A method for controlling underground rock migration in mining areas

Abstract

The present invention discloses a method for controlling the movement of underground rock strata in a mining area. The method adopts a method of pre-anchoring the overlying rock strata above the to-be-mined strata in the full-length direction of the buried depth of the to-be-mined strata before mining the strata, so as to solve the problem of surface subsidence in the mining area caused by the formation of goaf areas in the later mining of the strata. Each anchoring shaft unit assembly includes a plurality of rock strata anchoring convex ring structures formed by filling rock strata anchor holes with anchoring slurry, and all the anchoring shaft unit assemblies arranged in an array according to a set array spacing jointly form a group anchoring effect on the overlying rock strata, which can ensure the anchoring strength and effect of the overlying rock strata. In the later mining process of the strata, the exposed bottom end of the anchoring column is anchored and connected to the roof of the goaf, and the roof of the goaf is supported, which can minimize the movement of the rock strata above the goaf, thereby minimizing the problem of surface environmental damage in the mining area caused by the underground goaf.

Description

Technical Field

[0001] The present invention relates to a method for controlling the movement of underground rock layers in a mining area, in particular to a method for controlling the movement of rock layers above an underground goaf formed by mining, and belongs to the technical field of mining area management. 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. In the process of underground mining, large areas of underground goaf are often left after the underground ore layer is mined. Under the influence of overburden pressure and groundwater, the ore pillars and the ore layers on both sides of the mining area soften and lose strength, which not only easily leads to the subsidence and fall of the overburden rock mass, forming landslides, but also the harm of underground goaf to mining projects is significant and cumulative, mainly reflected in two aspects: first, the deformation and destruction of the ore pillars in the goaf, the large-scale fall of the roof, and the rock movement cause surface cracking or subsidence, destroy the ground environment and affect the surface operations. More seriously, the high-speed air waves and shock waves caused by the sudden collapse of the goaf often cause casualties and equipment damage; on the other hand, in the process of mining, the surrounding rock of the goaf is easily affected by the blasting vibration, which leads to the development of rock cracks, and even penetrates the surface or connects to the old kiln water accumulation, resulting in water inrush accidents, flooding tunnels and working faces, and causing huge economic losses. Therefore, underground goaf is one of the main sources of hazards affecting current mine safety production.

[0003] In the prior art, the treatment methods for goafs formed during mining usually adopt methods such as total collapse, backfill, and pillar support according to different conditions such as roof characteristics, ore layer thickness, and special requirements for protecting the surface. Among them, the treatment method of completely collapsing the roof behind the mining direction is simple, reliable, and low-cost, and is widely used in mining thin, medium-thick ore layers, and most thick ore layers. However, the total collapse method will inevitably cause the rock layer above the goaf to move, and then cause surface subsidence in the mining area or damage to the groundwater system.

[0004] In the prior art, there are three methods for treating goafs formed after the completion of mineral mining: caving method, filling method and closed method. The caving method is to fill the goaf with collapsed surrounding rock or form a buffering and protective rock cushion to prevent the sudden collapse of a large amount of rock from the upper part and impact the tunnel, equipment and personnel, so as to alleviate stress concentration and reduce rock support pressure; the filling method is to use waste rock stripped from the open air on the surface, waste rock from underground mining or tailings from ore dressing as the main filling aggregate, and fill the filling material by gravity (or pressurization) into the underground goaf through the boreholes, skylights or filling pipes in the goaf, and use the filling material to support the surrounding rock to slow down or prevent the deformation of the surrounding rock and keep it relatively stable; the closed method is to end the mining of the entire ore body when the stress concentration of the rock mass has not reached the limit value (the ore and the surrounding rock are in a relatively stable state), and close the goaf, allowing it to exist or fall.

