A method for joint control of upper and lower areas of rock burst wells in coal mines

Abstract

The invention discloses a method for joint control of upper and lower areas of a coal mine rock burst well, and relates to the technical field of coal mining. First, a key layer is identified, and the physical and mechanical parameters of the key layer and the weak rock layer are determined by experiment; strength identification is performed based on the experimental parameters, and the thickness of the rock layer overlying the key layer and bearing the load is calculated; the horizon of the high key layer and the low key layer is determined; the breaking criteria of the low key layer and the high key layer are established; the initial breaking step of the low key layer and the high key layer is calculated; the peak points of the bending moment accumulation of the low key layer and the low key layer are judged, and the location of the impact source is determined. For the low key layer that meets the conditions, composite blasting and top cutting are used to eliminate the impact source, and the high key layer is used to eliminate the impact source by ground fracturing, so as to prevent rock burst from occurring, and can effectively ensure the safe mining of the coal mine. The invention effectively reduces the probability of rock burst during coal mining, and improves the safety of coal mine production.

Description

Technical Field

[0001] The invention relates to the technical field of coal mining, and more particularly to a method for jointly controlling upper and lower areas of a coal mine rock burst well. Background Art

[0002] The key layer refers to the rock layer with high strength and good integrity in the mining area, generally sandstone layer, siltstone, etc. During the continuous advancement of the working face, the key layer will have a large area of ​​hanging roof and fail to collapse in time due to its unique characteristics of high hardness and large collapse step. When the hanging length of the key layer reaches the critical value of the maximum disaster energy, the roof suddenly collapses, causing coal mine geological disasters such as mine earthquakes in the working face and tunnels. Therefore, the key layer control method has always been one of the main problems that need to be solved in coal mines.

[0003] At present, two methods are generally used to solve the key layer problem: strengthening support or cutting the top to relieve pressure. Under the current conditions that coal mining is developing in the direction of deepening, thickening and extra-thickening, a ground fracturing control method for key layers in coal mines that is applicable to this in a large space is increasingly being used. Therefore, how to control the key layer, how to determine the energy stored in the key layer, and how to arrange ground fracturing are problems that technicians in this field need to solve urgently. Summary of the invention

[0004] In view of this, the present invention provides a method for jointly controlling the upper and lower areas of a coal mine rock burst well, which has the advantages of accurate calculation, precise operation, and source control.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A method for joint control of upper and lower areas of a coal mine rock burst well, used for working face mining under key layer conditions, comprises the following steps:

[0007] Step 1: Based on the load and collapse step of the overburden, identify the key layer and determine the scope of the overlying weak rock layer: determined by the pressure of the adjacent working face, its periodic fracture step is greater than 20m, its thickness is greater than 10m, and in terms of rock mechanics, its hardness coefficient is greater than IV and its tensile strength is greater than 6MPa;

[0008] The load of the key layer is greater than the load of each layer of the overlying weak rock layer, and its collapse step distance is greater than the collapse step distance of each layer of the overlying rock layer;

[0009] Step 2: Through uniaxial compression tests on rock samples of each rock layer, the uniaxial tensile strength σ of the key layer and the uniaxial tensile strength σ of each layer of the overlying weak rock layer are determined. 1 ,σ 2 ,…,σ n , shear strength τ 1 , τ 2, τ 3 ,…,τ n ;

[0010] Step 3, determine the main control key layers of rock burst pressure, including low key layers and high key layers;

[0011] The calculation method for determining the position of the low-level key layer is as follows: D =10T ξ , where T is the thickness of the coal seam in m, ξ is the correlation factor between the coal seam and the roof, when T≤10m, it is 0.65, when T>10m, it is 1.06;

[0012] The calculation formula for determining the horizon of the high-level key layer is as follows: G =20T ξ , if the key layer position satisfies H D <H M <H G , it is defined as the median key layer;

[0013] Step 4: Calculate the load on the key layer using the formula q = γH, where:

[0014]

[0015] In the formula The unit of q is MPa, the unit of γ is kN / m 3 , the unit of H is m, n is the intensity factor, its size increases from 0, the increment interval is 0.001, n>1 or H exceeds the actual burial depth of the key layer;

[0016] Step 5: Establish the fracture criteria of low-level and high-level key layers; the principal stress produces tensile failure, while the maximum shear stress produces shear failure. The corresponding fracture criterion of the key layer is σ max ≥σ t or τ max ≥τ s , where σ t and τ s are the tensile strength and shear strength of the high-level key layer, respectively, where σ xmax =max(σ x1 ,σ x2 );

[0017] Where σ x1 and σ x2 The calculation formula is as follows, and the breaking tensile stress of the low key layer is determined by the following two formulas:

[0018]

