CN115937294B - Prediction method for goaf caving zone height after coal mine ground fracturing - Google Patents
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Abstract
The invention discloses a prediction method for the height of a goaf caving zone after coal mine ground fracturing, which relates to the technical field of coal mining, and comprises the steps of firstly constructing and cutting a first terrace with edges and a second terrace with edges on a coal layer of an overlying strata, respectively constructing 3DVoronoi bodies in the first terrace with edges and a crack development area, and dividing grids; dividing a bending deformation area, and cutting and layering and grid division; and calculating and determining various parameters, setting related constraint conditions, obtaining a prediction model, and obtaining the goaf caving zone height after the ground fracturing of the coal mine according to the prediction model. According to the invention, the stope rock stratum is divided into a plurality of logic areas, a difference method and a discrete element method are applied to different areas, and a new Contact relation is applied to the intersection surfaces of the different areas, so that the goaf fracture zone height after the ground fracture of the coal mine is truly and accurately simulated, and compared with the traditional method, the method has the advantages of high efficiency, low cost, repeatability and the like.
Description
Technical Field
The invention relates to the technical field of coal mining, in particular to a method for predicting the height of a goaf fracture zone after coal mine ground fracturing.
Background
The ground fracturing of the coal mine is a novel technology for hydraulically fracturing a high-level key layer after ground drilling so as to control the mine pressure of a stope. When the working surface is covered with not only a high-level hard top plate (key layer) but also a high-level aquifer, the ground fracturing technology may increase the collapse zone of the goaf to induce the water body of the high-level aquifer to leak down. The ground fracturing technology is applied to the coal mine in a popularization and application stage, and has a changed fracture form of a high-level hard top plate, so that the collapse movement form of a stope for ground fracturing is different from the previous one.
Therefore, how to accurately predict the height of a fracture zone in a coal mine ground fracture goaf is a problem to be solved by those skilled in the art.
Disclosure of Invention
In view of the above, the invention provides a method for predicting the height of a goaf caving zone after ground fracturing of a coal mine, which is used for predicting the height of the goaf caving zone after ground fracturing and provides guidance for prevention and pre-control of water burst of a mine high-level aquifer.
In order to achieve the above object, the present invention provides the following technical solutions:
a prediction method for the height of a goaf caving zone after coal mine ground fracturing comprises the following steps:
step 1, constructing and cutting a first terrace (5) on a coal bed of an overlying strata, and dividing a region where the first terrace (5) is located into a broken migration region of the overlying strata;
step 2, constructing a 3D Voronoi body (10) in the range of the first prismatic table (5), and dividing grids;
step 3, constructing a second terrace (13) on the basis of the first terrace (5), and dividing the area of the second terrace (13) after the first terrace (5) is removed into a crack development area of the overlying strata;
step 4, connecting the four corners at the top of the first prismatic table (5) with the four corners at the bottom of the second prismatic table (13) in a two-to-two adjacent way, and dividing the crack development area into a crack development logic first area (14), a crack development logic second area (15) and a crack development logic third area (16) in sequence from left to right;
step 5, respectively constructing a 3D Voronoi body (10) in a first crack development logic region (14), a second crack development logic region (15) and a third crack development logic region (16), and performing grid division;
dividing an overlying strata beyond the range of the second prismatic table (13) into a bending deformation region (18), cutting and layering the bent deformation region according to strata distribution, and meshing the overlying strata of the bending deformation region;
step 7, inserting Cohesive units into contact surfaces (19) of the first crack development logic region and the bending deformation region and contact surfaces (20) of the third crack development logic region and the bending deformation region, and giving the mixed mode power function failure criteria to the Cohesive units;
step 8, determining friction coefficient mu of a contact surface (21) between the first crack development logic region and the second crack development logic region and a contact surface (22) between the third crack development logic region and the second crack development logic region 1 Friction coefficient mu of the contact surface (23) between the first crack development logic region and the fracture migration region and the contact surface (24) between the third crack development logic region and the fracture migration region 2 ；
Step 9, applying fixed constraint to the bottom (28) of the bottommost layer (27) of the overlying strata after the treatment in step 8, and applying horizontal constraint to the side wall of the overlying strata to obtain a prediction model;
and step 10, carrying out prediction solution according to the prediction model, and calculating the damage height of the 3D Voronoi body to obtain the height of a goaf caving zone after coal mine ground fracturing.
