Grouting treatment method for deep-buried thick bedrock water-rich collapse column in North China coal field

Abstract

The invention discloses a grouting treatment method for a deep-buried thick bedrock water-rich collapse column in a North China type coal field. The grouting treatment method comprises the following steps: step (1), determining a long axis of the collapse column and measuring the length of the long axis; (2) calculating the critical depth needing to be transformed below the collapse column coal seam floor; (3) determining the actual transformation depth of the collapse column and the length of the long axis of the collapse column on a transformation depth plane; (4) the number of grouting main holes is determined; (5) grouting slurry and grouting parameters are determined; (6) the number of directional grouting branch holes of each grouting main hole is determined; (7) the distance between every two adjacent directional grouting branch holes in the grouting main hole and the hole opening positions of the directional grouting branch holes are determined; (8) the track of each directional grouting branch hole is designed; (9) drilling and grouting are conducted; and (10) the grouting treatment effect is checked and evaluated. The technical problems that an existing collapse column treatment process conflicts with roadway tunneling and working face stoping of a coal mine and the like can be solved.

Description

Technical Field

[0001] This invention relates to the field of coal mine collapse column water hazard prevention technology. Specifically, it is a grouting treatment method for deep-buried, water-rich collapse columns in thick bedrock in North China-type coalfields. Background Technology

[0002] The North my country coalfields consist of Carboniferous and Permian strata, generally lacking Upper Ordovician, Silurian, Devonian, and Lower Carboniferous strata. They are directly deposited on top of a thick, highly aquifer-rich Ordovician limestone aquifer. The Upper and Middle Carboniferous strata contain several thin limestone layers, often hydraulically connected to the underlying Ordovician limestone aquifer, exhibiting high water content and relatively small distances (from tens of meters) from the coal seams. The Middle Ordovician Majiagou Formation limestone aquifer, due to its high water pressure and large volume, poses a significant threat of water inrush to coal seam mining.

[0003] The North China-type coalfields are widely distributed, extending from the Yinshan Mountains in the north to the Qinling and Dabie Mountains in the south, from the Helan Mountains in the west to the coast (including the Korean Peninsula) in the east. They encompass the entirety of Hebei, Shanxi, Henan, Beijing, and Tianjin; the southern parts of Jilin, Liaoning, and Inner Mongolia; central and western Shandong; northwestern Jiangsu; northern Anhui and Shaanxi; and eastern Gansu and Ningxia, covering a total area of ​​approximately 150,000 km². 2 The North China coalfield is one of China's most important coal industrial bases, playing a pivotal role in the country's economic development.

[0004] Karst collapse columns are a highly distinctive regional geological phenomenon widely developed in North China-type coalfields. They occur when thick layers of easily soluble limestone at the base of coal-bearing strata, under intense dissolution and mechanical action, form large karst caves that lose their supporting force on the overlying strata, causing the overlying strata to continuously collapse downwards, resulting in columnar collapse bodies. Karst collapse columns are widely developed and distributed in North China-type coalfields, with some reaching heights of 500 m and diameters of 10–200 m. The presence of collapse columns not only disrupts the stability and continuity of coal seams, reducing coal reserves and causing significant coal resource losses, but also affects the conventional layout of working faces, reduces the efficiency of fully mechanized mining machinery, and has a significant adverse impact on coal mine safety and economic benefits.

[0005] Currently, the common practice for controlling collapse columns is to first construct a drilling site in the underground roadway, and then perform grouting by drilling fan-shaped boreholes within the drilling site. However, this method of underground fan-shaped borehole grouting for collapse column control has two main drawbacks: first, for high-pressure, water-rich collapse columns, there is a risk of water inrush during drilling; second, it conflicts with coal mine roadway excavation and face mining, seriously affecting the safe and efficient production of the coal mine. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to provide a grouting treatment method for water-rich collapse columns in deep-buried thick bedrock of North China coalfields, so as to solve the technical problems of high risk of water inrush during drilling construction and conflict between the treatment process and the roadway excavation and working face mining of coal mines when treating water-rich collapse columns in deep-buried thick bedrock of North China coalfields.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0008] A grouting treatment method for water-rich collapse columns buried in thick bedrock in North China-type coalfields includes the following steps:

[0009] Step (1): Based on the extension shape of the water-rich collapse column on the contour map of the coal seam floor, determine the long axis of the collapse column and measure the length of the long axis of the collapse column; mark the midpoint of the long axis of the collapse column as point O0(x,y,z);

[0010] Step (2): Calculate the critical depth M required for the collapse column to be modified below the normal coal seam floor. c ;

[0011] Step (3): Determine the actual modification depth M of the collapse column based on the calculation results of step (2); delineate the projection of the collapse column on the contour map of the coal seam floor on the plane at depth M below the coal seam floor, and measure its major axis length L. M The midpoint of the major axis is denoted as O. M (x M , y M , z M )point;

[0012] Step (4): Based on the length of the major axis L M Determine the number N of grouting main holes required for ground directional drilling grouting to treat the collapsed column and the opening position of each grouting main hole on the ground, and design the trajectory of each grouting main hole;

[0013] Step (5): Determine the grouting slurry and select the grouting parameters;

[0014] Step (6): Determine the number n of directional grouting branch holes for each grouting main hole and the position of the final hole (target point) of each directional grouting branch hole according to the grouting parameters.