[0019] The fracture of the high-position key layer is caused by shearing, and its failure shear stress is:

[0020]

[0021] Where l is the overhang length of the key layer for the first break, E is the elastic modulus of the key layer, D is the bending stiffness of the key layer, h is the thickness of the key layer, α and β are the elastic ground elements under the key layer; where: D=EI, In the formula, k is the elastic foundation stiffness under the key layer, C is the shear stiffness of the key layer, and b is the unit width of the key layer;

[0022] Step 6: Give the initial breaking step and determine the fracturing and top cutting parameters; the breaking of the key layer is manifested in two modes, and the breaking step of the two breaking modes of the key layer is calculated through the following two processes:

[0023] When σ xmax =σ t The breaking step length L corresponding to the tensile failure of the low-level key layer is f for:

[0024]

[0025] When τ ymax =τ 0 The breaking step L corresponding to the shear failure of the high-position key layer is f for:

[0026]

[0027] If the tensile breaking step length of the lower key layer and the shear breaking step length of the higher key layer have the following relationship: L f1 >L f2 , then L f1 Assign a value to l and bring it into step 7 for calculation, directly judge that the high-level hard roof needs fracturing, and set L f2 Directly proceed to step 7 to determine the fracturing position of the high-level key layer; otherwise, L f2 Assign the value to l and bring it into step 7 for calculation. f1 Directly proceed to step 7 to determine the top cutting position of the low key layer;

[0028] Step 7: Determine the impact source position of the key layer. The position of the bending moment accumulation in the key layer is calculated by the following formula. Substitute the fracture step determined in step 6 into the following formula to calculate the distribution of the middle bending moment in the key layer. Draw the data into a chart to determine the maximum stress position in the key layer. The peak value of the bending moment accumulation is used as the fracturing position. If the peak value of the bending moment in the low-level key layer is 2000MN·m≤M max ≤4000MN·m, directly export the data for plotting, and take the peak point of the bending moment distribution as the cutting top position; if the bending moment peak value M max≤2000MN·m, it is determined that top cutting is not necessary, otherwise proceed as follows: take the value of l as 5m, 10m, 15m... and perform cyclic calculations, and draw its distribution diagram based on the data of M. When M≥4000MN·m or l>L f When the calculation is stopped, the data is exported for plotting, and the peak value of M is used as the cutting position; the peak value of the bending moment of the high-position key layer is 800MN·m≤M max ≤15000MN·m, directly export the data for plotting, and take the peak point of the bending moment distribution as the fracturing position; if the bending moment peak value ≤M max If the pressure is less than 800MN·m, it is determined that fracturing is not necessary. Otherwise, the following steps are performed: the value of l is 5m, 10m, 15m, etc., and the distribution diagram is drawn according to the data of M. When M≥1500MN·m or l>L f When , stop the calculation, export the data for plotting, and take the peak value of M as the fracturing position;

[0029] The formula is:

[0030]

[0031] Step 8: Use composite blasting to cut the top of the low-level key layer at the peak position of the bending moment to release the stress, and use ground fracturing to fracture the peak position of the bending moment of the high-level key layer to release the concentrated stress and eliminate the impact ground pressure source.

[0032] It can be known from the above technical scheme that the present invention provides a method for joint control of upper and lower areas of coal mine rock burst wells, which first identifies the key layer, and determines the physical and mechanical parameters of the key layer and the weak rock layer through experiments; performs strength identification based on the experimental parameters, and calculates the thickness of the rock layer bearing the overlying load of the key layer; determines the layer positions of the high key layer and the low key layer; establishes the breaking criteria of the low key layer and the high key layer; calculates the initial breaking step of the low key layer and the high key layer; determines the peak points of the bending moment accumulation of the low key layer and the low key layer, and determines the location of the impact source. For the low key layer that meets the conditions, composite blasting and top cutting are used to eliminate the impact source, and for the high key layer, ground fracturing is used to eliminate the impact source, so as to prevent rock burst and ensure the safe mining of coal mines. Compared with the prior art, it has the following features:

[0033] Beneficial effects:

[0034] (1) The present invention comprehensively analyzes parameters such as overburden load and collapse step distance to accurately identify the key layer and determine the scope of the overlying weak rock layer, providing a scientific basis for subsequent control measures.

[0035] (2) The present invention establishes the breaking criteria and calculation methods for the low-level key layers and the high-level key layers, and can take targeted control measures according to the characteristics of different layers to improve the control effect.

[0036] (3) The present invention combines underground composite blasting and top cutting with ground fracturing technology to jointly control the key layers, taking into account the actual conditions of the underground working face and making full use of the advantages of ground fracturing technology, thereby achieving effective release of key layer stress and elimination of impact ground pressure sources.

