Method for determining width and strength of roadside filling body of gob-side entry retaining

Abstract

The invention discloses a method for determining width and strength of a roadside filling body of a gob-side entry retaining. The method comprises the following steps: constructing a key block structure of the gob-side entry retaining; establishing a stability analysis mechanical model of the key block B; establishing an immediate roof stability mechanical analysis model to solve the supporting force of the immediate roof; establishing a mechanical criterion when the key block B is stable; judging the magnitude between the horizontal thrust and the shearing force; obtaining the supporting resistance of the roadside filling body; calculating the strength sigma F of the roadside filling body; fitting the strength sigma F of the roadside filling body and the width b of the roadside filling body; the minimum roadside filling body width bmin and the minimum roadside filling body strength sigma min when the minimum roadside filling body width bmin is met are obtained. According to the method, whether the width and the strength of the roadside filling body meet the entry retaining requirements or not is accurately judged by calculating the width and the supporting strength of the roadside filling body, the mine pressure display phenomena such as gob-side entry retaining roof cutting, wall caving, floor heaving, large deformation and supporting structure failure are avoided, and the stability of the gob-side entry retaining roof structure is guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of non-coal pillar mining, and in particular to a method for determining the width and strength of a filling body beside a gob-side lane retaining lane. Background Art

[0002] As a common coal pillar-free mining technology, gob-side lane retention is to retain the lane of the previous section of the working face through in-lane support and lane side filling. This technology improves the coal recovery rate, effectively reduces the excavation rate, alleviates the difficulty of mining and excavation connection, and realizes Y-shaped ventilation of the working face. Gob-side lane retention technology is one of the important development directions of green, safe and efficient coal mining. Among them, the stability of the lane side filling body is the key to determining whether the gob-side lane retention technology can be successful. The strength of the lane side filling body should be adapted to the mechanical properties of the coal body and the roof and floor. The width of the lane side filling body directly affects the support resistance.

[0003] During the strong lagging mining stress adjustment process, the strength of the side filling is insufficient and the risk of deformation and damage is high, which further leads to an increase in the lateral rotation and sinking of the roof and damage to the support structure system of the side leaving the road. When the width of the side filling is insufficient, the support strength of the side filling is relatively low, the integrity of the roof in the road may be seriously damaged, the roof delamination is significant, the amount of sinking is large, and the bearing capacity of the roof bearing structure is weakened. When the width of the side filling is too large, the corresponding side filling support strength is too large, and the overburden of the roadway transfers the load to the bottom plate of the side leaving the road, which is prone to bottom bulging and the cost of leaving the road will also increase. The method for determining the broken position of the roof of the side leaving the road has been given in the Chinese authorized patent announcement number CN117251919B, but the research on the relationship between the width and strength of the side filling and the stability of the roof structure is still insufficient.

[0004] At present, it is difficult to determine the width and strength of the side filling of gob-side entry retention. The width and strength of the side filling are not compatible with the mechanical properties of the retained entry roof, which is easy to cause damage and instability of the side filling under the influence of mining. Therefore, it is necessary to develop a method to determine the width and strength of the side filling of gob-side entry retention. Summary of the invention

[0005] The present invention provides a method for determining the width and strength of the filling body beside the goaf-retained lane, so as to solve the problems that the engineering analogy method is difficult to fully adapt to all specific situations due to the great differences in geological conditions and mechanical properties of coal seams in different mining areas, and inaccurate design parameters are prone to occur; and the technical problems that when the width of the filling body beside the lane is too large, excessive support will be provided, and the cost of retaining the lane will increase; when the width of the filling body beside the lane is too small, the strength is insufficient, and the roof of the retained lane is prone to instability and breakage.