[0015] Step (7): Determine the spacing between adjacent directional grouting branch holes on the main grouting hole, and the opening position of each directional grouting branch hole;

[0016] Step (8): Design the trajectory of each directional grouting branch hole;

[0017] Step (9): Drill and grout in the order of first grouting the main hole and then directional grouting branch hole. Drill and grout the directional grouting branch hole of each main hole in the order of bottom to top according to the opening position of the directional grouting branch hole.

[0018] Step (10): Construct directional branch inspection holes and use methods such as well logging and water pressure tests to inspect and evaluate the effect of grouting treatment of the collapse column.

[0019] In the above-mentioned grouting treatment method for deep-buried, thick bedrock, water-rich collapse columns in North China coalfields, in step (2), the critical depth M c The calculation formula is:

[0020] (1);

[0021] In equation (1), M c P represents the critical depth (m) below the normal coal seam floor where the collapse column requires modification. L h1 represents the water pressure of the Ordovician limestone aquifer (hereinafter referred to as "Ordovician limestone") at the lowest point of the collapse column on the contour map of the coal seam floor, in MPa; h1 represents the depth of the water-conducting failure zone of the coal seam floor caused by mining, in m; where:

[0022] (2);

[0023] In equation (2), H O The water level (m) is measured in a surface observation well of the Ordovician limestone aquifer near the collapse column; H L The elevation, in meters, is the lowest point (Lowest point) where the collapse column intersects the contour line of the coal seam floor.

[0024] In the above-mentioned grouting treatment method for water-rich collapse columns in deep bedrock of North China coalfields, step (3) is as follows: The formula for calculating the actual modification depth M of the collapse column is:

[0025] M=k a M c (3);

[0026] In equation (3), M is the actual modification depth of the collapse column, in meters; k a For safety factors, the value is taken as 1.2 to 1.5.

[0027] In the above-mentioned grouting treatment method for water-rich collapse columns in deep-buried thick bedrock of North China coalfields, the method for determining the number N of grouting main holes and the opening position of each grouting main hole on the ground in step (4) is as follows:

[0028] (4-1) When L M When the depth is ≤100m, N=1; at this time, the midpoint O of the major axis of the collapse column is...M The ground projection O1 serves as the ground opening location for the main grouting hole, and the final hole of the main grouting hole is located at a depth of M below the coal seam floor elevation. M point;

[0029] (4-2) When 100m <L M When the length is ≤200m, N=2. In this case, the length of the major axis L is respectively... M O at 1 / 4 and 3 / 4 M ′、O M Points O1′ and O1″, projected onto the ground, serve as the opening positions for the main grouting boreholes. The final holes of the main grouting boreholes are located at depths M below the coal seam floor. M ′、O M "Point; when L" M When the length is greater than 200m, N=3. At this time, the length of the major axis L is... M O at 1 / 6, 1 / 2 and 5 / 6 M ′、O M "、O M The projection points O1′, O1″, and O1′″ of point ′″ on the ground are used as the ground opening locations for the main grouting boreholes. The final holes of the main grouting boreholes are located at depths M below the coal seam floor. M ′、O M "、O M '"point;

[0030] The grouting main borehole adopts a three-stage structure: the first stage uses a Φ311.15 mm drill bit to drill to a depth of 30-50 m, and a Φ244.5×8.94 mm oil casing is installed; the second stage uses a Φ215.9 mm drill bit to drill to 10-20 m below the bedrock surface, and a Φ177.8×8.05 mm oil casing is installed; the third stage uses a Φ152.4 mm drill bit to drill to the final hole.

[0031] In the above-mentioned grouting treatment method for water-rich collapse columns in deep-buried thick bedrock of North China coalfield, step (5) involves determining the grouting slurry by: conducting a water pumping (injection) test through the collapse column section of the grouting main hole to determine the permeability coefficient k of the formation; when the permeability coefficient k of the collapse column formation is greater than or equal to 0.01 m / d, single-liquid cement slurry is used; when k is less than 0.01 m / d, cement-water glass slurry is used; single-liquid cement slurry is prepared by mixing ordinary Portland cement with a strength grade greater than or equal to PO32.5 and water, with a water-cement ratio of 1:(1~2); cement-water glass slurry is prepared by mixing cement slurry and water glass in a volume ratio of 1:(0.4~1), with a water-cement ratio of (0.6~1):1 in the cement slurry, a water glass concentration of 35~42 Baume degrees, and a water glass modulus of 2.4~3.4;

[0032] Selection of grouting parameters: The effective diffusion radius r of the grouting slurry is 6 to 10 m, and the final grouting pressure of the grouting section should be 2 to 4 times the hydrostatic pressure.

[0033] In the above-mentioned grouting treatment method for water-rich collapse columns in deep-buried thick bedrock of North China coalfields, step (6) determines the number of directional grouting branch holes n for each main grouting hole based on the grouting area of ​​the collapse column covered by each main grouting hole and the effective diffusion radius r of the grouting slurry; the specific method for determining the number of directional grouting branch holes n is as follows:

[0034] Using the target point (final hole) of the main grouting hole as the base point, and the long axis of the projection of the intersection line of the collapse column and the plane at depth M below the coal seam floor onto the horizontal plane as the baseline, the final holes of each directional grouting branch hole are arranged in a staggered pattern according to row spacing and row spacing. Figure 2 Row spacing = row spacing = R, where R is less than or equal to 1.6r (r is the effective diffusion radius of the grout). Figure 2 Except for the main hole target point (final hole) O 11 The number of target points is the number of directional grouting branch holes, n.

