A method and system for determining the step distance of ground fracturing in coal mine rock burst

Abstract

The present invention discloses a method and system for determining the ground fracturing step distance of coal mine rock burst, which relates to the technical field of underground coal mining, by determining the hydraulic fracturing target layer; measuring the mechanical parameters of the roof of the hydraulic fracturing target layer and its underlying rock layer; establishing a regression equation to determine the length of the clamping end of the hydraulic fracturing target layer; calculating the energy density of the hydraulic fracturing target layer according to the satisfied conditions and the boundary deflection and the rotation angle; accumulating the energy density of the hydraulic fracturing target layer to obtain energy, combining the cantilever length of the hydraulic fracturing target layer to determine the impact load borne by the support; and then determining the fracturing step distance of the hydraulic fracturing target layer. The present invention thus performs fracturing on the target layer, prevents the accumulation of elastic energy of the roof, prevents rock burst in underground coal mines, and ensures safe coal mining.

Description

Technical Field

[0001] The present invention relates to the technical field of coal mine underground mining, and more particularly to a method and system for determining ground fracturing step distances for coal mine rock burst. Background Art

[0002] At present, rock burst is one of the common dynamic disasters in deep coal mining, and it becomes more serious as the depth of the mine increases. When rock burst occurs, it is accompanied by severe impact and vibration, causing damage to coal mining sites and tunnel equipment, resulting in equipment cost losses and increased tunnel maintenance costs. When the rock burst is severe, it may even cause casualties. Ground fracturing to control the breakage of the roof and release the elastic energy accumulated in the roof in advance is one of the effective means to control rock burst.

[0003] However, since the application of surface fracturing technology in the prevention and control of rock burst in coal mines, there has been no specific method for determining the fracturing step distance. It is mostly based on experience, and the target layer is fractured indiscriminately, resulting in a large loss of fracturing funds. The waste of useless work also causes the pressure of the underground hydraulic support to increase. The excessive pressure has posed new challenges to the performance of the hydraulic support.

[0004] Therefore, how to reasonably determine the fracturing step distance in ground fracturing technology is an urgent problem that technicians in this field need to solve. Summary of the invention

[0005] In view of this, the present invention provides a method and system for determining the ground fracturing step distance for preventing and controlling rock burst in coal mines, which solves the problems of the inability to reasonably determine the fracturing step distance, excessively high fracturing costs, and increased static load of hydraulic supports after fracturing when using ground fracturing technology to prevent and control rock burst.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A method for determining the step distance of ground fracturing in coal mine rock burst, comprising:

[0008] Step 1: Determine the target layer for hydraulic fracturing according to the thickness of the roof, lithology, and the ore pressure manifestation data of the adjacent working face;

[0009] Step 2, measuring the roof mechanical parameters of the hydraulic fracturing target layer and its underlying rock layer;

[0010] Step 3: Establish a regression equation based on the obtained roof mechanical parameters, and determine the length of the hydraulic fracturing target layer clamping end based on the regression equation;

[0011] Step 4, establishing the conditions for satisfying the cantilever section deflection and the clamping end of the hydraulic fracturing target layer, and determining the boundary deflection and rotation angle of the hydraulic fracturing target layer, and calculating the energy density of the hydraulic fracturing target layer based on the conditions and the boundary deflection and rotation angle;

[0012] Step 5: Accumulate the energy density of the hydraulic fracturing target layer to obtain energy, and determine the impact load borne by the support in combination with the cantilever length of the hydraulic fracturing target layer;

[0013] Step 6, increasing the cantilever length of the target layer at a fixed length, repeating steps 4 and 5 until the cantilever length is greater than a first preset threshold or the impact load borne by the support is greater than a second preset threshold, outputting the cantilever length of the hydraulic fracturing target layer at this time, and taking 3 / 4 of the cantilever length as the fracturing step distance;

[0014] Optionally, step 2 includes: measuring the elastic modulus E, cohesion c, internal friction angle φ, Poisson's ratio υ of the target layer by drilling and coring, and measuring the elastic modulus E1, E2, ... E of the rock layer 5 times the thickness of the target layer. r , cohesion c1, c2…c r 、Internal friction angle φ1、φ2…φ r Poisson's ratio υ1, υ2…υ r ; Determine the vertical load q on the target layer according to the key layer theory;

[0015] Optionally, the step 3 specifically includes:

[0016] According to the obtained mechanical parameters of the top plate, the regression equation is established as follows:

[0017]

[0018] in,

[0019] Determine the hydraulic fracturing target layer clamp end L2 according to the regression equation = (h1+h2+h3+h4) t , where t is the target factor, t starts from 0 and increases by 0.02. When L2≥100 or t>2, stop the loop and output L2;

[0020] Optionally, step 4 specifically includes:

[0021] The cantilever end of the target layer is divided into m segments, and the clamped end of the target layer is divided into n segments, m ≥ 100, n ≥ 100, wherein the three adjacent nodes of the cantilever segment L1 of the target layer are set as i-1, i, i+1 respectively, and the three adjacent nodes of the clamped segment L2 of the target rock layer are set as j-1, j, j+1 respectively, and the distance between the adjacent nodes is α; wherein the deflection of the target cantilever segment satisfies the following relationship:

[0022]

[0023] The clamping section satisfies the following relationship:

[0024]

[0025] Where: k = k0b, k0 is the base coefficient of the underlying rock layer, b is the width of the target layer for fracturing; E is the elastic modulus of the target layer; I is the moment of inertia of the target layer section about the z-axis; G is the shear modulus of the target layer; A is the cross-sectional area of ​​the target layer, κ is the shear correction coefficient of the target layer section; w (·) is the disturbance of the corresponding node; ψ (·) is the rotation angle of the corresponding node;

[0026] Similarly, the target layer boundary deflection and rotation are determined by the following formula:

[0027]

[0028] Substituting each quantity into the energy density expression, we get:

[0029]

[0030] Optionally, the step 5 specifically includes: accumulating the energy density to obtain energy, that is, Combined with the cantilever length of the hydraulic fracturing target layer, determine the impact load borne by the support:

[0031]

[0032] In the formula, l ZJ Control the top distance of the hydraulic support on the working surface; γ ZJD is the average bulk density of the immediate roof of coal rock; d ZJD is the thickness of the immediate roof of coal rock; g is the acceleration of gravity; β is the fracture angle of the overburden rock; b ZJ is the center distance of the bracket; s is the dynamic load transfer efficiency, K ZJD is the stiffness of the immediate roof of coal rock, p D The thick hard top plate bears the load, and L1 is the cantilever length of the target layer.

[0033] Optionally, step 1 includes: collecting comprehensive borehole geological maps of the mine, observation data on mine pressure manifestation in adjacent working faces, and determining the roof thickness and lithology of the rock strata based on the comprehensive borehole geological maps of the mine; and then determining the target layer for ground fracturing based on the roof thickness, lithology, and mine pressure manifestation data of adjacent working faces.

[0034] Optionally, the first preset threshold in step 6 is 100m; the second preset threshold is 15000kN.

[0035] A coal mine rock burst ground fracturing step determination system, comprising the following modules:

[0036] The target layer determination module determines the hydraulic fracturing target layer based on the roof thickness, lithology, and the ore pressure data of the adjacent working face;

[0037] Mechanical parameter determination module, which determines the roof mechanical parameters of the hydraulic fracturing target layer and its underlying rock layer;

[0038] The module for determining the length of the clamping branch end of the target layer establishes a regression equation according to the obtained roof mechanical parameters, and determines the length of the clamping branch end of the hydraulic fracturing target layer according to the regression equation;

[0039] The energy density calculation module sets up the cantilever section deflection and the satisfying conditions of the clamping end of the hydraulic fracturing target layer, determines the boundary deflection and rotation angle of the hydraulic fracturing target layer, and calculates the energy density of the hydraulic fracturing target layer based on the satisfying conditions and the boundary deflection and rotation angle;

[0040] The impact load calculation module accumulates the energy density of the hydraulic fracturing target layer to obtain energy, and determines the impact load borne by the support in combination with the cantilever length of the hydraulic fracturing target layer;

[0041] The fracturing step output module increases the cantilever length of the target layer by a fixed length and repeatedly calculates the impact load borne by the bracket until the cantilever length is greater than the first preset threshold or the impact load borne by the bracket is greater than the second preset threshold. The cantilever length of the hydraulic fracturing target layer at this time is output, and 3 / 4 of the cantilever length is taken as the fracturing step.

