A method for determining the advanced support strength of the gateway in the coal mining face

Abstract

The present invention provides a method for determining the advanced support strength of the extraction roadway in a coal mining face, which relates to the technical field of coal mine roadway support. The present invention fully considers the influence of the advanced abutment pressure in the coal mining face and the bolt / anchor cable support applied during the roadway driving on the roof, makes up for the deficiencies of the traditional method for determining the advanced support strength, makes the determination of the advanced support strength more in line with the actual engineering situation, and realizes the accurate determination of the advanced support strength; starting from avoiding the occurrence of three types of failures, namely the failure of the anchored roof support, the tensile fracture of the end of the anchored roof rock stratum, and the shear fracture of the end of the anchored roof rock stratum, the present invention comprehensively compares and determines the minimum value of the advanced support strength, effectively avoids the occurrence of disasters of the instability of the anchored roof in the extraction roadway of the coal mining face, and ensures the safety and stability of the roof support of the extraction roadway when affected by the advanced mining movement.

Description

Technical Field

[0001] The present invention relates to the technical field of coal mine roadway support, and specifically relates to a method for determining the advanced support strength of the extraction roadway in a coal mining face. Background Art

[0002] The advanced support of the extraction roadway in the underground coal mine is an important guarantee means for the safety passage of the coal mining face, and its support effect directly affects the life safety of the personnel in the coal mining face. Whether the advanced support technology is reasonable and effective depends on the accuracy of determining the advanced support strength.

[0003] Generally, three methods are used to determine the advanced support strength of the coal mining face: theoretical calculation, numerical simulation or empirical method. Among them, in theoretical calculation, it is assumed that the load borne by the roof of the extraction roadway in the coal mining face is only the self-weight of the roof. At this time, theoretical models such as caving arch or self-stabilizing arch are used to obtain the failure range and action range of the roof coal and rock strata, and then based on the overall idea of suspension control, the advanced support force of the roadway is obtained. In numerical simulation, by simulating a variety of advanced support schemes, a relatively reasonable advanced support scheme is obtained, and the support strength is the support strength provided by the proposed scheme, rather than the actual required support strength; the empirical method is to calculate according to the weight of the rock stratum range that is a multiple of the mining height of the coal mining face according to the actual engineering geology situation, which is similar to theoretical calculation and has poor accuracy. These methods can determine the advanced support strength to a certain extent, but in the determination process, not only the action process of the advanced support pressure is not considered, but also the influence of the original support (bolt / cable support) on the roof during roadway driving is ignored, resulting in inaccurate determination of the advanced support strength. Summary of the Invention

[0004] The present invention provides a method for determining the advanced support strength of the extraction roadway in a coal mining face, which comprehensively considers the action process of the advanced support pressure and the influence of the original roadway support on the roof, so as to accurately determine the advanced support strength of the extraction roadway.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A method for determining the advanced support strength of the extraction roadway in a coal mining face, the method comprising the following steps:

[0007] Step 1, obtaining the engineering geological characteristics and support conditions of the surrounding rock of the extraction roadway;

[0008] Step 2, measuring the working load and increment of bolts / cables under the action of the advanced support pressure of the extraction roadway;

[0009] Step 3, predicting the strength of the anchored roof of the extraction roadway;

[0010] Step 4, determining the conditions for the effective anchored support of the roof of the extraction roadway;

[0011] Step 5: Determine the advanced support strength of the extraction roadway.

[0012] Preferably, the specific process of the said Step 2 is as follows:

[0013] Monitor and obtain the variation law of the working load of the roof bolts / cable bolts under the advanced abutment pressure of the extraction roadway, and obtain the working load F of the bolts ibolt of the cable bolts, jcable the working load increment ΔF of the i-th bolt, ibolt and the working load increment ΔF of the j-th cable bolt. jcable .

[0014] Preferably, the said Step 3 includes the following steps:

[0015] Step 31: Determine the support strength of the bolts / cable bolts

[0016] According to the support parameters and working load of the roof bolts / cable bolts in the extraction roadway, determine the support strength P0 of the bolts / cable bolts according to Equation 1.

[0017]

[0018] In the formula,

[0019] n and m are the numbers of bolts and cable bolts per row on the roof of the extraction roadway respectively; d0 and d1 are the row distances of the bolts and cable bolts on the roof of the extraction roadway respectively; D is the width of the extraction roadway.

[0020] Step 32: Determine the strength of the anchored roof

[0021] According to the principal stress expression of the Coulomb failure criterion, substitute P0 = σ3 into Equation 2 to obtain the strength σ1 of the anchored roof.

