Method for predicting vertical subsidence of repeated mining overlying strata under coal pillar group
By constructing a prediction model for vertical subsidence of overburden under repeated mining of coal pillar groups, the problem of accurately predicting vertical subsidence of overburden under repeated mining of coal pillar groups was solved, realizing accurate prediction and effective management of overburden subsidence during deep coal seam mining.
Patent Information
- Application Number
- CN202510917137.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-03
- Publication Date
- 2025-11-21
AI Technical Summary
The lack of effective methods for predicting vertical subsidence of overburden under repeated mining in existing technologies makes it difficult to accurately predict the impact of vertical subsidence of overburden during deep coal seam mining, which affects the surface ecological environment.
The vertical subsidence of the overburden caused by repeated mining under the coal pillar group is equivalently converted into the superimposed effects of coal seam mining and coal pillar group fracturing under the coal pillar group. A prediction model for vertical subsidence of the overburden group is constructed, and a prediction method for vertical subsidence of the overburden group is established through stochastic medium theory and coordinate system transformation.
The method achieves accurate prediction of vertical subsidence of overburden, with a low average absolute error between the prediction results and the measured values, verifying the accuracy and effectiveness of the method and meeting the needs of deep coal seam mining.
Smart Images
Figure CN120995650A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of subsidence prediction, and more particularly to a method for predicting vertical subsidence of overburden under repeated mining of coal pillar groups. Background Technology
[0002] In the early days, coal mining equipment and technology were not advanced, and many coal mines adopted the room-type mining method, using coal pillars as a roof support. This method has a short construction period, low equipment investment, and simple operation. However, due to the backward production technology, the production process not only wastes a lot of coal resources, but also the coal pillar groups left behind can become unstable over time or due to the influence of underground mining activities, posing a potential impact on the surface ecological environment.
[0003] As mining activities continue, exploitable shallow mineral resources are dwindling, leading many mining areas to gradually engage in deeper coal seam mining, resulting in repeated mining under coal pillars. The mining impact under coal pillars can cause instability and subsequent collapse of the pillars. Therefore, when conducting mining activities under coal pillars, the disturbance effects of pillar collapse on the surface and overburden must be considered. Many Chinese scholars have studied the instability and stability of coal pillars left in goaf areas, analyzing the dynamic load pressure mechanism and prevention methods through theoretical analysis and numerical simulation. However, there is a lack of research on methods for predicting vertical subsidence of the overburden under repeated mining under coal pillars.
[0004] Therefore, there is an urgent need to propose a method for predicting vertical subsidence of overburden under repeated mining under coal pillar groups to adapt to the mining of deep coal seams. Summary of the Invention
[0005] To address the problems in the background technology, this invention proposes a method for predicting vertical subsidence of overburden caused by repeated mining under coal pillar groups. This method converts the vertical subsidence of overburden caused by repeated mining under coal pillar groups into the superimposed effects of coal seam mining (coal seam goaf) and coal pillar group fracturing (coal pillar group fracturing equivalent goaf). A prediction model for vertical subsidence of overburden caused by repeated mining under coal pillar groups has been successfully constructed, and the average absolute error between the prediction results and the measured values is low, verifying the accuracy and effectiveness of the method.
[0006] Specifically, the present invention is achieved through the following technical solutions: A method for predicting vertical subsidence of overburden under repeated mining of coal pillar groups, comprising: S1) Construct a calculation model of the equivalent goaf after coal pillar crushing, and transform the disturbance effect of coal pillar crushing on the overlying strata into the mining effect of the equivalent goaf of the coal pillar group crushing. S2) Determine the correspondence between the expected coordinate system of the goaf area under the coal pillar group and the local expected coordinate system of the subsidence of the equivalent goaf area of the broken coal pillar group, and unify the overall expected coordinate system of the vertical subsidence of the overburden caused by repeated mining; S3) The vertical subsidence of the overburden caused by repeated mining under the coal pillar group is equivalently converted into the superposition of the coal seam goaf area under the coal pillar group and the equivalent goaf area of the broken coal pillar group. Based on the stochastic medium theory, a prediction model for the vertical subsidence of the overburden caused by repeated mining under the coal pillar group is constructed. S4) Based on the prediction model, predict the vertical subsidence of the overburden under repeated mining in the coal pillar group.