[0042] It can be seen from the above technical scheme that compared with the prior art, the present invention discloses a method and system for determining the ground fracturing step distance of coal mine rock burst pressure, which determines the hydraulic fracturing target layer according to the roof thickness, lithology, and mine pressure manifestation data of adjacent working faces; measures the roof mechanical parameters of the hydraulic fracturing target layer and its underlying rock layer; establishes a regression equation based on the obtained roof mechanical parameters, and determines the length of the clamping end of the hydraulic fracturing target layer according to the regression equation; establishes the deflection of the cantilever section of the hydraulic fracturing target layer and the satisfying conditions of the clamping end, and determines the boundary deflection and rotation angle of the hydraulic fracturing target layer, and calculates the energy density of the hydraulic fracturing target layer according to the satisfying conditions and the boundary deflection and rotation angle; accumulates the energy density of the hydraulic fracturing target layer to obtain energy, and determines the impact load borne by the bracket in combination with the cantilever length of the hydraulic fracturing target layer; and then determines the fracturing step distance of the hydraulic fracturing target layer. The present invention breaks through the traditional ground impact geopressure ground fracturing method of using continuous fracturing, and further optimizes the fracturing step distance for ground fracturing to prevent and control coal mine impact geopressure, reduces the drilling length of ground fracturing, reduces fracturing projects under the same conditions, reduces fracturing consumables, saves fracturing costs, and ensures safe coal mining. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0044] Figure 1 A flow chart of the method provided by the present invention;

[0045] Figure 2 It is a schematic diagram of the engineering construction provided by the present invention;

[0046] Among them, 1 is the coal seam, 2 is the underlying rock layer 5 times thicker, 3 is the target layer for fracturing, 4 is the overlying rock layer, 5 is the fracturing well, and 6 is the hydraulic support. DETAILED DESCRIPTION

[0047] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] The embodiment of the present invention discloses a method for determining the step distance of ground fracturing in coal mine rock burst, such as Figure 1 As shown, including:

[0049] Step 1: Determine the hydraulic fracturing target layer 3 according to the roof thickness, lithology, and the ore pressure manifestation data of the adjacent working face;

[0050] Step 1 specifically includes: collecting the comprehensive borehole geological map of the mine, the observation data of the mine pressure manifestation of the adjacent working face, and determining the roof thickness and lithology of the rock layer based on the comprehensive borehole geological map of the mine; and then determining the ground fracturing target layer based on the roof thickness, lithology, and the mine pressure manifestation data of the adjacent working face.

[0051] The comprehensive geological drilling column diagram basically includes the stratigraphic position, lithology, thickness and other information of each stratum in the mine. The target layer needs to be identified based on the lithology, thickness and occurrence position of the stratum. Generally, the lithology of the stratum is soft mudstone, silty mudstone, etc., and the thin rock layer with a thickness of no more than 5m will not become the target layer. Therefore, sandstone and other rock layers with harder lithology and larger thickness should be selected as the target layer for fracturing.

[0052] Step 2, measuring the roof mechanical parameters of the hydraulic fracturing target layer 3 and its underlying rock formation;

[0053] Step 2 specifically includes: measuring the elastic modulus E, cohesion c, internal friction angle φ, Poisson's ratio υ of the target layer through drilling and coring, and measuring the elastic modulus E1, E2...E of the rock layer 5 times the thickness under the target layer. r , cohesion c1, c2…c r 、Internal friction angle φ1、φ2…φ r Poisson's ratio υ1, υ2…υ r ; Determine the vertical load q on the target layer according to the key layer theory;

[0054] Step 3: Establish a regression equation based on the obtained roof mechanical parameters, and determine the length of the clamping end of the hydraulic fracturing target layer 3 according to the regression equation;

[0055] Step 3 specifically includes:

[0056] According to the obtained mechanical parameters of the top plate, the regression equation is established as follows:

[0057]

[0058] in,

[0059] Determine the hydraulic fracturing target layer 3 branch end L2 according to the regression equation = (h1+h2+h3+h4) t , where t is the target factor, t starts from 0 and increases by 0.02. When L2≥100 or t>2, stop the loop and output L2;

[0060] Step 4, establishing the conditions for satisfying the cantilever section deflection and the clamping end of the hydraulic fracturing target layer 3, and determining the boundary deflection and rotation angle of the hydraulic fracturing target layer 3, and calculating the energy density of the hydraulic fracturing target layer 3 based on the conditions and the boundary deflection and rotation angle;

