A combined filling mining method based on raw magnesium slag and modified magnesium slag

Abstract

The present invention discloses a combined filling mining method based on original magnesium slag and modified magnesium slag, including the steps of: 1. dividing a plurality of vertical strip coal pillars along the extension direction of the coal seam; 2. mining a plurality of vertical strip coal pillars at intervals, and forming an interval filling area after the strip coal pillars are mined; 3. preparing original magnesium slag-based filling materials and modified magnesium slag-based filling materials; 4. determining the spatial size of the filling area; 5. calculating the filling height of the original magnesium slag-based filling body and the modified magnesium slag-based filling body; 6. filling the filling area with the modified magnesium slag-based filling material; 7. filling the filling area with the original magnesium slag-based filling material to form an interval filling support body; 8. mining the strip coal pillars between adjacent filling supports. The method of the present invention has simple steps, can be effectively applied in combined filling mining, improves the safety of mining, and realizes the resource utilization of two major industrial solid wastes, coal gasification slag and optimized magnesium slag, with significant effects and easy promotion.

Description

Technical Field

[0001] The invention belongs to the technical field of resource recycling, and in particular relates to a combined filling mining method based on original magnesium slag and modified magnesium slag. Background Art

[0002] In recent years, most coal mining companies have adopted the backfill method, which has achieved good control effects on surface subsidence and environmental damage. However, the amount of space to be filled is relatively large, the backfill material is in short supply, and the cost of the backfill process material is high.

[0003] The coal chemical industry can achieve efficient utilization of coal resources and is directly related to the country's energy strategic development plan.

[0004] As "green engineering materials of the 21st century", magnesium metal and its alloys play an important role in my country's economic development.

[0005] At present, the disposal method for industrial solid waste materials such as magnesium slag and coal gasification slag is still mainly landfill. Generally, natural gullies are used, and slag yards are built after anti-seepage treatment for landfilling. The surface is reclaimed after landfilling. A large amount of land is occupied, and there is a risk of serious pollution to the atmosphere, water sources and surface ecology. At the same time, a large amount of magnesium slag and coal gasification slag is landfilled, resulting in a huge waste of resources.

[0006] If coal gasification slag and magnesium slag can be used as filling materials for backfill mining, it will greatly reduce resource waste and achieve resource recycling. However, it is found in practice that coal gasification slag itself has low hydration activity, resulting in a long coagulation time and low strength in the early and middle stages. Magnesium slag itself contains a high amount of free MgO, that is, an unstable component. Over time, the free MgO will gradually hydrate and expand, resulting in insufficient strength. Therefore, it is necessary to eliminate the influence of unstable components (free MgO), modify the magnesium slag, and improve its strength.

[0007] During the filling process, good top connection can make the filling body play the role of supporting the top plate. However, in practice, due to reasons such as segregation of filling materials, the filling body shrinks and cannot be connected to the top, and the bearing function of the filling body cannot be fully exerted. Summary of the invention

[0008] The technical problem to be solved by the present invention is to provide a combined filling mining method based on original magnesium slag and modified magnesium slag in view of the deficiencies in the above-mentioned prior art. The method has simple steps, reasonable design, and convenient implementation. It can be effectively applied in combined filling mining, thereby reducing mining costs and improving mining safety. At the same time, it realizes the resource utilization of two major industrial solid wastes, namely, gasification slag and optimized magnesium slag, with remarkable effects and easy promotion.

[0009] In order to solve the above technical problems, the technical solution adopted by the present invention is: a combined filling mining method based on original magnesium slag and modified magnesium slag, comprising the following steps:

[0010] Step 1: Divide the coal seam into a plurality of vertical strip-shaped coal pillars along the extension direction of the coal seam;

[0011] Step 2: mining multiple vertical strip-shaped coal pillars at intervals, and forming interval filling areas after the strip-shaped coal pillars are mined;

[0012] Step 3, preparing original magnesium slag-based filling material and modified magnesium slag-based filling material;

[0013] Step 4: Determine the space size of the filling area;

[0014] Step 5, calculating the filling height of the original magnesium slag-based filling body and the modified magnesium slag-based filling body;

[0015] Step 6: Filling the filling area with modified magnesium slag-based filling material;

[0016] Step 7: Fill the filling area with the original magnesium slag-based filling material to form a spaced filling support;

[0017] Step eight, mining the strip-shaped coal pillars between adjacent filling supports.