[0035] In the above-mentioned grouting treatment method for water-rich collapse columns in deep-buried thick bedrock of North China coalfield, in step (7), the height H of the opening point of the deepest directional grouting branch hole on the grouting main hole from the top boundary O2 point of the collapse column, the spacing h of adjacent directional grouting branch holes on the grouting main hole, and the opening sequence and depth of each directional grouting branch hole are determined according to the number of directional grouting branch holes on the grouting main hole and the length of the bare hole above the top boundary of the collapse column at the grouting main hole; H is 20-30 m; h is 2-3 m.

[0036] In the above-mentioned grouting treatment method for deep-buried thick bedrock water-rich collapse columns in North China coalfields, in step (8), the trajectory of each directional grouting branch hole is "S" shaped, that is, the directional grouting branch hole is side-drilled from the grouting main hole, and after two inclines in opposite directions, it finally enters the vertical section. The radius of the two inclines is 200-300m; the diameter of each directional grouting branch hole is 108-152.4mm.

[0037] In the above-mentioned grouting treatment method for water-rich collapse columns in deep-buried thick bedrock of North China coalfield, in step (10), the number of directional branch inspection holes is 2 to 5; the directional branch inspection holes are nearly evenly distributed on the projection plane of the collapse column at a depth M below the coal seam floor on the contour line of the coal seam floor.

[0038] In the above-mentioned grouting treatment method for deep-buried, thick bedrock, water-rich collapse columns in North China coalfields, in step (2), the critical depth M c The calculation formula is:

[0039] (1);

[0040] In equation (1), M c P represents the critical depth (m) below the normal coal seam floor where the collapse column requires modification. L h1 represents the water pressure of the Ordovician limestone aquifer (hereinafter referred to as "Ordovician limestone") at the lowest point of the collapse column on the contour map of the coal seam floor, in MPa; h1 represents the depth of the water-conducting failure zone of the coal seam floor caused by mining, in m; where:

[0041] (2);

[0042] In equation (2), H O The water level in the surface observation well of the Ordovician limestone aquifer near the collapse column, in meters (m); H L The elevation, in meters, is the lowest point (Lowest point) where the collapse column intersects the contour line of the coal seam floor.

[0043] In step (3), the formula for calculating the actual modification depth M of the collapse column is:

[0044] M=k a M c (3);

[0045] In equation (3), M is the actual modification depth of the collapse column, in meters; k a For safety margin, a value of 1.2 to 1.5 is used;

[0046] In step (4), the method for determining the number N of grouting main holes and the opening position of each grouting main hole on the ground is as follows:

[0047] (4-1) When L M When the depth is ≤100m, N=1; at this time, the midpoint O of the major axis of the collapse column is... M The ground projection O1 serves as the ground opening location for the main grouting hole, and the final hole of the main grouting hole is located at a depth of M below the coal seam floor elevation. M point;

[0048] (4-2) When 100m <L M When the length is ≤200m, N=2. In this case, the length of the major axis L is respectively... M O at 1 / 4 and 3 / 4 M ′、O M Points O1′ and O1″, projected onto the ground, serve as the opening positions for the main grouting boreholes. The final holes of the main grouting boreholes are located at depths M below the coal seam floor. M ′、O M "Point; when L" M When the length is greater than 200m, N=3. At this time, the length of the major axis L is... M O at 1 / 6, 1 / 2 and 5 / 6 M ′、OM "、O M The projection points O1′, O1″, and O1′″ of point ′″ on the ground are used as the ground opening locations for the main grouting boreholes. The final holes of the main grouting boreholes are located at depths M below the coal seam floor. M ′、O M "、O M '"point;

[0049] The grouting main borehole adopts a three-section structure: Section 1, drilled with a Φ311.15 mm drill bit to a depth of 30-50 m, and a Φ244.5×8.94 mm oil casing is installed; Section 2, drilled with a Φ215.9 mm drill bit to a depth of 10-20 m below the bedrock surface, and a Φ177.8×8.05 mm oil casing is installed; Section 3, drilled with a Φ152.4 mm drill bit to the final borehole.

[0050] In step (5), the method for determining the grouting slurry is as follows: a water pumping (injection) test is conducted through the grouting main hole in the collapsed column section to determine the permeability coefficient k of the formation; when the permeability coefficient k of the collapsed column formation is greater than or equal to 0.01 m / d, single-component cement slurry is used; when k is less than 0.01 m / d, cement-water glass slurry is used; single-component cement slurry is prepared by mixing ordinary Portland cement with a strength grade greater than or equal to PO32.5 and water, with a water-cement ratio of 1:(1~2); cement-water glass slurry is made by mixing cement slurry and water glass in a volume ratio of 1:(0.4~1), with a water-cement ratio of (0.6~1):1 in the cement slurry, a water glass concentration of 35~42 Baume degrees, and a water glass modulus of 2.4~3.4; selection of grouting parameters: the effective diffusion radius r of the grouting slurry is 6~10 m, and the final grouting pressure of the grouting section should be 2~4 times the hydrostatic pressure.