Optionally, in the step 1, the specific method for constructing and cutting the first land (5) on the coal seam of the overburden layer is as follows:
setting the trend length (1) of the working surface as the bottom edge and setting alpha as 1 A first trapezoid (2) is arranged in the right direction of the base angle, and a is established by taking the inclined length (3) of the working surface as the base 2 The first trapezoid (4) is inclined towards the right of the base angle, and the first trapezoid (2) and the inclination are inclined towardsThe heights of the first trapezoids (4) are H 1 And the bottom plates are positioned on the same horizontal plane to move towards the first trapezoid (2) and to incline towards the first trapezoid (4) and to have a height H 1 Constructing a first terrace (5) which is positioned above a coal layer (26) of the overburden;
the working surface direct top (25) is used as the bottommost layer of the first prismatic table (5) to be higher than H 1 The first land (5) formed in step a is cut at a formation interface (6) within the range.
Optionally, in the step 1, α 1 And alpha 2 Respectively and basically the lithology coefficient gamma 1 Angle alpha of collapse of working face trend 01 The working surface tends to collapse by an angle alpha 02 The correlation, the relation is: alpha 1 ＝γ 1 α 01 、α 2 ＝γ 1 α 02 The method comprises the steps of carrying out a first treatment on the surface of the Basic top lithology coefficient gamma 1 The value is taken according to the basic top lithology softness degree of the working surface,the arrangement can ensure that the divided broken migration areas can completely cover the formation area of the working face collapse zone, and reduce the calculation time as much as possible so as to improve the calculation efficiency;
H 1 height H of caving zone of overlying strata of stope 01 The integrity k of the basic roof is related to the relation: when k is less than 0.15, H 1 ＝1.4H 01 The method comprises the steps of carrying out a first treatment on the surface of the When k is more than or equal to 0.15 and less than 0.55, H 1 ＝1.3H 01 The method comprises the steps of carrying out a first treatment on the surface of the When k is more than or equal to 0.55 and less than 0.75, H 1 ＝1.2H 01 The method comprises the steps of carrying out a first treatment on the surface of the When k is greater than or equal to 0.75, H 1 ＝1.1H 01 The method comprises the steps of carrying out a first treatment on the surface of the Height H of caving belt 01 The relation with the working face height M is as follows:through the arrangement, the divided broken migration areas can be ensured to completely cover the working face collapse zone, meanwhile, the generation quantity of 3D Voronoi bodies is reduced, the calculation time is shortened, and the calculation efficiency is improved.
Optionally, in the step 2, a specific method for constructing the 3D Voronoi body (10) within the range of the first prism table (5) and performing meshing is as follows:
randomly generating a 2D Voronoi diagram (8) on the upper surface (7) of the first prismatic table (5) by adopting a secondary generation method, and stopping generating when the number of polygons of the 2D Voronoi diagram (8) exceeds n;
adopting an integral simplification algorithm based on triangle area coordinates to perform P times of regularity adjustment on the 2D Voronoi diagram (8);
projecting the adjusted 2D Voronoi diagram (8) layer by layer in the range of the first prismatic table (5) by taking the rock stratum interface (6) as a plane from top to bottom until reaching the lower surface (9) of the first prismatic table;
2D Voronoi diagrams (8) of the upper surface (7) of the first pyramid (5), the rock stratum interface (6) in the range of the first pyramid and the lower surface (9) of the first pyramid are mapped and stretched layer by layer from top to bottom in the range of the first pyramid (5) to form a 3D Voronoi body (10);
using a grid size q 1 The hexahedron of (2) grid-divides the 3D Voronoi body (10) within the range of the first pyramid (5).
Optionally, in the step 2, the number n of polygons of the 2D Voronoi diagram is equal to the basic top coefficient f and the longest feature size L of the basic top 1 Basic top shortest feature size L 2 The correlation, relation is: when f is more than or equal to 10,when 6 is less than or equal to f<10 times, 10 +>When 0 is<f<6, the _on>Middle []Representing rounding;
the degree of regularity adjustment times p of the 2D Voronoi diagram is related to the basic top Prussian coefficient f, and the relation is as follows: when 0< f <6, p=25; when 6.ltoreq.f <10, p=20; when f is equal to or greater than 10, p=15; the arrangement can ensure that rock strata with different integrity degrees can be broken to form broken forms, sizes and characteristics under the actual working conditions.
Grid size q 1 And the coefficient lambda of the structural development degree of the geological structure in the fracture migration area 1 Thinnest formation thickness L in fracture migration zone 3 The correlation, the relation is: when lambda is 1 When the temperature is more than or equal to 0.3,when 0.3 > lambda 1 When the temperature is more than or equal to 0.15, the drug is added>When 0.15 > lambda 1 When not less than 0, the weight is added>This is to ensure that the region can generate a grid with a certain fineness, thereby improving the model calculation accuracy and enabling the strain to be more continuous.