[0037] In summary, the present invention effectively reduces the probability of rock burst during coal mining and improves the safety of coal mine production. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] 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.

[0039] Figure 1 This is a schematic diagram of the exported data corresponding to the low-level key layer;

[0040] Figure 2 This is a schematic diagram of the exported data corresponding to the high-level key layer;

[0041] Figure 3 It is a flow chart of a method for joint control of upper and lower areas of a rock burst well in a coal mine;

[0042] Figure 4 This is a diagram showing an embodiment of a method for joint control of upper and lower areas of a coal mine rock burst well;

[0043] Among them: 1 - coal seam, 2 - weak rock layer above the coal seam, 3 - K 1 The key layer is covered by a weak rock layer, 4-K 2 The key layer is covered with soft rock layers, 5 - fracturing well, 6 - impact source (fracturing point), 7 - composite blasting drilling hole (impact source of low-level key layer), 8 - hydraulic support of the working face. DETAILED DESCRIPTION

[0044] 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.

[0045] The embodiment of the present invention takes the specific values ​​of a certain underground coal mine as an example. According to the mine data, the steps of the method of the present invention are adopted to determine the impact source elimination sources of the high-level key layer and the low-level key layer, and according to the location of the elimination source, composite blasting is performed on the low-level key layer, and hydraulic fracturing is performed on the high-level key layer, thereby eliminating the impact sources of the low-level and high-level key layers, preventing the occurrence of rock bursts, and ensuring the safe mining of the working face. The coal seam thickness of a certain mine is 10m, and a 10m hard rock layer is present 45m above the coal seam, named K 1 ; 230m above the coal seam there is a 20m thick hard rock layer named K 2 According to the data of the adjacent working faces of the mine, the initial breaking step distance of the mine is 70m, and the step distance of the strong pressure after the initial pressure is 75m. 1 The hardness coefficient is IV, the uniaxial tensile strength is 6.5MPa, and the shear strength is 12.2MPa; K 2 The hardness coefficient is II, the uniaxial tensile strength is 8.2MPa, the shear strength is 25MPa, and K 1 Buried depth 120m, K 2 Buried depth 350m. Average rock density γ = 2800kg / m 3 ; K 1 Elastic modulus E D =6.0GPa, Poisson's ratio 0.2, K 2 Elastic modulus E D =8.5GPa, Poisson's ratio 0.18.

[0046] For specific control methods, see Figure 3-Figure 4 , where 1 represents the coal seam, 2 represents the soft rock layer above the coal seam, and 3 represents K 1 The key layer is covered by a weak rock layer, 4 means K 2 The key layer is covered with a soft rock layer, 5 represents a fracturing well, 6 represents an impact source (fracturing point), 7 represents a composite blasting borehole (impact source of a low-level key layer), and 8 represents a hydraulic support on the working face.

[0047] Step 1: Based on the load and collapse step of the overburden, identify the key layer and determine the scope of the overlying weak rock layer: Determine through the pressure of the adjacent working face, its periodic fracture step is greater than 20m, its thickness is greater than 10m in size, and its hardness coefficient is greater than IV and its tensile strength is greater than 6MPa in rock mechanics. The load of the key layer is greater than the load of each layer of the overlying weak rock layer, and its collapse step is greater than the collapse step of each layer of the overlying rock layer.

[0048] According to the preliminary data of the mine, it is determined that K 1 , K 2 All are key layers.

[0049] Step 2: Through uniaxial compression tests on rock samples of each rock layer, the uniaxial tensile strength σ of the key layer and the uniaxial tensile strength σ of each layer of the overlying weak rock layer are determined. 1 ,σ 2 ,…,σ n , shear strength τ 1 , τ 2 , τ 3 ,…,τ n .

[0050] It is known that in K 1 There are 9 layers of weak rock and key layer K above. 2 , K 2 There are 5 layers of soft rock strata above, and their uniaxial tensile strengths are: 2MPa, 2.3MPa, 2.5MPa, 2.7MPa, 8.2MPa, 3.2MPa, 3.0MPa, 5.0MPa, 2.0MPa, 1.8MPa; and their shear strengths are: 6.2MPa, 7.3MPa, 7.5MPa, 8.6MPa, 25MPa, 5.8MPa, 6.7MPa, 8.2MPa, 5.7MPa, 4.3MPa.

[0051] Step 3: Determine the main key layers controlling rock burst pressure, including low-level key layers and high-level key layers.

[0052] The breaking of the low-level key layer directly impacts the working face equipment and the tunnels near the breaking position. The calculation method for determining the position of the low-level key layer is as follows: H D =10T ξ , where T is the thickness of the coal seam in m, ξ is the correlation factor between the coal seam and the roof, when T≤10m, it is 0.65, when T>10m, it is 1.06; Substituting the coal seam thickness of 10m into the above formula, the position of the low-level key layer is obtained as follows: H D =10×10 0.65 =45m.