[0051] In step (6), the number of directional grouting branch holes n for each main grouting hole is determined based on the grouting area of ​​the collapsed column covered by each main grouting hole and the effective diffusion radius r of the grouting slurry; the specific method for determining the number of directional grouting branch holes n is as follows:

[0052] Using the target point (final hole) of the main grouting hole as the base point, and the long axis of the projection of the intersection line of the collapse column and the plane at depth M below the coal seam floor onto the horizontal plane as the baseline, the final holes of each directional grouting branch hole are arranged in a staggered pattern according to row spacing and row spacing. Figure 2 Row spacing = row spacing = R, where R is less than or equal to 1.6r (r is the effective diffusion radius of the grout). Figure 2 Except for the main hole target point (final hole) O 11 The number of target points is the number of directional grouting branch holes, n.

[0053] In step (7), based on the number of directional grouting branch holes of the main grouting hole and the length of the bare hole above the top boundary of the sinkhole at the main grouting hole, the height H of the opening point of the deepest directional grouting branch hole on the main grouting hole from the top boundary O2 of the sinkhole, the spacing h of adjacent directional grouting branch holes on the main grouting hole, and the opening sequence and depth of each directional grouting branch hole are determined; H is 20-30 m; h is 2-3 m.

[0054] In step (8), the trajectory of each directional grouting branch hole is “S” shaped, that is, the directional grouting branch hole is side-drilled from the grouting main hole, and after two skewed sections in opposite directions, it finally enters the vertical section. The radius of the two skewed sections is 200-300m. The diameter of each directional grouting branch hole is 108-152.4 mm.

[0055] In step (10), the number of directional branch inspection holes is 2 to 5; the directional branch inspection holes are nearly uniformly distributed on the projection plane of the M-depth collapse column below the coal seam floor on the contour line of the coal seam floor.

[0056] The technical solution of the present invention achieves the following beneficial technical effects:

[0057] This invention discloses a grouting treatment method for water-rich collapse columns in deep, thick bedrock of North China-type coalfields. Utilizing surface directional drilling technology, several small-displacement branch holes (also known as "S"-shaped holes) are drilled at different depths along the main hole. These "S"-shaped holes are arranged at equal intervals on the main hole and drilled and grouted in a bottom-up sequence. After all the "S"-shaped holes are drilled and grouted, a certain number of more "S"-shaped holes are constructed. Well logging and water pressure tests are used to detect and evaluate the grouting treatment effect on the collapse column, ensuring safe and efficient mine roadway excavation and working face recovery. This invention solves the technical problems of existing collapse column treatment methods in North China-type coalfields, such as the high risk of water inrush during drilling and the conflict between the treatment process and mine roadway excavation and working face recovery. Attached Figure Description

[0058] Figure 1 Flowchart of grouting treatment for water-rich collapse columns in deep, thick bedrock of North China type coalfields in this invention embodiment;

[0059] Figure 2 A plan view showing the arrangement of the main grouting hole and the directional grouting branch holes in an embodiment of the present invention;

[0060] Figure 3 In this embodiment of the invention, the grouting main hole is used as the final hole (O) 11 A schematic diagram showing the projected positional relationship of the final holes of adjacent directional branch holes centered on the center on a plane;

[0061] Figure 4 In this embodiment of the invention, the grouting main hole is used as the final hole (O) 11 The diagram shows the positional relationship of each grouting borehole (main hole + branch hole) and the structure of the main hole on the cross-section with the long axis of the collapse column as the baseline. Detailed Implementation

[0062] like Figure 1 As shown in this embodiment, the grouting treatment method for water-rich collapse columns in deep, thick bedrock of North China type coalfields includes the following steps:

[0063] (1) Based on the extension shape of the water-rich collapse column on the contour map of the coal seam floor, determine the long axis of the collapse column and measure the length of the long axis of the collapse column. The midpoint of the long axis of the collapse column is recorded as point O(x,y,z).

[0064] (Note: The geological structure of the coal mine (faults, collapse columns and scour zones, etc.) must be drawn on the contour map of the coal seam floor (or the coal seam mining engineering plan); determining the long axis and midpoint of the collapse column on the contour map of the coal seam floor, and thus determining the section where the long axis is located, is the premise for determining the number and location of the main boreholes in step (4).

[0065] (2) Based on the water level of the surface observation well of the Ordovician limestone aquifer near the collapse column, the elevation of the lowest point of the intersection of the contour lines of the collapse column and the coal seam floor, the theoretical or empirical value of the depth (h1) of the water-conducting failure zone of the coal seam floor caused by mining, and the critical water inrush coefficient (after grouting and modification of the collapse column, the water inrush coefficient is taken as 0.1 MPa / m in the section where the aquitard is intact and there is no fracture structure damage), calculate the critical depth M that the collapse column needs to be modified below the normal coal seam floor. c :

[0066] (1);

[0067] In equation (1): M c —The critical depth below the coal seam floor of the collapse column that requires modification, in meters;

[0068] P L —The Ordovician limestone water pressure borne by the collapse column at the lowest point on the contour map of the coal seam floor, in MPa;

[0069] h1—Depth of the water-conducting failure zone in the coal seam floor caused by mining, in meters;

[0070] (2);

[0071] In equation (2), H O The water level in the surface observation well of the Ordovician limestone aquifer near the collapse column, in meters (m); H LThe elevation, in meters, is the lowest point (Lowest point) where the collapse column intersects the contour line of the coal seam floor.