Optionally, in the step 3, the specific method for constructing the second land (13) on the basis of the first land (5) is as follows:
the lower bottom edge of the first trapezoid (2) is taken as the upper bottom edge to divide into an inverted shape and the lower bottom angle is beta 1 The second trapezoid (11) is divided into an inverted shape by taking the lower bottom edge of the first trapezoid (4) as the upper bottom edge and the lower bottom angle is beta 2 A trend toward the second trapezoid (12), the heights of the trend toward the second trapezoid (11) and the trend toward the second trapezoid (12) are H 2 And H is 2 ＞H 1 To run toward the second trapezoid (11) and to lean toward the second trapezoid (12) and to have a height H 2 Constructing a second land (13).
Optionally, in the step 3, β 1 、β 2 Respectively and keyword lithology coefficient gamma 2 Angle beta of face strike rock movement 01 Angle beta of inclination of working face 02 The correlation, the relation is: beta 1 ＝γ 2 β 01 、β 2 ＝γ 2 β 02 The method comprises the steps of carrying out a first treatment on the surface of the The key word lithology coefficient gamma is valued according to the basic top lithology softness degree of the working surface,this is to ensure that the divided fracture development zone is capable of completely covering the fracture of the working surfaceThe area of the fertility area reduces the calculation time as much as possible so as to improve the calculation efficiency;
H 2 height of development of fracture zone with working face H 02 The correlation, the relation is: h 2 ＝(1.1～1.2)H 02 The method comprises the steps of carrying out a first treatment on the surface of the Working face fracture zone development height H 02 The relation with the working face height M is as follows:this is in order to ensure that the partitioned fracture development zone can fully cover the working face fracture development zone while reducing the number of 3D Voronoi body formations, reducing the computation time to improve the computational efficiency.
Optionally, in the step 5, 3D Voronoi bodies (10) are respectively constructed in the first area (14) of the crack development logic, the second area (15) of the crack development logic and the third area (16) of the crack development logic, and the specific method for performing the meshing is as follows:
for the second zone (15) of the fracture development logic, a height H is used 1 ～H 2 The rock stratum interface (6) within the range cuts the crack development logic second region (15), and a 3DVoronoi body (10) is constructed in the crack development logic second region (15); using a grid size q 2 The hexahedron of the (2) is used for carrying out grid division on the 3D Voronoi body (10) in the second area (15) of the crack development logic; grid size q 2 Coefficient lambda of structural development degree of geological structure in fracture development area 2 The thinnest formation thickness L in the second zone of the fracture development logic 4 The correlation, the relation is: when lambda is 2 When the temperature is more than or equal to 0.3,when 0.3 > lambda 2 When the temperature is more than or equal to 0.15, the drug is added>When 0.15 > lambda 2 When not less than 0, the weight is added>This is to ensure that the region can generate a grid with certain fineness, thereby improving the model calculation accuracyThe strain is more continuous, and meanwhile, the calculation efficiency is improved as much as possible.
For the first region (14) and the third region (16), the direct top (25) of the working surface is used as the bottommost layer of the first region (14) and the third region (16) to raise the height H 2 The rock stratum interface (6) within the range cuts the first crack development logic region (14) and the third crack development logic region (16), and then a 3D Voronoi body (10) is built in the first crack development logic region (14) and the third crack development logic region (16); using a grid size q 3 The hexahedron or triangular prism (17) is used for meshing the 3D Voronoi body (10) in the first area (14) of the crack development logic and in the third area (16) of the crack development logic; grid size q 3 Coefficient lambda of structural development degree of geological structure in fracture development area 2 The thinnest formation thickness L in the first zone of the fracture development logic and the third zone of the fracture development logic 5 The correlation, the relation is: when lambda is 2 When the temperature is more than or equal to 0.3,when 0.3 > lambda 2 When the temperature is more than or equal to 0.15, the drug is added>When 0.15 > lambda 2 When not less than 0, the weight is added>Therefore, in order to ensure that the area can generate a grid with certain fineness, the model calculation accuracy is improved, the strain is more continuous, and the calculation efficiency is improved as much as possible.
Optionally, in the step 6, a grid size q is adopted 4 Grid division is carried out on the overlying strata of the bending deformation zone by the regular hexahedron; grid size q 4 And the thinnest formation thickness L in the bending deformation zone 6 The correlation, the relation is:this is to ensure that the region can be createdThe method forms a grid with certain fineness, thereby improving the calculation precision of the model, enabling the strain to be more continuous, and simultaneously improving the calculation efficiency as much as possible.