[0022]

[0023] In the formula,

[0024] c is the cohesion of the coal and rock strata on the roof of the extraction roadway within the support range of the bolts / cable bolts; is the internal friction angle of the coal and rock strata on the roof of the extraction roadway within the support range of the bolts / cable bolts.

[0025] Preferably, the said Step 4 includes the following steps:

[0026] Step 41: Determine the allowable deformation amount after the pre-tightening support of the bolts / cable bolts

[0027] According to the support situation of the bolts / cable bolts in the extraction roadway, determine the allowable deformation amount [L support after the pre-tightening support of the bolts / cable bolts from Equation 3 to Equation 9.

[0028] L b2 = L b - L b1 - L b3 ; Equation 3

[0029] L c2 = L c - L c1 - L c3 ; Equation 4

[0030]

[0031] [ε b0 = L b2 δ b - L b0 ; Equation 7

[0032] [ε c0 = L c2 δ c - L c0 ; Equation 8

[0033] [L support ={[ε b0 ,[ε c0} Equation 9

[0034] Wherein,

[0035] L b 、L c are the lengths of the bolt and cable, respectively; L b0 、L c0 are the tensile amounts during pre-tightening of the bolt and cable, respectively; L b1 、L c1 are the anchorage lengths of the bolt and cable, respectively; L b2 、L c2 are the free lengths of the bolt and cable, respectively; L b3 、L c3 are the exposed lengths of the bolt and cable, respectively; F b0 、F c0 are the pre-tightening forces of the bolt and cable, respectively; F by 、F cy are the yield loads of the bolt and cable, respectively; δ by 、δ cy are the elongation ratios at yield of the bolt and cable, respectively; δ b 、δ c are the total elongation ratios at fracture of the bolt and cable, respectively; [ε b0 、[ε c0 are the allowable deformation amounts after pre-tightening support of the bolt and cable, respectively;

[0036] Step 42: Determine the allowable subsidence requirement of the roof when the anchoring is effective

[0037] To ensure the effective anchoring support of the roof in the mining roadway, when the roof rock layer bends and subsides to the allowable position, the roof bolts / cable bolts do not break and fail, that is, it meets the requirement that the allowable subsidence ω of the coal and rock layers of the anchored roof is not greater than the allowable deformation [L support , that is, ω ≤ [L support .

[0038] Preferably, the said Step 5 includes the following steps:

[0039] Step 51: Determine the minimum value q of the advanced support strength from the effectiveness of the anchored roof support 20

[0040] Simplify the anchored roof rock layer into a built-in beam structure. The anchored roof is subjected to its own weight, the upper part of the anchored roof is subjected to the action of the advanced abutment pressure, and the lower part of the anchored roof is subjected to the action of the advanced support,

[0041] Then the maximum bending subsidence ω0 of the coal and rock layers of the anchored roof is:

[0042]

[0043] In the formula,

[0044] q0 is the self-load intensity of the coal and rock layers of the anchored roof, q0 is taken as γm0; γ is the unit weight of the roof coal and rock layer; m0 is the thickness of the coal and rock layers of the anchored roof, m0 = L b2 ; q1 is the increment of the support body under the action of the advanced abutment pressure, q2 is the intensity of the advanced support; E is the deformation modulus of the coal and rock layers of the anchored roof;

[0045] The allowable subsidence ω of the coal and rock layers of the anchored roof is:

[0046] ω = min{ω0, ω1} ≤ [L support ; Formula 11

[0047] In the formula,

[0048] ω1 is the allowable subsidence of the anchored roof in the field project;

[0049] Then the minimum value q of the advanced support strength 20 is:

[0050]

[0051] Step 52: Determine the minimum value q of the advanced support strength from the tensile fracture at the end of the anchored roof rock layer 21

[0052] According to the tensile failure condition at the end of the built-in beam:

[0053]

[0054] When the end of the anchored roof rock stratum is not damaged by tension, the minimum value q of the advanced support strength 21 is:

[0055]

[0056] Step 53: Determine the minimum value q of the advanced support strength from the anti-shearing of the end of the anchored roof rock stratum 22

[0057] The maximum shear stress τ on the anti-shearing surface at the end of the embedded beam max is:

[0058]

[0059] According to the Mohr-Coulomb criterion, the shear strength τ of coal and rock is:

[0060]

[0061] According to the loading characteristics at the end of the anchored roof rock stratum, σ = 0. When the end of the anchored roof rock stratum is not sheared, the minimum value q of the advanced support strength 22 is:

[0062]

[0063] Step 54: Determine the minimum value q2 of the advanced support strength

[0064] The minimum value q2 of the advanced support strength is:

[0065] q2 = max{q 20 , q 21 , q 22}.