[0053] The high-level key layer has high strength, thickness and hardness, so the breaking step of the high-level key layer is large and the impact energy is high. The calculation formula for determining the layer position of the high-level key layer is as follows: H G =20T ξ , if the key layer position satisfies H D <H M <H G , then it is defined as the middle key layer. Similarly, substituting the coal seam thickness into the above formula, the position of the high key layer is obtained as: H G =20×10 1.06 =229m. Therefore, K 1 is the low key layer, K 2 It is a high-level key layer.

[0054] Step 4: Based on the above experimental results, the load borne by the key layer is calculated using the formula q=γH, where:

[0055]

[0056] In the formula The unit of q is MPa, the unit of γ is kN / m 3 The unit of H is m, n is the intensity factor, its size increases from 0, the increasing interval is 0.001, n>1 or H exceeds the actual burial depth of the key layer.

[0057] According to the parameters measured in step 2, the data of the low key layer and the high key layer are respectively substituted into the above formula to obtain the load depth of the low key layer: H = 341m, n = 1.201; the load depth of the high key layer is: H = 120m, n = 3.09. The overburden load on the low key layer q = 341m × 2800kg / m 3 =9.5MPa; Overburden load on high critical layer q = 120m × 2800kg / m 3 =3.3MPa.

[0058] Step 5: Establish the fracture criteria for low and high key layers. The principal stress produces tensile failure, while the maximum shear stress produces shear failure. The corresponding fracture criteria for the key layer are σ max ≥σ t or τ max ≥τ s , where σ t and τ s are the tensile strength and shear strength of the high-level key layer, respectively, where σ xmax =max(σ x1 ,σ x2 ).

[0059] Where σ x1 and σ x2 The calculation formula is as follows. The breaking of the low-level key layer is easily subject to tensile stress and leads to failure. Therefore, the breaking tensile stress of the low-level key layer is determined by the following two formulas:

[0060]

[0061] The fracture of the high-position key layer is caused by shearing, and its failure shear stress is:

[0062]

[0063] Where l is the overhang length of the key layer for the first break, E is the elastic modulus of the key layer, D is the bending stiffness of the key layer, h is the thickness of the key layer, α and β are the elastic ground elements under the key layer; where: D=EI, Where k is the stiffness of the elastic foundation under the key layer, k = 1 × 10 9 N / m, C is the shear stiffness of the key layer, C=εGA, ε is the shear correction coefficient of the target layer section, which is related to the cross-sectional shape, here it is taken as 5 / 6, G is the shear modulus, b is the key layer unit width.

[0064] Substituting the parameters of the low-level key layer and the high-level key layer into the above formula, the tensile stress of the low-level key layer is calculated as follows: x1 =5.8MPa,σ x2 =6.5MPa; the shear force of the high key layer is: τ=25.03MPa.

[0065] Step 6: Give the initial breaking step and determine the fracturing and top cutting parameters; the breaking of the key layer mainly manifests in two modes, and the breaking step of the two breaking modes of the key layer is calculated through the following two processes:

[0066] When σ xmax =σ t The breaking step length L corresponding to the tensile failure of the low-level key layer is f for:

[0067]

[0068] When τ ymax =τ 0 The breaking step L corresponding to the shear failure of the high-position key layer is f for:

[0069]

[0070] If the tensile breaking step length of the lower key layer and the shear breaking step length of the higher key layer have the following relationship: L f1 >L f2 , then L f1 Assign a value to l and bring it into step 7 for calculation, directly judge that the high-level hard roof needs fracturing, and set L f2 Directly proceed to step 7 to determine the fracturing position of the high-level key layer; otherwise, L f2 Assign the value to l and bring it into step 7 for calculation. f1 Go directly to step 7 to determine the cutting position of the low-level key layer.

[0071] Substituting the parameters of the low-level key layer and the high-level key layer into the above formula, the breaking step distance of the low-level key layer is calculated as: L f1 =71.65m; the breaking step distance of the high key layer is: L f2 =78.31m. Through calculation, it is determined that the low-level key layer needs to be topped and the high-level key layer needs to be fractured.

