A method for reducing subsidence by grouting in the entire fissure zone to prevent water seepage in the roof

Abstract

The present invention discloses a method for reducing subsidence by full-area grouting in a fracture zone which can prevent water seepage in a roof. According to the burial range of the stratum to be mined, before mining the stratum, a plurality of anchoring shafts arranged in an array are firstly drilled from the ground to the water-proof key stratum, and holes are made in each overlying rock stratum above the water-proof key stratum to form rock stratum anchoring holes. Then, corresponding anchoring grouting pipes are respectively placed in each anchoring shaft and cementing operation is performed. Finally, before mining the stratum to be mined or during mining, anchoring slurry is injected into the anchoring grouting pipe in the anchoring shaft in a continuous pressure grouting manner for anchoring. After the anchoring slurry is completely solidified, a full-length anchoring manner is formed in the direction of the buried depth of the water-proof key stratum. All the array-arranged anchoring shaft unit assemblies jointly form a group anchoring effect on the overlying rock stratum above the water-proof key stratum, which can greatly reduce the destructive effect of mining on the water-proof key stratum, thereby minimizing the probability of water seepage accidents in the roof.

Description

Technical Field

[0001] The invention relates to a method for preventing water seepage from the roof of a coal mining face in an underground coal mine, in particular to a method for reducing subsidence by grouting the entire area of ​​a fracture zone which can prevent water seepage from the roof, and belongs to the technical field of mine safety. Background Art

[0002] In underground mineral mining, underground mining is still the main mining method. Taking coal mining as an example, underground mining accounts for 60% of the world's coal production. During the construction and production of mines, artificial underground engineering will inevitably cause changes in the geological conditions of the surrounding rock, resulting in geological changes such as fissures, faults, and subsidence areas. Surface water and groundwater often enter the mine through fissures, faults, subsidence areas and other channels. Therefore, corresponding water prevention and control measures must be implemented during the construction and production of mines. If surface water and groundwater flow into the mine working face uncontrollably due to inadequate water prevention and control measures, it will cause casualties of workers or property losses in the mine. Flood accidents, usually also called seepage accidents, are often in the form of influx through cracks or faults in the roof of the mine working face.

[0003] When there are multiple rock layers in the rock layer covering the mining area, the bearing capacity and anti-permeability of each layer are not the same. The key water-proof layer refers to the part of the rock layer that water must pass through in the end. The natural channels in the geological structure and the penetration of mining cracks are the two main ways for water to break through the key water-proof layer. The key to avoiding water seepage accidents is not to destroy the key water-proof layer during mining and to maintain the integrity of the key water-proof layer. However, on the one hand, after the underground ore layer is mined in the process of underground mining, a large area of ​​underground goaf is often left. Under the influence of overburden pressure and groundwater, the ore layers on both sides of the pillars and mining area soften and lose strength, which often easily leads to the subsidence and fall of the overburden rock mass, forming landslides, and then easily causing the destruction of the key water-proof layer; on the other hand, in the mining process, the surrounding rock of the goaf is easily affected by the blasting vibration, which leads to the development of rock cracks and damages the key water-proof layer, and even penetrates the surface or connects to the old kiln water, thus causing water seepage accidents. Summary of the invention

[0004] In response to the problems existing in the above-mentioned prior art, the present invention provides a method for reducing subsidence by grouting in the entire fracture zone, which can prevent water seepage in the roof, and can minimize the damage to the key waterproof layer during the mining process, thereby minimizing the probability of roof water seepage accidents.