[0018] In the above-mentioned combined filling mining method based on original magnesium slag and modified magnesium slag, the specific process of dividing a plurality of vertical strip coal pillars along the extension direction of the coal seam in step one includes: determining the span of the division so that the unmined strip coal pillars after interval mining can support the direct roof and ensure that the direct roof does not collapse.

[0019] In the above-mentioned combined filling mining method based on raw magnesium slag and modified magnesium slag, the raw magnesium slag-based filling material in step three is made by mixing and gelling raw magnesium slag with industrial solid waste materials, and the raw magnesium slag is magnesium slag produced by Pidgeon process magnesium smelting.

[0020] In the above-mentioned combined filling mining method based on original magnesium slag and modified magnesium slag, the specific preparation process of the modified magnesium slag-based filling material in step 3 includes:

[0021] Step 401, according to the weight percentage of each raw material in the modified magnesium-refining pellets, the raw materials are sent to a grinder for mixing and fine grinding, and then sieved, and the sieved material is pressed to obtain modified magnesium-refining pellets;

[0022] Step 402, the modified magnesium-refining pellets are loaded into a reduction tank, and reduced for 7h to 8h under the conditions of a vacuum degree of 5Pa to 10Pa and a temperature of 1200°C to 1220°C. After the reduction is completed, the tank is opened to take out the crude magnesium ingot, and the magnesium slag in the reduction tank is scraped out to obtain a block of modified magnesium slag;

[0023] Step 403, pre-treating the modified magnesium slag raw material by screening, coarse crushing and fine crushing to obtain modified magnesium slag material;

[0024] Step 404, pre-processing the coal gasification slag by screening, coarse crushing and fine crushing to obtain coal gasification slag material;

[0025] Step 405, pre-processing the coal gangue by screening, coarse crushing and fine crushing to obtain coal gangue material;

[0026] Step 406: Mix the modified magnesium slag, coal gasification slag, coal gangue, and fly ash according to a pre-designed weight percentage;

[0027] Step 407: pour the mixture into a ball mill for grinding to obtain a modified magnesium slag-based filling material.

[0028] In the above-mentioned combined filling mining method based on original magnesium slag and modified magnesium slag, the specific process of calculating the filling height of the original magnesium slag-based filling body and the modified magnesium slag-based filling body in step 5 includes:

[0029] Step 501, calculating the shrinkage rate of the modified magnesium slag-based filling body during the consolidation process;

[0030] Step 502, calculating the expansion coefficient of the original magnesium slag-based filling body during the consolidation process;

[0031] Step 503, establishing the equilibrium equation, deformation coordination equation and physical equation of the modified magnesium slag-based filling body and the original magnesium slag-based filling body;

[0032] Step 504: perform critical state analysis on the modified magnesium slag-based filling body and the original magnesium slag-based filling body to obtain the filling heights of the modified magnesium slag-based filling body and the original magnesium slag-based filling body.

[0033] In the above-mentioned combined filling mining method based on original magnesium slag and modified magnesium slag, the shrinkage rate calculation formula of the modified magnesium slag-based filling body is:

[0034]

[0035] Among them, R c is the shrinkage rate of the modified magnesium slag-based filling body, x is the vertical shrinkage of the modified magnesium slag-based filling body, and H is the total height of the modified magnesium slag-based filling body and the original magnesium slag-based filling body.

[0036] In the above-mentioned combined filling mining method based on original magnesium slag and modified magnesium slag, the expansion coefficient calculation formula of the original magnesium slag-based filling body is:

[0037]

[0038] Among them, R eis the expansion coefficient of the original magnesium slag-based filling body, y is the vertical expansion of the original magnesium slag-based filling body, and H is the total height of the modified magnesium slag-based filling body and the original magnesium slag-based filling body.