[0072] Step 7: Determine the impact source position of the key layer. The position of the bending moment accumulation in the key layer is calculated by the following formula. Substitute the fracture step determined in step 6 into the following formula to calculate the distribution of the middle bending moment in the key layer. Draw the data into a chart to determine the maximum stress position in the key layer. The peak value of the bending moment accumulation is used as the fracturing position. If the peak value of the bending moment in the low-level key layer is 2000MN·m≤M max ≤4000MN·m, directly export the data for plotting, and take the peak point of the bending moment distribution as the cutting top position; if the bending moment peak value M max ≤2000MN·m, it is determined that top cutting is not necessary, otherwise proceed as follows: take the value of l as 5m, 10m, 15m... and perform cyclic calculations, and draw its distribution diagram based on the data of M. When M≥4000MN·m or l>L f When the calculation is stopped, the data is exported for plotting, and the peak value of M is used as the cutting position; the peak value of the bending moment of the high-position key layer is 800MN·m≤M max ≤15000MN·m, directly export the data for plotting, and take the peak point of the bending moment distribution as the fracturing position; if the bending moment peak value ≤M max If the pressure is less than 800MN·m, it is determined that fracturing is not necessary. Otherwise, the following steps are performed: the value of l is 5m, 10m, 15m, etc., and the distribution diagram is drawn according to the data of M. When M≥1500MN·m or l>L f When , stop the calculation, export the data for plotting, and take the peak value of M as the fracturing position;

[0073] The formula is:

[0074]

[0075] According to step 7, it is determined that the low-level key layer needs to be top-cut. The relevant data of the low-level key layer is substituted into the above formula, and the data is exported and plotted. Figure 1 :

[0076] (-50.96839758,0.51229762),(-49.97926534,0.677257033),(-48.65954138,0.956612602),(-47.99937216,1.125750114),(-46.70839412,1.522070876),(-45.73082136,1.887074462),(-44.76130395,2.310860319),(-43.77166561,2.812377586),(-42.80060668,3.37640915),(-41.80089463,4.034006589),(-40.83699624,4.741546059),(-39.86267104,5.525734112),(-38.87838177,6.37842285),(-37.89197886,7.276254276),(-36.89692208,8.197581542),(-35.92770509,9.070113652),(-34.95771272,9.863584346),(-33.97751346,10.50829201),(-32.64859474,10.94289274),(-31.66830592,10.75433218),(-30.69993724,9.942566403),(-29.73270215,8.282861099),(-28.72750827,5.354764605),(-27.74941216,0.95982441),(-26.77170993,-5.402343238),(-25.81600458,-14.03521685),(-24.81989871,-26.220106),(-23.83292472,-42.27602896),(-22.87129141,-62.60308083),(-21.87216991,-89.67645892),(-20.9098135,-122.6490977),(-19.92903678,-164.5473966),(-18.94377251,-216.5741634),(-17.97844783,-278.8163981)(-16.9893156,-355.9486646),(-15.66959163,-483.215482),(-14.71185059,-595.406054),(-13.71844438,-731.4481832),(-12.74087161,-886.4877828),(-11.7713542,-1062.194684),(-10.78171586,-1264.705512),(-9.810656929,-1485.859829),(-8.810944886,-1735.11074),(-7.84704649,-1992.818727),(-6.872721295,-2264.982458),(-5.888432021,-2542.934546),(-4.902029107,-2811.355994),(-3.906972328,-3053.034733),(-2.937755342,-3235.758707),(-