[0005] The above-mentioned methods of dealing with the goaf will inevitably cause the movement of the rock strata above the goaf, which will in turn cause problems such as surface collapse, ground subsidence, and ground fissures in the mining area, and may even lead to various forms of environmental damage such as landslides, mudslides, and destruction of surface vegetation. Summary of the invention

[0006] In view of the problems existing in the above-mentioned prior art, the present invention provides a method for controlling the migration of underground rock strata in a mining area, which can minimize the migration amount of rock strata above the goaf, thereby minimizing the problem of surface environmental damage in the mining area caused by underground goaf.

[0007] To achieve the above purpose, the underground rock migration control method of the mining area specifically includes the following steps:

[0008] a. Preparation for shaft construction: Detect and determine the burial depth, thickness and burial range of the layer to be mined, and detect and determine the number, burial depth, thickness and lithology of the overlying rock layers to be mined, and construct a geological mathematical model; based on the geological mathematical model, and on the premise of removing the layer to be mined, 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 columns matched with the anchor shaft according to the burial depth and burial range of the layer to be mined, the number and lithology of each overlying rock layer above the layer to be mined; calculate and determine the number, position and spatial size of multiple rock stratum anchor holes set in layers along the anchor shaft according to the number, burial depth, thickness and lithology of each overlying rock layer above the layer to be mined; after selecting an anchoring agent with good fluidity, generate a bearing mathematical model of each anchor shaft unit assembly including rock stratum anchor holes, anchor columns and anchor slurry filling bodies according to the designed anchoring strength of the anchoring agent; fit the bearing mathematical model of each anchor shaft unit assembly with the geological mathematical model to generate an overall rock stratum anchor bearing mathematical model;

[0009] b. Well construction: According to the overall rock stratum anchoring bearing mathematical model, various anchoring shafts are set from the ground to the layer to be mined, and hole making operations are performed at the set positions of multiple rock stratum anchoring holes above the layer to be mined along each anchoring shaft to form rock stratum anchoring holes;

[0010] c. Overburden anchoring construction: Place the corresponding anchoring columns into each anchoring shaft respectively, ensure that the bottom end of the anchoring column is located at the bottom of the anchoring shaft and is in a compacted state; inject the prepared anchoring slurry into the space between the wall of the anchoring shaft and the outer wall of the anchoring column by pressure grouting, and fill the space between the wall of the anchoring shaft and the outer wall of the anchoring column from bottom to top, and fill each rock stratum anchor hole in turn, until the entire space between the wall of the anchoring shaft and the outer wall of the anchoring column is completely filled, wait for the anchoring slurry to solidify, and complete the anchoring of the anchoring columns of each anchoring shaft unit along the full length of the anchoring shaft;

[0011] d. Mining of ore layers and anchoring of goaf roof: Mining of the ore layers to be mined is carried out underground; during the advancement of the working face, each time an anchor column is exposed, the bottom end of the exposed anchor column is anchored and connected with the formed goaf roof until the mining of the entire ore layer to be mined and the bottom ends of all exposed anchor columns are anchored with the goaf roof;

[0012] e. Goaf support: Support the goaf roof.

[0013] The specific calculation method in step a is as follows:

[0014] When the working face advances forward by a distance of L, due to the rock formation crushing angle (θ 1 ,θ 2 ) is different. When the separation space first appears below the jth layer (key layer), the hanging top length (a j ) and L is

[0015]

[0016] The overhang 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:

[0017]

[0018]

[0019] S 1 =LB

[0020] S 2 =a n+1 b n+1

[0021] 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 advance distance of the working face, in meters; θ 1 is the rock fracture angle on the side of the cut hole; θ 2 is the rock fracture angle on the working face side; S 1 Indicates the area of ​​the working face that has been mined; S 2 It represents the suspended area of ​​the overburden detached rock layer;

[0022] 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 n needs to be set in the direction of the working face 1 =L / L p The number of anchor grouting pipes needs to be set in the inclination direction of the working face. 2 =B / L p The number of anchor grouting pipes is N = n. 1 ·n 2 Number of anchor grouting pipes;

[0023] The weight that each anchor grouting pipe needs to bear is

[0024]

[0025] In the formula, is the average density of the overlying rock;

[0026] 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:

[0027]

[0028]

[0029] 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;

[0030] The weight that the anchor grouting pipe needs to bear is

[0031]

[0032] Where k is the anchoring environment influence coefficient.