Optionally, in the step 8, μ 1 Coefficient of lithology with formation A 1 、A 2 And frictional resistance T n The correlation, the relation is:the built model can be ensured to be closer to actual engineering conditions, the crack development characteristics of the second area of the crack development logic can be accurately inverted, and meanwhile, the calculation accuracy of simulation is improved.
μ 2 Coefficient of lithology with formation A 1 、A 2 、A 3 And the collapse speed V of the overlying strata is related, and the relation is as follows:the model built can be ensured to be closer to actual engineering conditions, deformation collapse characteristics of the fracture migration area can be accurately inverted, and meanwhile, the calculation accuracy of simulation is improved.
According to the technical scheme, the invention provides a method for predicting the height of a goaf caving zone after coal mine ground fracturing, which has the following beneficial effects compared with the prior art:
the invention divides the stope rock stratum into a plurality of logic areas, namely a fracture migration area, a fracture development logic first area, a fracture development logic second area, a fracture development logic third area and a bending deformation area, and applies a new Contact relation on the intersection surfaces of different areas by using a differential method and a discrete element method in different areas, thereby truly and accurately simulating the fracture zone height of a goaf after the ground fracture of a coal mine, further obtaining the overlying rock fracture degree and the fracture development height of a mining area after the ground fracture, and providing guidance for the prevention and pre-control of fracture water burst of a mine high-level aquifer.
The invention can provide a feasible prediction method for judging whether the ground fracturing technology can increase the height of the goaf fracture zone so as to induce the water body of the high-level aquifer to leak, and the practical prediction method is verified by adopting an example, so that the method has the advantages of high efficiency, low cost, repeatability and the like compared with the traditional method.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only embodiments of the present invention, and that other drawings can be obtained according to the provided drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic representation of the relative position of the face orientation and inclination and overburden of the present invention;
FIG. 2 is a running cross-sectional view of the working surface of the present invention;
FIG. 3 is a cross-sectional view of the working surface of the present invention;
FIG. 4 is a schematic diagram of a broken migration zone according to the present invention;
FIG. 5 is a state diagram of the generation of a 2D Voronoi diagram of the upper surface of a first pyramid in accordance with the present invention;
FIG. 6 is a 3D Voronoi volume generation state diagram of a broken migration zone of the present invention;
FIG. 7 is a schematic view of the spatial structure of a first land and a second land according to the present invention;
FIG. 8 is a schematic diagram of the spatial location structure of each logic region according to the present invention;
wherein 1 represents the trend length of the working surface; 2 represents going to a first trapezoid; 3 represents a working face inclined length; 4 represents a trend toward a first trapezoid; 5 represents a first land; 6 represents a formation interface; 7 represents an upper surface; 8 represents a 2D Voronoi diagram; 9 denotes a lower surface; 10 represents a 3D Voronoi body; 11 denotes going to a second trapezoid; 12 denotes a trend toward a second trapezoid; 13 denotes a second land; 14 represents a fracture development logic first zone; 15 represents a fracture development logic second region; 16 represents a third zone of fracture development logic; 17 denotes a triangular prism; 18 denotes a bending deformation region; 19 represents the contact surface between the first crack development logic region and the bending deformation region; 20 represents the interface between the third zone of the crack development logic and the bending deformation zone; 21 represents the contact surface of the first crack development logic region and the second crack development logic region; 22 represents the interface of the third zone of the fracture development logic with the second zone of the fracture development logic; 23 represents the interface of the fracture development logic first zone and the fracture migration zone; 24 represents the interface between the third zone of the fracture development logic and the fracture migration zone; 25 denotes a direct roof; 26 represents a coal seam; 27 represents the bottommost formation; 28 denotes the bottom.