Caving control method along goaf side'bare board 'structure

Abstract

The invention relates to a caving control method of a gob-side bare board structure, belongs to the technical field of gob-side entry retaining pre-splitting roof cutting, and solves the technical problems of insufficient gob-side entry retaining gob side filling density, wind flow turbulence, abnormal prolonging of a top plate movement period and the like caused by delayed caving of an existing gob top plate. According to the solution, the caving control method for the goaf side bare board structure comprises the following steps that (1) parameters are obtained; the method comprises the following steps of (1) calculating the roof cutting height, (2) calculating the load borne by the immediate roof left section, the immediate roof middle section and the immediate roof right section, and (4) calculating the critical weakening coefficient to achieve timely caving of the roof.. Compared with the prior art, the method has the advantages of being high in operability, achieving timely caving of the goaf roof and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of gob-side entry retaining pre-splitting roof cutting, and particularly relates to a method for controlling the caving of an "empty plate" structure on the gob side. Background Art

[0002] During the advancement of the mining face in a mine, the roof of the gob will present an "O-X" type of fracture form. This fracture form is due to the existence of a support area of an "empty plate" structure jointly formed by the gob boundary, the coal wall, and the support at the end position, resulting in the roof at the end not caving synchronously with the support movement of the working face, but having a certain lag interval.

[0003] This phenomenon of delayed caving will lead to a series of problems such as insufficient filling density on the gob side of the gob-side entry retaining, affecting the air flow distribution in the roadway, which may cause air flow disorder, affecting the mine ventilation effect, abnormal prolongation of the roof movement cycle, and in severe cases, even causing large-area roof weighting, posing a major threat to the safe production of the mine. However, there is still a lack of a systematic analysis model for the mechanical evolution mechanism of the "empty plate" structure at the end of the gob-side entry retaining, and the relevant control theory is still under-researched. Summary of the Invention

[0004] In order to overcome the deficiencies of the prior art and solve the technical problems such as insufficient filling density on the gob side of the gob-side entry retaining, air flow disorder, and abnormal prolongation of the roof movement cycle caused by the delayed caving of the existing gob roof, the present invention provides a method for controlling the caving of an "empty plate" structure on the gob side.

[0005] The present invention is realized through the following technical solutions.

[0006] The present invention provides a method for controlling the caving of an "empty plate" structure on the gob side, including the following steps: 1) Obtain parameters: Through borehole exploration, obtain the rock stratum structure characteristics and mechanical property parameters of the mining area; The rock stratum composition of the mining area includes the coal wall, the unmined area on the right side of the coal wall from top to bottom, the mining face, and the gob. An entry retaining roadway is provided between the coal wall and the gob. The rock stratum above the gob is divided into the immediate roof and the main roof from bottom to top; 2) Calculate the roof cutting height: Calculate the roof cutting height based on the relationship between the roof cutting height and the rock stratum structure characteristics of the mining area; 3) Calculate the loads on the left section, middle section, and right section of the immediate roof: Divide the roof cutting height into the height of the weakening layer and the height of the bearing layer; If the pre-splitting roof cutting occurs in the immediate roof, the strata above the goaf are divided into the immediate roof bearing layer, the immediate roof weakening layer, the remaining immediate roof, and the main roof from bottom to top. Analyze the stress conditions of the left section, the middle section, and the right section of the immediate roof, and calculate the loads borne by the left section, the middle section, and the right section of the immediate roof. If the pre-splitting roof cutting occurs in the immediate roof and the main roof, the strata above the goaf are divided into the immediate roof bearing layer, the immediate roof weakening layer, the main roof weakening layer, and the main roof bearing layer from bottom to top. Analyze the stress conditions of the left section, the middle section, and the right section of the immediate roof, and calculate the loads borne by the left section, the middle section, and the right section of the immediate roof. 4) Calculate the critical weakening coefficient to achieve timely caving of the roof: Regard the immediate roof as a cantilever beam to establish a cantilever beam model, and calculate the bearing layer height and the weakening layer height in combination with the cantilever beam formula and the load borne by the middle section of the immediate roof. Calculate the critical weakening coefficient based on the critical weakening coefficient = weakening layer height / bearing layer height. When the ratio of the actual weakening layer height to the actual bearing layer height is greater than the critical weakening coefficient, timely caving of the roof is achieved.