[0033] As a further improvement of the present invention, in step a, different anchoring agents are selected according to the lithology of each overlying rock formation above the layer to be mined; in step c, pressure grouting is used to inject the prepared anchoring slurry into the space between the wall of the anchor shaft and the outer wall of the anchor column through the grouting auxiliary casing, and the grouting auxiliary casing that matches the shaft diameter clearance of the anchor shaft is slid into the anchor shaft, and an anchoring slurry flow channel is formed between the inner surface of the grouting auxiliary casing and the outer surface of the anchor column, and the anchoring slurry is pressure-injected into the anchor holes of each rock formation. The filling method adopts the method of anchoring one by one from bottom to top. When the rock formation anchor holes located in the lower rock formation are pressure-injected with anchor slurry for filling, the bottom end of the grouting auxiliary casing stops at the top of the lower rock formation. After the rock formation anchor holes of the lower rock formation are pressure-injected with anchor slurry for the lower rock formation, the grouting auxiliary casing is lifted and its bottom end is stopped at the top of the upper rock formation. After the anchor slurry is replaced with the anchor slurry for the upper rock formation, the rock formation anchor holes of the upper rock formation are pressure-injected with anchor slurry.

[0034] As a further improvement of the present invention, during the advancement of the working face in step d, the exposed bottom end of the anchor column is anchored and connected to the formed goaf top plate by an anchor tray assembly coaxially installed on the bottom end of the exposed anchor column and the formed goaf top plate. The anchor tray assembly includes an anchor tray and an anchor lock. The anchor tray is a smoothly transitioned trumpet structure that is small at the top and large at the bottom. The conical outer surface of the trumpet structure is embedded in and fits on the goaf top plate. The anchor lock applies an anchoring force to the anchor column through the anchor tray. The anchor locks at the bottom ends of two adjacent exposed anchor columns are connected by a steel strand fit on the conical inner surface of the anchor tray trumpet structure, and a bearing block is provided between the steel strand and the goaf top plate.

[0035] As a further improvement of the present invention, a protruding structure is provided on the outer surface of the anchoring column.

[0036] As a further improvement of the present invention, in step e, the top plate of the goaf is supported by advancing the working face forward while supporting the goaf formed at the rear.

[0037] Compared with the prior art, the present method for controlling the movement of underground rock formations in a mining area adopts a method of pre-anchoring the overlying rock formation above the layer to be mined along the entire length of the buried depth direction of the layer to be mined before the mining of the mineral layer, and forming a group anchoring effect to solve the problem of surface subsidence in the mining area caused by the formation of goaf areas due to the mining of the mineral layer in the later stage. Each anchoring shaft unit assembly corresponds to the array structure arranged within the buried range of the layer to be mined. The shaft diameter of the anchoring shaft, the size of the anchoring column and the spatial size of the rock formation anchoring hole are different according to the different bearing positions. Since the overlying rock formation is anchored before the mining of the mineral layer, there is sufficient anchoring hardening time to ensure the anchoring strength and effect of the overlying rock formation. Not only each anchoring shaft unit assembly is anchored along the entire length of the anchoring shaft, but also each anchoring shaft unit assembly includes a plurality of anchoring mortars. The rock formation anchoring convex ring structure is formed by the liquid-filled rock formation anchoring hole. Each rock formation anchoring convex ring structure can not only provide the supporting force of the rock formation, but also evenly apply the load to the entire anchoring support body of the anchoring shaft unit including the anchoring column and the anchoring slurry filling body. All the anchoring shaft unit assemblies arranged in an array according to the set array spacing within the buried range of the corresponding layer to be mined jointly form a group anchoring effect on the overlying rock formation. In addition, in the later mining process of the mineral layer, the bottom end of the anchoring column exposed by the advancement of the working face is anchored and connected to the roof of the goaf formed by the advancement of the working face, and the roof of the goaf formed is supported. This can greatly reduce the amount of settlement of the mining area surface caused by the formation of the goaf after the mining of the mineral layer, thereby minimizing the problem of surface environmental damage caused by underground goaf. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of the structure of the anchoring column of the present invention being anchored along the entire length of the anchoring shaft;

