is entirely generated by the first layer, and the roof strata only generate water-conducting fracture zones; assuming the caving ratio is a, then M1 = aM2 (2) S3: For each layer of top coal caving, half the thickness M3 is used as the machine-mined layer, and half the thickness M3 is used as the caving layer; the first layer is divided into n parts in height, and each part is released during the caving of a single layer of top coal caving. Then: M1=n(b-1)M3 (3) In the formula, b is the top coal release ratio, which is the ratio of the total height of the top coal released to the height of the machine-mined layer; S4: Under the condition that formulas (1), (2), and (3) are satisfied at the same time, determine the thickness of the first layer, the second layer, and the nth layer of top coal caving; S5: Mining the second layer, the first layer collapsed due to the mining of the second layer, becoming a collapse zone; S6: The top coal caving mining process is adopted to mine each top coal caving layer sequentially from top to bottom. When mining each top coal caving layer, the first layer of coal seam with a thickness of n is released.

2. The method for layered top-coal caving mining of extra-thick coal seams according to claim 1, characterized in that, In step S2, the cross-mining ratio a = 5 to 7.

3. The method for layered top-coal caving mining of extra-thick coal seams according to claim 1, characterized in that, In step S2, the second layer is mined using the traditional longwall caving method without any release mining.

4. The method for layered top-coal caving mining of extra-thick coal seams according to claim 1, characterized in that, In step S3, the release-to-sampling ratio b = 2.5.

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