[0039] In the above-mentioned combined filling mining method based on original magnesium slag and modified magnesium slag, the equilibrium equation of the modified magnesium slag-based filling body and the original magnesium slag-based filling body is:

[0040] F1+ρ1gh1+ρ2gh2-F2=0

[0041] Among them, F1 is the restraint reaction force provided by the top plate, F2 is the restraint reaction force provided by the bottom plate, ρ1 is the density of the original magnesium slag-based filling body, ρ2 is the density of the modified magnesium slag-based filling body, h1 is the filling height of the original magnesium slag-based filling body, h2 is the filling height of the modified magnesium slag-based filling body, and h1+h2=H, g is the acceleration of gravity;

[0042] The deformation coordination equation of the modified magnesium slag-based filling body and the original magnesium slag-based filling body is:

[0043] Δl1=Δl2

[0044] Among them, Δl1 is the deformation of the original magnesium slag-based filling body, and Δl2 is the deformation of the modified magnesium slag-based filling body;

[0045] The physical equations of the modified magnesium slag-based filling body and the original magnesium slag-based filling body are:

[0046]

[0047] Among them, F N1 is the internal axial force of the original magnesium slag-based filling body, and F N1 =F1+ρ1gx,F N2 is the internal axial force of the modified magnesium slag-based filling body, and F N2 =F2-ρ2gy, E1 is the elastic modulus of the original magnesium slag-based filling body, and E2 is the elastic modulus of the modified magnesium slag-based filling body.

[0048] In the above-mentioned combined filling mining method based on original magnesium slag and modified magnesium slag, when the original magnesium slag-based filling body is in a state of just contacting with the roof, the restraining reaction force F1 provided by the roof is 0, and the filling volume of the modified magnesium slag-based filling body reaches the maximum value, at this time F N1 =ρ1gx, according to the equilibrium equation, deformation coordination equation and physical equation, we get:

[0049] g(2E1ρ1-E2ρ1-E1ρ2)h1 2 +2E1[E2(R e +R c )-gH(ρ1-ρ2)]h1-E1H(2E2 R c+ρ2gH)=0

[0050] Let parameter a1 = g(2E1ρ1-E2ρ1-E1ρ2),

[0051] b1=2E1[E2(R e +R c )-gH(ρ1-ρ2)],

[0052] c1=E1H(2E2R c +ρ2gH);

[0053] Solve to get the filling height of the original magnesium slag-based filling body Filling height of modified magnesium slag-based filling body

[0054] Compared with the prior art, the present invention has the following advantages:

[0055] 1. The method of the present invention has simple steps, reasonable design and convenient implementation.

[0056] 2. The present invention uses coal gasification slag and magnesium slag as filling materials for coal mine backfill mining, which greatly reduces resource waste and realizes resource recycling.

[0057] 3. The modified magnesium slag-based filling material of the present invention utilizes the mutual excitation effect of optimized magnesium slag and coal gasification slag to achieve gelling effect, eliminate the influence of unstable components (free MgO), and effectively improve the strength.

[0058] 4. The present invention calculates the shrinkage rate of the modified magnesium slag-based filling body during the consolidation process and the expansion coefficient of the original magnesium slag-based filling body during the consolidation process, and establishes the equilibrium equation, deformation coordination equation and physical equation of the modified magnesium slag-based filling body and the original magnesium slag-based filling body, and then performs critical state analysis on the modified magnesium slag-based filling body and the original magnesium slag-based filling body to obtain the filling heights of the modified magnesium slag-based filling body and the original magnesium slag-based filling body, respectively, to achieve quantitative analysis, which can serve as a theoretical support to guide the filling operation.

[0059] 5. The present invention divides the coal seam into a plurality of vertical strip-shaped coal pillars along the extension direction, and then carries out interval mining, and then fills the interval filling area to form a continuous beam bridge structure to support the direct top and prevent collapse. In order to ensure the filling strength, the modified magnesium slag-based filling body is filled first. At the same time, in order to solve the problem that the filling body shrinks and cannot connect to the top due to reasons such as segregation of the filling material, the original magnesium slag-based filling body is filled on top of the modified magnesium slag-based filling body. The expansion property of the original magnesium slag-based filling body is used to solve the connection problem, so that the original magnesium slag-based filling body is in full contact with the direct top, thereby improving the bearing effect.