[0039] Figure 2 yes Figure 1 A top view of

[0040] Figure 3 It is a structural schematic diagram of the present invention during the advancement of the working face;

[0041] Figure 4 It is a schematic diagram of the structure after the goaf area is supported in the present invention;

[0042] Figure 5 It is a schematic diagram of the structure of anchoring the bottom end of the anchor column of the present invention to the top plate of the goaf;

[0043] Figure 6 Schematic diagram of the structure of the present invention when pressure grouting is performed through a grouting auxiliary casing, wherein (a) is a schematic diagram of the structure when pressure injection of anchor slurry is performed to a rock formation anchor hole located in a lower rock formation, and (b) is a schematic diagram of the structure when pressure injection of anchor slurry is performed to a rock formation anchor hole located in an upper rock formation;

[0044] Figure 7 It is a schematic diagram of the load on the overlying strata during mining.

[0045] In the figure: 1. Anchor shaft, 2. Anchor column, 3. Rock stratum anchor hole, 5. Anchor tray assembly, 51. Anchor tray, 52. Anchor lock, 53. Steel strand, 54. Bearing block, 6. Grouting auxiliary casing, 7. Layer to be mined. DETAILED DESCRIPTION

[0046] The present invention will be further described below in conjunction with the accompanying drawings.

[0047] The underground rock migration control method of the mining area includes the following steps:

[0048] a. Preparation for well construction: detect and determine the burial depth, thickness and burial range of the layer 7 to be mined, and detect and determine the number, burial depth, thickness and lithology of the overlying strata above the layer 7 to be mined, and construct a geological mathematical model; based on the geological mathematical model, on the premise of removing the layer 7 to be mined, calculate and determine the diameter of the anchor shaft 1 corresponding to the burial range of the layer 7 to be mined, the number of anchor shafts 1, the array spacing and the size of the anchor column 2 matched with the anchor shaft 1 according to the burial depth and burial range of the layer 7 to be mined, the number and lithology of each overlying stratum above the layer 7 to be mined, and calculate and determine the number, position and spatial size of multiple rock stratum anchor holes 3 arranged in layers along the anchor shaft 1 according to the number, burial depth, thickness and lithology of each overlying stratum above the layer 7 to be mined. The rock stratum anchor holes 3 are correspondingly arranged in each overlying stratum or between each overlying stratum, and the structure of the rock stratum anchor hole 3 preferably includes an upper arch The shell-shaped structure of the structure and the lower arch bottom structure, after selecting anchoring agents with good fluidity, permeability, adhesion and strength such as composite grouting materials and composite rebar glue, generate the bearing mathematical model of each anchoring shaft unit assembly including the rock formation anchoring hole 3, anchoring column 2 and anchoring slurry filling body according to the designed anchoring strength of the anchoring agent, and fit the bearing mathematical model of each anchoring shaft unit assembly with the geological mathematical model to generate the overall rock formation anchoring bearing mathematical model; under the premise of meeting the anchoring support strength, according to the hardness of each overlying rock formation, the setting of the rock formation anchoring hole 3 can be in the form of a large number and small spatial size, or in the form of a small number and large spatial size. In order to make full use of the supporting effect of the overlying rock formation itself, the spatial size of the rock formation anchoring hole 3 corresponding to the main key layer above the layer to be mined 7 can be designed to be larger than the spatial size of the rock formation anchoring hole 3 corresponding to other overlying rock formations.