[0005] To achieve the above purpose, the method for reducing subsidence by grouting in the entire crack zone to prevent water seepage in the roof specifically comprises the following steps:

[0006] a. Preparation for well construction: Detect and determine the depth, thickness and burial range of the layer to be mined, and detect and determine the number, depth, thickness and lithology of the overlying rock layers of the layer to be mined, determine the stratigraphic position and depth of the main key layer and the water-proof key layer, and construct a geological mathematical model; based on the geological mathematical model, calculate and determine the diameter of the anchor shaft corresponding to the burial range of the layer to be mined, the number of anchor shafts, the array spacing and the size of the anchor grouting pipes that match the anchor shaft according to the depth of the water-proof key layer, the number and lithology of each overlying rock layer above the water-proof key layer, and the size of the water-proof key layer. The bottom end of the key layer is taken as the starting point, and the number, position and spatial size of multiple rock stratum anchor holes set in layers along the anchor shaft are determined at least according to the number, burial depth, thickness and lithology of each rock layer between the main key layer and the water-proof key layer. After selecting the grouting anchor, the bearing mathematical model of each anchor shaft unit assembly including the rock stratum anchor hole, the anchor grouting pipe and the anchor slurry filling body is generated according to the designed anchoring strength of the grouting anchor. The bearing mathematical model of each anchor shaft unit assembly is fitted with the geological mathematical model to generate the overall rock stratum anchor bearing mathematical model;

[0007] b. Well construction: According to the overall rock formation anchor bearing mathematical model, each anchor shaft is set from the ground to the water-proof key layer, and the hole making operation is carried out at the set position of the rock formation anchor hole, and the corresponding anchor grouting pipe is placed in each anchor shaft, and the cementing operation is carried out after ensuring that the bottom end of the anchor grouting pipe is located at the bottom of the anchor shaft;

[0008] c. Rock layer anchoring construction and ore mining: before or during the mining of the mining layer, pressure grouting is used to inject anchoring slurry into the anchoring grouting pipe in the anchoring shaft. When pressure grouting is performed during the mining of the mining layer, during the advancement of the working face, every time the working face passes through the ore layer area corresponding to the bottom of the anchoring shaft, pressure grouting is used to inject anchoring slurry into the anchoring grouting pipe in the anchoring shaft; after the anchoring slurry completely fills the entire anchoring shaft space, pressure grouting is continued; after the anchoring slurry is completely solidified, the pressure grouting equipment is removed.

[0009] As a further improvement of the present invention, during the advancement of the working face in step c, the working face is advanced forward while filling the goaf formed behind, or the working face is advanced forward while supporting the roof of the goaf formed behind.

[0010] As a further improvement of the present invention, at least the anchor grouting pipe section located between the main key layer and the waterproof key layer is a flower pipe structure including a plurality of radial through holes penetrating the pipe wall in the radial direction.

[0011] As a preferred embodiment of the present invention, the structure of the rock formation anchoring hole is a shell-shaped structure including an upper arch structure and a lower arch bottom structure.

[0012] As a further improvement of the present invention, the rock formation anchoring holes are correspondingly arranged in each rock formation.

[0013] As a further improvement of the present invention, a plurality of rock formation anchoring holes are provided in the same thick rock formation according to the lithology and thickness of each rock formation.

[0014] As a further improvement of the present invention, according to the lithology and thickness of each rock formation, the rock formation anchoring holes in the same thick rock formation can be arranged in large number and small spatial dimensions along the axial direction of the anchoring shaft, or in small number and large spatial dimensions along the axial direction of the anchoring shaft.

[0015] As a further improvement of the present invention, a protruding structure which can increase the strength of the anchoring connection is provided on the outer surface and / or the inner surface of the anchoring grouting pipe.

[0016] As a further improvement of the present invention, the protrusion structure is a protrusion ring structure evenly distributed along the axial direction of the anchor grouting pipe, or a spiral protrusion structure arranged along the axial direction of the anchor grouting pipe.