1.967762968,-3334.524296),(-0.987563713,-3306.642312),(0,-3093.384457),(0.368032352,-2971.657078),(1.771679355,-2519.210598),(2.106176403,-2414.151704),(3.167776099,-2087.76423),(4.222710096,-1774.031933),(5.260773777,-1475.636945),(6.338602316,-1176.644114),(7.381429581,-897.8652592),(8.07549515,-718.047024),(9.130186958,-453.5587847),(10.19546456,-197.1431038),(11.25916985,48.13721638),(12.31526942,281.0297858),(13.72120082,574.6258929),(14.78462019,784.2230334),(15.11095645,846.3887894),(16.17617578,1042.267841),(17.22486152,1224.57669),(18.30836845,1401.965364),(19.34634098,1561.439599),(20.38688381,1711.03551),(21.09885558,1807.466916),(22.16134349,1942.417813),(23.22638264,2066.929731),(24.28728247,2180.244537),(25.34171851,2282.274137),(26.02169636,2342.468345),(27.07096965,2426.735311),(28.13097348,2501.243797),(29.19325354,2565.203597),(30.26485315,2618.862868),(31.30862529,2660.640868),(32.35323246,2692.089995),(33.07026958,2707.67721),(34.13187838,2721.785776),(35.161256,2725.242026),(36.21589352,2718.343157),(37.29931755,2700.252952),(38.33836497,2672.428309),(39.38617423,2633.982552),(40.11601768,2601.040767),(41.16892776,2544.601111),(42.19814891,2479.252141),(43.27087832,2400.430259),(44.33377338,2311.548747),(45.00780994,2249.623308),(46.06534918,2143.766269),(47.15138154,2023.999195),(48.18273884,1899.888677),(49.24883901,1760.975831),(50.31225838,1611.655573),(51.01261282,1507.447638),(52.0451973,1345.306476),(53.12505517,1164.906825),(54.1564686,982.2566696),(55.22629067,782.1270795),(56.27906135,574.5728968),(57.32315701,358.3296827),(58.38892138,126.917736),(59.09029076,-31.25947379),(60.1592,-281.3148454),(61.19848957,-534.8485225),(62.26994717,-806.9720462),(63.32001836,-1084.245797),(64.02270825,-1275.64303),(65.07411308,-1570.782775),(66.1158187,-1873.55678),(67.18198319,-2194.114657),(68.25493103,-2527.614037),(69.29838714,-2862.436419),(70.63909424,-3255.902445),(70.97349531,-3305.057665),(71.14180416,-3321.599839),(71.31011301,-3333.062387),(71.39386747,-3336.965042),(71.72278193,-3341.485531),(72.11654166,-3326.369451),(73.28254198,-3178.552725),(74.2606381,-2971.939194),(75.23834032,-2722.002552),(76.19404567,-2457.005093),(77.19015155,-2175.487276),(78.17712553,-1902.941176),(79.13875884,-1651.141072),(80.13788034,-1408.918492),(81.10023675,-1196.969091),(82.08101347,-1003.648147),(83.06627774,-832.4622054),(84.03160242,-686.2950669),(85.02073466,-557.2701874),(86.34045862,-414.8009664),(87.00062784,-354.9830804),(88.29160588,-257.2995154),(89.26917864,-198.1898245),(90.23869605,-150.3273517),(91.22833439,-110.9097234),(92.19939332,-80.06927132),(93.19910537,-55.09574939),(94.16300376,-36.41149182),(95.13732896,-21.93918819),(96.12161823,-10.98045685),(97.10802114,-2.960594393),(98.10307792,2.751375359),(99.07229491,6.519510229),(100.0422873,8 .922423851),(101.0224865,10.29510515),(102.3514053,10.94103815),(102.6497377,10.94281757),(103.629044,10.68103376),(104.3000628,10.31925614),(105.2672978,9.62310103),(106.2724917,8.7656 39264),(107.2505878,7.870629769),(108.2282901,6.966757432),(109.1839954,6.108048468),(110.1801013,5.263099307),(111.1670753,4.491302098),(112.1287086,3.80972942),(113.1278301,3.1781900 77),(114.0901865,2.643064226),(115.0709632,2.168478395),(116.0562275,1.758914331),(117.0215522,1.41740821),(118.0106844,1.122671345),(119.3304084,0.805425402),(120.0105776,0.675169887). .