[0061] Step 4 specifically includes:

[0062] The cantilever end of the target layer is divided into m segments, and the clamped end of the target layer is divided into n segments, m ≥ 100, n ≥ 100, wherein the three adjacent nodes of the cantilever segment L1 of the target layer are set as i-1, i, i+1 respectively, and the three adjacent nodes of the clamped segment L2 of the target rock layer are set as j-1, j, j+1 respectively, and the distance between the adjacent nodes is α; wherein the deflection of the target cantilever segment satisfies the following relationship:

[0063]

[0064] The clamping section satisfies the following relationship:

[0065]

[0066] Where: k = k0b, k0 is the base coefficient of the underlying rock layer, b is the width of the target layer for fracturing; E is the elastic modulus of the target layer; I is the moment of inertia of the target layer section about the z-axis; G is the shear modulus of the target layer; A is the cross-sectional area of ​​the target layer, κ is the shear correction coefficient of the target layer section; w (·) is the disturbance of the corresponding node; ψ (·) is the rotation angle of the corresponding node;

[0067] Similarly, the target layer boundary deflection and rotation are determined by the following formula:

[0068]

[0069] Substituting each quantity into the energy density expression, we get:

[0070]

[0071] Step 5, accumulating the energy density of the hydraulic fracturing target layer 3 to obtain energy, and combining the cantilever length of the hydraulic fracturing target layer 3 to determine the impact load borne by the support;

[0072] Step 5 specifically includes: accumulating the energy density to obtain energy, that is, Combined with the cantilever length of the hydraulic fracturing target layer 3, the impact load borne by the support is determined:

[0073]

[0074] In the formula, l ZJ Control the top distance of the hydraulic support 6 on the working surface; γ ZJD is the average bulk density of the immediate roof of coal rock; d ZJD is the thickness of the immediate roof of coal rock; g is the acceleration of gravity; β is the fracture angle of the overburden rock; b ZJ is the center distance of the bracket; s is the dynamic load transfer efficiency, K ZJD is the stiffness of the immediate roof of coal rock, p D The thick hard top plate bears the load, and L1 is the cantilever length of the target layer.

[0075] Step 6, increasing the cantilever length of the target layer at a fixed length, repeating steps 4 and 5 until the cantilever length is greater than a first preset threshold or the impact load borne by the support is greater than a second preset threshold, outputting the cantilever length of the hydraulic fracturing target layer 3 at this time, and taking 3 / 4 of the cantilever length as the fracturing step distance;

[0076] Specifically: First, set L1 to 1m, 3m, 5m, etc. Use MATLAB to loop through steps 4 and 5 until L1>100 or the impact load F borne by the bracket is ZJ When >15000kN, the corresponding cantilever length at this time is output, and 3 / 4 of the cantilever length at this time is taken as the fracturing step distance of the hydraulic fracturing target layer 3.

[0077] The embodiment of the present invention takes the specific values ​​of a certain coal mine as an example, determines the thickness of the target layer for fracturing through the borehole geological map, performs a series of rock physical and mechanical parameter measurements on the rock layer 5 times thicker than the target layer, determines the target layer for fracturing, and after a series of cyclic calculations, determines the fracturing step distance for ground fracturing to prevent and control rock bursts in the coal mine, thereby implementing ground fracturing, reducing roof energy accumulation, preventing the occurrence of rock bursts, and ensuring safe production at the working face of the coal mine.

[0078] (1) Identify the target layer for fracturing based on the comprehensive geological drilling column chart:

[0079] Taking the specific data of a mine as an example, after collecting relevant information of the mine, the width of the working face is L = 240m, and the thickest and hardest rock layer among the overlying rock layers 4 is sandstone, and its mechanical parameters are: thickness d = 10m, tensile strength 5.5MPa, elastic modulus E = 4GPa, Poisson's ratio υ = 0.2, cohesion c = 6MPa, internal friction angle 35°, so this rock layer is determined as the target layer. The overburden load q = 0.94MPa transferred to the thick hard roof is calculated by the key layer theory, the coal rock foundation stiffness k = 1000MN / m in the mining bearing area, and the hydraulic support 6 top control distance l ZJ =7.0m, bracket center distance b ZJ =1.75m, thickness of coal rock immediate roof d ZJD =16m, average bulk density of direct top coal stratum γ ZJD =1600kg / m 3 , gravitational acceleration g = 9.8 m / s 2 .