[0017] The specific calculation method in step a is as follows:

[0018] When the working face advances forward by a distance of L, due to the different crushing angles (θ1, θ2) of the rock formation in the strike direction, when the separation space first appears below the jth layer (key layer), the hanging length (a j ) and L is

[0019]

[0020] The hanging width of the key layer in the inclined direction (b j The relationship between the working surface width (B, in meters) and the working surface width (B, in meters) is:

[0021]

[0022]

[0023] S1=LB

[0024] S2=a n+1 b n+1

[0025] In the formula, a n+1 b is the length of the overhang along the strike direction of the rock mass, in meters; n+1 is the length of the overhang of the rock mass along the inclined direction, in meters; h is the vertical distance between the overburden and the coal seam, in meters; h n+1is the maximum height of the overburden stratum, in meters; L is the distance of advancement of the working face, in meters; θ1 is the rock stratum breaking angle on the side of the cut; θ2 is the rock stratum breaking angle on the side of the working face; S1 is the area of ​​the working face that has been mined; S2 is the suspended area of ​​the overburden stratum;

[0026] Assume that the spacing between the anchor grouting pipes is L j , the row spacing is L p , then the anchoring area of ​​each anchor grouting pipe is A = L j ·L p , then n1=L / L needs to be set in the direction of the working face p The number of anchor grouting pipes that need to be set in the inclination direction of the working face is n2 = L / L p If there are a total of N = n1·n2 anchor grouting pipes, then a total of N = n1·n2 anchor grouting pipes need to be installed within the working surface;

[0027] The weight that each anchor grouting pipe needs to bear is

[0028]

[0029] In the formula, is the average density of the overlying rock;

[0030] Assuming that the rock mass and the bonding material are elastic materials with the same properties, using the displacement solution of the Mindlin problem, the rock mass is regarded as half-space, the anchor grouting pipe is semi-infinite, and the displacement of the rock mass at the orifice is equal to the total elongation of the anchor body. The ultimate pull-out force Pu of the full-length bonded anchor grouting pipe is derived as follows:

[0031]

[0032]

[0033] Where, E is the elastic modulus of the rock mass; μ is the Poisson's ratio of the rock mass; E b is the elastic modulus of the anchor grouting pipe; τ u is the ultimate bonding stress between the anchor grouting pipe and the anchor grouting pipe, and α is the radius of the anchor grouting pipe;

[0034] The weight that the anchor grouting pipe needs to bear is

[0035]

[0036] Where k is the anchoring environment influence coefficient.

[0037] Compared with the prior art, the present invention can prevent water seepage in the fracture zone by full-area grouting to reduce settlement. According to the buried range of the layer to be mined, before mining the ore layer, multiple arrayed anchor shafts are firstly set from the ground to the water-proof key layer, and holes are made in each overlying rock layer above the water-proof key layer to form rock layer anchor holes, and then the corresponding anchor grouting pipes are respectively placed in each anchor shaft to carry out cementing operation, and finally, before mining or during mining of the layer to be mined, continuous pressure grouting is used to inject the anchor grouting pipes in the anchor shaft into the anchor grouting pipes. Anchoring slurry is injected into the rock to anchor it. After the anchoring slurry is completely solidified, it forms a full-length anchoring method along the buried depth direction of the waterproof key layer to solve the problem of damage to the waterproof key layer caused by mining in the later period. The diameter of the anchoring shaft unit assembly, the size of the anchoring grouting pipe and the spatial size of the rock anchor hole can be different according to the different bearing positions. Continuous pressure grouting is carried out for anchoring, or when the working face advances during the mining process, continuous pressure grouting and anchoring is carried out on the anchoring shaft every time it passes through the ore layer area corresponding to the bottom of an anchoring shaft. Therefore, there is sufficient anchoring hardening time to ensure the anchoring strength and effect of each overlying rock layer above the key waterproof layer. Not only is each anchoring shaft unit assembly anchored along the entire length of the anchoring shaft, but each anchoring shaft unit assembly includes a plurality of rock layer anchoring convex ring structures formed by filling rock layer anchor holes with anchoring slurry. Each rock layer anchoring convex ring structure can not only provide the supporting force of the rock layer where it is located, but also can evenly apply the load to the entire anchoring support body of the anchoring shaft unit including the anchoring grouting pipe and the anchoring slurry filling body. Moreover, all the anchoring shaft unit assemblies arranged in an array according to a set spacing within the buried range of the corresponding layer to be mined jointly form a group anchoring effect on the overlying rock layer above the key waterproof layer, which can greatly reduce the destructive effect of mining on the key waterproof layer, thereby minimizing the probability of roof water seepage accidents. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of the structure of the present invention for setting up an anchoring shaft and making a hole;