[0072] (3) To ensure safe mining of the coal seam, the actual depth of the collapse column is modified to M below the bottom of the coal seam;

[0073] M=k a M c (3);

[0074] In equation (3), M is the actual modification depth of the collapse column, in meters; k a For safety factors, the selection is based on parameters such as the extent of the collapse column, the dip angle of the coal seam, the dip angle of the collapse column boundary, and the water level of the Ordovician limestone aquifer. Generally, k is taken as the safety factor. a =1.2~1.5; Determine the projection of the collapse column on the contour map of the coal seam floor on the plane at depth M below the coal seam floor, and measure its major axis length L. M The midpoint of the major axis is denoted as O. M (x M , y M , z M )point.

[0075] (4) Based on the projected major axis length of the collapse column at depth M below the coal seam floor on the contour line of the coal seam floor and the thickness of the bedrock overlying the collapse column, determine the number of grouting main holes for surface directional drilling grouting to treat the collapse column, generally 1 to 3 grouting main holes. For the projected major axis length L of the collapse column... M For collapse columns ≤100m, design one main grouting hole. The projection O1 of point O on the ground can be used as the opening position of the main grouting hole for the directional drilling grouting treatment project of the collapse column. When 100m <L M When the length is ≤200m, N=2. In this case, the length of the major axis L is respectively... M O at 1 / 4 and 3 / 4 M ′、O M Points O1′ and O1″, projected onto the ground, serve as the opening positions for the main grouting boreholes. The final holes of the main grouting boreholes are located at depths M below the coal seam floor. M ′、O M "Point; when L" M When the length is greater than 200m, N=3. At this time, the length of the major axis L is... M O at 1 / 6, 1 / 2 and 5 / 6 M ′、O M "、O M The projection points O1′, O1″, and O1′″ of point ′″ on the ground are used as the ground opening locations for the main grouting boreholes. The final holes of the main grouting boreholes are located at depths M below the coal seam floor. M ′、O M "、O MPoint ′″. In this step, the long axis of the projection of the M-depth collapse column on the contour line of the coal seam floor is on the same cross section as the long axis of the collapse column in step (1) (see Figure 4 ).

[0076] (5) According to the "Code for Construction of Coal Mine Tunneling Engineering" (GB50511-2010), the grouting parameters should be selected. The effective diffusion radius r of the grout should be 6 to 10 m. The final grouting pressure of the grouting section (single-component cement grout or cement-water glass grout) should be 2 to 4 times the hydrostatic pressure. The method for determining the grouting grout is as follows: a pumping (injection) test is conducted through the collapse column section of the grouting main hole to determine the permeability coefficient k of the formation. When the permeability coefficient k of the collapse column formation is ≥ 0.01 m / d, single-component cement grout is used; when k < 0.01 m / d, cement-water glass grout is used.

[0077] (6) Determine the number of directional branch holes for each main hole based on the grouting area of ​​the collapsed column covered by each main grouting hole and the effective diffusion radius r of the grout.

[0078] In this embodiment, the rock mass inside the water-rich collapse column is relatively broken and has higher permeability than the aquifer of the coal-bearing strata. Therefore, the effective diffusion radius r of the slurry is taken as 10 m.

[0079] In this embodiment, the long axis of the collapsed column projection is less than 100 m. Therefore, one grouting main hole is designed. This grouting main hole starts at point O1 on the ground and ends at point O2, a depth M below the normal floor elevation of the coal seam. The grouting main hole intersects with the top boundary of the collapsed column at point O3. In this embodiment, the grouting main hole adopts a three-section structure: the first section uses a Φ311.15 mm drill bit to drill to a depth of 30-50 m, and a Φ244.5×8.94 mm oil casing is installed; the second section uses a Φ215.9 mm drill bit to drill to a depth of 10-20 m below the bedrock surface, and a Φ177.8×8.05 mm oil casing is installed; the third section uses a Φ152.4 mm drill bit to drill to the final hole. The grout stop plug is lowered to above the collapsed column (10-20 m) for grouting. Grouting is performed at point O2 (O 11 Using the point as the base point and the long axis of the collapse column as the baseline, the final holes of each directional grouting branch hole are arranged in a staggered pattern according to the row spacing and row spacing R (see point). Figure 2 , Figure 3 ).

[0080] Figure 3 In the middle, O 11 O 13 =DO 21 =R, C is an isosceles triangle O 11 O 13 O 21 The center of is such that the isosceles ⊿O 11 O 13 O 21 If the radius of the circumcircle is r0, then:

[0081] ;

[0082] ;

[0083] ;

[0084] ;

[0085] ;

[0086] ;Right now, ;thereby .