[0080] Construction diagram Figure 2 As shown, the figure includes a coal seam 1, an underlying rock layer 2 with a thickness of 5 times, a hydraulic fracturing target layer 3, an overlying rock layer 4, a fracturing well 5, and a hydraulic support 6;

[0081] (2) Carry out a series of roof mechanical parameter measurements on the rock layer 5 times thicker than the target layer, and finally determine whether the target layer is the target layer for fracturing: The specific implementation method is: through drilling and coring, 10 layers of rock layer 5 times thicker than the target layer are cored, and their elastic modulus E, cohesion c, internal friction angle are measured respectively. Poisson's ratio υ, and determine the vertical load q on the target layer; measure the elastic modulus E1, E2...E of the rock layer 5 times the thickness under the target layer i , cohesion c1, c2…c i Internal friction angle Poisson's ratio υ1, υ2…υ i .

[0082] (3) Determine the influence range L2 of the target layer clamping end, which is specifically implemented as follows: the cantilever length is determined by the cycle pressure step of the adjacent working face or the average value is taken based on the statistical step of the cycle pressure of different working faces of the same coal seam 1 in the mine; the determination of the clamping end length L2 is implemented as follows: According to the mine data, the maximum cantilever length is L1=33m.

[0083]

[0084] in,

[0085] L2=(h1+h2+h3+h4) t , where t is the target factor, t starts from 0 and increases by 0.02. When L2≥100 or t>2, the loop stops and L2 is output.

[0086] The results are shown in Table 1:

[0087] Table 1 Mechanical parameters of the rock layer 5 times the size of the target layer

[0088]

[0089]

[0090] After the cycle is completed, the output is L2=139.99m, t=0.38.

[0091] (4) Determine the deflection, rotation angle, and energy density distribution of the target layer for fracturing. The specific implementation method is as follows: divide the cantilever end of the target layer into m sections, and divide the clamp end of the target layer into n sections, m≥100, n≥100. The three adjacent nodes of the cantilever section L1 of the target rock layer are set as i-1, i, i+1, respectively, and the three adjacent nodes of the clamp section L2 of the target rock layer are set as j-1, j, j+1, respectively. The distance between adjacent nodes is α, where α=0.6. The deflection of the target cantilever section satisfies the following relationship:

[0092]

[0093] The clamping section satisfies the following relationship:

[0094]

[0095] In the formula: k = k0b, k0 is the base coefficient of the underlying rock layer, b is the width of the target layer for fracturing; E is the elastic modulus of the target layer; I is the moment of inertia of the target layer section about the z-axis; G is the shear modulus of the target layer; A is the cross-sectional area of ​​the target layer, and κ is the shear correction coefficient of the target layer section, which is related to the cross-sectional shape and is taken as 5 / 6 here.

[0096] Similarly, the target layer boundary deflection and rotation are determined by the following formula:

[0097]

[0098] Substituting each quantity into the energy density expression, we get:

[0099]

[0100] (5) Determine the impact load borne by the bracket, and the specific implementation method is: according to the energy density in step 4, accumulate the energy density to obtain energy, that is, Combined with the impact load borne by the hydraulic support 6:

[0101]

[0102] In the formula, l ZJ Control the top distance of the hydraulic support 6 on the working surface; γ ZJD is the average bulk density of the immediate roof of coal rock; d ZJD is the thickness of the immediate roof of coal rock; g is the acceleration of gravity; β is the fracture angle of the overburden rock; b ZJ is the center distance of the bracket; s is the dynamic load transfer efficiency, which is taken as 1 / 20, K ZJD is the stiffness of the immediate roof of coal rock, p D The thick hard top plate bears the load, and L1 is the cantilever length of the target layer.

[0103] (6) Determine the fracturing step distance of the target layer. The specific implementation method is as follows: First, set L1 to 1m, 3m, 5m, etc. Use MATLAB to loop through steps 4 and 5 until L1>100 or the impact load F borne by the support is ZJ When >15000kN, the corresponding cantilever length is output, and 3 / 4 of the cantilever length at this time is taken as the fracturing step distance of hydraulic fracturing.