[0060] 6. The present invention can be effectively applied in combined backfill mining, which reduces mining costs, improves mining safety, and realizes resource utilization of two major industrial solid wastes, namely, coal gasification slag and optimized magnesium slag, with significant effects and easy promotion.

[0061] In summary, the method of the present invention has simple steps, reasonable design, and easy implementation. It can be effectively applied in combined filling mining, reduces mining costs, improves mining safety, and simultaneously realizes the resource utilization of two major industrial solid wastes, namely, coal gasification slag and optimized magnesium slag, with significant effects and easy promotion.

[0062] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 is a flow chart of the method of the present invention;

[0064] Figure 2 It is a schematic diagram of the coal seam status during the combined filling mining process of the present invention. DETAILED DESCRIPTION

[0065] like Figure 1 As shown, the combined filling mining method based on original magnesium slag and modified magnesium slag of the present invention comprises the following steps:

[0066] Step 1: Divide the coal seam into a plurality of vertical strip-shaped coal pillars along the extension direction of the coal seam;

[0067] Step 2: mining multiple vertical strip-shaped coal pillars at intervals, and forming interval filling areas after the strip-shaped coal pillars are mined;

[0068] Step 3, preparing original magnesium slag-based filling material and modified magnesium slag-based filling material;

[0069] Step 4: Determine the space size of the filling area;

[0070] Step 5, calculating the filling height of the original magnesium slag-based filling body and the modified magnesium slag-based filling body;

[0071] Step 6: Filling the filling area with modified magnesium slag-based filling material;

[0072] Step 7: Fill the filling area with the original magnesium slag-based filling material to form a spaced filling support;

[0073] Step eight, mining the strip-shaped coal pillars between adjacent filling supports.

[0074] When implementing it, Figure 2 As shown in (a), first divide the coal into multiple vertical strips; then the strips are mined at intervals to form interval filling areas. The mining effect is as follows: Figure 2(b) As shown; the filling area is first filled with modified magnesium slag-based filling materials, and then the original magnesium slag-based filling materials are filled above the modified magnesium slag-based filling materials in the filling area to form an interval filling support body, the effect is as follows Figure 2 (c); then the strip-shaped coal pillars between the adjacent filling supports are mined, and the mining effect is as follows: Figure 2 The modified magnesium slag-based filling body is used to ensure the filling strength, and the original magnesium slag-based filling body uses its own expansion to solve the roof connection problem and achieve effective support for the direct roof.

[0075] In this embodiment, the specific process of dividing a plurality of vertical strip coal pillars along the extension direction of the coal seam in step 1 includes: determining the span of the division so that the unmined strip coal pillars after interval mining can support the direct roof and ensure that the direct roof does not collapse.

[0076] In this embodiment, the raw magnesium slag-based filling material in step three is prepared by mixing and gelling raw magnesium slag with industrial solid waste materials, and the raw magnesium slag is magnesium slag produced by Pidgeon process magnesium smelting.

[0077] During the specific implementation, industrial solid waste materials include fly ash and coal gangue, which do not eliminate the unstable components (free MgO) in the original magnesium slag, so as to maintain the expansibility of the original magnesium slag, utilize the expansibility to solve the top connection problem, and make the original magnesium slag-based filling body fully contact with the direct top.

[0078] In this embodiment, the specific preparation process of the modified magnesium slag-based filling material in step 3 includes:

[0079] Step 401, according to the weight percentage of each raw material in the modified magnesium-refining pellets, the raw materials are sent to a grinder for mixing and fine grinding, and then sieved, and the sieved material is pressed to obtain modified magnesium-refining pellets;

[0080] In specific implementation, the weight percentage of each raw material in the modified magnesium-smelting pellets is as follows: calcined white 81% to 82.8%, ferrosilicon 15% to 16.6%, fluorite 1.25% to 2.71%, and ferroboron alloy 0.23% to 0.29%, preferably calcined white (CaO / MgO molar ratio is close to 1) 81%, ferrosilicon (containing Si content of about 75%) 16.5%, fluorite (CaF2 content in fluorite is not less than 95%) 2.25%, and ferroboron alloy 0.25%.