[0007] Furthermore, the strata structure characteristics in the mining area in step 1) include the thickness of the coal seam, the thickness of the immediate roof, the thickness of the main roof, the actual mining height, the roof subsidence, the floor heave, and the swelling coefficient.

[0008] Furthermore, the mechanical property parameters in the mining area in step 1) include the unit weight of the immediate roof, the uniaxial tensile strength of the immediate roof, and the unit weight of the main roof.

[0009] Furthermore, the calculation formula of the relationship between the roof cutting height and the strata structure characteristics in the mining area in step 2) is , where is the roof cutting height, is the actual mining height, is the roof subsidence, is the floor heave, is the swelling coefficient.

[0010] Furthermore, if the pre-splitting roof cutting occurs in the immediate roof in step 3), the load borne by the left section of the immediate roof is , where is the load borne by the left section of the immediate roof, is the elastic modulus of the immediate roof, is the height of the immediate roof, is the unit weight of the immediate roof, is the unit weight of the main roof, is the height of the main roof, is the elastic modulus of the main roof.

[0011] Further, if the pre-splitting roof cutting occurs in the immediate roof in step 3), the load on the middle section of the immediate roof is , where is the load on the middle section of the immediate roof, is the elastic modulus of the immediate roof, is the moment of inertia of the immediate roof when the pre-splitting roof cutting occurs in the immediate roof, , where is the width of the empty plate of the cantilever beam model, 1 m, is the height of the bearing layer of the immediate roof, is the height of the remaining immediate roof; is the elastic modulus of the main roof, is the moment of inertia of the main roof when the pre-splitting roof cutting occurs in the immediate roof, , where is the width of the empty plate of the cantilever beam model, 1 m, is the height of the main roof; is the sum of the self-weights of the immediate roof and the main roof, , where is the unit weight of the immediate roof, is the height of the immediate roof, is the unit weight of the main roof, is the height of the main roof. Substituting , , into the load on the middle section of the immediate roof when the pre-splitting roof cutting occurs in the immediate roof and arranging, we get .

[0012] Further, if the pre-splitting roof cutting occurs in the immediate roof in step 3), the load on the right section of the immediate roof is equal to the load on the left section of the immediate roof.

[0013] Further, if the pre-splitting roof cutting occurs in the immediate roof and the main roof in step 3), the load on the middle section of the immediate roof is , where is the load on the middle section of the immediate roof, is the elastic modulus of the immediate roof, is the moment of inertia of the immediate roof when the pre-splitting roof cutting occurs in the immediate roof and the main roof, , where is the width of the empty plate of the cantilever beam model, 1 m, is the height of the bearing layer of the immediate roof; is the elastic modulus of the main roof, is the moment of inertia of the main roof when the pre-splitting roof cutting occurs in the immediate roof and the main roof, , where is the width of the empty plate of the cantilever beam model, 1 m, is the height of the bearing layer of the main roof; Substituting , , Substitute the load on the middle section of the immediate roof when the pre-splitting roof cutting occurs in the immediate roof and the main roof, and organize to obtain .

[0014] The beneficial effects achieved by the present invention are as follows: The present invention regards the immediate roof as a cantilever beam to establish a cantilever beam model, calculates the bearing layer height and the weakening layer height based on the cantilever beam formula and the load on the middle section of the immediate roof, and thus calculates the critical weakening coefficient. Taking the critical weakening coefficient as a quantitative index, a pre-splitting roof cutting and caving control method is established, which has strong operability in engineering practice; according to the pre-splitting roof cutting and caving control method, the problem of delayed caving of the goaf roof is solved, and the problems of insufficient filling density on the goaf side of the gob-side entry retaining, air flow disorder, and abnormal extension of the roof movement cycle are avoided.