[0039] Figure 2 It is a schematic diagram of the structure of the anchor grouting pipe of the present invention after being placed in the anchor vertical shaft;

[0040] Figure 3 It is a schematic diagram of the structure in which the working face is advanced forward while filling the goaf formed at the rear;

[0041] Figure 4 It is a schematic diagram of the load on the overlying rock layer during mining.

[0042] In the figure: 1. Anchoring shaft, 2. Anchoring grouting pipe, 3. Rock stratum anchoring hole, 4. Main key layer, 5. Water-proof key layer, 6. Layer to be mined. DETAILED DESCRIPTION

[0043] The present invention will be further described below in conjunction with the accompanying drawings.

[0044] The method for reducing subsidence by grouting the entire fissure zone to prevent water seepage in the roof comprises the following steps:

[0045] a. Preparation for well construction: Detect and determine the burial depth, thickness and burial range of the layer 6 to be mined, and detect and determine the number, burial depth, thickness and lithology of the overlying strata of the layer 6 to be mined, determine the stratigraphic position and depth of the main key layer 4 and the water-proof key layer 5, and construct a geological mathematical model; based on the geological mathematical model, calculate and determine the diameter of the anchor shaft 1 corresponding to the burial range of the layer 6 to be mined, the number of anchor shafts 1, and the array arrangement according to the depth of the water-proof key layer 5, the number and lithology of each overlying stratum above the water-proof key layer 5. The distance and the size of the anchor grouting pipe 2 matched with the anchor shaft 1 are taken as the starting point, and the number, position and spatial size of multiple rock layer anchor holes 3 arranged in layers along the anchor shaft 1 are determined at least according to the number, burial depth, thickness and lithology of each rock layer between the main key layer 4 and the waterproof key layer 5. The rock layer anchor holes 3 are correspondingly arranged in each rock layer or between each rock layer. The structure of the rock layer anchor hole 3 is preferably a shell-shaped structure including an upper arch structure and a lower arch bottom structure. The composite grouting is selected After the grouting anchoring agent with good fluidity, permeability, adhesion and strength such as slurry and compound rebar glue is used, the bearing mathematical model of each anchoring shaft unit assembly including the rock formation anchoring hole 3, the anchoring grouting pipe 2 and the anchoring slurry filling body is generated according to the designed anchoring strength of the grouting anchoring agent, and the bearing mathematical model of each anchoring shaft unit assembly is fitted with the geological mathematical model to generate the overall rock formation anchoring bearing mathematical model; on the premise of meeting the anchoring support strength, according to the lithology and thickness of each rock formation, the rock formation anchoring hole 3 in the same large thickness rock formation can be set to multiple, the setting of the rock formation anchoring hole 3 in the same large thickness rock formation can be a large number and small space size along the axial direction of the anchoring shaft 1, or a small number and large space size along the axial direction of the anchoring shaft 1. In order to make full use of the supporting role of the main key layer 4 and the waterproof key layer 5 themselves, the spatial size of the rock formation anchoring hole 3 corresponding to the main key layer 4 and the waterproof key layer 5 can be designed to be larger than the spatial size of the rock formation anchoring hole 3 corresponding to other rock formations.

[0046] b. Well construction: Figure 1 As shown, according to the overall rock formation anchoring bearing mathematical model, each anchoring shaft 1 is set from the ground to the water-proof key layer 5, and the hole making operation is carried out at the set position of the rock formation anchor hole 3. The hole making method can adopt the hole making method of hydraulic cutting, such as Figure 2As shown, the corresponding anchor grouting pipes 2 are respectively placed in each anchor shaft 1, and cementing operations are performed after ensuring that the bottom end of the anchor grouting pipe 2 is located at the bottom of the anchor shaft 1.