[0049] b. Shaft construction: Based on the overall rock stratum anchoring bearing mathematical model, various anchor shafts 1 are drilled from the ground to the layer to be mined 7, and hole making operations are performed at set positions of multiple rock stratum anchor holes 3 above the layer to be mined 7 along each anchor shaft 1 to form rock stratum anchor holes 3. The hole making method can be a hydraulic cutting hole making method.

[0050] c. Overburden anchoring construction: Place the corresponding anchoring column 2 into each anchoring shaft 1, ensure that the bottom end of the anchoring column 2 is located at the bottom of the anchoring shaft 1 and is in a compacted state; use pressure grouting to inject the prepared anchoring slurry into the space between the wall of the anchoring shaft 1 and the outer wall of the anchoring column 2, such as Figure 1 , Figure 2 As shown, while the anchoring slurry fills the space between the wall of the anchoring shaft 1 and the outer wall of the anchoring column 2 from bottom to top, each rock formation anchor hole 3 is filled in turn until the entire space between the wall of the anchoring shaft 1 and the outer wall of the anchoring column is completely filled. After the anchoring slurry solidifies, the anchoring columns 2 of each anchoring shaft unit are anchored along the entire length of the anchoring shaft 1.

[0051] d. Mining of ore layer and anchoring of roof in goaf area: mining of the ore layer 7 to be mined is carried out underground; Figure 3 As shown, during the advancement of the working face, each time an anchor column 2 is exposed, the bottom end of the exposed anchor column 2 is anchored and connected to the formed goaf roof until the mining of the entire layer 7 to be mined and the bottom ends of all exposed anchor columns 2 are anchored to the goaf roof.

[0052] e. Goaf support: Figure 4 As shown in the figure, the roof of the goaf is supported to further reduce the surface subsidence in the mining area.

[0053] The present underground rock stratum movement control method adopts a method of pre-anchoring the overlying rock stratum above the to-be-mined layer 7 along the full length of the buried depth direction of the to-be-mined layer 7 before the mining of the ore layer, and forming a group anchor effect to solve the problem of surface subsidence in the mining area caused by the formation of goaf areas due to the later mining of the ore layer. Each anchor shaft unit assembly corresponds to the array structure arranged within the buried range of the to-be-mined layer 7. The shaft diameter of the anchor shaft 1, the size of the anchor column 2 and the spatial size of the rock stratum anchor hole 3 are different according to the different bearing positions. Since the anchoring of the overlying rock stratum is carried out before the mining of the ore layer, there is sufficient anchoring hardening time to ensure the anchoring strength and effect of the overlying rock stratum. Not only each anchor shaft unit assembly is anchored along the full length of the anchor shaft 1, but each anchor shaft unit assembly also includes a plurality of rock stratum anchor holes 3 formed by filling the rock stratum anchor holes 3 with anchor slurry. Layer anchoring convex ring structure, each rock layer anchoring convex ring structure can not only provide the supporting force of the rock layer, but also evenly apply the load to the entire anchoring support body of the anchoring shaft unit including the anchoring column 2 and the anchoring slurry filling body, and all the anchoring shaft unit assemblies arranged in an array according to the set array spacing within the burial range of the corresponding layer 7 to be mined jointly form a group anchoring effect on the overlying rock layer. In addition, in the later mining process of the mineral layer, the bottom end of the anchoring column 2 exposed by the advancement of the working face is anchored and connected to the roof of the goaf formed by the advancement of the working face, and the roof of the goaf formed is supported, which can greatly reduce the amount of settlement of the mining area surface caused by the goaf after the mining of the mineral layer, and can minimize the settlement of the mining area surface above the goaf, thereby minimizing the problem of surface environmental damage caused by underground goaf.