[0015] Compared with the prior art, the present invention has the advantages of strong operability and realizing timely caving of the goaf roof. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic diagram of the overall fracture of the goaf in the present invention; Figure 2 is the present invention Figure 1 schematic diagram before pre-splitting roof cutting of the I-I section in; Figure 3 is the present invention Figure 1 schematic diagram after pre-splitting roof cutting of the I-I section in; Figure 4 is a schematic diagram of the pre-splitting roof cutting occurring in the immediate roof in the present invention; Figure 5 is a schematic diagram of the pre-splitting roof cutting occurring in the immediate roof and the main roof in the present invention.

[0017] In the figure: 1, coal wall; 2, unmined area; 3, mining face; 4, goaf; 5, gob-side entry retaining roadway; 6, immediate roof; 7, main roof; 8, pre-splitting roof cutting; 9, immediate roof bearing layer; 10, immediate roof weakening layer; 11, remaining immediate roof; 12, main roof weakening layer; 13, main roof bearing layer; 14, working face advancing direction; 15, working face hydraulic support; 16, uncollapsed area; 17, new fracture line; 18, O-X fracture; 19, pre-splitting area; 20, gas producer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] The present invention will be further described in detail below with reference to the drawings and embodiments. Embodiment 1

[0019] As Figures 1 to 5As shown, 14 is the advancing direction of the working face, 15 is the hydraulic support of the working face, 16 is the uncollapsed area, 17 is the new fracture line, 18 is the O-X fracture, 19 is the pre-splitting area, and 20 is the gas production tool. During the advancement of the mining face 3, the pre-splitting roof cutting 8 will cut off the stress transmission of the rock formation, form a new fracture line 17, realize the active guidance of the rock formation fracture line, and change the original O-X fracture 18 in the goaf 4. This embodiment applies pre-splitting roof cutting to establish a caving control method for a "hollow plate" structure along the goaf side, including the following steps: 1) Obtain parameters: Through borehole exploration, obtain the rock formation structure characteristics and mechanical property parameters of the mining area; The rock formation composition of the mining area includes the coal wall 1, and the unmined area 2 on the right side of the coal wall 1 from top to bottom, the mining face 3 and the goaf 4. An along-gob entry retaining roadway 5 is provided between the coal wall 1 and the goaf 4. The rock formation above the goaf 4 is divided into the immediate roof 6 and the main roof 7 from bottom to top; The rock formation structure characteristics of the mining area include the thickness of the coal seam, the thickness of the immediate roof 6, the thickness of the main roof 7, the actual mining height, the roof subsidence, the floor heave, and the swelling coefficient; the mechanical property parameters of the mining area include the unit weight of the immediate roof 6, the uniaxial tensile strength of the mudstone of the immediate roof 6, and the unit weight of the main roof 7; In this embodiment, the average thickness of the coal seam is 0.8 m, the immediate roof 6 is mudstone, the thickness of the immediate roof 6 is 5.23 m, and the unit weight of the immediate roof 6 is 25 kN / m 3 , the uniaxial tensile strength of the immediate roof 6 is 1.38 Mpa; the main roof 7 is siltstone, cemented with muddy calcite, the thickness of the main roof 7 is 6 m, and the unit weight of the main roof 7 is 26 kN / m 3 ; in this embodiment, the actual mining height is 1.2 m, the roof subsidence is 0.06 m, the floor heave is 0.04 m, and the swelling coefficient is 1.33.

[0020] 2) Calculate the roof cutting height: When pre-splitting the roof cutting 8, it is necessary to ensure that the gangue collapsed from the roof of the goaf 4 completely fills the goaf. Calculate the roof cutting height based on the relational formula between the roof cutting height and the rock formation structure characteristics of the mining area; the calculation formula of the relational formula between the roof cutting height and the rock formation structure characteristics of the mining area is , where is the roof cutting height, is the actual mining height, is the roof subsidence, is the floor heave, is the swelling coefficient. Substituting the data in this embodiment, the roof cutting height can be obtained.