[0066] The beneficial technical effects of the present invention are:

[0067] 1. The method for determining the advanced support strength of the gob-side entry in the coal mining face of the present invention fully considers the influence of the advanced abutment pressure in the coal mining face and the support effect of bolts / cables applied during the roadway driving on the roof, makes up for the deficiencies of the traditional method for determining the advanced support strength, makes the determination of the advanced support strength more in line with the actual engineering situation, and realizes the accurate determination of the advanced support strength;

[0068] 2. The method for determining the advanced support strength of the mining roadway in the coal mining face of the present invention starts from avoiding three types of failures: the failure of the anchored roof support, the tensile fracture of the end of the anchored roof rock stratum, and the shear fracture of the end of the anchored roof rock stratum. By comprehensively comparing, the minimum value of the advanced support strength is determined, effectively avoiding the occurrence of disasters of the instability of the anchored roof in the mining roadway of the coal mining face, and ensuring the safety and stability of the roof support of the mining roadway when affected by advanced mining. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 It is a schematic flow chart of the method for determining the advanced support strength of the mining roadway in the coal mining face of the present invention;

[0070] Figure 2 It is a load-bearing model diagram of the anchored roof rock stratum of the present invention;

[0071] Figure 3 It is a schematic diagram of the deformation of the anchored roof rock stratum under the action of load of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0072] To make the objectives, technical solutions, and beneficial effects of the present invention clearer and more understandable, the following further details the present invention with reference to specific embodiments and the accompanying drawings. Some but not all of the embodiments of the present invention will be described more comprehensively with reference to the attached drawings later. In fact, various embodiments of the present invention can be implemented in many different forms and should not be construed as limited to the embodiments described herein; on the contrary, these embodiments are provided to make the present invention meet the applicable legal requirements.

[0073] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "inner", "outer", "upper", "lower", "front", "rear", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0074] In the embodiment of the present invention, taking an actual working face of a certain mine as an example, the buried depth of the return airway of the mine is 500 m, the cross-sectional shape is rectangular, the roadway size is width × height = 5.4 × 3.8 m, the roof of the roadway is sandy mudstone with a thickness of 8.5 m, the uniaxial compressive strength is 12.6 MPa, the cohesion is 3.5 MPa, the internal friction angle is 32°, and the deformation modulus is 4.5 MPa; the roof is supported by a combined bolt-cable support. Among them, the bolts are right-handed equal-strength threaded steel bolts with a yield strength of 500 MPa, a diameter of Φ20 mm, a length of 2.4 m, a row spacing of 1.0 × 1.0 m, arranged in a rectangle, with 6 bolts in each row; the cables are 1 × 7 core with a diameter of Φ21.6 mm, a length of 7.3 m, a row spacing of 2.0 × 2.0 m, arranged in a rectangle, with 3 cables in each row.

[0075] Please refer to Figures 1 to 3 As shown, a method for determining the advanced support strength of a coal mining face return airway includes the following steps.

[0076] Step 1: Obtain the engineering geological characteristics and support conditions of the surrounding rock of the return airway.

[0077] Conduct research on the return airway for which the advanced support strength needs to be determined, and obtain the engineering geological characteristics and support conditions of the surrounding rock of the return airway. Among them, the engineering geological characteristics include roadway cross-sectional dimensions, roadway buried depth, coal-rock columnar and physical and mechanical parameters (strength, cohesion, internal friction angle, deformation modulus, etc.); the support conditions are mainly the parameters and performance of the bolt / cable support materials used, the support row spacing, the layout method, etc.

[0078] Step 2: Measure the working load and increment of bolts / cables under the action of the advanced abutment pressure of the return airway.

[0079] The specific process of Step 2 is as follows:

[0080] Adopt the bolt / cable working load measurement method (in this embodiment, it is measured according to the corresponding regulations of the mining safety industry standard KA / T - 2023), monitor and obtain the change law of the working load of the roof bolts / cables under the action of the advanced abutment pressure of the return airway, and obtain the bolt working load F ibolt of the return airway, the cable working load F jcable , the working load increment ΔF ibolt of the i-th bolt and the working load increment ΔF jcable of the j-th cable.

[0081] Step 3: Estimate the strength of the anchored roof of the return airway.