[0006] The technical solution adopted by the present invention is: a method for determining the width and strength of the filling body beside the gob-side entry retaining, comprising the following steps:

[0007] S1. Construct the key block structure of gob-side lane retention: divide the block formed by breaking the arc-shaped triangular block at the end of the working face into key block A, key block B and key block C. Under the support of the direct roof, caving gangue, lane-side backfill and solid coal seam, and the active support of anchor bolts (cables) in the lane and backfill area, key block B forms the key block structure of gob-side lane retention with key block A and key block C;

[0008] S2. Establishment of the mechanical model for stability analysis of key block B: Based on the key block structure constructed in S1, simplify the key block B, caving gangue, roadside filling, solid coal sill and direct roof, generate the mechanical model diagram for stability analysis of key block B, and perform the following steps:

[0009] S2.1. Calculate the geometric parameters of key block B, including the breaking length L in the advancing direction of the working face and the lateral breaking length L2. Use the relevant data of the return air chute of the coal mine working face on the mechanical model of key block B stability analysis to solve L and L2;

[0010] S2.2. Calculate the roof fracture position and the supporting force of the solid coal wall σ y The width of the limit equilibrium zone of the elastic-plastic interface of the coal body x0: Based on the mechanical model of stability analysis of the key block B, the relevant data of the return air chute of the coal mine working face are used to solve σ y and x0;

[0011] S3. Establish a mechanical analysis model of the stability of the immediate roof to solve the supporting force of the immediate roof: Ignore the influence of the broken angle of the immediate roof, set the right side of the immediate roof as fixed support, and its left boundary as a free end, simplify the supporting structure of the immediate roof, the backfill body beside the roadway and the solid coal seam into a mechanical analysis model of the stability of the immediate roof, and solve the supporting force of the immediate roof by performing the following steps:

[0012] S3.1. Force analysis of the direct roof mechanical model: including obtaining the reaction load F of the key block B on the direct roof upper boundary M , the lower boundary is subject to the resistance of the tunnel support f s , the supporting stress σ provided by the solid coal wall to the direct roof y , roadside support resistance f d and the supporting stress F provided by the falling gangue to the key block B g ;

[0013] S3.2 Derivation and M o : and F M 、f s , σ y 、f d and F g The moment corresponding to the solid coal support point O, M ois the direct top bending moment, and M o The expression is:

[0014]

[0015] Where a is the width of the gob-side entry; b is the width of the filling body beside the entry; γ is the bulk density of the overlying stratum; h1 is the thickness of the immediate top rock stratum; σ t is the tensile strength of the direct top;

[0016] S3.3. Further solution and F M :According to the moment balance equation, the following formula is derived:

[0017]

[0018] S4. Establish the mechanical criterion for the stability of key block B: When key block B is rotating, the horizontal thrust on both sides is equal, that is, it satisfies

[0019] T AB =T CB (13)

[0020] The calculation formula of the occlusal contact length s of key block A and key block C to key block B is as follows:

[0021]

[0022] Where, θ is the rotation and sinking angle of key block B;

[0023] When the key block B is stressed at point A, the total bending moment is 0, that is, ΣM A = 0, horizontal thrust T CB The calculation formula is as follows:

[0024]

[0025] Where Δ is the rotational sinking amount of the key block B; q is the load transferred by the upper weak rock layer and its deadweight borne by the basic top rock layer;

[0026] According to formula (12), formula (13) and formula (14), the horizontal thrust T is obtained AB The calculation formula is as follows:

[0027]

[0028] S5. Determine the magnitude of horizontal thrust and shear force: When there is no extrusion failure at the hinge between key block B and key block C, the following expression is used:

[0029]

[0030] Where ψ is the contact friction coefficient between key block B and key block C; σ c is the compressive strength of key block B;

[0031] When the horizontal thrust and shear force satisfy the judgment condition of formula (17), the support resistance calculation f of the roadside filling body is d1 The formula is as follows:

[0032]

[0033] Otherwise, the support resistance f of the backfill body beside the roadway d2 The calculation formula is as follows:

[0034]

[0035] In the formula, is the internal friction angle of the interface between coal and rock;

[0036] S6. The calculation formula for the supporting resistance of the backfill body beside the roadway corresponding to the stability of the key block B of the gob-side roadway retention is:

[0037] f dm2 =max(f d1 ,f d2 ) (20)

[0038] S7. Calculate the strength of the backfill beside the roadway σ F , σ F The calculation formula is as follows:

[0039]

[0040] S8. According to equations (19), (20) and (21), the relationship curve between the support resistance and strength of the roadside filling body and the width of the roadside filling body is drawn. According to the relationship curve, the strength σ of the roadside filling body is fitted. F and the width b of the backfill beside the roadway, the fitting curve σ F The expression is:

[0041] σ F =V-Iln(bO),R 2 =P (22)

[0042] In the formula, V, I, and O are fitting coefficients; R 2 is the correlation coefficient;

[0043] S9, according to σ F The fitting curve of the minimum lane filling width b is obtained min , and meet the minimum lane filling width b min The minimum strength of the filling body beside the road is min.

[0044] In the calculation of b min and σ min After that, the width and strength of the backfill beside the roadway are appropriately enhanced during on-site construction. When the width and support of the backfill beside the roadway along the gob-retained roadway reach σ0 and b0, the requirements of the gob-retained roadway can be met. The expressions of σ0 and b0 are:

[0045] b0=k0b min (twenty three)

[0046] σ0=k0σ min (twenty four)

[0047] In the formula, k0 is the safety factor, and k0>1;

[0048] In S1, when the key block B is in a stable state, the deformation of the surrounding rock of the gob-side entry below the support structure is small, and the stability of the surrounding rock structure of the entry depends on the stability of the key block B.

[0049] In S2.1, the calculation formulas for the working face periodic pressure step L and the roof lateral breaking length L2 are as follows:

[0050]

[0051] Where h is the thickness of the basic top rock layer; R T is the tensile strength of the basic top rock layer; L s is the inclination length of the working face.

[0052] In S2.2, the roof fracture position and the supporting force of the solid coal wall σ y The calculation formula for the width x0 of the limit equilibrium zone of the elastic-plastic interface with the coal body is as follows:

[0053]

[0054] In the formula, h c is the height of gob-side entry; c0 is the cohesion of the interface between coal and rock; k is the stress concentration coefficient; λ represents the lateral pressure coefficient; H is the burial depth of the coal seam; P x is the support strength of the solid coal seam; α is the inclination of the coal seam.

[0055] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects:

[0056] 1. By establishing a mechanical model of gob-side entry retention, it is analyzed that the stability of the roof structure depends on the stability of the key block B. The width and strength of the filling body beside the entry must not only prevent the key block B from sliding and becoming unstable when the turning angle is small, but also prevent the extrusion deformation and becoming unstable when the turning angle increases;

[0057] 2. It is convenient for relevant practitioners to quickly calculate the width and support strength of the filling body beside the roadway, accurately judge whether the width and strength of the filling body beside the roadway meet the requirements of retaining the roadway, ensure the stability of the roof structure along the goaf, avoid the occurrence of mining pressure phenomena such as roof cutting, slab spalling, bottom bulging, large deformation and support structure failure along the goaf, and ensure safe and efficient mining of the mine. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] 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 are briefly introduced below.

[0059] Figure 1 This is a mechanical analysis model diagram of the stability of the direct roof of the gob-side entry retaining according to the present invention;

[0060] Figure 2 This is a model diagram of the stress distribution of the solid coal ridge of the present invention;

[0061] Figure 3 This is a schematic diagram of the simplified process of the lateral length L2 of the key block B of the present invention;

[0062] Figure 4 This is a mechanical model diagram for stability analysis of key block B of gob-side entry retention in the present invention;

[0063] Figure 5 This is a diagram of the rotation and sinking state of the key block B of the present invention;

[0064] Figure 6 It is the relationship curve between the supporting strength of the tunnel side filling body and the width of the tunnel side filling body of the present invention. DETAILED DESCRIPTION

[0065] The present invention is further described in detail below in conjunction with the accompanying drawings and specific preferred embodiments.