[0021] 3) Calculate the loads on the left section, middle section, and right section of the immediate roof: The cutting height is divided into the height of the weakening layer and the height of the bearing layer; In this embodiment, the pre-splitting cutting roof 8 occurs in the immediate roof 6. The strata above the goaf 4 are divided into the immediate roof bearing layer 9, the immediate roof weakening layer 10, the remaining immediate roof 11, and the main roof 7 from bottom to top. Analyze the stress conditions of the left section, the middle section, and the right section of the immediate roof, and calculate the loads borne by the left section, the middle section, and the right section of the immediate roof; The pre-splitting cutting roof 8 occurs in the immediate roof 6. In addition to its own weight, the left section of the immediate roof is also subjected to the load of the overlying strata. The load borne by the left section of the immediate roof is where is the load borne by the left section of the immediate roof, is the elastic modulus of the immediate roof 6, is the height of the immediate roof 6, is the unit weight of the immediate roof 6, is the unit weight of the main roof 7, is the height of the main roof 7, is the elastic modulus of the main roof 7; The pre-splitting cutting roof 8 occurs in the immediate roof 6. In addition to its own weight, the middle section of the immediate roof is also subjected to the load of the overlying strata. Different from the left section of the immediate roof, due to the pre-splitting cutting roof 8, the middle section of the immediate roof loses the constraints on the left and right, so that the middle section of the immediate roof can no longer bear shear force and bending moment. However, because the strata are combined together, the curvature of the upper and lower layers must tend to be the same. Based on the principle of curvature coordination, the load equation is corrected to obtain the load borne by the middle section of the immediate roof as where is the load borne by the middle section of the immediate roof, is the elastic modulus of the immediate roof 6, is the moment of inertia of the immediate roof 6 when the pre-splitting cutting roof 8 occurs in the immediate roof 6. At this time, mainly the immediate roof bearing layer 9 and the remaining immediate roof 11 provide bending moment, where is the width of the empty plate of the cantilever beam model, 1 m, is the height of the immediate roof bearing layer 9, is the height of the remaining immediate roof 11; is the elastic modulus of the main roof 7, is the moment of inertia of the main roof 7 when the pre-splitting cutting roof 8 occurs in the immediate roof 6, where is the width of the empty plate of the cantilever beam model, 1 m, is the height of the main roof 7; is the sum of the self-weights of the immediate roof 6 and the main roof 7, where is the unit weight of the immediate roof 6, is the height of the immediate roof 6, is the unit weight of the main roof 7, is the height of the main roof 7, substitute , , into the load on the middle section of the immediate roof 6 when the pre-splitting roof cutting 8 occurs in the immediate roof 6, and organize to obtain ; When the pre-splitting roof cutting 8 occurs in the immediate roof 6, the load on the right section of the immediate roof is equal to the load on the left section of the immediate roof; 4) Calculate the critical weakening coefficient to achieve timely caving of the roof: Regard the immediate roof 6 as a cantilever beam to establish a cantilever beam model, and calculate the height of the bearing layer and the height of the weakening layer by combining the cantilever beam formula and the load on the middle section of the immediate roof; In this embodiment, the pre-splitting roof cutting 8 occurs in the immediate roof 6. The immediate roof 6 is mudstone, the elastic modulus of the immediate roof 6 is 8.6 GPa, the main roof 7 is siltstone, and the elastic modulus of the main roof 7 is 9.6 GPa. When the cantilever roof length is 10 m, substitute into the formula by combining the cantilever beam formula and the load on the middle section of the immediate roof, where is the uniaxial tensile strength of the direct roof bearing layer 9, and get {H}_{Z1}=\sqrt {\frac {246.6\left ( {{H}_{Z1}+1.9} \right )^{3}} {\left [ {8.6\left ( {{H}_{Z1}+1.9} \right )^{3}+2073} \right ]\times 1.38}} Use Matlab to solve and calculate The three solutions of are: -8.81, -0.49, 2.07. At this time, the height of the direct roof bearing layer 9 is 2.07 m, the height of the direct roof weakening layer 10 is 1.26 m, and the height of the remaining immediate roof 11 is 1.9 m. The calculated critical weakening coefficient is 0.61.