[0054] The specific calculation method in step a is as follows:

[0055] like Figure 7 As shown in the figure, when the working face advances forward by a distance of L, due to the crushing angle (θ 1 ,θ 2 ), when the separation space first appears below the jth layer (key layer), the hanging length of the key layer in the strike direction (a j ) and S is

[0056]

[0057] 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:

[0058]

[0059]

[0060] S 1=LB

[0061] S 2 =a n+1 b n+1

[0062] 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 advance distance of the working face, in meters; θ 1 is the rock fracture angle on the side of the cut hole; θ 2 is the rock fracture angle on the working face side; S 1 Indicates the area of ​​the working face that has been mined; S 2 It represents the suspended area of ​​the overburden detached rock layer;

[0063] Assume that the spacing between anchor columns is L j , the array spacing is L p , then the anchoring area of ​​each anchor column is A = L j ·L p , then n needs to be set in the direction of the working face 1 =L / L p Number of anchor columns, n number of anchor columns need to be set in the inclination direction of the working face 2 =L / L p The number of anchor columns is N = n. 1 ·n 2 Number of anchor posts.

[0064] The weight that each anchor column needs to bear is:

[0065]

[0066] In the formula, is the average density of the overlying rock layer, which is generally taken as 2500kg / m based on experience. 3 .

[0067] Considering the situation where the full-length bonded anchor column 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 column is semi-infinite, and the displacement of the rock mass at the hole mouth is equal to the total elongation of the anchor body. The ultimate pull-out force Pu of the full-length bonded anchor column is derived as follows:

[0068]

[0069]

[0070] 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 column; τ u is the ultimate bonding stress between the anchor grout and the anchor column, and α is the radius of the anchor column;

[0071] The weight that the anchor column needs to bear is

[0072]

[0073] Where k is the anchoring environmental impact coefficient, which is mainly related to rock properties, burial depth, anchoring length, etc.

[0074] In order to achieve a better anchoring effect of the anchoring slurry on the rock formation, as a further improvement of the present invention, in step a, different anchoring agents are selected according to the lithology of each overlying rock formation above the layer to be mined 7; Figure 6 As shown, in step c, the prepared anchoring slurry is injected into the space between the wall of the anchoring shaft 1 and the outer wall of the anchoring column 2 by means of pressure grouting through the auxiliary grouting casing 6, and the auxiliary grouting casing 6 matching the well diameter clearance of the anchoring shaft 1 is slidably fitted into the anchoring shaft 1, and an anchoring slurry flow channel is formed between the inner surface of the auxiliary grouting casing 6 and the outer surface of the anchoring column 2. The method of pressure-injecting the anchoring slurry to fill each rock formation anchor hole 3 is to anchor one by one from bottom to top. When the rock formation anchor hole 3 located in the lower rock formation is pressure-injected with the anchoring slurry to fill, as shown in FIG. Figure 6 As shown in (a), the bottom end of the grouting auxiliary casing 6 is parked at the top of the lower rock layer, and the anchor grout for the lower rock layer is pressure-injected into the rock layer anchor hole 3 of the lower rock layer to fill the anchor grout. Figure 6 As shown in (b), the grouting auxiliary casing 6 is lifted up and its bottom end is parked on the top of the upper rock layer, and the anchoring slurry is replaced with the anchoring slurry for the upper rock layer, and then the rock layer anchor hole 3 of the upper rock layer is pressure-grouted and filled. The setting of the grouting auxiliary casing 6 matched with the well diameter clearance of the anchoring shaft 1 can, on the one hand, facilitate the discharge of gas in the anchoring shaft 1 during the pressure injection of the anchoring slurry, and on the other hand, different anchoring slurries can be used for overlying rock layers of different lithology.