[0082] Step 3 includes the following steps:

[0083] Step 31: Determine the support strength of bolts / cables

[0084] According to the support parameters and working loads of roof bolts / anchor cables in the extraction roadway, the support strength P0 of bolts / anchor cables is determined according to Equation 1.

[0085]

[0086] Wherein,

[0087] n and m are the numbers of bolts and anchor cables per row of the roof of the extraction roadway respectively; d0 and d1 are the row spacings of bolts and anchor cables of the roof of the extraction roadway respectively; D is the width of the extraction roadway.

[0088] In this embodiment, the support strength of bolts / anchor cables is 327.8 kN / m 2 .

[0089] Step 32: Determine the strength of the anchored roof

[0090] According to the principal stress expression of the Coulomb failure criterion, substituting P0 = σ3 into Equation 2, the strength σ1 of the anchored roof is obtained.

[0091]

[0092] Wherein,

[0093] c is the cohesion of the coal and rock strata of the roof of the extraction roadway within the support range of bolts / anchor cables; is the internal friction angle of the coal and rock strata of the roof of the extraction roadway within the support range of bolts / anchor cables;

[0094] In this embodiment, the strength of the anchored roof is 18.4 MPa.

[0095] Step 4: Determine the conditions for the effective anchored support of the roof of the extraction roadway.

[0096] Step 4 includes the following steps:

[0097] Step 41: Determine the allowable deformation amount after the pre-tightening support of bolts / anchor cables

[0098] According to the support situation of bolts / anchor cables in the extraction roadway, the allowable deformation amount [L support after the pre-tightening support of bolts / anchor cables is determined by Equations 3 - 9.

[0099] L b2 = L b - L b1 - L b3 ; Equation 3

[0100] L c2 = L c - L c1 - L c3 ; Equation 4

[0101]

[0102] [ε b0 = L b2 δ b -L b0 ; Equation 7

[0103] [ε c0 = L c2 δ c -L c0 ; Equation 8

[0104] [L support = {[ε b0 , [ε c0} Equation 9

[0105] Wherein,

[0106] L b 、L c are the lengths of the bolt and cable, respectively; L b0 、L c0 are the tensile amounts during pre-tightening of the bolt and cable, respectively; L b1 、L c1 are the anchorage section lengths of the bolt and cable, respectively; L b2 、L c2 are the free section lengths of the bolt and cable, respectively; L b3 、L c3 are the exposed section lengths of the bolt and cable, respectively; F b0 、F c0 are the pre-tightening forces of the bolt and cable, respectively; F by 、F cy are the yield loads of the bolt and cable, respectively; δ by 、δ cy are the elongation rates at yield of the bolt and cable, respectively; δ b 、δ c are the total elongation rates at fracture of the bolt and cable, respectively; [ε b0 、[ε c0 are the allowable deformation amounts after pre-tightening support of the bolt and cable, respectively;

[0107] Step 42: Determine the requirement for the allowable roof subsidence amount when the anchorage is effective

[0108] To ensure the effectiveness of the roof anchorage support in the extraction roadway, when the roof strata bend and subside to the allowable position, the roof bolts / cables do not fail due to fracture, that is, it satisfies that the allowable subsidence amount ω of the roof coal and rock strata does not exceed the allowable deformation amount [L support after pre-tightening support of the bolts / cables, that is, ω ≤ [L support .

[0109] Step 5: Determine the advanced support strength of the extraction roadway.

[0110] Step 5 includes the following steps:

[0111] Step 51: Determine the minimum value q of the advanced support strength from the effective support of the anchored roof 20

[0112] As Figure 2 shown, simplify the rock stratum of the anchored roof into a fixed-ended beam structure. The anchored roof is subjected to its own weight, the upper part of the anchored roof is subjected to the advanced abutment pressure, and the lower part of the anchored roof is subjected to the advanced support.