[0104] Steps (4) to (5) are executed cyclically. After the cycle is completed, the output energy density data is as follows:

[0105] (0,0), (0.60467,5.01E-05), (1.2046,7.90E-04), (1.80973,0.00402), (2.4177,0.01281), (3.01486,0.03098), (3.61452,0.06401)(4.21789,0.1 187), (4.82536,0.20332), (5.42361,0.3245), (6.03059,0.49603), (6.63642,0.72745), (7.24141,1.03124), (7.84644,1.42153), (8.44228,1.90 504), (9.04237,2.50723), (9.64789,3.24934), (10.24587,4.13297), (10.86074,5.21799), (11.46099,6.47075), (12.05613,7.92315), (12.6627 7,9.64232),(13.26837,11.62349),(13.86567,13.86212),(14.47318,16.4559),(15.06911,19.33822),(15.67544,22.64355),(16.27721,26.32 609), (16.87979,30.44627), (17.48075,35.01919), (18.08492,40.11737), (18.68706,45.733), (19.28906,51.9171), (19.90515,58.87461), (20 .5041,66.28712),(21.10665,74.42912),(21.70225,83.19274),(22.30508,92.82854),(22.9134,103.37705),(23.51742,114.71618),(24.1196 ,126.92473),(24.2685,130.0881),(24.87402,143.56543),(25.472,157.87687),(26.08687,173.68156),(26.68712,190.22731),(27.28226,20 7.77224), (27.88891,226.87775), (28.4945,247.23521), (29.0918,268.62627), (29.69931,291.77722), (30.26288,312.91605), (30.49161,318.47559),(30.62023,320.6587),(30.91068,323.21421),(31.07221,323.28613),(31.38495,320.90439),(32.2627,299.44504),(33.27741,256.48699),(34.25974,207.01129),(35.27245,156.44851),(36.2901,111.50791),(37.28247,75.83415),(38.30267,48.02811)(39.29309,28.85819),(40.30677,15.79676),(41.29964,7.8877),(42.30347,3.35181),(43.30631,1.09116),(44.32119,0.1809),(45.33179,0.00129),(46.32949,0.13019),(47.34806,0.33782),(48.33632,0.50113),(49.33641,0.58898),(50.35362,0.59959),(51.35085,0.55217),(52.3633,0.46961),(53.37664,0.37372),(54.37991,0.28111),(55.38359,0.19999),(56.38466,0.13466),(57.38455,0.08548),(58.39311,0.05048),(59.40638,0.02734),(60.40165,0.01343),(61.40108,0.0056),(62.4067,0.00173),(63.41915,2.49E-04),(64.41624,1.04E-05),(65.42787,2.86E-04),(66.43758,6.69E-04),(67.4459,9.65E-04),(68.45429,0.00111),(69.44735,0.00111),(70.4475,0.00102),(71.4567,8.58E-04),(72.45334,6.81E-04),(73.47811,5.06E-04),(74.47853,3.58E-04),(75.47044,2.41E-04),(75.73051,2.15E-04),(76.72773,1.33E-04),(77.74019,7.64E-05), (78.75352,3.99E-05), (79.7568,1.85E-05), (80.76079893,5.64E-05), (81 .7698575,2.80189E-05), (82.77891607,6.33703E-06), (83.78797464,3.99227E-05) , (84.79703321,0.000018517), (85.80609179,1.49843E-05), (86.81515036,4.78789 E-05), (87.82420893,2.28988E-05), (88.8332675,4.62424E-07), (89.84232607,5.64 222E-05), (90.85138464,2.80189E-05), (91.86044321,6.33703E-06), (92.86950179 ,4.62424E-07), (93.87856036,3.35392E-05), (94.88761893,1.49843E-05), (95.8966 775,6.33703E-06), (96.90573607,3.99227E-05), (97.91479464,0.000018517), (98. 92385321,1.49843E-05), (99.93291179,4.78789E-05), (100.1851764,3.99227E-05). .