[0007] Specifically, the basic assumption is that when the upper coal pillar group is broken due to disturbance caused by the mining of the lower coal seam, its bearing capacity is completely lost, and the broken coal body naturally accumulates under gravity. By spreading the volume of the broken coal pillar at the bottom of the original coal pillar area, an equivalent goaf model can be constructed to assess the impact of coal pillar breakage on the subsidence of the overlying strata and the surface.
[0008] Further, in step S1), the actual length of the equivalent goaf of the broken coal pillar group is calculated using the following formula. L : ,in, S This refers to the actual length of the coal seam goaf. The vertical distance between the floor of the equivalent goaf of the coal pillar group and the roof of the goaf of the coal seam. Angle of influence; The thickness of the equivalent goaf zone due to coal pillar breakage is calculated using the following formula. M : ,in, This refers to the height of the coal pillar; The equivalent thickness of the broken coal pillar group is calculated using the following formula: ,in, The coefficient of thermal expansion of the coal pillar; d The diameter of the coal pillar; D This refers to the distance between coal pillars.
[0009] Further, in step S2), the predicted coordinate system of the coal seam goaf is used ( x , y , z This serves as the overall coordinate system for predicting vertical subsidence of the overlying strata caused by repeated mining. The calculation boundary on the left side of the coal seam goaf is used as the reference point. x Axis 0, dip direction is calculated based on the boundary of the coal seam goaf uphill. y Axis 0, with the Earth's surface as the reference point. z The expected local coordinate system for subsidence of the equivalent goaf area at point 0 (coal pillar group fracture) is ( x 1, y 1, z 1) Transform it through its geometric relationship with the global coordinate system ( x - Δx , y - Δy ,z ),in, Δx and Δy Calculated using the following formula: ,in, This represents the offset distance from the inflection point of the left boundary of the equivalent goaf area of the broken coal pillar group. The offset distance of the inflection point in the uphill direction of the equivalent goaf area of the broken coal pillar group.
[0010] Furthermore, in step S3), the superposition effect is specifically obtained through the following general formula: ,in, A This refers to the vertical subsidence of the overburden under the coal pillar group caused by repeated mining during limited mining. This refers to the vertical subsidence of the overlying rock corresponding to the goaf area of the coal seam under the coal pillar group during limited mining. The vertical subsidence of the overlying rock corresponding to the equivalent goaf area caused by the fracturing of the coal pillar group during limited mining. r The subsidence influence coefficient based on overburden depth is calculated using the following formula: ,in, H The depth of coal seam mining. h This refers to the depth of the coal pillar group.
[0011] Specifically, r The overburden depth subsidence influence coefficient is given. Coal pillar fracturing only disturbs the overburden above the coal pillar layer. The movement and deformation of the overburden below the coal pillar layer are only affected by coal seam mining. Therefore, the overburden depth subsidence influence coefficient is... r Whether the overburden movement is affected by the collapse of the coal pillar can be determined based on the expected depth.
[0012] Furthermore, the vertical subsidence of the overlying strata corresponding to the goaf area of the coal seam under the coal pillar group during limited mining, and the vertical subsidence of the overlying strata corresponding to the equivalent goaf area of the broken coal pillar group during limited mining, are respectively equivalent to the difference in vertical subsidence of the overlying strata during two semi-unlimited mining operations.
[0013] Furthermore, the vertical subsidence of the overlying rock during semi-infinite mining is derived based on the theory of stochastic media.
[0014] Furthermore, the vertical subsidence of the overburden includes the movement and deformation of the strike main cross section and the dip main cross section within the overburden.