[0066] In the description of the present invention, it should be understood that the terms "left side", "right side", "upper part", "lower part" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. "First", "second" and the like do not indicate the importance of the components, and therefore cannot be understood as limiting the present invention. The specific dimensions used in this embodiment are only for illustrating the technical solution, and do not limit the scope of protection of the present invention.

[0067] like Figure 1-6 As shown, a method for determining the width and strength of the filling body beside the gob-side entry retaining includes the following steps:

[0068] S1. Constructing the key block structure of gob-side lane retention: The blocks formed after the arc-shaped triangular block at the end of the working face is broken are divided into key blocks A, B and C. Key blocks A and C are located at the two ends of key block B respectively. Under the support of the direct roof, caving gangue, lane-side backfill and solid coal seam, and the active support of anchor bolts (cables) in the lane and backfill area, key block B forms the key block structure of gob-side lane retention with key blocks A and C. Key block B rotates and sinks, forming a mutually articulated "large structure" with key blocks A and C.

[0069] S2. Establishment of the mechanical model for stability analysis of key block B: Based on the key block structure constructed in S1, simplify the key block B, caving gangue, roadside filling, solid coal sill and direct roof, generate the mechanical model diagram for stability analysis of key block B, and perform the following steps:

[0070] S2.1. Calculate the geometric parameters of key block B, including the breaking length L in the advancing direction of the working face and the lateral breaking length L2. Use the relevant data of the return air chute of the coal mine working face on the mechanical model of key block B stability analysis to solve L and L2;

[0071] S2.2. Calculate the roof fracture position and the supporting force of the solid coal wall σ y The width of the limit equilibrium zone of the elastic-plastic interface of the coal body x0: Based on the mechanical model of stability analysis of the key block B, the relevant data of the return air chute of the coal mine working face are used to solve σ y and x0;

[0072] S3. Establish a mechanical analysis model of the stability of the immediate roof to solve the supporting force of the immediate roof: Ignore the influence of the broken angle of the immediate roof, set the right side of the immediate roof as fixed support, and its left boundary as a free end, simplify the supporting structure of the immediate roof, the backfill body beside the roadway and the solid coal seam into a mechanical analysis model of the stability of the immediate roof, and solve the supporting force of the immediate roof by performing the following steps:

[0073] S3.1. Force analysis of the direct roof mechanical model: including obtaining the reaction load F of the key block B on the direct roof upper boundary M , the lower boundary is subject to the resistance of the tunnel support f s , the supporting stress σ provided by the solid coal wall to the direct roof y , roadside support resistance f d and the supporting stress F provided by the falling gangue to the key block B g ;

[0074] S3.2 Derivation and M o : and F M 、f s , σ y 、f dand F g The moment corresponding to the solid coal support point O, M o is the direct top bending moment, and M o The expression is:

[0075]

[0076] Where a is the width of the gob-side entry; b is the width of the filling body beside the entry; γ is the bulk density of the overlying stratum; h1 is the thickness of the immediate top rock stratum; σ t is the tensile strength of the direct top;

[0077] S3.3. Further solution and F M :According to the moment balance equation, the following formula is derived:

[0078]

[0079]

[0080] S4. Establish the mechanical criterion for the stability of key block B: When key block B is rotating, the horizontal thrust on both sides is equal, that is, it satisfies

[0081] T AB =T CB (13)

[0082] The calculation formula of the occlusal contact length s of key block A and key block C to key block B is as follows:

[0083]

[0084] Where, θ is the rotation and sinking angle of key block B;

[0085] When the key block B is stressed at point A, the total bending moment is 0, that is, ΣM A = 0, horizontal thrust T CB The calculation formula is as follows:

[0086]

[0087] Where Δ is the rotational sinking amount of the key block B; q is the load transferred by the upper weak rock layer and its deadweight borne by the basic top rock layer;

[0088] According to formula (12), formula (13) and formula (14), the horizontal thrust T is obtained AB The calculation formula is as follows:

[0089]