[0113] Then the maximum bending settlement ω0 of the coal and rock stratum of the anchored roof is:

[0114]

[0115] In the formula,

[0116] q0 is the self-load intensity of the coal and rock stratum of the anchored roof, and q0 is taken as γm0; γ is the unit weight of the roof coal and rock stratum; m0 is the thickness of the coal and rock stratum of the anchored roof, and m0 = L b2 ; q1 is the increment of the support body under the action of the advanced abutment pressure, In this embodiment, q1 is 145.8 kN / m 2 ; q2 is the intensity of the advanced support; E is the deformation modulus of the coal and rock stratum of the anchored roof;

[0117] Referring to Figure 3 shown, the allowable settlement ω of the coal and rock stratum of the anchored roof is:

[0118] ω = min{ω0, ω1} ≤ [L support ; Formula 11

[0119] In the formula,

[0120] ω1 is the allowable settlement of the anchored roof in the on-site project;

[0121] Then the minimum value q of the advanced support strength 20 is:

[0122]

[0123] In this embodiment, the minimum value q of the advanced support strength 20 is 122.5 kN / m 2 ;

[0124] Step 52: Determine the minimum value q of the advanced support strength from the tensile fracture at the end of the anchored roof rock stratum 21

[0125] According to the tensile failure condition at the end of the fixed-ended beam:

[0126]

[0127] When the end of the anchored roof rock stratum is not damaged by tension, the minimum value q of the advanced support strength 21 is as follows:

[0128]

[0129] In this embodiment, the minimum value q of the advanced support strength 21 is 19.8 kN / m 2 ;

[0130] Step 53: Determine the minimum value q of the advanced support strength from the anti-shearing of the end of the anchored roof rock stratum 22

[0131] The maximum shear stress τ on the anti-shearing surface at the end of the embedded beam max is as follows:

[0132]

[0133] According to the Mohr-Coulomb criterion, the shear strength τ of coal and rock is as follows:

[0134]

[0135] According to the loading characteristics at the end of the anchored roof rock stratum, σ = 0. When the end of the anchored roof rock stratum is not sheared, the minimum value q of the advanced support strength 22 is as follows:

[0136]

[0137] In this embodiment, the minimum value q of the advanced support strength 22 is 177.8 kN / m 2 ;

[0138] Step 54: Determine the minimum value q2 of the advanced support strength

[0139] The minimum value q2 of the advanced support strength is as follows:

[0140] q2 = max{q 20 , q 21 , q 22};

[0141] Then in this embodiment, the minimum value q2 of the advanced support strength is 177.8 kN / m 2 .

[0142] So far, this embodiment has been described in detail with reference to the accompanying drawings. Based on the above description, those skilled in the art should have a clear understanding of the method for determining the advanced support strength of the mining roadway in the coal mining face of the present invention. The method for determining the advanced support strength of the mining roadway in the coal mining face of the present invention fully considers the influence of the advanced abutment pressure in the coal mining face and the bolt / cable support effect applied during the roadway driving on the roof, makes up for the deficiencies of the traditional method for determining the advanced support strength, makes the determination of the advanced support strength more in line with the actual engineering situation, and realizes the accurate determination of the advanced support strength; starting from avoiding the occurrence of three types of failures, namely the failure of the anchored roof support, the tensile fracture of the end of the anchored roof rock layer, and the shear fracture of the end of the anchored roof rock layer, the minimum value of the advanced support strength is determined through comprehensive comparison, effectively avoiding the occurrence of disasters of the instability of the anchored roof in the mining roadway of the coal mining face, and ensuring the safety and stability of the roof support of the mining roadway when affected by the advanced mining movement.