[0087] (7) Based on the number n of directional grouting branch holes of the main grouting hole ( Figure 3 The following parameters are used to determine the height H of the deepest directional grouting branch hole on the grouting main hole from the top boundary of the sinkhole, the distance h between adjacent directional grouting branch holes on the grouting main hole, and the opening (side drilling) sequence and depth of each directional grouting branch hole. In this embodiment, the spacing between adjacent directional grouting branch holes on the grouting main hole is h = 2-3 m, and H = 20-30 m; H is determined according to the lithology of the overlying rock above the top boundary of the collapse column. This side drilling point is generally located in intact hard rock (sandstone or limestone). If the h value is too small, the disturbance to the hole wall of the grouting main hole is strong, and the drilling near the opening of the subsequent directional grouting branch holes is prone to collapse, making hole formation difficult; if the h value is too large, the trajectory length of each subsequent directional grouting branch hole is too long, resulting in poor economic efficiency. In principle, the closer the final horizontal displacement of the hole is to the grouting main hole, the lower the opening position (elevation), and the earlier the hole is opened.

[0088] (8) Trajectory design of each directional grouting branch hole: The trajectory of each directional grouting branch hole is "S" shaped, that is, the directional grouting branch hole is side-drilled from the main grouting hole, and after two oblique drillings in opposite directions, it finally enters the vertical section. Figure 4 The sloping radius is generally 200-300m. The diameter of each directional grouting branch hole is Φ108-152.4 mm. Based on step (7), the distance between the trajectories of adjacent directional grouting branch holes after entering the collapse column is controlled to be ≤1.6r (r=10 m).

[0089] (9) Grouting of the main grouting hole and directional grouting branch holes, the grout is single-component cement grout or cement-water glass grout. The single-component cement grout is prepared by mixing ordinary Portland cement with a strength grade greater than or equal to PO32.5 and water, with a water-cement ratio of 1:(1~2); the cement-water glass grout is made by mixing cement grout and water glass in a volume ratio of 1:(0.4~1), with a water-cement ratio of (0.6~1):1 in the cement grout, a water glass concentration of 35~42 Baume degrees, and a water glass modulus of 2.4~3.4.

[0090] (10) After all the “S” shaped boreholes have been drilled and grouted, a certain number of directional branch inspection holes (generally 2 to 5) are constructed. The directional branch inspection holes are nearly evenly distributed on the projection plane of the M-depth collapse column below the coal seam floor on the contour line of the coal seam floor. The target point of the inspection hole is located at the center of the triangle formed by the target points of the three adjacent grouting branch holes. Figure 2 The grouting effect was verified and evaluated using methods such as well logging and water pressure testing. Well logging was mainly used to determine the integrity of the rock mass within the collapse column after grouting; water pressure testing was mainly used to determine the integrity and permeability of the rock mass within the collapse column after grouting (Table 1).

[0091] Table 1. Classification of permeability of soil and rock masses

[0092]

[0093] The grouting treatment method for water-rich collapse columns in deep, thick bedrock of North China type coalfields, as described in this embodiment, is used to treat water-rich collapse columns in deep, thick bedrock of North China type coalfields. There is no risk of water inrush during the treatment process, and the entire treatment process can avoid conflict with the roadway excavation and working face mining of coal mines, thereby significantly improving construction efficiency.

[0094] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of the claims of this patent application.

Claims

1. A grouting treatment method for water-rich collapse columns in deep-buried thick bedrock of North China type coalfields, characterized in that, Includes the following steps: Step (1): Based on the extension shape of the water-rich collapse column on the contour map of the coal seam floor, determine the long axis of the collapse column and measure the length of the long axis of the collapse column; mark the midpoint of the long axis of the collapse column as point O0(x,y,z); Step (2): Calculate the critical depth M required for the collapse column to be modified below the normal coal seam floor. c ; Step (3): Determine the actual modification depth M of the collapse column based on the calculation results of step (2); delineate the projection of the collapse column on the contour map of the coal seam floor on the plane at depth M below the coal seam floor, and measure its major axis length L. M The midpoint of the major axis is denoted as O. M (x M ,y M , z M )point; Step (4): Based on the length of the major axis L M Determine the number N of grouting main holes required for ground directional drilling grouting to treat the collapsed column and the opening position of each grouting main hole on the ground, and design the trajectory of each grouting main hole; Step (5): Determine the grouting slurry and select the grouting parameters; Step (6): Determine the number n of directional grouting branch holes for each grouting main hole and the final hole position of each directional grouting branch hole according to the grouting parameters. Step (7): Determine the spacing between adjacent directional grouting branch holes on the main grouting hole, and the opening position of each directional grouting branch hole; Step (8): Design the trajectory of each directional grouting branch hole; Step (9): Drill and grout in the order of first grouting the main hole and then directional grouting branch hole. Drill and grout the directional grouting branch hole of each main hole in the order of bottom to top according to the opening position of the directional grouting branch hole. Step (10): Construct directional branch inspection holes and use logging and water pressure tests to inspect and evaluate the effect of grouting treatment for collapse columns.

2. The grouting treatment method for water-rich collapse columns in deep-buried thick bedrock of North China-type coalfields according to claim 1, characterized in that, In step (2), the critical depth M c The calculation formula is: （1）； In equation (1), M c P represents the critical depth (m) below the normal coal seam floor where the collapse column requires modification. L h1 represents the water pressure of the Ordovician limestone aquifer at the lowest point of the collapse column on the contour map of the coal seam floor, in MPa; h1 represents the depth of the water-conducting failure zone of the coal seam floor caused by mining, in meters; where: （2）； In equation (2), H O The water level at the Ordovician limestone surface hydrological observation well near the collapse column, in meters (m); H L The elevation (m) is the lowest point of the intersection of the collapse column and the contour line of the coal seam floor.