[0077] Export data of high-level key layers and draw pictures Figure 2 :

[0078] (-50.96839758,0.448775377),(-49.97926534,0.587079134),(-48.65954138,0.815544377),(-47.99937216,0.951030664),(-46.70839412,1.261797105),(-45.73082136,1.541142244),(-44.76130395,1.858685532),(-43.77166561,2.226495854),(-43.43264469,2.362869454),(-42.80060668,2.631294736),(-41.80089463,3.092959799),(-40.83699624,3.578753569),(-39.86267104,4.105234126),(-38.87838177,4.664527422),(-37.89197886,5.239250029),(-36.89692208,5.81385122),(-35.92770509,6.342731388),(-34.95771272,6.807866947),(-33.97751346,7.168347924),(-32.64859474,7.377004962),(-31.66830592,7.225644898),(-30.69993724,6.718507406),(-29.73270215,5.744327144),(-28.72750827,4.091303929),(-27.74941216,1.685730149),(-26.77170993,-1.703786562),(-25.81600458,-6.190088411),(-24.81989871,-12.37149483),(-23.83292472,-20.32557282),(-22.87129141,-30.1677838),(-21.87216991,-42.98110482),(-20.9098135,-58.23843888),(-19.92903678,-77.19878306),(-18.94377251,-100.2193383),(-17.97844783,-127.1532826),(-16.9893156,-159.7916063),(-15.66959163,-212.221095),(-14.71185059,-257.2494256),(-13.71844438,-310.6193105),(-12.74087161,-370.0423356),(-11.7713542,-435.831922),(-10.78171586,-509.8600951),(-9.810656929,-588.7353733),(-8.810944886,-675.3744035),(-7.177906198,-824.059864),(-6.202840094,-912.7449382),(-5.210885011,-998.0601899),(-3.906972328,-1093.051304),(-2.13160602,-1160.427599),(-1.301942788,-1151.807407),(0,-1060.065648),(0,-1060.06565),(0.368032352,-1017.781402),(1.771679355,-860.6157832),(2.810726782,-748.462012),(3.858536039,-638.9704331),(4.940769703,-529.685238),(5.963636366,-429.9478316),(7.034666839,-329.2144171),((8.07549515,-234.9484363),(9.130186958,-143.0735742),(10.19546456,-54.00286404),(11.25916985,31.19977351),(12.31526942,112.0992976),(13.0103222,163.3335657),(14.07137602,238.4723025),(15.11095645,308.487162),(16.17617578,376.5293591),(17.22486152,439.8576959),(18.30836845,501.4769195),(19.34634098,556.8732328),(20.04966789,592.3888403),(21.09885558,642.3353533),(22.16134349,689.2130334),(23.22638264,732.4645417),(24.28728247,771.826527),(25.34171851,807.2683879),(26.02169636,828.1779551),(26.36987068,838.2937821)(27.07096965,857.4496381),(28.13097348,883.3315332)(29.19325354,905.5491477),(30.26485315,924.1886841),(31.30862529,938.701042),(32.35323246,949.6254756),(33.07026958,955.0399818),(34.13187838,959.940852),(35.161256,961.1414442),(36.21589352,958.7449948),(37.29931755,952.4610291),(38.33836497,942.7956269),(39.0626834,933.9504459),(40.11601768,917.9978491),(41.16892776,898.3924949),(42.19814891,875.6923263),(43.27087832,848.3120936),(44.33377338,817.4374631),(45.00780994,795.9265212),(46.06534918,759.1551285),(47.15138154,717.5518291),(48.18273884,674.4397546),(49.24883901,626.1858184),(50.31225838,574.3166764),(51.01261282,538.1181305),(52.0451973,481.795411),(53.12505517,419.130269),(54.1564686,355.683373),(55.22629067,286.1646733),(56.27906135,214.0669046),(57.32315701,138.9508407),(58.38892138,58.56563822),(59.43467715,-23.95383855),(60.1592,-83.24146899),(61.19848957,-171.3110621),(62.26994717,-265.8381809),(63.32001836,-362.1543258),(64.02270825,-428.6396806),(65.07411308,-531.1619078),(66.1158187,-636.3360358),(67.18198319,-747.6877193),(68.25493103,-863.5348722),(69.29838714,-979.8415947),(70,-1060.06565),(71.31011301,-1152.056746),(71.95573523,-1161.229473),(72.44365434,-1155.938073),(72.94150638,-1141.520635),(73.28254198,-1127.164088),(74.2606381,-1069.990527),(75.23834032,-995.8112004),(76.19404567,-913.5301326),(77.19015155,-822.9342182),(78.17712553,-732.4318393),(79.13875884,-646.4442431),(80.13788034,-561.5152409),(81.10023675,-485.2997829),(82.08101347,-414.0808136),(83.06627774,-349.4913577),(84.03160242,-293.0422939),(85.02073466,-242.0548003),(86.34045862,-184.2352841),(87.00062784,-159.3874477),(88.29160588,-117.908787),(89.26917864,-92.1432192),(90.23869605,-70.81078341),(91.22833439,-52.84445341),(92.19939332,-38.46756662),(93.19910537,-26.55816343),(94.16300376,-17.4415166),(95.13732896,-10.21647353),(96.12161823,-4.61466572),(97.10802114,-0.413102093),(98.10307792,2.658259604),(99.07229491,4.742257887),(100.0422873,6.114738248),(101.0224865,6.933459682),(102.3514053,7.363526183), (103.3316941,7.31863783),(104.3000628,7.065104632),(105.2672978,6.6688134),(106.2724917,6.16000705),(107.2505878,5.611743922),(108.2282901,5.042761287),(1 09.1839954,4.488623249),(110.1801013,3.930241866),(111.1670753,3.408156511),(112.1287086,2.936665849),(113.1278301,2.4900234),(114.0901865,2.103209474),(1 15.0709632,1.752740619),(116.0562275,1.443726321),(117.0215522,1.180550021),(118.0106844,0.948581209),(119.3304084,0.692699497),(120.2881494,0.541065268). .

[0079] according to Figure 1 and Figure 2 It shows that the cutting positions of the low-level key layers are 0m, 35m, and 72m, and the fracturing positions of the high-level key layers are 0m, 35m, and 75m.

[0080] Step 8: Use composite blasting to cut the top of the low-level key layer at the peak position of the bending moment to release the stress, and use ground fracturing to fracture the peak position of the bending moment of the high-level key layer to release the concentrated stress and eliminate the impact ground pressure source.