[0047] c. Rock layer anchoring construction and ore mining: Before or during the mining of the mining layer 6, the prepared anchor slurry is injected into the anchor grouting pipe 2 in the anchor shaft 1 by continuous pressure grouting. Figure 3 As shown, when pressure grouting is performed during the mining of the mining layer 6, during the advancement of the working face, each time a ore layer area corresponding to the bottom end of an anchor shaft 1 is passed, the prepared anchor slurry is injected into the anchor grouting pipe 2 in the anchor shaft 1 by pressure grouting; the anchor slurry fills the space between the wall of the anchor shaft 1 and the outer wall of the anchor grouting pipe 2 from bottom to top, and at the same time, each rock formation anchor hole 3 is filled in turn. After the entire anchor shaft 1 space is completely filled, pressure grouting is continued to fill the anchor slurry with the cracks around the anchor shaft 1 and the rock formation anchor hole 3. After the anchor slurry is completely solidified, the anchor grouting pipe 2 of each anchor shaft unit along the entire length of the anchor shaft 1 is anchored, and the pressure grouting equipment is removed.

[0048] The method for reducing subsidence by grouting the entire fracture zone to prevent water seepage in the roof is based on the burial range of the layer 6 to be mined. Before mining the ore layer, multiple arrayed anchor shafts 1 are first set from the ground to the water-proof key layer 5, and holes are made in each overlying rock layer above the water-proof key layer 5 to form rock layer anchor holes 3, and then corresponding anchor grouting pipes 2 are respectively placed in each anchor shaft 1 to carry out cementing operations, and finally, before or during the mining of the layer 6 to be mined, continuous pressure grouting is used to inject the anchor grouting pipes 2 in the anchor shaft 1. The anchoring slurry is used for anchoring. After the anchoring slurry is completely solidified, a full-length anchoring method is formed along the buried depth direction of the waterproof key layer 5 to solve the problem of damage to the waterproof key layer 5 caused by the mining of the later ore layer. Each anchor shaft unit assembly corresponding to the array structure arrangement within the buried range of the mining layer 6, the diameter of the anchor shaft 1, the size of the anchor grouting pipe 2 and the spatial size of the rock formation anchor hole 3 may be different according to the different bearing positions. Since the anchor shaft 1 is grouted before the mining layer 6 is mined, the anchor grouting pipe 2 is grouted and the spatial size of the rock formation anchor hole 3 is different. Continuous pressure grouting is performed for anchoring, or during the mining process, when the working face advances through the ore layer area corresponding to the bottom end of an anchor shaft 1, continuous pressure grouting is performed for anchoring shaft 1, so that sufficient anchoring hardening time can be provided to ensure the anchoring strength and effect of each overlying rock layer above the key water-proof layer 5. Not only each anchor shaft unit assembly is anchored along the entire length of the anchor shaft 1, but each anchor shaft unit assembly also includes a plurality of rock formation anchoring convex ring structures formed by filling the rock formation anchoring holes 3 with anchoring slurry. Each rock formation anchoring convex ring structure can not only provide the supporting force for the rock formation, but also evenly apply the load to the entire anchoring support body of the anchoring shaft unit including the anchoring grouting pipe 2 and the anchoring slurry filling body. All the anchoring shaft unit assemblies arranged in an array according to the set row spacing within the burial range of the mining layer 6 to be mined can jointly form a group anchoring effect on the overlying rock formation above the waterproof key layer 5, which can greatly reduce the destructive effect of mining on the waterproof key layer 5, thereby minimizing the probability of roof water seepage accidents.