[0015] Furthermore, the movement and deformation of the main cross-section within the overburden during semi-infinite mining are obtained using the following formula: ,in, For the sinking prediction model, For horizontal movement prediction models, For the tilt prediction model, For curvature prediction models, For horizontal deformation prediction model; For coal seam mining thickness, This is the subsidence coefficient. The dip angle of the coal seam. It is the horizontal movement coefficient of the earth's surface.
[0016] Furthermore, the predicted models for subsidence, tilt, and curvature of the overburden inclined to the main cross-section during semi-infinite mining are the same as those for the main cross-section of the overburden inclined to the main cross-section during semi-infinite mining. The predicted models for horizontal movement and horizontal deformation of the overburden inclined to the main cross-section during semi-infinite mining should be supplemented with the components of horizontal movement and horizontal deformation caused by coal seam tilt.
[0017] Specifically, the movement of strata within the overburden can be predicted using the same method as for any point on the surface, but strata parameters on the horizontal plane are required. It is assumed that the coal seam has been fully mined along the dip direction but not along the strike direction. When predicting the movement and deformation of the strike-oriented main cross-section within the overburden in limited mining, it can be equivalent to the difference between two and a half infinite mining operations. Similarly, the equivalent goaf of the broken coal pillar group can be assumed in the same way, and the equivalent goaf of the broken coal pillar group can be equivalently converted into the difference between two and a half infinite mining operations along the strike. Therefore, the formula for predicting the movement and deformation of the strike-oriented main cross-section within the repeatedly mined overburden group under limited mining can be expressed as follows: sink :
[0018] tilt :
[0019] curvature :
[0020] Horizontal movement :
[0021] along Horizontal deformation in direction :
[0022] along Vertical deformation of direction :
[0023] in, Indicates the coal seam goaf area z levelx The sinking results and the predicted parameters in the calculation process are all parameters corresponding to the coal seam. This represents the equivalent goaf of a coal pillar group fractured under a unified coordinate system. z level x The sinking results and the expected parameters in the calculation process are all parameters corresponding to the equivalent goaf of the coal pillar group. The meanings of other movement and deformation symbols and subsequent formulas are the same.
[0024] The length of the coal seam goaf is calculated based on its strike. , S This refers to the actual length of the coal seam goaf. , The offset distance between the left and right boundary inflection points of the coal seam goaf direction. , These represent the calculation parameters for the left and right sides of the coal seam goaf, respectively. The length of the equivalent goaf strike zone for the broken coal pillar group is calculated. , L This represents the actual length of the equivalent goaf area due to the coal pillar group's fracture. , The offset distance between the left and right boundary inflection points of the equivalent goaf area in the direction of the coal pillar group's fracture. , These represent the calculation parameters for the left and right sides of the equivalent goaf of the broken coal pillar group, respectively. To fully activate the inclined mining, the direction is semi-infinite during mining. Vertical deformation in the direction can be used The meanings of other movement and deformation symbols and subsequent formulas are similar.
[0025] The predicted movement and deformation of the main cross-section within the overburden can be derived using the same principle as the predicted movement and deformation formula for the main cross-section within the overburden under repeated mining under coal pillars in limited mining. The predicted formula for the movement and deformation of the main cross-section within the overburden under repeated mining under coal pillars in limited mining is as follows: sink :
[0026] tilt :
[0027] curvature :
[0028] Horizontal movement :
[0029] along Horizontal deformation in direction :
[0030] along Vertical deformation of direction :
[0031] In the formula , These represent the calculated parameters for the coal seam goaf dipping downhill and uphill, respectively. , These represent the calculation parameters for the downhill and uphill dip directions of the equivalent goaf area of the coal pillar group, respectively. Calculate the length of the goaf in the dip direction. The length of the equivalent goaf in the direction of the coal pillar group's fracture can be calculated using the following formula:
[0032] in, The actual mining length of the coal seam goaf; , These are the offset distances of the inflection points of the coal seam goaf in the downhill and uphill directions, respectively; The actual length of the equivalent goaf inclination zone for coal pillar group fracture; , These are the offset distances of the inflection points of the equivalent goaf area of the broken coal pillar group in the downhill and uphill directions, respectively. To influence the propagation angle of mining, , It is a coefficient less than 1, and its value is generally between 0.5 and 0.8.