[0106] Output energy data corresponding to different cantilever lengths L1 are:

[0107] (1,4437.681), (3,7103.105), (5,11369.47), (7,18198.37), (9,29128.94),

[0108] (11,46624.77), (13,74629.21), (15,119454.1), (17,191202.3), (19,306045), (21,489866.1), (23,784096.5), (25,1255052), (27,2008879), (29,3215480), (31,5146808), (33,8238158)

[0109] Output The impact load of the hydraulic support 6 corresponding to different cantilever lengths L1 is:

[0110] (1,5413.568102), (3,5900.920843), (5,6432.147178), (7,7011.196798),

[0111] (9,7642.374962), (11,8330.374505), (13,9080.310733), (15,9897.759454),

[0112] (17,10788.79843), (19,11760.05258), (21,12818.74322), (23,13972.74175), (25,15230.6282), (27,16601.75502), (29,18096.31658), (31,19725.42502),

[0113] (33,21501.19282),

[0114] Since the impact load borne by the hydraulic support 6 exceeds 15000 kN when the cantilever length is 25 m, the fracturing step distance is determined as:

[0115] The present invention preliminarily determines the target layer for fracturing by comprehensively analyzing the geological drilling column chart, and then performs core drilling of the target layer and the upper and lower overburden rocks to determine a series of rock physical and mechanical parameters, calibrates the target layer for fracturing, cyclically divides the cantilever section and the clamping section, obtains the deflection and rotation angle of the target layer, and then calibrates the cantilever length, and based on this, determines the fracturing step distance, thereby fracturing the target layer, preventing the elastic energy of the roof from accumulating, preventing and controlling rock burst in underground coal mines, and ensuring safe coal mining.

[0116] A coal mine rock burst ground fracturing step determination system, comprising the following modules:

[0117] The target layer determination module determines the hydraulic fracturing target layer based on the roof thickness, lithology, and the ore pressure data of the adjacent working face;

[0118] Mechanical parameter determination module, which determines the roof mechanical parameters of the hydraulic fracturing target layer and its underlying rock layer;

[0119] The module for determining the length of the clamping branch end of the target layer establishes a regression equation according to the obtained roof mechanical parameters, and determines the length of the clamping branch end of the hydraulic fracturing target layer according to the regression equation;

[0120] The energy density calculation module sets up the cantilever section deflection and the satisfying conditions of the clamping end of the hydraulic fracturing target layer, determines the boundary deflection and rotation angle of the hydraulic fracturing target layer, and calculates the energy density of the hydraulic fracturing target layer based on the satisfying conditions and the boundary deflection and rotation angle;

[0121] The impact load calculation module accumulates the energy density of the hydraulic fracturing target layer to obtain energy, and determines the impact load borne by the support in combination with the cantilever length of the hydraulic fracturing target layer;

[0122] The fracturing step output module increases the cantilever length of the target layer by a fixed length and repeatedly calculates the impact load borne by the bracket until the cantilever length is greater than the first preset threshold or the impact load borne by the bracket is greater than the second preset threshold. The cantilever length of the hydraulic fracturing target layer at this time is output, and 3 / 4 of the cantilever length is taken as the fracturing step.

[0123] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred 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 parts can be referred to the method part.

[0124] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for determining the step distance of ground fracturing in coal mine rock burst, characterized in that: include: Step 1: Determine the target layer for hydraulic fracturing according to the thickness of the roof, lithology, and the ore pressure manifestation data of the adjacent working face; Step 2, measuring the roof mechanical parameters of the hydraulic fracturing target layer and its underlying rock layer; Step 3: Establish a regression equation based on the obtained roof mechanical parameters, and determine the length of the hydraulic fracturing target layer clamping end based on the regression equation; Step 4, establishing the conditions for satisfying the cantilever section deflection and the clamping end of the hydraulic fracturing target layer, and determining the boundary deflection and rotation angle of the hydraulic fracturing target layer, and calculating the energy density of the hydraulic fracturing target layer based on the conditions and the boundary deflection and rotation angle; Step 5: Accumulate the energy density of the hydraulic fracturing target layer to obtain energy, and determine the impact load borne by the support in combination with the cantilever length of the hydraulic fracturing target layer; Step 6, increasing the cantilever length of the target layer at a fixed length, repeating steps 4 and 5 until the cantilever length is greater than a first preset threshold or the impact load borne by the support is greater than a second preset threshold, outputting the cantilever length of the hydraulic fracturing target layer at this time, and taking 3 / 4 of the cantilever length as the fracturing step distance; The step 2 comprises: measuring the elastic modulus E, cohesion c, internal friction angle φ, Poisson's ratio υ of the target layer by drilling and coring, and measuring the elastic modulus E1, E2, ... E of the rock layer 5 times the thickness under the target layer. r , cohesion c1, c2…c r 、Internal friction angle φ1、φ2…φ r Poisson's ratio υ1, υ2…υ r ; Determine the vertical load q on the target layer according to the key layer theory; The step 3 specifically includes: According to the obtained mechanical parameters of the top plate, the regression equation is established as follows: in, Determine the hydraulic fracturing target layer clamp end L2 according to the regression equation = (h1+h2+h3+h4) t , where t is the target factor, t starts from 0 and increases by 0.