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In the embodiment, a certain working face of a Tashan coal mine is taken as an example, the working face adopts a height of 15m and a trend collapse angle alpha 01 =80°, working face tends to collapse by an angle α 02 Work face strike rock displacement angle β=70° 01 Work face inclined rock displacement angle β=70° 02 The basic roof is mainly sandy mudstone and belongs to a softer rock stratum, the Prussian coefficient f=6.3, the integrity k=0.80 and the longest characteristic dimension L 1 =1000m, shortest feature size L 2 =10m, from which α is obtained 1 ＝88°、α 2 Height H of first land=77° 1 =46 m, second land height H 2 ＝91m、β 1 ＝77°、β 2 Number n=2500 of 2D Voronoi diagrams=71.5, regularity adjustment p=20; thickness L of thinnest rock layer in fracture migration zone 3 =2.5m, coefficient of development of geologic structure within fracture migration zone λ 1 =0.26, and the mesh size q is calculated from this 1 =0.056m; the thinnest formation thickness L in the second zone of the fracture development logic 4 =3.0m, coefficient of extent of geologic structure development λ in fracture development zone 2 =0.17, and the mesh size q is calculated therefrom 2 =0.06 m; the thinnest in the first zone of the fracture development logic and the third zone of the fracture development logicFormation thickness L 5 =2.5m, and thus the mesh size q 3 =0.056m; thickness L of the thinnest rock layer in the bending deformation zone 6 To this end, the mesh size q is calculated =2.5m 4 =0.06 m. In addition, the friction coefficient A of the rock with different lithology of the overburden layer of the working surface is obtained through a physical and mechanical experiment 1 、A 2 、A 3 Friction resistance T n The collapse speed V of the overlying strata, and accordingly, the friction coefficient mu of the rock contact surfaces with different lithology is obtained 1 、μ 2 Values, e.g., mudstone: mu (mu) 1 ＝0.23、μ 2 =0.25; siltstone: mu (mu) 1 ＝0.31、μ 2 =0.36; medium grain sandstone: mu (mu) 1 ＝0.42、μ 2 =0.47, etc. Referring to fig. 8, a schematic diagram of the spatial location structure of each logic area is shown.
The specific prediction process is as follows:
step a, setting up a forward trend first trapezoid 2 with a working face trend length 1 as a bottom edge and a working face trend length 3 as a bottom edge, setting up a forward trend first trapezoid 4 with a working face trend length of 77 degrees as a bottom edge, wherein the heights of the trend first trapezoid 2 and the trend first trapezoid 4 are 46m, the bottom plates are positioned on the same horizontal plane, setting up a first terrace 5 with the trend first trapezoid 2, the trend first trapezoid 4 and the height 46m, and the first terrace is positioned above a coal seam 26 of an overlying strata, and dividing a region where the first terrace 5 is positioned into a broken migration region of the overlying strata, as shown in figures 1, 2, 4 and 7;
step b, taking the direct top 25 of the working surface as the bottommost layer of the first prismatic table 5, and cutting the first prismatic table 5 formed in the step a by using a rock stratum interface 6 with the upward height of 46m, as shown in fig. 4;
step c, randomly generating a 2D Voronoi diagram 8 on the upper surface 7 of the first prismatic table 5 by adopting a secondary generation method, and stopping generating when the number of polygons exceeds 2500, as shown in fig. 5;
step D, adopting an integral simplification algorithm based on triangle area coordinates to perform 20 times of regularity adjustment on the 2D Voronoi diagram 8 in the step c;
step e, projecting the 2D Voronoi diagram 8 adjusted in the step D layer by layer in the range of the first pyramid 5 from top to bottom by taking the stratum interface 6 as a plane until reaching the lower surface 9 of the first pyramid;
step f, mapping and stretching the 2D Voronoi diagram 8 of the upper surface 7 of the first pyramid 5, the rock layer interface 6 in the first pyramid range and the lower surface 9 of the first pyramid layer by layer from top to bottom in the first pyramid 5 range to form a 3D Voronoi body 10, as shown in fig. 6;
step g, adopting hexahedron with a grid size of 0.056m to grid-divide the 3D Voronoi body 10 after the treatment of the step f;
step h, dividing an inverted trend second trapezoid 11 with a lower bottom angle of 77 DEG by taking a lower bottom edge of the trend first trapezoid 2 as an upper bottom edge, dividing an inverted trend second trapezoid 12 with a lower bottom angle of 71.5 DEG by taking a lower bottom edge of the trend first trapezoid 4 as an upper bottom edge, and constructing a second terrace 13 by taking the trend second trapezoid 11, the trend second trapezoid 12 and the height 91m of the trend second trapezoid 12, wherein the first terrace 5 is contained in the second terrace 13; dividing the area of the second land 13 after the first land 5 is removed into a crack development area of the overburden layer, as shown in fig. 1, 3 and 7;
step i, connecting the four corners at the top of the first prismatic table 5 with the four corners at the bottom of the second prismatic table 13 in a two-by-two adjacent manner, and dividing the crack development area into a crack development logic first area 14, a crack development logic second area 15 and a crack development logic third area 16 in sequence from left to right, as shown in fig. 2 and 3;
step j, cutting the crack development logic second area 15 divided in the step i by adopting a rock stratum interface 6 with the height ranging from 46m to 91m according to the step b, and then constructing the 3D Voronoi body 10 in the crack development logic second area 15 according to the steps c to f;