3. The grouting treatment method for water-rich collapse columns in deep-buried thick bedrock of North China-type coalfields according to claim 1, characterized in that, In step (3), the formula for calculating the actual modification depth M of the collapse column is: M=k a M c (3); In equation (3), M is the actual modification depth of the collapse column, in meters; k a For safety factors, the value is taken as 1.2 to 1.

5.

4. The grouting treatment method for water-rich collapse columns in deep-buried thick bedrock of North China-type coalfields according to claim 1, characterized in that, In step (4), the method for determining the number N of grouting main holes and the opening position of each grouting main hole on the ground is as follows: (4-1) When L M When the depth is ≤100m, N=1; at this time, the midpoint O of the major axis of the collapse column is... M The ground projection O1 serves as the ground opening location for the main grouting hole, and the final hole of the main grouting hole is located at a depth of M below the coal seam floor elevation. M point; (4-2) When 100m <L M When the length is ≤200m, N=2. In this case, the length of the major axis L is respectively... M O at 1 / 4 and 3 / 4 M ′、O M Points O1′ and O1″, projected onto the ground, serve as the opening positions for the main grouting boreholes. The final holes of the main grouting boreholes are located at depths M below the coal seam floor. M ′、O M "point; (4-3) When L M When the length is greater than 200m, N=3. At this time, the length of the major axis L is... M O at 1 / 6, 1 / 2 and 5 / 6 M ′、O M "、O M The projection points O1′, O1″, and O1′″ of point ′″ on the ground are used as the ground opening locations for the main grouting boreholes. The final holes of the main grouting boreholes are located at depths M below the coal seam floor. M ′、O M "、O M '"point; The grouting main borehole adopts a three-stage structure: the first stage uses a Φ311.15 mm drill bit to drill to a depth of 30-50 m, and a Φ244.5×8.94 mm oil casing is installed; the second stage uses a Φ215.9 mm drill bit to drill to 10-20 m below the bedrock surface, and a Φ177.8×8.05 mm oil casing is installed; the third stage uses a Φ152.4 mm drill bit to drill to the final hole.

5. The grouting treatment method for water-rich collapse columns in deep-buried thick bedrock of North China-type coalfields according to claim 1, characterized in that, In step (5), the method for determining the grouting slurry is as follows: a water pumping (injection) test is conducted through the grouting main hole in the collapsed column section to determine the permeability coefficient k of the formation; when the permeability coefficient k of the collapsed column formation is greater than or equal to 0.01 m / d, single-component cement slurry is used; when k is less than 0.01 m / d, cement-water glass slurry is used; single-component cement slurry is prepared by mixing ordinary Portland cement with a strength grade greater than or equal to PO32.5 and water, with a water-cement ratio of 1:(1~2); cement-water glass slurry is made by mixing cement slurry and water glass in a volume ratio of 1:(0.4~1), with a water-cement ratio of (0.6~1):1 in the cement slurry, a water glass concentration of 35~42 Baume degrees, and a water glass modulus of 2.4~3.4; Selection of grouting parameters: The effective diffusion radius r of the grout is 6 to 10 m, and the final grouting pressure of the grouting section should be 2 to 4 times the hydrostatic pressure.

6. The grouting treatment method for water-rich collapse columns in deep-buried thick bedrock of North China-type coalfields according to claim 1, characterized in that, In step (6), the number of directional grouting branch holes n for each main grouting hole is determined based on the grouting area of ​​the collapsed column covered by each main grouting hole and the effective diffusion radius r of the grouting slurry; the specific method for determining the number of directional grouting branch holes n is as follows: With the final hole of the main grouting hole as the base point, and the long axis of the projection of the intersection line of the collapse column and the plane at depth M below the coal seam floor onto the horizontal plane as the baseline, the final holes of each directional grouting branch hole are arranged in a staggered pattern according to row spacing and row spacing, where row spacing = row spacing = R, R is less than or equal to 1.6r, and r is the effective diffusion radius of the grouting slurry.

7. The grouting treatment method for water-rich collapse columns in deep-buried thick bedrock of North China-type coalfields according to claim 1, characterized in that, In step (7), based on the number of directional grouting branch holes of the grouting main hole and the length of the bare hole above the top boundary of the sinkhole at the grouting main hole, the height H of the opening point of the deepest directional grouting branch hole on the grouting main hole from the top boundary O2 of the sinkhole, the spacing h of adjacent directional grouting branch holes on the grouting main hole, and the opening sequence and depth of each directional grouting branch hole are determined; H is 20-30m; h is 2-3m.

8. The grouting treatment method for water-rich collapse columns in deep-buried thick bedrock of North China-type coalfields according to claim 1, characterized in that, In step (8), the trajectory of each directional grouting branch hole is "S" shaped, that is, the directional grouting branch hole is side-drilled from the grouting main hole, and after two skewed sections in opposite directions, it finally enters the vertical section. The radius of the two skewed sections is 200-300m. The diameter of each directional grouting branch hole is 108-152.4 mm.