[0081] Step 402, the modified magnesium-refining pellets are loaded into a reduction tank, and reduced for 7h to 8h under the conditions of a vacuum degree of 5Pa to 10Pa and a temperature of 1200°C to 1220°C. After the reduction is completed, the tank is opened to take out the crude magnesium ingot, and the magnesium slag in the reduction tank is scraped out to obtain a block of modified magnesium slag;

[0082] Step 403, pre-treating the modified magnesium slag raw material by screening, coarse crushing and fine crushing to obtain modified magnesium slag material;

[0083] Step 404, pre-processing the coal gasification slag by screening, coarse crushing and fine crushing to obtain coal gasification slag material;

[0084] Step 405, pre-processing the coal gangue by screening, coarse crushing and fine crushing to obtain coal gangue material;

[0085] Step 406: Mix the modified magnesium slag, coal gasification slag, coal gangue, and fly ash according to a pre-designed weight percentage;

[0086] During specific implementation, the pre-designed weight percentages are as follows: 13% to 22% modified magnesium slag, 55% to 70% coal gasification slag, 10% to 18% coal gangue, and 10% to 22% fly ash, preferably 18% modified magnesium slag, 60% coal gasification slag, 12% coal gangue, and 10% fly ash.

[0087] Step 407: pour the mixture into a ball mill for grinding to obtain a modified magnesium slag-based filling material.

[0088] In this embodiment, the specific process of calculating the filling height of the original magnesium slag-based filling body and the modified magnesium slag-based filling body in step 5 includes:

[0089] Step 501, calculating the shrinkage rate of the modified magnesium slag-based filling body during the consolidation process;

[0090] Step 502, calculating the expansion coefficient of the original magnesium slag-based filling body during the consolidation process;

[0091] Step 503, establishing the equilibrium equation, deformation coordination equation and physical equation of the modified magnesium slag-based filling body and the original magnesium slag-based filling body;

[0092] Step 504: perform critical state analysis on the modified magnesium slag-based filling body and the original magnesium slag-based filling body to obtain the filling heights of the modified magnesium slag-based filling body and the original magnesium slag-based filling body.

[0093] In the specific implementation, the physical properties of the modified magnesium slag-based filling body and the original magnesium slag-based filling body are comprehensively analyzed by calculating the shrinkage rate of the modified magnesium slag-based filling body during the consolidation process and the expansion coefficient of the original magnesium slag-based filling body during the consolidation process, and establishing the equilibrium equation, deformation coordination equation and physical equation of the modified magnesium slag-based filling body and the original magnesium slag-based filling body; then, the critical state analysis is carried out to obtain the filling heights of the modified magnesium slag-based filling body and the original magnesium slag-based filling body, respectively, to achieve quantitative analysis, which can serve as a theoretical support to guide the filling operation.

[0094] In this embodiment, the shrinkage calculation formula of the modified magnesium slag-based filling body is:

[0095]

[0096] Among them, R c is the shrinkage rate of the modified magnesium slag-based filling body, x is the vertical shrinkage of the modified magnesium slag-based filling body, and H is the total height of the modified magnesium slag-based filling body and the original magnesium slag-based filling body.

[0097] In this embodiment, the expansion coefficient calculation formula of the original magnesium slag-based filling body is:

[0098]

[0099] Among them, R e is the expansion coefficient of the original magnesium slag-based filling body, y is the vertical expansion of the original magnesium slag-based filling body, and H is the total height of the modified magnesium slag-based filling body and the original magnesium slag-based filling body.

[0100] In this embodiment, the equilibrium equation of the modified magnesium slag-based filling body and the original magnesium slag-based filling body is:

[0101] F1+ρ1gh1+ρ2gh2-F2=0

[0102] Among them, F1 is the restraint reaction force provided by the top plate, F2 is the restraint reaction force provided by the bottom plate, ρ1 is the density of the original magnesium slag-based filling body, ρ2 is the density of the modified magnesium slag-based filling body, h1 is the filling height of the original magnesium slag-based filling body, h2 is the filling height of the modified magnesium slag-based filling body, and h1+h2=H, g is the acceleration of gravity;