step k, adopting hexahedron with grid size of 0.06m to carry out grid division on the 3D Voronoi body 10 in the second area 15 of the crack development logic obtained by processing the step j;
step l, also according to step b, taking the direct top 25 of the working surface as the bottommost layer of the first region 14 and the third region 16 of the crack development logic, cutting the first region 14 and the third region 16 of the crack development logic divided in the step i by the rock stratum interface 6 in the range of 91m upwards, and then constructing the 3DVoronoi body 10 in the first region 14 of the crack development logic and the third region 16 of the crack development logic according to steps c-f;
step m, adopting hexahedron or triangular prism 17 with grid size of 0.056m to carry out grid division on the 3D Voronoi body 10 in the first area 14 of the crack development logic and in the third area 16 of the crack development logic obtained by processing the step l;
dividing an overlying strata beyond the range of the second prismatic table 13 into a bending deformation region 18, cutting and layering the bent deformation region according to strata distribution, and adopting a regular hexahedron with a grid size of 0.06m to grid-divide the overlying strata of the bending deformation region;
step o, inserting Cohesive units into the contact surface 19 between the first crack development logic region and the bending deformation region and the contact surface 20 between the third crack development logic region and the bending deformation region; the Cohesive unit is constructed by adopting Python language, so that the calculation efficiency is improved, and the reliability of a simulation calculation result is ensured;
step p, endowing a mixed mode power function failure criterion to the Cohesive unit in the step o;
step q, defining each lithologic Friction coefficient mu of the joint surface 21 between the first region of the crack development logic and the second region of the crack development logic and the joint surface 22 between the third region of the crack development logic and the second region of the crack development logic by using the Friction Model 1 (Friction Model 1) 1 (e.g. mudstone: mu) 1 =0.23; siltstone: mu (mu) 1 =0.31; medium grain sandstone: mu (mu) 1 =0.42, etc.);
step r, defining each lithologic friction coefficient mu of a joint development logic first region and a fracture migration region contact surface 23 and a joint development logic third region and fracture migration region contact surface 24 by adopting a static dynamic friction model of a new contact function of an ABAQUS platform 2 (e.g. mudstone: mu) 2 =0.25; siltstone: mu (mu) 2 =0.36; medium grain sandstone: mu (mu) 2 =0.47, etc.);
step s, applying fixed constraint to the bottom 28 of the bottommost stratum 27 of the overlying strata after the treatment in step r, and applying horizontal constraint to the side wall of the overlying strata to obtain a prediction model;
and (t) solving the prediction model obtained in the step(s) by adopting an ABAQUS display solver, wherein the damage process of the 3D Voronoi body is the development and expansion process of the crack, and obtaining the prediction result of the goaf caving zone height after coal mine ground fracturing by calculating the damage height of the 3D Voronoi body.
In the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant points refer to the description of the method section.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (5)
1. The method for predicting the height of the caving zone of the goaf after the ground fracturing of the coal mine is characterized by comprising the following steps:
step 1, constructing and cutting a first terrace (5) on a coal bed of an overlying strata, and dividing a region where the first terrace (5) is located into a broken migration region of the overlying strata; the specific method for constructing and cutting the first terrace (5) on the coal layer of the overburden layer comprises the following steps:
setting the trend length (1) of the working surface as the bottom edge and setting alpha as 1 A first trapezoid (2) is arranged in the right direction of the base angle, and a is established by taking the inclined length (3) of the working surface as the base 2 The right inclined first trapezoid (4) with the base angle is inclined to the first trapezoid (2) and the height of the inclined first trapezoid (4) is H 1 And the bottom plates are positioned on the same horizontal plane to move towards the first trapezoid (2) and to incline towards the first trapezoid (4)Height H 1 Constructing a first terrace (5) which is positioned above a coal layer (26) of the overburden; the working surface direct top (25) is used as the bottommost layer of the first prismatic table (5) to be higher than H 1 A first land (5) is cut at a formation interface (6) in the range;
α 1 and alpha 2 Respectively and basically the lithology coefficient gamma 1 Angle alpha of collapse of working face trend 01 The working surface tends to collapse by an angle alpha 02 The correlation, the relation is: alpha 1 ＝γ 1 α 01 、α 2 ＝γ 1 α 02 The method comprises the steps of carrying out a first treatment on the surface of the Basic top lithology coefficient gamma 1 The value is taken according to the basic top lithology softness degree of the working surface,