[0143] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for determining the advanced support strength of the extraction roadway in a coal mining face, characterized in that, The method includes the following steps: Step 1: Obtain the engineering geological characteristics and support conditions of the surrounding rock of the extraction roadway; Step 2: Measure the working load and increment of bolts / cable bolts under the advanced abutment pressure of the extraction roadway; The specific process of Step 2 is as follows: Monitor and obtain the variation law of the working load of the roof bolts / cable bolts under the advanced abutment pressure of the extraction roadway, and obtain the working load of each bolt in each row of the roof, the working load of each cable bolt in each row, the increment of the working load of the i-th bolt in each row, and the increment of the working load of the j-th cable bolt in each row under the advanced abutment pressure of the extraction roadway; Wherein, i = 1, 2......n; j = 1, 2......m; n and m are the numbers of bolts and cable bolts in each row of the roof of the extraction roadway respectively; Step 3: Estimate the strength of the anchored roof of the extraction roadway; Step 3 includes the following steps: Step 31: Determine the supporting strength of bolts / cable bolts According to the support parameters and working load conditions of the roof bolts / cable bolts of the extraction roadway, determine the supporting strength P0 of bolts / cable bolts according to Equation 1, In the formula, n and m are the numbers of bolts and cable bolts in each row of the roof of the extraction roadway respectively; d0 and d1 are the row spacings of the roof bolts and cable bolts of the extraction roadway respectively; D is the width of the extraction roadway; Step 32: Determine the strength of the anchored roof According to the principal stress expression of the Coulomb failure criterion, substitute P0 = σ3 into Equation 2 to obtain the strength σ1 of the anchored roof; In the formula, $c$ is the cohesion of the coal and rock strata in the roof of the mining roadway within the range of bolt / cable support; $\varphi$ is the internal friction angle of the coal and rock strata in the roof of the mining roadway within the range of bolt / cable support; Step 4: Determine the conditions for the effectiveness of the roof anchored support of the extraction roadway; Step 4 includes the following steps: Step 41: Determine the allowable deformation amount after the pre-tightening support of bolts / cable bolts According to the bolting / cable bolting support conditions of the extraction roadway, the allowable deformation [L support after pre-tightening support of bolts / cable bolts is determined by Equations 3 - 9 L b2 = L b - L b1 - L b3 ; Equation 3 L c2 = L c - L c1 - L c3 ; Equation 4 [ε b0 = L b2 δ b -L b0 ; Equation 7 [ε c0 = L c2 δ c -L c0 ; Equation 8 [L support = {[ε b0 ,[ε c0} Equation 9 In the formula, L b and L c are the lengths of the bolt and cable, respectively; L b0 and L c0 are the tensile amounts during the pre-tightening of the bolt and cable, respectively; L b1 and L c1 are the anchorage lengths of the bolt and cable, respectively; L b2 and L c2 are the free lengths of the bolt and cable, respectively; L b3 and L c3 are the exposed lengths of the bolt and cable, respectively; F b0 and F c0 are the pre-tightening forces of the bolt and cable, respectively; F by and F cy are the yield loads of the bolt and cable, respectively; δ by and δ cy are the elongation rates at yield of the bolt and cable, respectively; δ b and δ c are the total elongation rates at fracture of the bolt and cable, respectively; [ε b0 and [ε c0 are the allowable deformation amounts after the pre-tightening support of the bolt and cable, respectively; Step 42: Determine the requirement for the allowable subsidence amount of the roof when the anchoring is effective To ensure the effective bolt support of the roof of the extraction roadway, the roof bolts / anchor cables do not break and fail when the roof rock stratum bends and sinks to the allowable position, that is, it meets the requirement that the allowable subsidence amount ω of the roof coal and rock strata does not exceed the allowable deformation amount [L support , that is, ω ≤ [L support ; Step 5: Determine the advanced support strength of the extraction roadway; Step 5 includes the following steps: Step 51: Determine the minimum value q of the advanced support strength based on the effective support of the anchored roof 20 Simplify the rock stratum of the anchored roof into a fixed-ended beam structure. The anchored roof is subjected to its own weight, the upper part of the anchored roof is subjected to the advanced abutment pressure, and the lower part of the anchored roof is subjected to the advanced support; Then the maximum bending subsidence amount ω0 of the coal and rock stratum of the anchored roof is: In the formula, $q_0$ is the self-load intensity of the anchored roof coal and rock strata, and $q_0$ takes $\gamma m_0$; $\gamma$ is the unit weight of the roof coal and rock strata; $m_0$ is the thickness of the anchored roof coal and rock strata, and $m_0 = L$ b2 ; $q_1$ is the increment of the support body under the action of the advanced abutment pressure, $q_2$ is the intensity of the advanced support; $E$ is the deformation modulus of the anchored roof coal and rock strata; The allowable subsidence amount ω of the coal and rock stratum of the anchored roof is: ω = min{ω0, ω1} ≤ [L support ; Equation 11 In the formula, ω1 is the allowable subsidence amount of the anchored roof in the on-site project; Then the minimum value of the advanced support strength q 20 is: Step 52: Determine the minimum value q of the advanced support strength based on the tensile fracture at the end of the anchored roof rock stratum 21 According to the tensile failure condition at the end of the fixed-ended beam: When the end of the anchored roof rock stratum is not damaged by tension, the minimum value q of the advanced support strength 21 is as follows: Step 53: Determine the minimum value q of the advanced support strength based on the anti-shearing at the end of the anchored roof strata 22 The maximum shear stress τ on the anti-shear plane at the end of the embedded beam max is as follows: According to the Mohr-Coulomb criterion, the shear strength τ of coal and rock is: According to the characteristics of the end loading of the anchored roof rock stratum, σ = 0, when the end of the anchored roof rock stratum is not sheared off, the minimum value q of the advanced support strength 22 is as follows: Step 54: Determine the minimum value q2 of the advanced support strength The minimum value q2 of the advanced support strength is: q2 = max{q 20 , q 21 , q 22}.

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