[0103] The deformation coordination equation of the modified magnesium slag-based filling body and the original magnesium slag-based filling body is:

[0104] Δl1=Δl2

[0105] Among them, Δl1 is the deformation of the original magnesium slag-based filling body, and Δl2 is the deformation of the modified magnesium slag-based filling body;

[0106] The physical equations of the modified magnesium slag-based filling body and the original magnesium slag-based filling body are:

[0107]

[0108] Among them, F N1 is the internal axial force of the original magnesium slag-based filling body, and F N1 =F1+ρ1gx,F N2 is the internal axial force of the modified magnesium slag-based filling body, and F N2 =F2-ρ2gy, E1 is the elastic modulus of the original magnesium slag-based filling body, and E2 is the elastic modulus of the modified magnesium slag-based filling body.

[0109] In this embodiment, when the original magnesium slag-based filling body is in a state of just contacting the top plate, the restraining reaction force F1 provided by the top plate is 0, and the filling volume of the modified magnesium slag-based filling body reaches the maximum value. At this time, F N1 =ρ1gx, according to the equilibrium equation, deformation coordination equation and physical equation, we get:

[0110] g(2E1ρ1-E2ρ1-E1ρ2)h1 2 +2E1[E2(R e +R c )-gH(ρ1-ρ2)]h1-E1H(2E2R c +ρ2gH)=0

[0111] Let parameter a1 = g(2E1ρ1-E2ρ1-E1ρ2),

[0112] b1=2E1[E2(R e +R c )-gH(ρ1-ρ2)],

[0113] c1=E1H(2E2R c +ρ2gH);

[0114] Solve to get the filling height of the original magnesium slag-based filling body Filling height of modified magnesium slag-based filling body

[0115] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural change made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A combined filling mining method based on raw magnesium slag and modified magnesium slag, characterized in that: The following steps are involved: Step 1: dividing a plurality of vertical strip coal pillars along the extension direction of the coal seam. The specific process of dividing a plurality of vertical strip coal pillars along the extension direction of the coal seam includes: determining the span of the division so that the unmined strip coal pillars after the interval mining can support the direct roof and ensure that the direct roof does not collapse; Step 2: mining multiple vertical strip-shaped coal pillars at intervals, and forming interval filling areas after the strip-shaped coal pillars are mined; Step 3: preparing raw magnesium slag-based filling materials and modified magnesium slag-based filling materials, wherein the raw magnesium slag-based filling materials are prepared by mixing raw magnesium slag with industrial solid waste materials and gelling them, wherein the raw magnesium slag is magnesium slag produced by Pidgeon process magnesium smelting, and the specific preparation process of the modified magnesium slag-based filling materials includes: Step 301, according to the weight percentage of each raw material in the modified magnesium-refining pellets, the raw materials are sent to a grinder for mixing and fine grinding, and then sieved, and the sieved material is pressed to obtain modified magnesium-refining pellets; Step 302, the modified magnesium-refining pellets are loaded into a reduction tank, and reduced for 7h to 8h under the conditions of a vacuum degree of 5Pa to 10Pa and a temperature of 1200°C to 1220°C. After the reduction is completed, the tank is opened to take out the crude magnesium ingot, and the magnesium slag in the reduction tank is scraped out to obtain a block of modified magnesium slag; Step 303, pre-treating the modified magnesium slag raw material by screening, coarse crushing and fine crushing to obtain modified magnesium slag material; Step 304, pre-processing the coal gasification slag by screening, coarse crushing and fine crushing to obtain coal gasification slag material; Step 305, pre-processing the gangue by screening, coarse crushing and fine crushing to obtain gangue material; Step 306: Mix the modified magnesium slag, coal gasification slag, coal gangue, and fly ash according to a pre-designed weight percentage; Step 307, pouring the mixture into a ball mill for grinding to obtain a modified magnesium slag-based filling material; Step 4: Determine the space size of the filling area; Step 5, calculating the filling height of the original magnesium slag-based filling body and the modified magnesium slag-based filling body; Step 6: Filling the filling area with modified magnesium slag-based filling material; Step 7: Fill the filling area with the original magnesium slag-based filling material to form a spaced filling support; Step eight, mining the strip-shaped coal pillars between adjacent filling supports.