[0033] The calculation formula for horizontal movement and deformation in semi-infinite mining should add the components of horizontal movement and deformation caused by coal seam inclination to the values calculated by the corresponding strike formula. Taking coal seam mining as an example, the calculation formula is as follows:
[0034] in, , , , The following formula can be used for calculation:
[0035] in, , and These represent the mining depth, horizontal movement coefficient, and radius of influence of the coal seam goaf dipping downhill. , and These represent the mining depth, horizontal movement coefficient, and radius of influence of the coal seam goaf dipping in the uphill direction. This is the main influence radius index related to lithology.
[0036] The components of horizontal movement and horizontal deformation in the dip direction of the equivalent goaf of the broken coal pillar group are derived similarly, and the corresponding parameters are calculated by replacing them with the corresponding parameters of the equivalent goaf of the broken coal pillar group.
[0037] Furthermore, based on the derivation principle of the movement and deformation of any point within the surface moving basin, the prediction formula for the movement and deformation of any point inside the overburden is obtained, which is the prediction model for the vertical subsidence of the overburden under repeated mining under the coal pillar group.
[0038] Specifically, the formula for predicting the movement and deformation of any point inside the overburden is as follows: sink :
[0039] tilt :
[0040] curvature :
[0041] Horizontal movement :
[0042] Horizontal deformation :
[0043] Vertical deformation :
[0044] in, For coal seam mining thickness, M The thickness of the equivalent goaf due to the fracturing of the coal pillar group. This is the subsidence coefficient. As the angle of influence, This indicates the angle between the expected direction and the orientation of the main cross-section. The dip angle of the coal seam. and express z The dip direction of the goaf in a planar coal seam primarily affects the radius. and express z The orientation of the goaf in a planar coal seam primarily affects the radius. and express z The radius of influence of the strike of the equivalent goaf of a broken coal pillar group is mainly determined by the direction of the goaf. and express z The radius of the equivalent goaf in a broken coal pillar group mainly affects the radius. Calculate the length of the goaf in the dip direction. The length of the equivalent goaf in the direction of the coal pillar group's fracture is calculated. The length of the coal seam goaf is calculated based on its strike. The calculated length of the equivalent goaf area due to the fracturing of the coal pillar group. L This represents the actual length of the equivalent goaf area due to the coal pillar group's fracture. , , , , , , , and They are respectively , , , , , , , and The first derivative, and the meanings of the other parameters are as described above.
[0045] The subsidence coefficient within the overburden is related not only to the surface subsidence coefficient and the predicted level, but also to the lithology of the overburden. It can be determined by using a comprehensive overburden evaluation coefficient. P Determined by geological and mining technology conditions. P The coefficient depends on the lithology and thickness of the overlying strata. P coefficient and subsidence coefficient Calculated using the following formula:
[0046]
[0047] in, For the first i Normal thickness of the overlying strata; For the first i The strata lithology evaluation coefficient can be determined based on empirical values for different rock strata.
[0048] Beneficial effects: 1. This invention converts the vertical subsidence of overburden caused by repeated mining under coal pillar groups into the superimposed effects of coal seam mining (coal seam goaf) and coal pillar group fracturing (coal pillar group fracturing equivalent goaf). It successfully constructs a prediction model for vertical subsidence of overburden caused by repeated mining under coal pillar groups, and the average absolute error between the prediction results and the measured values is low, which verifies the accuracy and effectiveness of the method.