[0022] The critical weakening coefficient is calculated based on the critical weakening coefficient = weakening layer height / bearing layer height. If the ratio of the actual weakening layer height to the actual bearing layer height is greater than the critical weakening coefficient, timely caving of the roof is achieved. In this embodiment, if the ratio of the actual weakening layer height to the actual bearing layer height is greater than the critical weakening coefficient 0.61, timely caving of the roof is achieved.

[0023] Embodiment 2 This embodiment applies pre-splitting roof cutting to establish a caving control method for an "empty plate" structure along the goaf side, including the following steps: 1) Through borehole exploration, obtain the rock stratum structure characteristics and mechanical property parameters of the mining area; The rock formation in the mining area includes the coal wall 1, the unmined area 2, the coal face 3, and the goaf 4 from top to bottom on the right side of the coal wall 1. An along-gob entry 5 is provided between the coal wall 1 and the goaf 4. The rock formation above the goaf 4 is divided into the immediate roof 6 and the main roof 7 from bottom to top. The structural characteristics of the rock formation in the mining area include the thickness of the coal seam, the thickness of the immediate roof 6, the thickness of the main roof 7, the actual mining height, the roof subsidence, the floor heave, and the swelling coefficient. The mechanical property parameters of the mining area include the bulk density of the immediate roof 6, the uniaxial tensile strength of the mudstone of the immediate roof 6, and the bulk density of the main roof 7. In this embodiment, the average thickness of the coal seam is 2.4 m, the immediate roof 6 is mudstone, the thickness of the immediate roof 6 is 5.5 m, and the bulk density of the immediate roof 6 is 25 kN / m 3 , and the uniaxial tensile strength of the immediate roof 6 is 1.38 Mpa; the main roof 7 is siltstone, cemented with argillaceous calcite, the thickness of the main roof 7 is 6 m, and the bulk density of the main roof 7 is 26 kN / m 3 ; in this embodiment, the actual mining height is 2.41 m, the roof subsidence is 0.06 m, the floor heave is 0.04 m, and the swelling coefficient is 1.33.

[0024] 2) Calculate the cutting height: When pre-splitting and cutting the roof 8, it is necessary to ensure that the gangue falling from the roof of the goaf 4 completely fills the goaf. The cutting height is calculated based on the relationship formula between the cutting height and the structural characteristics of the rock formation in the mining area. The calculation formula of the relationship formula between the cutting height and the structural characteristics of the rock formation in the mining area is Where is the cutting height, is the actual mining height, is the roof subsidence, is the floor heave, is the swelling coefficient. Substituting the data in this embodiment, the cutting height can be obtained as .

[0025] ) 3) Calculate the loads on the left section, middle section, and right section of the immediate roof: The cutting height is divided into the height of the weakening layer and the height of the bearing layer; In this embodiment, pre-splitting and cutting the roof 8 occurs in the immediate roof 6 and the main roof 7. The rock formation above the goaf 4 is divided into the immediate roof bearing layer 9, the immediate roof weakening layer 10, the main roof weakening layer 12, and the main roof bearing layer 13 from bottom to top. Analyze the stress conditions of the left section, middle section, and right section of the immediate roof, and calculate the loads on the left section, middle section, and right section of the immediate roof; Pre-splitting and cutting the roof 8 occurs in the immediate roof 6 and the main roof 7. The load on the middle section of the immediate roof is , where is the load on the middle section of the immediate roof, is the elastic modulus of the immediate roof 6, is the moment of inertia of the immediate roof 6 when the pre-splitting roof cutting 8 occurs in the immediate roof 6. At this time, the moment is mainly provided by the immediate roof bearing layer 9 and the remaining immediate roof 11. At this time, the moment is mainly provided by the immediate roof bearing layer 9, , where is the width of the empty plate of 1 m in the cantilever beam model, is the height of the immediate roof bearing layer 9; is the elastic modulus of the main roof 7, is the moment of inertia of the main roof 7 when the pre-splitting roof cutting 8 occurs in the immediate roof 6. At this time, the moment is mainly provided by the main roof bearing layer 13, , where is the width of the empty plate of 1 m in the cantilever beam model, is the height of the main roof bearing layer 13; Substitute , , into the load on the middle section of the immediate roof when the pre-splitting roof cutting occurs in the immediate roof 6 and the main roof 7, and after sorting, we get ; 4) Calculate the critical weakening coefficient to achieve the timely collapse of the roof: Regard the immediate roof 6 as a cantilever beam to establish a cantilever beam model, and calculate the height of the bearing layer and the height of the weakening layer by combining the cantilever beam formula and the load on the middle section of the immediate roof; In this embodiment, the pre-splitting roof cutting occurs in the immediate roof 6 and the main roof 7. The immediate roof 6 is mudstone, and the elastic modulus of the immediate roof 6 is 8.6 Gpa. The main roof 7 is siltstone, and the elastic modulus of the main roof 7 is 9.6 Gpa. When the hanging roof length is 10 m, substitute it into the formula by combining the cantilever beam formula and the load on the middle section of the immediate roof , where is the uniaxial tensile strength of the immediate roof bearing layer 9, and we get {H}_{Z1}=\sqrt {\frac {257.14\times {H}_{Z1}} {\left [ {8.6\times {H}_{Z1}+87.75} \right ]\times 1.38}} , use Matlab to solve and calculate The three solutions of are: -4.83, 0.48, 4.35. At this time, the height of the immediate roof bearing layer 9 is 4.35 m, the height of the immediate roof weakening layer 10 is 1.15 m, and the height of the main roof weakening layer 12 is 1.5 m. The calculated critical weakening coefficient is 0.61.