[0049] The specific calculation method in step a is as follows:

[0050] like Figure 4 As shown in the figure, when the working face advances forward by a distance of L, due to the different crushing angles (θ1, θ2) of the rock formation in the strike direction, when the separation space first appears below the jth layer (key layer), the hanging length (a j ) and L is

[0051]

[0052] The hanging width of the key layer in the inclined direction (b j The relationship between the working surface width (L, in meters) and the working surface width (L, in meters) is:

[0053]

[0054]

[0055] S1=LB

[0056] S2=a n+1 b n+1

[0057] In the formula, a n+1 b is the length of the overhang along the strike direction of the rock mass, in meters; n+1 is the length of the overhang of the rock mass along the inclined direction, in meters; h is the vertical distance between the overburden and the coal seam, in meters; h n+1 is the maximum height of the overburden stratum, in meters; L is the distance of advancement of the working face, in meters; θ1 is the rock stratum breaking angle on the side of the cut; θ2 is the rock stratum breaking angle on the side of the working face; S1 is the area of ​​the working face that has been mined; S2 is the suspended area of ​​the overburden stratum;

[0058] Assume that the spacing between the anchor grouting pipes is L j , the row spacing is L p , then the anchoring area of ​​each anchor grouting pipe is A = L j ·L p , then n1=L / L needs to be set in the direction of the working face p The number of anchor grouting pipes that need to be set in the inclination direction of the working face is n2 = L / L p If there are a total of N=n1·n2 anchor grouting pipes, then a total of N=n1·n2 anchor grouting pipes need to be installed within the working surface.

[0059] The weight that each anchor grouting pipe needs to bear is:

[0060]

[0061] In the formula, is the average density of the overlying rock layer, which is generally taken as 2500kg / m based on experience. 3 .

[0062] Considering the situation where the full-length bonded anchor grouting pipe is buried in the rock mass and its end is subjected to pull-out force, it is assumed that the rock mass and the bonding material are elastic materials with the same properties. Using the displacement solution of the Mindlin problem, the rock mass is regarded as half-space, the anchor grouting pipe is semi-infinite, and the displacement of the rock mass at the orifice is equal to the total elongation of the anchor rod. The ultimate pull-out force Pu of the full-length bonded anchor grouting pipe is derived as follows:

[0063]

[0064]

[0065] Where, E is the elastic modulus of the rock mass; μ is the Poisson's ratio of the rock mass; E b is the elastic modulus of the anchor grouting pipe; τ u is the ultimate bonding stress between the anchor grouting pipe and the anchor grouting pipe, and α is the radius of the anchor grouting pipe;

[0066] The weight that the anchor grouting pipe needs to bear is

[0067]

[0068] Where k is the anchoring environmental impact coefficient, which is mainly related to rock properties, burial depth, anchoring length, etc.

[0069] In order to facilitate the anchoring slurry to quickly fill the space between the wall of the anchoring shaft 1 and the outer wall of the anchoring grouting pipe 2 and each rock stratum anchoring hole 3, as a further improvement scheme of the present invention, at least the anchoring grouting pipe 2 section located between the main key layer 4 and the waterproof key layer 5 is a flower pipe structure including multiple radial through holes penetrating the pipe wall in the radial direction.

[0070] In order to achieve a better full-length anchoring effect for the anchor grouting pipe 2, as a further improvement scheme of the present invention, a protrusion structure that can increase the anchoring connection strength is provided on the outer surface and / or inner surface of the anchor grouting pipe 2. The protrusion structure can be a protrusion ring structure evenly distributed along the axial direction of the anchor grouting pipe 2, or it can be a spiral protrusion structure arranged along the axial direction of the anchor grouting pipe 2, or other structural forms.