[0075] In order to achieve a better effect of supporting the roof of the goaf, as a further improvement of the present invention, during the advancement of the working face in step d, the bottom end of the exposed anchor column 2 is anchored and connected to the formed roof of the goaf by an anchor tray assembly 5 coaxially installed on the bottom end of the exposed anchor column 2 and the formed roof of the goaf, such as Figure 5As shown, the anchor tray assembly 5 includes an anchor tray 51 and an anchor lock 52. The anchor tray 51 is a smooth transition bell-mouth structure with a small top and a large bottom. The conical outer surface of the bell-mouth structure is embedded in and attached to the top plate of the goaf. The anchor lock 52 applies an anchoring force to the anchor column 2 through the anchor tray 51. Figures 3 to 5 As shown, the anchor locks 52 at the bottom ends of two adjacent exposed anchor columns 2 are connected by a steel strand 53 attached to the conical inner surface of the bell-mouth structure of the anchor tray 51, and a bearing block 54 is provided between the steel strand 53 and the top plate of the goaf.

[0076] In order to achieve a better rock anchoring effect, as a further improvement of the present invention, in step c, after the anchoring slurry solidifies, the top of the anchor column 2 is anchored to the ground through an anchor.

[0077] In order to achieve a better anchoring effect of the anchor column 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 of the anchor column 2. The protrusion structure can be a protrusion ring structure evenly distributed along the axial direction of the anchor column 2, or it can be a spiral protrusion structure arranged along the axial direction of the anchor column 2, or other structural forms.

[0078] As an implementation method of the present invention for supporting the roof of the goaf, Figure 3 As shown, in step e, the support of the goaf roof can be carried out by advancing the working face forward while supporting the goaf roof formed at the rear, or by completing the mining of the entire layer 7 to be mined and then supporting the goaf roof; in step e, the support of the goaf roof can be carried out by filling the goaf with waste such as gangue, or by Figures 3 to 5 As shown, a method of reconstructing a ladle support column at the bottom end of the exposed anchor column 2 is adopted. For the specific mining layer 7 where the bottom plate of the goaf is soft rock or water-swelling rock, which is prone to bottom heave phenomenon, it is also possible to artificially drill holes or cut grooves on the bottom plate of the goaf so that the bottom plate of the goaf can be artificially controlled to bulge and then contact the top plate of the goaf and bear the load, and then support the top plate of the goaf by utilizing the bottom heave and top connection method.

Claims

1. A method for controlling underground rock migration in a mining area, 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 (7), and detect and determine the number, depth, thickness and lithology of the overlying rock layer to be mined (7), and construct a geological mathematical model; Based on the geological mathematical model, on the premise of removing the layer (7) to be mined, the diameter of the anchor shaft (1) corresponding to the burial range of the layer (7) to be mined, the number of anchor shafts (1), the array spacing and the size of the anchor column (2) matched with the anchor shaft (1) are calculated and determined according to the burial depth and burial range of the layer (7) to be mined, the number of overlying rock layers above the layer (7) to be mined and the lithology; the number, position and spatial size of multiple rock layer anchor holes (3) arranged in layers along the anchor shaft (1) are calculated and determined according to the number, burial depth, thickness and lithology of each overlying rock layer above the layer (7) to be mined; after selecting an anchoring agent with good fluidity, a bearing mathematical model of each anchor shaft unit assembly including the rock layer anchor hole (3), the anchor column (2) and the anchor slurry filling body is generated according to the designed anchoring strength of the anchoring agent; the bearing mathematical model of each anchor shaft unit assembly is fitted with the geological mathematical model to generate an overall rock layer anchor bearing mathematical model; b. Well construction: according to the overall rock stratum anchoring bearing mathematical model, each anchoring shaft (1) is set from the ground to the mining layer (7), and a hole-making operation is performed at the set positions of multiple rock stratum anchoring holes (3) above the mining layer (7) along each anchoring shaft (1) to form rock stratum anchoring holes (3); c. Overburden anchoring construction: Place the corresponding anchoring column (2) into each anchoring shaft (1) respectively, ensure that the bottom end of the anchoring column (2) is located at the bottom of the anchoring shaft (1) and is in a compacted state; inject the prepared anchoring slurry into the space between the wall of the anchoring shaft (1) and the outer wall of the anchoring column (2) by pressure grouting, and fill the space between the wall of the anchoring shaft (1) and the outer wall of the anchoring column (2) from bottom to top while filling each rock stratum anchor hole (3) in turn until the entire space between the wall of the anchoring shaft (1) and the outer wall of the anchoring column is completely filled, wait for the anchoring slurry to solidify, and complete the anchoring of the anchoring column (2) of each anchoring shaft unit along the entire length of the anchoring shaft (1); d. Mining the ore layer and anchoring the top plate of the goaf: mining the ore layer (7) underground; during the advancement of the working face, each time an anchor column (2) is exposed, the bottom end of the exposed anchor column (2) is anchored and connected to the top plate of the goaf, until the mining of the entire ore layer (7) is completed and the bottom ends of all exposed anchor columns (2) are anchored to the top plate of the goaf; e. Goaf support: Support the goaf roof.