[0026] The critical weakening coefficient is calculated based on the critical weakening coefficient = height of the weakening layer / height of the bearing layer. When the ratio of the actual height of the weakening layer to the actual height of the bearing layer is greater than the critical weakening coefficient, timely caving of the roof is achieved. In this embodiment, when the ratio of the actual height of the weakening layer to the actual height of the bearing layer is greater than the critical weakening coefficient of 0.61, timely caving of the roof is achieved.

[0027] The present invention uses the critical weakening coefficient as a quantitative index to establish a pre-splitting roof cutting and caving control method, which has strong operability in engineering practice, realizes timely caving of the roof, and is of great significance for ensuring mining safety and improving resource recovery rate.

[0028] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those of ordinary skill in the art, the embodiments can still be changed. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A caving control method for the "hollow slab" structure along the goaf side, characterized in that: It includes the following steps: 1) Obtain parameters: Through borehole exploration, obtain the rock stratum structure characteristics and mechanical property parameters of the mining area; The rock stratum composition of the mining area includes a coal wall (1), an unmined area (2) on the right side of the coal wall (1) from top to bottom, a coal mining face (3) and a goaf (4). An along - gob entry - retaining roadway (5) is provided between the coal wall (1) and the goaf (4). The rock strata above the goaf (4) are divided into a direct roof (6) and a main roof (7) from bottom to top; 2) Calculate the roof - cutting height: Calculate the roof - cutting height based on the relationship formula between the roof - cutting height and the rock stratum structure characteristics of the mining area; 3) Calculate the loads on the left section, middle section and right section of the direct roof: Divide the roof - cutting height into a weakening layer height and a bearing layer height; If the pre - splitting roof - cutting (8) occurs in the direct roof (6), the rock strata above the goaf (4) are divided into a direct - roof bearing layer (9), a direct - roof weakening layer (10), the remaining direct roof (11) and the main roof (7) from bottom to top. Analyze the stress conditions of the left section, middle section and right section of the direct roof, and calculate the loads on the left section, middle section and right section of the direct roof; If the pre - splitting roof - cutting (8) occurs in the direct roof (6) and the main roof (7), the rock strata above the goaf (4) are divided into a direct - roof bearing layer (9), a direct - roof weakening layer (10), a main - roof weakening layer (12) and a main - roof bearing layer (13) from bottom to top. Analyze the stress conditions of the left section, middle section and right section of the direct roof, and calculate the loads on the left section, middle section and right section of the direct roof; 4) Calculate the critical weakening coefficient to achieve timely caving of the roof: Regard the direct roof (6) as a cantilever beam to establish a cantilever beam model, and calculate the bearing layer height and the weakening layer height in combination with the cantilever beam formula and the load on the middle section of the direct roof; Calculate the critical weakening coefficient based on Critical weakening coefficient = Weakening layer height / Bearing layer height. When the ratio of the actual weakening layer height to the actual bearing layer height is greater than the critical weakening coefficient, timely caving of the roof is achieved.