[0071] In order to further reduce the destructive effect of mining on the key water-proof layer 5, as a further improvement of the present invention, Figure 3 As shown, in the process of advancing the working face in step c, the working face is advanced forward while filling the goaf formed at the rear with waste materials such as gangue, or the working face is advanced forward while supporting the roof of the goaf formed at the rear. The roof of the goaf can be supported by a recycled steel ladle support column. For the specific mining layer 6 where the bottom plate of the goaf is soft rock or water-swelling rock mass that is prone to bottom drum phenomenon, artificial drilling or grooving can be carried out on the bottom plate of the goaf so that the bottom plate of the goaf is artificially controlled to bulge and then contact the top plate of the goaf and bear the load, and the top plate of the goaf can be supported by a bottom drum connection method.

Claims

1. A method for reducing subsidence by grouting in the entire fracture zone to prevent water seepage in the roof, characterized in that: The specific steps include: a. Preparation for well construction: Detect and determine the depth, thickness and burial range of the layer to be mined (6), and detect and determine the number, depth, thickness and lithology of the overlying strata of the layer to be mined (6), determine the position and depth of the main key layer (4) and the water-proof key layer (5), and construct a geological mathematical model; Based on the geological mathematical model, according to the depth of the waterproof key layer (5), the number of overlying rock layers above the waterproof key layer (5) and the lithology, the diameter of the anchor shaft (1), the number of anchor shafts (1), the array spacing and the size of the anchor grouting pipe (2) matched with the anchor shaft (1) corresponding to the burial range of the mining layer (6) are determined. With the bottom end of the waterproof key layer (5) as the starting point, at least according to the number of each rock layer between the main key layer (4) and the waterproof key layer (5), the number of overlying rock layers between the main key layer (4) and the waterproof key layer (5) is calculated. The number, position and spatial size of multiple rock stratum anchor holes (3) arranged in layers along the anchor shaft (1) are determined by calculating the amount, burial depth, thickness and lithology; after selecting a grouting anchor, a bearing mathematical model of each anchor shaft unit assembly including the rock stratum anchor hole (3), the anchor grouting pipe (2) and the anchor slurry filling body is generated according to the designed anchoring strength of the grouting anchor; the bearing mathematical model of each anchor shaft unit assembly is fitted with the geological mathematical model to generate an overall rock stratum anchor bearing mathematical model; b. Well construction: according to the overall rock formation anchor bearing mathematical model, each anchor shaft (1) is set from the ground to the water-proof key layer (5), and the hole making operation is carried out at the set position of the rock formation anchor hole (3), and the corresponding anchor grouting pipe (2) is respectively placed in each anchor shaft (1), and the cementing operation is carried out after ensuring that the bottom end of the anchor grouting pipe (2) is located at the bottom of the anchor shaft (1); c. Rock layer anchoring construction and ore layer mining: before or during the mining of the ore layer (6) to be mined, anchoring slurry is injected into the anchoring grouting pipe (2) in the anchoring shaft (1) by pressure grouting. When pressure grouting is performed during the mining of the ore layer (6), anchoring slurry is injected into the anchoring grouting pipe (2) in the anchoring shaft (1) by pressure grouting every time the working face passes through the ore layer area corresponding to the bottom end of the anchoring shaft (1). After the anchoring slurry completely fills the entire anchoring shaft (1), pressure grouting is continued. After the anchoring slurry is completely solidified, the pressure grouting equipment is removed.

2. The method for reducing subsidence by grouting in the entire crack zone to prevent water seepage in the roof according to claim 1, characterized in that: During the advancement of the working face in step c, the working face is advanced forward while filling the goaf formed behind, or the working face is advanced forward while supporting the roof of the goaf formed behind.

3. The method for reducing subsidence by grouting in the entire crack zone to prevent water seepage in the roof according to claim 1 or 2, characterized in that: At least the anchor grouting pipe (2) section located between the main key layer (4) and the waterproof key layer (5) is a flower pipe structure including a plurality of radial through holes penetrating the pipe wall in the radial direction.

4. The method for reducing subsidence by grouting in the entire crack zone to prevent water seepage in the roof according to claim 1 or 2, characterized in that: The structure of the rock formation anchoring hole (3) is a shell-shaped structure comprising an upper arch structure and a lower arch bottom structure.