2. The method for controlling underground rock migration in a mining area according to claim 1, 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 top length (a j ) and L is The overhang 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 direction of the working face is n2 = B / 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.

3. The method for controlling underground rock migration in a mining area according to claim 1 or 2, characterized in that: In step a, different anchoring agents are selected according to the lithology of each overlying rock layer above the mining layer (7); in step c, the prepared anchoring slurry is injected into the space between the wall of the anchoring shaft (1) and the outer wall of the anchoring column (2) through the grouting auxiliary casing (6) by pressure grouting, and the grouting auxiliary casing (6) that matches the hole diameter clearance of the anchoring shaft (1) is slidably inserted into the anchoring shaft (1), and an anchoring slurry flow channel is formed between the inner surface of the grouting auxiliary casing (6) and the outer surface of the anchoring column (2), and the anchoring slurry is pressure-injected into each rock stratum anchor hole (3). The filling method adopts a method of anchoring one by one from bottom to top. When the rock formation anchor hole (3) located in the lower rock formation is filled with anchor slurry under pressure, the bottom end of the grouting auxiliary casing (6) is parked at the top of the lower rock formation. After the rock formation anchor hole (3) of the lower rock formation is filled with anchor slurry targeted at the lower rock formation, the grouting auxiliary casing (6) is lifted up and its bottom end is parked at the top of the upper rock formation. After the anchor slurry is replaced with the anchor slurry targeted at the upper rock formation, the rock formation anchor hole (3) of the upper rock formation is again filled with anchor slurry under pressure by injection.

4. The method for controlling underground rock migration in a mining area according to claim 1 or 2, characterized in that: During the advancement of the working face in step d, the bottom end of the exposed anchor column (2) is anchored and connected to the formed top plate of the goaf by an anchor tray assembly (5) coaxially installed on the bottom end of the exposed anchor column (2). The anchor tray assembly (5) includes an anchor tray (51) and an anchor lock (52). The anchor tray (51) is a smoothly transitioned trumpet structure that is small at the top and large at the bottom. The conical outer surface of the trumpet structure is embedded in and fits on the top plate of the goaf. The anchor lock (52) applies an anchoring force to the anchor column (2) through the anchor tray (51). The anchor locks (52) at the bottom ends of two adjacent exposed anchor columns (2) are connected by a steel strand (53) fit on the conical inner surface of the trumpet structure of the anchor tray (51), and a bearing block (54) is provided between the steel strand (53) and the top plate of the goaf.

5. The method for controlling underground rock migration in a mining area according to claim 1 or 2, characterized in that: A protruding structure is provided on the outer surface of the anchoring column (2).

6. The method for controlling underground rock migration in a mining area according to claim 1 or 2, characterized in that: In step e, the top plate of the goaf is supported by advancing the working face forward while supporting the goaf formed at the rear.

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