2. A caving control method for an "empty plate" structure along the goaf side according to claim 1, characterized in that: The rock stratum structure characteristics of the mining area in step 1) include the thickness of the coal seam, the thickness of the direct roof (6), the thickness of the main roof (7), the actual mining height, the roof subsidence, the floor heave, and the swelling coefficient.

3. A caving control method for an "empty plate" structure along the goaf side according to claim 2, characterized in that: The mechanical property parameters of the mining area in step 1) include the unit weight of the direct roof (6), the uniaxial tensile strength of the direct roof (6), and the unit weight of the main roof (7).

4. A caving control method for an "empty plate" structure along the goaf side according to claim 3, characterized in that: The calculation formula for the relationship between the roof cutting height and the rock stratum structure characteristics in step 2) is , where is the roof cutting height, is the actual mining height, is the roof subsidence amount, is the floor heave amount, is the swelling coefficient.

5. A caving control method for an "empty plate" structure along the goaf side according to claim 4, characterized in that: If the pre-splitting roof cutting (8) occurs in the immediate roof (6) in step 3), the load borne by the left section of the immediate roof is , where is the load borne by the left section of the immediate roof, is the elastic modulus of the immediate roof (6), is the height of the immediate roof (6), is the unit weight of the immediate roof (6), is the unit weight of the main roof (7), is the height of the main roof (7), is the elastic modulus of the main roof (7).

6. A caving control method for an "empty plate" structure along the goaf side according to claim 4, characterized in that: If the pre-splitting roof cutting (8) occurs in the immediate roof (6) in step 3), the load on the middle section of the immediate roof is , where is the load on the middle section of the immediate roof, is the elastic modulus of the immediate roof (6), is the moment of inertia of the immediate roof (6) when the pre-splitting roof cutting (8) occurs in the immediate roof (6), , where is the width of the empty plate of the cantilever beam model, 1 m, is the height of the immediate roof bearing layer (9), is the height of the remaining immediate roof (11); is the elastic modulus of the main roof (7), is the moment of inertia of the main roof (7) when the pre-splitting roof cutting (8) occurs in the immediate roof (6), , where is the width of the empty plate of the cantilever beam model, 1 m, is the height of the main roof (7); is the sum of the self-weights of the immediate roof (6) and the main roof (7), , where is the unit weight of the immediate roof (6), is the height of the immediate roof (6), is the unit weight of the main roof (7), is the height of the main roof (7). Substituting , , into the load on the middle section of the immediate roof when the pre-splitting roof cutting (8) occurs in the immediate roof (6), and after arrangement, we get .

7. A caving control method for the "hollow slab" structure along the goaf side according to claim 4, characterized in that: In step 3), if the pre - splitting roof - cutting (8) occurs in the direct roof (6), the load on the right section of the direct roof is equal to the load on the left section of the direct roof.

8. A caving control method for an "empty plate" structure along the goaf side according to claim 4, characterized in that: If the pre-splitting roof cutting (8) occurs in the immediate roof (6) and the main roof (7) in step 3), the load on the middle section of the immediate roof is , where is the load on the middle section of the immediate roof, is the elastic modulus of the immediate roof (6), is the moment of inertia of the immediate roof (6) when the pre-splitting roof cutting (8) occurs in the immediate roof (6) and the main roof (7), , where is the width of the empty plate of the cantilever beam model, 1 m, is the height of the bearing layer of the immediate roof (9); is the elastic modulus of the main roof (7), is the moment of inertia of the main roof (7) when the pre-splitting roof cutting (8) occurs in the immediate roof (6) and the main roof (7), , where is the width of the empty plate of the cantilever beam model, 1 m, is the height of the bearing layer of the main roof (13); Substituting , , into the load on the middle section of the immediate roof when the pre-splitting roof cutting (8) occurs in the immediate roof (6) and the main roof (7), and after arrangement, we get .

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