[0081] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0082] 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 joint control of upper and lower areas of a coal mine rock burst well, used for working face mining under key layer conditions, characterized in that: The steps include: Step 1: Based on the load and collapse step of the overburden, identify the key layer and determine the scope of the overlying weak rock layer: determined by the pressure of the adjacent working face, its periodic fracture step is greater than 20m, its thickness is greater than 10m, and in terms of rock mechanics, its hardness coefficient is greater than IV and its tensile strength is greater than 6MPa; The load of the key layer is greater than the load of each layer of the overlying weak rock layer, and its collapse step distance is greater than the collapse step distance of each layer of the overlying rock layer; Step 2: Through uniaxial compression tests on rock samples of each rock layer, the uniaxial tensile strength σ of the key layer and the uniaxial tensile strength σ1, σ2, …, σ of each layer of the overlying weak rock layer are determined. n , shear strength τ1, τ2, τ3, …, τ n ; Step 3, determine the main control key layers of rock burst pressure, including low key layers and high key layers; The calculation method for determining the position of the low-level key layer is as follows: D =10T ξ , where T is the thickness of the coal seam in m, ξ is the correlation factor between the coal seam and the roof, when T≤10m, it is 0.65, when T>10m, it is 1.06; The calculation formula for determining the high-level key layer is as follows: H G =20T ξ , if the key layer position satisfies H D <H M <H G , it is defined as the median key layer; Step 4: Calculate the load on the key layer using the formula q = γH, where: In the formula The unit of q is MPa, the unit of γ is kN / m 3 , the unit of H is m, n is the intensity factor, its value increases from 0, the increment interval is 0.001, n>1 or H exceeds the actual burial depth of the key layer; Step 5: Establish the fracture criteria of low-level and high-level key layers; the principal stress produces tensile failure, while the maximum shear stress produces shear failure. The corresponding fracture criteria of the key layer are σ max ≥σ t or τ max ≥τ s , where σ t and τ s are the tensile strength and shear strength of the high-level key layer, respectively, where σ xmax =max(σ x1 ,σ x2 ); Where σ x1 and σ x2 The calculation formula is as follows, and the breaking tensile stress of the low key layer is determined by the following two formulas: The fracture of the high-position key layer is caused by shearing, and its failure shear stress is: Where l is the overhang length of the key layer for the first break, E is the elastic modulus of the key layer, D is the bending stiffness of the key layer, h is the thickness of the key layer, α and β are the elastic ground elements under the key layer; In the formula, k is the elastic foundation stiffness under the key layer, C is the shear stiffness of the key layer, and b is the unit width of the key layer; Step 6: Give the initial breaking step and determine the fracturing and top cutting parameters; the breaking of the key layer is manifested in two modes, and the breaking step of the two breaking modes of the key layer is calculated through the following two processes: When σ xmax =σ t The breaking step length L corresponding to the tensile failure of the low-level key layer is f for: When τ ymax =τ0, corresponding to the shear failure of the high-level key layer. f for: If the tensile breaking step length of the lower key layer and the shear breaking step length of the higher key layer have the following relationship: L f1 >L f2 , then L f1 Assign a value to l and bring it into step 7 for calculation, directly judge that the high-level hard roof needs fracturing, and set L f2 Directly proceed to step 7 to determine the fracturing position of the high-level key layer; otherwise, L f2 Assign the value to l and bring it into step 7 for calculation. f1 Directly proceed to step 7 to determine the top cutting position of the low key layer; Step 7: Determine the impact source position of the key layer. The position of the bending moment accumulation in the key layer is calculated by the following formula. Substitute the fracture step determined in step 6 into the following formula to calculate the distribution of the middle bending moment in the key layer. Draw the data into a chart to determine the maximum stress position in the key layer. The peak value of the bending moment accumulation is used as the fracturing position. If the peak value of the bending moment in the low-level key layer is 2000MN·m≤M max ≤4000MN·m, directly export the data for plotting, and take the peak point of the bending moment distribution as the cutting top position; if the bending moment peak value M max ≤2000MN·m, it is determined that top cutting is not necessary, otherwise proceed as follows: take the value of l as 5m, 10m, 15m... and perform cyclic calculations, and draw its distribution diagram based on the data of M. When M≥4000MN·m or l>L f When the calculation is stopped, the data is exported for plotting, and the peak value of M is used as the cutting position; the peak value of the bending moment of the high-position key layer is 800MN·m≤M max ≤15000MN·m, directly export the data for plotting, and take the peak point of the bending moment distribution as the fracturing position; if the bending moment peak value ≤M max If the pressure is less than 800MN·m, it is determined that fracturing is not necessary. Otherwise, the following steps are performed: the value of l is 5m, 10m, 15m, etc., and the distribution diagram is drawn according to the data of M. When M≥1500MN·m or l>L f When , stop the calculation, export the data for plotting, and take the peak value of M as the fracturing position; The formula is: Step 8: Use composite blasting to cut the top of the low-level key layer at the peak position of the bending moment to release the stress, and use ground fracturing to fracture the peak position of the bending moment of the high-level key layer to release the concentrated stress and eliminate the impact ground pressure source.

Images