5. The method for reducing subsidence by grouting in the entire crack zone to prevent water seepage in the roof according to claim 1 or 2, characterized in that: The rock layer anchor holes (3) are correspondingly arranged in each rock layer.

6. The method for reducing subsidence by grouting in the entire crack zone to prevent water seepage in the roof according to claim 5, characterized in that: According to the lithology and thickness of each rock layer, a plurality of rock layer anchoring holes (3) are provided in the same thick rock layer.

7. The method for reducing subsidence by grouting in the entire crack zone to prevent water seepage in the roof according to claim 6, characterized in that: According to the lithology and thickness of each rock layer, the rock layer anchor holes (3) in the same thick rock layer are arranged in a large number with small spatial dimensions along the axial direction of the anchor shaft (1), or in a small number with large spatial dimensions along the axial direction of the anchor shaft (1).

8. The method for reducing subsidence by grouting in the entire crack zone to prevent water seepage in the roof according to claim 1 or 2, characterized in that: The outer surface and / or the inner surface of the anchor grouting pipe (2) is provided with a protruding structure which can increase the anchor connection strength.

9. The method for reducing subsidence by grouting in the entire fracture zone to prevent water seepage in the roof according to claim 4, characterized in that: The protruding structure is a protruding ring structure evenly distributed along the axial direction of the anchoring grouting pipe (2), or a spiral protruding structure arranged along the axial direction of the anchoring grouting pipe (2).

10. The method for reducing subsidence by grouting in the entire crack zone to prevent water seepage in the roof according to claim 1 or 2, characterized in that: The specific calculation method in step a is as follows: When the working face advances forward by a distance of L, due to the different crushing angles (θ1, θ2) of the rock formation in the strike direction, when the separation space first appears below the jth layer (key layer), the hanging length (a j ) and L is The hanging width of the key layer in the inclined direction (b j The relationship between the working surface width (B, in meters) and the working surface width (B, in meters) is: S1=LB S2=a n+1 b n+1 In the formula, a n+1 b is the length of the overhang along the strike direction of the rock mass, in meters; n+1 is the length of the overhang of the rock mass along the inclined direction, in meters; h is the vertical distance between the overburden and the coal seam, in meters; h n+1 is the maximum height of the overburden stratum, in meters; L is the distance of advancement of the working face, in meters; θ1 is the rock stratum breaking angle on the side of the cut; θ2 is the rock stratum breaking angle on the side of the working face; S1 is the area of ​​the working face that has been mined; S2 is the suspended area of ​​the overburden stratum; Assume that the spacing between the anchor grouting pipes is L j , the row spacing is L p , then the anchoring area of ​​each anchor grouting pipe is A = L j ·L p , then n1=L / L needs to be set in the direction of the working face p The number of anchor grouting pipes that need to be set in the inclination direction of the working face is n2 = L / L p If there are a total of N = n1·n2 anchor grouting pipes, then a total of N = n1·n2 anchor grouting pipes need to be installed within the working surface; The weight that each anchor grouting pipe needs to bear is In the formula, is the average density of the overlying rock; Assuming that the rock mass and the bonding material are elastic materials with the same properties, using the displacement solution of the Mindlin problem, the rock mass is regarded as half-space, the anchor grouting pipe is semi-infinite, and the displacement of the rock mass at the orifice is equal to the total elongation of the anchor body. The ultimate pull-out force Pu of the full-length bonded anchor grouting pipe is derived as follows: Where, E is the elastic modulus of the rock mass; μ is the Poisson's ratio of the rock mass; E b is the elastic modulus of the anchor grouting pipe; τ u is the ultimate bonding stress between the anchor grouting pipe and the anchor grouting pipe, and α is the radius of the anchor grouting pipe; The weight that the anchor grouting pipe needs to bear is Where k is the anchoring environment influence coefficient.

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