H 1 height H of caving zone of overlying strata of stope 01 The integrity k of the basic roof is related to the relation: when k is less than 0.15, H 1 ＝1.4H 01 The method comprises the steps of carrying out a first treatment on the surface of the When k is more than or equal to 0.15 and less than 0.55, H 1 ＝1.3H 01 The method comprises the steps of carrying out a first treatment on the surface of the When k is more than or equal to 0.55 and less than 0.75, H 1 ＝1.2H 01 The method comprises the steps of carrying out a first treatment on the surface of the When k is greater than or equal to 0.75, H 1 ＝1.1H 01 The method comprises the steps of carrying out a first treatment on the surface of the Height H of caving belt 01 The relation with the working face height M is as follows:
step 2, constructing a 3D Voronoi body (10) in the range of the first prismatic table (5), and dividing grids;
step 3, constructing a second terrace (13) on the basis of the first terrace (5), and dividing the area of the second terrace (13) after the first terrace (5) is removed into a crack development area of the overlying strata; the specific method for constructing the second pyramid (13) on the basis of the first pyramid (5) comprises the following steps:
the lower bottom edge of the first trapezoid (2) is taken as the upper bottom edge to divide into an inverted shape and the lower bottom angle is beta 1 The second trapezoid (11) is divided into an inverted shape by taking the lower bottom edge of the first trapezoid (4) as the upper bottom edge and the lower bottom angle is beta 2 A trend toward the second trapezoid (12)(11) The height of the inclined second trapezoid (12) is H 2 And H is 2 ＞H 1 To run toward the second trapezoid (11) and to lean toward the second trapezoid (12) and to have a height H 2 Constructing a second terrace (13);
β 1 、β 2 respectively and keyword lithology coefficient gamma 2 Angle beta of face strike rock movement 01 Angle beta of inclination of working face 02 The correlation, the relation is: beta 1 ＝γ 2 β 01 、β 2 ＝γ 2 β 02 The method comprises the steps of carrying out a first treatment on the surface of the The key word lithology coefficient gamma is valued according to the basic top lithology softness degree of the working surface,
H 2 height of development of fracture zone with working face H 02 The correlation, the relation is: h 2 ＝(1.1～1.2)H 02 The method comprises the steps of carrying out a first treatment on the surface of the Working face fracture zone development height H 02 The relation with the working face height M is as follows:
step 4, connecting the four corners at the top of the first prismatic table (5) with the four corners at the bottom of the second prismatic table (13) in a two-to-two adjacent way, and dividing the crack development area into a crack development logic first area (14), a crack development logic second area (15) and a crack development logic third area (16) in sequence from left to right;
step 5, respectively constructing a 3D Voronoi body (10) in a first crack development logic region (14), a second crack development logic region (15) and a third crack development logic region (16), and performing grid division;
dividing an overlying strata beyond the range of the second prismatic table (13) into a bending deformation region (18), cutting and layering the bent deformation region according to strata distribution, and meshing the overlying strata of the bending deformation region;
step 7, inserting Cohesive units into the contact surface (19) of the first crack development logic region (14) and the bending deformation region and the contact surface (20) of the third crack development logic region (16) and the bending deformation region, and giving the mixed mode power function failure criteria to the Cohesive units;
step 8, determining friction coefficient mu of the contact surface (21) between the first crack development logic region (14) and the second crack development logic region and the contact surface (22) between the third crack development logic region (16) and the second crack development logic region 1 Friction coefficient mu of fracture development logic first region (14) and fracture migration region contact surface (23) and fracture migration region contact surface (24) of fracture development logic third region (16) 2 ；
μ 1 Coefficient of lithology with formation A 1 、A 2 And frictional resistance T n The correlation, the relation is:
μ 2 coefficient of lithology with formation A 1 、A 2 、A 3 And the collapse speed V of the overlying strata is related, and the relation is as follows:
step 9, applying fixed constraint to the bottom (28) of the bottommost layer (27) of the overlying strata after the treatment in step 8, and applying horizontal constraint to the side wall of the overlying strata to obtain a prediction model;
and step 10, carrying out prediction solution according to the prediction model, and calculating the damage height of the 3D Voronoi body to obtain the height of a goaf caving zone after coal mine ground fracturing.