[0049] 2. Based on the fact that coal pillar crushing only disturbs the overlying rock above the coal pillar layer, and that the movement and deformation of the overlying rock below the coal pillar layer are only affected by coal seam mining, this invention constructs a superimposed influence calculation formula based on the overlying rock depth subsidence influence coefficient, which is more accurate. Attached Figure Description
[0050] Figure 1 This is a prediction result diagram of Embodiment 1 of the present invention. Detailed Implementation
[0051] The present invention will now be described in detail through specific embodiments, but the scope of the present invention is not limited to the listed embodiments. In order to make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.
[0052] Example 1:
[0053] To verify the effectiveness of the invention method, the subsidence of the main cross section of a near-horizontal mining area was studied. The roof management method of this mining area is the full collapse method. The main coal seams mined are No. 3-5 of the Carboniferous period. The average mining depth is 450 m, the mining thickness is 9.75 m, the average dip angle of the coal seam is 3°, the strike length of the working face is 740 m, and the dip width is 210 m.
[0054] The mining area contains a large area of Jurassic coal seam goaf, with an average mining thickness of 5 m and an average mining depth of 100 m. The mining method is room-and-pillar mining, with an average pillar width of 15 m and a distance of 60 m between pillars.
[0055] Based on measured data from the mining area, the influence angle α is taken as 56°, and the expansion coefficient of the coal pillar is... If it is 1.15, then according to the formula The failure range of the coal pillar group, i.e., the actual length of the equivalent goaf area due to the fracturing of the coal pillar group, is obtained. L It is 274.6m, according to the formula The equivalent thickness of the coal pillar after crushing can be obtained. If the thickness is 1.15m, then the equivalent thickness of the broken coal pillar group is... M The depth is 3.85m. The vertical subsidence prediction model for overburden under repeated mining under the coal pillar group of this invention is used to predict the vertical subsidence of the overburden in coal seam mining under repeated mining conditions. The results are as follows: Figure 1As shown, the subsidence of the main cross-section during the mid-term mining phase is predicted. Figure 1 The study shows the extent to which coal seams and coal pillars affect the subsidence of overlying strata and the surface. Comparison with measured data shows that the average absolute error between the predicted and measured values is 32.46 mm, verifying the accuracy and effectiveness of the method of this invention.
[0056] The embodiments of the present invention have been described in detail above. The description of the embodiments above is only for the purpose of helping to understand the method and core idea of the present invention, and is not intended to limit the scope of implementation of the present invention. Therefore, all equivalent changes or modifications made to the structure, features and principles described in the patent claims of the present invention should be included in the patent application scope of the present invention. In summary, the content of this specification should not be construed as a limitation of the present invention.
Claims
1. A method for predicting vertical subsidence of overburden under repeated mining of coal pillar groups, characterized in that, include: S1) Construct a calculation model of the equivalent goaf after coal pillar crushing, and transform the disturbance effect of coal pillar crushing on the overlying strata into the mining effect of the equivalent goaf of the coal pillar group crushing. S2) Determine the correspondence between the expected coordinate system of the goaf area under the coal pillar group and the expected local coordinate system of the subsidence of the equivalent goaf area of the broken coal pillar group, and unify the overall coordinate system of the expected vertical subsidence of the overburden caused by repeated mining. S3) The vertical subsidence of the overburden caused by repeated mining under the coal pillar group is equivalently converted into the superposition of the coal seam goaf and the broken goaf of the coal pillar group. Based on the stochastic medium theory, a prediction model for the vertical subsidence of the overburden caused by repeated mining under the coal pillar group is constructed. S4) Based on the prediction model, predict the vertical subsidence of the overburden under repeated mining in the coal pillar group.