9. The grouting treatment method for water-rich collapse columns in deep-buried thick bedrock of North China-type coalfields according to claim 1, characterized in that, In step (10), the number of directional branch inspection holes is 2 to 5; the directional branch inspection holes are nearly uniformly distributed on the projection plane of the M-depth collapse column below the coal seam floor on the contour line of the coal seam floor.

10. The grouting treatment method for water-rich collapse columns in deep-buried thick bedrock of North China-type coalfields according to claim 1, characterized in that, In step (2), the critical depth M c The calculation formula is: （1）； In equation (1), M c P represents the critical depth (m) below the normal coal seam floor where the collapse column requires modification. L h1 represents the water pressure of the Ordovician limestone aquifer at the lowest point of the collapse column on the contour map of the coal seam floor, in MPa; h1 represents the depth of the water-conducting failure zone of the coal seam floor caused by mining, in meters; where: （2）； In equation (2), H O The water level at the Ordovician limestone surface hydrological observation well near the collapse column, in meters (H). L The elevation of the lowest point of the intersection of the collapse column and the contour line of the coal seam floor, in meters; In step (3), the formula for calculating the actual modification depth M of the collapse column is: M=k a M c (3); In equation (3), M is the actual modification depth of the collapse column, in meters; k a The safety factor is between 1.2 and 1.

5. In step (4), the method for determining the number N of grouting main holes and the opening position of each grouting main hole on the ground is as follows: (4-1) When L M When the depth is ≤100m, N=1; at this time, the midpoint O of the major axis of the collapse column is... M The ground projection O1 serves as the ground opening location for the main grouting hole, and the final hole of the main grouting hole is located at a depth of M below the coal seam floor elevation. M point; (4-2) When 100m <L M When the length is ≤200m, N=2. In this case, the length of the major axis L is respectively... M O at 1 / 4 and 3 / 4 M ′、O M Points O1′ and O1″, projected onto the ground, serve as the opening positions for the main grouting boreholes. The final holes of the main grouting boreholes are located at depths M below the coal seam floor. M ′、O M "point; (4-3) When L M When the length is greater than 200m, N=3. At this time, the length of the major axis L is... M O at 1 / 6, 1 / 2 and 5 / 6 M ′、O M "、O M The projection points O1′, O1″, and O1′″ of point ′″ on the ground are used as the ground opening locations for the main grouting boreholes. The final holes of the main grouting boreholes are located at depths M below the coal seam floor. M ′、O M "、O M '"point; The grouting main borehole adopts a three-section structure: Section 1, drilled with a Φ311.15 mm drill bit to a depth of 30–50 m, and a Φ244.5×8.94 mm oil casing is installed; Section 2, drilled with a Φ215.9 mm drill bit to a depth of 10–20 m below the bedrock surface, and a Φ177.8×8.05 mm oil casing is installed; Section 3, drilled with a Φ152.4 mm drill bit to the final borehole. In step (5), the method for determining the grouting slurry is as follows: a water injection test is conducted through the grouting main hole in the collapsed column section to determine the permeability coefficient k of the formation; when the permeability coefficient k of the collapsed column formation is greater than or equal to 0.01 m / d, single-component cement slurry is used; when k is less than 0.01 m / d, cement-water glass slurry is used; single-component cement slurry is prepared by mixing ordinary Portland cement with a strength grade greater than or equal to PO32.5 and water, with a water-cement ratio of 1:(1~2); cement-water glass slurry is prepared by mixing cement slurry and water glass in a volume ratio of 1:(0.4~1), with a water-cement ratio of (0.6~1):1 in the cement slurry, a water glass concentration of 35~42 Baume degrees, and a water glass modulus of 2.4~3.4; Selection of grouting parameters: The effective diffusion radius r of the grouting slurry is 6-10m, and the final grouting pressure of the grouting section should be 2-4 times the hydrostatic pressure. In step (6), the number of directional grouting branch holes n for each main grouting hole is determined based on the grouting area of ​​the collapsed column covered by each main grouting hole and the effective diffusion radius r of the grouting slurry; the specific method for determining the number of directional grouting branch holes n is as follows: With the final hole of the main grouting hole as the base point, and the long axis of the projection of the intersection line of the collapse column and the plane at depth M below the coal seam floor onto the horizontal plane as the baseline, the final holes of each directional grouting branch hole are arranged in a staggered pattern according to row spacing and row spacing, row spacing = row spacing = R, R is less than or equal to 1.6r, and r is the effective diffusion radius of the grouting slurry. In step (7), based on the number of directional grouting branch holes of the main grouting hole and the length of the bare hole above the top boundary of the sinkhole at the main grouting hole, the height H of the opening point of the deepest directional grouting branch hole on the main grouting hole from the top boundary O2 of the sinkhole, the spacing h of adjacent directional grouting branch holes on the main grouting hole, and the opening sequence and depth of each directional grouting branch hole are determined; H is 20-30m; h is 2-3m. In step (8), the trajectory of each directional grouting branch hole is "S" shaped, that is, the directional grouting branch hole is side-drilled from the grouting main hole, and after two skewed sections in opposite directions, it finally enters the vertical section. The radius of the two skewed sections is 200-300m. The diameter of each directional grouting branch hole is 108-152.4 mm. In step (10), the number of directional branch inspection holes is 2 to 5; the directional branch inspection holes are nearly uniformly distributed on the projection plane of the M-depth collapse column below the coal seam floor on the contour line of the coal seam floor.

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