2. A combined filling mining method based on original magnesium slag and modified magnesium slag according to claim 1, characterized in that: The specific process of calculating the filling height of the original magnesium slag-based filling body and the modified magnesium slag-based filling body described in step 5 includes: Step 501, calculating the shrinkage rate of the modified magnesium slag-based filling body during the consolidation process; Step 502, calculating the expansion coefficient of the original magnesium slag-based filling body during the consolidation process; Step 503, establishing the equilibrium equation, deformation coordination equation and physical equation of the modified magnesium slag-based filling body and the original magnesium slag-based filling body; Step 504: perform critical state analysis on the modified magnesium slag-based filling body and the original magnesium slag-based filling body to obtain the filling heights of the modified magnesium slag-based filling body and the original magnesium slag-based filling body.

3. A combined filling mining method based on original magnesium slag and modified magnesium slag according to claim 2, characterized in that: The shrinkage calculation formula of the modified magnesium slag-based filling body is: Among them, R c is the shrinkage rate of the modified magnesium slag-based filling body, x is the vertical shrinkage of the modified magnesium slag-based filling body, and H is the total height of the modified magnesium slag-based filling body and the original magnesium slag-based filling body.

4. A combined filling mining method based on original magnesium slag and modified magnesium slag according to claim 2, characterized in that: The expansion coefficient calculation formula of the original magnesium slag-based filling body is: Among them, R e is the expansion coefficient of the original magnesium slag-based filling body, y is the vertical expansion of the original magnesium slag-based filling body, and H is the total height of the modified magnesium slag-based filling body and the original magnesium slag-based filling body.

5. A combined filling mining method based on original magnesium slag and modified magnesium slag according to claim 2, characterized in that: The equilibrium equation of the modified magnesium slag-based filling body and the original magnesium slag-based filling body is: F1+ρ1gh1+ρ2gh2-F2=0 Among them, F1 is the restraint reaction force provided by the top plate, F2 is the restraint reaction force provided by the bottom plate, ρ1 is the density of the original magnesium slag-based filling body, ρ2 is the density of the modified magnesium slag-based filling body, h1 is the filling height of the original magnesium slag-based filling body, h2 is the filling height of the modified magnesium slag-based filling body, and h1+h2=H, g is the acceleration of gravity; The deformation coordination equation of the modified magnesium slag-based filling body and the original magnesium slag-based filling body is: Δl1=Δl2 Among them, Δl1 is the deformation of the original magnesium slag-based filling body, and Δl2 is the deformation of the modified magnesium slag-based filling body; The physical equations of the modified magnesium slag-based filling body and the original magnesium slag-based filling body are: Among them, F N1 is the internal axial force of the original magnesium slag-based filling body, and F N1 =F1+ρ1gx,F N2 is the internal axial force of the modified magnesium slag-based filling body, and F N2 =F2-ρ2gv, E1 is the elastic modulus of the original magnesium slag-based filling body, and E2 is the elastic modulus of the modified magnesium slag-based filling body.

6. A combined backfill mining method based on raw magnesium slag and modified magnesium slag according to claim 5, characterized in that: When the original magnesium slag-based filling body is in a state of just contact with the top plate, the restraining reaction force F1 provided by the top plate is 0, and the filling volume of the modified magnesium slag-based filling body reaches the maximum value. N1 =ρ1gx, according to the equilibrium equation, deformation coordination equation and physical equation, we get: g(2E1ρ1-E2ρ1-E1ρ2)h1 2 +2E1[E2(R e +R c )-gH(ρ1-ρ2)]h1-E1H(2E2R c +ρ2gH)=0 Let parameter a1 = g(2E1ρ1-E2ρ1-E1ρ2), b1=2E1[E2(R e +R c )-gH(ρ1-ρ2)], c1=E1H(2E2R c +ρ2gH); Solve to get the filling height of the original magnesium slag-based filling body Filling height of modified magnesium slag-based filling body And h1+h2=H, where R e is the expansion coefficient of the original magnesium slag-based filling body, R c It is the shrinkage rate of modified magnesium slag based filling body.

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