2. The method according to claim 1, characterized in that, In step S1), the actual length of the equivalent goaf of the broken coal pillar group is calculated using the following formula. L : ,in, S This refers to the actual length of the coal seam goaf. The vertical distance between the floor of the equivalent goaf of the coal pillar group and the roof of the goaf of the coal seam. Angle of influence; The thickness of the equivalent goaf zone due to coal pillar breakage is calculated using the following formula. M : ,in, This refers to the height of the coal pillar; The equivalent thickness of the broken coal pillar group is calculated using the following formula: ,in, The coefficient of thermal expansion of the coal pillar; d The diameter of the coal pillar; D This refers to the distance between coal pillars.
3. The method according to claim 1, characterized in that, In step S2), the predicted coordinate system of the coal seam goaf is used. x , y , z This serves as the overall coordinate system for predicting vertical subsidence of the overlying strata caused by repeated mining. The calculation boundary on the left side of the coal seam goaf is used as the reference point. x Axis 0, dip direction is calculated based on the boundary of the coal seam goaf uphill. y Axis 0, with the Earth's surface as the reference point. z The expected local coordinate system for subsidence of the equivalent goaf area at point 0 (coal pillar group fracture) is ( x 1, y 1, z 1) Transform it through its geometric relationship with the global coordinate system ( x - Δx , y - Δy , z ),in, Δx and Δy Calculated using the following formula: ,in, This represents the offset distance from the inflection point of the left boundary of the equivalent goaf area of the broken coal pillar group. The offset distance of the inflection point in the uphill direction of the equivalent goaf area of the broken coal pillar group. The vertical distance between the floor of the equivalent goaf of the coal pillar group and the roof of the goaf of the coal seam. The angle of influence.
4. The method according to claim 1, characterized in that, In step S3), the superposition effect is specifically obtained through the following general formula: ,in, A This refers to the vertical subsidence of the overburden under the coal pillar group caused by repeated mining during limited mining. This refers to the vertical subsidence of the overlying rock corresponding to the goaf area of the coal seam under the coal pillar group during limited mining. The vertical subsidence of the overlying rock corresponding to the equivalent goaf area caused by the fracturing of the coal pillar group during limited mining. ρ The subsidence influence coefficient based on overburden depth is calculated using the following formula: ,in, H The depth of coal seam mining. h This refers to the depth of the coal pillar group.
5. The method according to claim 4, characterized in that, The vertical subsidence of the overlying strata corresponding to the goaf area of the coal seam under the coal pillar group during limited mining, and the vertical subsidence of the overlying strata corresponding to the equivalent goaf area of the broken coal pillar group during limited mining, are respectively equivalent to the difference in vertical subsidence of the overlying strata during two semi-unlimited mining operations.
6. The method according to claim 5, characterized in that, The vertical subsidence of the overlying rock during semi-infinite mining is derived from the theory of stochastic media.
7. The method according to claim 6, characterized in that, The vertical subsidence of the overburden includes the movement and deformation of the strike main cross section and the dip main cross section within the overburden.
8. The method according to claim 7, characterized in that, The movement and deformation of the main cross-section within the overburden during semi-unlimited mining are obtained using the following formula: ,in, For the sinking prediction model, For horizontal movement prediction models, For the tilt prediction model, For curvature prediction models, For horizontal deformation prediction model; For coal seam mining thickness, This is the subsidence coefficient. The dip angle of the coal seam. It is the horizontal movement coefficient of the earth's surface.
9. The method according to claim 8, characterized in that, The predicted models for subsidence, tilt, and curvature of the overburden inclined to the main cross section during semi-infinite mining are the same as those for the overburden inclined to the main cross section during semi-infinite mining. The predicted models for horizontal movement and horizontal deformation of the overburden inclined to the main cross section during semi-infinite mining should be supplemented with the components of horizontal movement and horizontal deformation caused by coal seam tilt.
10. The method according to claim 1, characterized in that, Based on the derivation principle of the movement and deformation of any point within the surface moving basin, the formula for predicting the movement and deformation of any point inside the overburden is obtained, which is the prediction model for the vertical subsidence of the overburden under repeated mining under the coal pillar group.