02. When L2≥100 or t>2, stop the loop and output L2; The step 4 specifically includes: The cantilever end of the target layer is divided into m segments, and the clamped end of the target layer is divided into n segments, m ≥ 100, n ≥ 100, wherein the three adjacent nodes of the cantilever segment L1 of the target layer are set as i-1, i, i+1 respectively, and the three adjacent nodes of the clamped segment L2 of the target rock layer are set as j-1, j, j+1 respectively, and the distance between the adjacent nodes is α; wherein the deflection of the target cantilever segment satisfies the following relationship: The clamping section satisfies the following relationship: Where: k = k0b, k0 is the base coefficient of the underlying rock layer, b is the width of the target layer for fracturing; E is the elastic modulus of the target layer; I is the moment of inertia of the target layer section about the z-axis; G is the shear modulus of the target layer; A is the cross-sectional area of ​​the target layer, κ is the shear correction coefficient of the target layer section; w (·) is the disturbance of the corresponding node; ψ (·) is the rotation angle of the corresponding node; The target layer boundary deflection and rotation are determined by the following formula: Substituting each quantity into the energy density expression, we get: The step 5 specifically includes: accumulating the energy density to obtain energy, that is, Combined with the cantilever length of the hydraulic fracturing target layer, determine the impact load borne by the support: In the formula, l ZJ Control the top distance of the hydraulic support on the working surface; γ ZJD is the average bulk density of the immediate roof of coal rock; d ZJD is the thickness of the immediate roof of coal rock; g is the acceleration of gravity; β is the fracture angle of the overburden rock; b ZJ is the center distance of the bracket; s is the dynamic load transfer efficiency, K ZJD is the stiffness of the immediate roof of coal rock, p D The thick hard top plate bears the load, and L1 is the cantilever length of the target layer.

2. The method for determining the step distance of ground fracturing in coal mine rock burst according to claim 1, characterized in that: The step 1 comprises: collecting the comprehensive borehole geological map of the mine and the observation data of the mine pressure manifestation of the adjacent working face, and determining the roof thickness and lithology of the rock layer according to the comprehensive borehole geological map of the mine; and then determining the ground fracturing target layer according to the roof thickness, lithology and the mine pressure manifestation data of the adjacent working face.

3. The method for determining the step distance of ground fracturing in coal mine rock burst according to claim 1, characterized in that: The first preset threshold in step 6 is 100m; the second preset threshold is 15000kN.

4. A coal mine rock burst ground fracturing step determination system, characterized in that: A method for determining the step distance of ground fracturing in coal mine rock burst according to any one of claims 1 to 3 is applied, comprising the following modules: The target layer determination module determines the hydraulic fracturing target layer based on the roof thickness, lithology, and the ore pressure data of the adjacent working face; Mechanical parameter determination module, which determines the roof mechanical parameters of the hydraulic fracturing target layer and its underlying rock layer; The module for determining the length of the clamping branch end of the target layer establishes a regression equation according to the obtained roof mechanical parameters, and determines the length of the clamping branch end of the hydraulic fracturing target layer according to the regression equation; The energy density calculation module sets up the cantilever section deflection and the satisfying conditions of the clamping end of the hydraulic fracturing target layer, determines the boundary deflection and rotation angle of the hydraulic fracturing target layer, and calculates the energy density of the hydraulic fracturing target layer based on the satisfying conditions and the boundary deflection and rotation angle; The impact load calculation module accumulates the energy density of the hydraulic fracturing target layer to obtain energy, and determines the impact load borne by the support in combination with the cantilever length of the hydraulic fracturing target layer; The fracturing step output module increases the cantilever length of the target layer by a fixed length and repeatedly calculates the impact load borne by the bracket until the cantilever length is greater than the first preset threshold or the impact load borne by the bracket is greater than the second preset threshold. The cantilever length of the hydraulic fracturing target layer at this time is output, and 3 / 4 of the cantilever length is taken as the fracturing step.

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