2. The method for predicting the height of a goaf caving zone after coal mine ground fracturing according to claim 1, wherein in the step 2, a 3D Voronoi body (10) is constructed in the range of a first prism table (5), and the specific method for meshing is as follows:
randomly generating a 2D Voronoi diagram (8) on the upper surface (7) of the first prismatic table (5) by adopting a secondary generation method, and stopping generating when the number of polygons of the 2D Voronoi diagram (8) exceeds n;
adopting an integral simplification algorithm based on triangle area coordinates to perform P times of regularity adjustment on the 2D Voronoi diagram (8);
projecting the adjusted 2D Voronoi diagram (8) layer by layer in the range of the first prismatic table (5) by taking the rock stratum interface (6) as a plane from top to bottom until reaching the lower surface (9) of the first prismatic table;
2D Voronoi diagrams (8) of the upper surface (7) of the first pyramid (5), the rock stratum interface (6) in the range of the first pyramid and the lower surface (9) of the first pyramid are mapped and stretched layer by layer from top to bottom in the range of the first pyramid (5) to form a 3D Voronoi body (10);
using a grid size q 1 The hexahedron of (2) grid-divides the 3D Voronoi body (10) within the range of the first pyramid (5).
3. The method for predicting the height of a goaf caving zone after coal mine ground fracturing according to claim 2, wherein in the step 2, the number n of polygons of the 2D Voronoi diagram, the basic roof Prussian coefficient f and the longest feature size L of the basic roof 1 Basic top shortest feature size L 2 The correlation, relation is: when f is more than or equal to 10,when 6 is less than or equal to f<At the time of 10 a, the time of the reaction,when 0 is<f<6, the _on>Middle []Representing rounding;
the degree of regularity adjustment times p of the 2D Voronoi diagram is related to the basic top Prussian coefficient f, and the relation is as follows: when 0< f <6, p=25; when 6.ltoreq.f <10, p=20; when f is equal to or greater than 10, p=15;
grid size q 1 And the coefficient lambda of the structural development degree of the geological structure in the fracture migration area 1 Thinnest formation thickness L in fracture migration zone 3 The correlation, the relation is: when lambda is 1 When the temperature is more than or equal to 0.3,when 0.3 > lambda 1 When the temperature is more than or equal to 0.15, the drug is added>When 0.15 > lambda 1 When not less than 0, the weight is added>
4. The method for predicting the height of a fracture zone in a goaf after ground fracture of a coal mine according to claim 1, wherein in the step 5, 3D Voronoi bodies (10) are respectively constructed in a first fracture development logic region (14), a second fracture development logic region (15) and a third fracture development logic region (16), and the specific method for meshing is as follows:
for the second zone (15) of the fracture development logic, a height H is used 1 ～H 2 The rock stratum interface (6) within the range cuts a crack development logic second region (15), and a 3D Voronoi body (10) is built in the crack development logic second region (15); using a grid size q 2 The hexahedron of (2) performs grid division on the 3DVoronoi bodies (10) in the second area (15) of the crack development logic; grid size q 2 Coefficient lambda of structural development degree of geological structure in fracture development area 2 The thinnest formation thickness L in the second zone of the fracture development logic 4 The correlation, the relation is: when lambda is 2 When the temperature is more than or equal to 0.3,when 0.3 > lambda 2 When the temperature is more than or equal to 0.15, the drug is added>When 0.15 > lambda 2 When not less than 0, the weight is added>
Logic of crack developmentA first region (14) and a third region (16) of crack development logic, the direct top (25) of the working surface is used as the bottommost layer of the first region (14) and the third region (16) of crack development logic, so as to raise the height H upwards 2 The rock stratum interface (6) within the range cuts the first crack development logic region (14) and the third crack development logic region (16), and then a 3D Voronoi body (10) is built in the first crack development logic region (14) and the third crack development logic region (16); using a grid size q 3 The hexahedron or triangular prism (17) is used for meshing the 3D Voronoi body (10) in the first area (14) of the crack development logic and in the third area (16) of the crack development logic; grid size q 3 Coefficient lambda of structural development degree of geological structure in fracture development area 2 The thinnest formation thickness L in the first zone (14) and the third zone (16) of the fracture development logic 5 The correlation, the relation is: when lambda is 2 When the temperature is more than or equal to 0.3,when 0.3 > lambda 2 When the temperature is more than or equal to 0.15, the drug is added>When 0.15 > lambda 2 When not less than 0, the weight is added>
5. The method for predicting the height of a goaf caving zone after coal mine ground fracturing according to claim 1, wherein in the step 6, a grid size q is adopted 4 Grid division is carried out on the overlying strata of the bending deformation zone by the regular hexahedron; grid size q 4 And the thinnest formation thickness L in the bending deformation zone 6 The correlation, the relation is:
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