[0090] S5. Determine the magnitude of horizontal thrust and shear force: When there is no extrusion failure at the hinge between key block B and key block C, the following expression is used:

[0091]

[0092] Where ψ is the contact friction coefficient between key block B and key block C; σ c is the compressive strength of key block B;

[0093] When the horizontal thrust and shear force satisfy the judgment condition of formula (17), the support resistance calculation f of the roadside filling body is d1 The formula is as follows:

[0094]

[0095] Otherwise, the support resistance f of the backfill body beside the roadway d2 The calculation formula is as follows:

[0096]

[0097] In the formula, is the internal friction angle of the interface between coal and rock;

[0098] S6. The calculation formula for the supporting resistance of the backfill body beside the roadway corresponding to the stability of the key block B of the gob-side roadway retention is:

[0099] f dm2 =max(f d1 ,f d2 ) (20)

[0100] S7. Calculate the strength of the backfill beside the roadway σ F , σ F The calculation formula is as follows:

[0101]

[0102] S8. According to equations (19), (20) and (21), the relationship curve between the support resistance and strength of the roadside filling body and the width of the roadside filling body is drawn. According to the relationship curve, the strength σ of the roadside filling body is fitted. F and the width b of the backfill beside the roadway, the fitting curve σ F The expression is:

[0103] σ F =V-Iln(bO),R 2 =P (22)

[0104] In the formula, V, I, and O are fitting coefficients; R 2 is the correlation coefficient;

[0105] S9, according to σF The fitting curve of the minimum lane filling width b is obtained min , and meet the minimum lane filling width b min The minimum strength of the filling body beside the road is min .

[0106] In the calculation of b min and σ min After that, the width and strength of the backfill beside the roadway are appropriately enhanced during on-site construction. When the width and support of the backfill beside the roadway along the gob-retained roadway reach σ0 and b0, the requirements of the gob-retained roadway can be met. The expressions of σ0 and b0 are:

[0107] b0=k0b min (twenty three)

[0108] σ0=k0σ min (twenty four)

[0109] In the formula, k0 is the safety factor, and k0>1. Preferably, the safety factor k0=1.2. Therefore, the width b0 and strength σ0 of the filling body beside the gob-side tunnel are calculated. When the width of the filling body beside the tunnel is b0 and the support strength is σ0, the stability of the roof structure of the gob-side tunnel can be guaranteed, meeting the requirements of the gob-side tunnel.

[0110] In order to verify the feasibility of the present invention, the following embodiments are provided:

[0111] The width of the filling body and the support strength of the side of the goaf-retaining lane along the return air chute of the 150110 fully-mechanized top coal caving working face in a certain mine are analyzed based on the engineering geological conditions of the 150110 working face by using a method for determining the width of the filling body and the support strength of the side of the goaf-retaining lane along the return air chute of the 150110 working face provided by the present invention.

[0112] According to the relevant data of the return air chute of the 150110 working face of a certain mine, the average thickness of the direct roof is 4.8m, the average thickness of the basic roof is 6.4m, the thickness of the coal seam is 3.5m, and the average inclination of the coal seam is 7°; the average length of the working face is 150m and the mining depth is 250m.

[0113] The geological technical parameters of the return air chute of the 150110 working face are as follows: H = 250m, a = 3.5m, α = 5°, b = 2.0m, λ = 0.4, k = 2.0, γ = 2.5×10 -2 MN / m 3 , c0=3.45MPa, θ=75°,P x =0.1MPa, f s =0.2MPa, F g =6.4MPa,σ t=1MPa, R T =4.6MPa,h c =3.5m, h1=4.8m, h=6.4m, s=150m; according to the comprehensive columnar diagram of the 150110 working face, the load q of the soft rock stratum above the basic top is 0.3525MN / m.

[0114] Establish the mechanical model for stability analysis of key block B:

[0115] Breaking length L in the advancing direction of the working face:

[0116]

[0117] Lateral breaking length of working surface L2:

[0118]

[0119] Limit equilibrium zone width x0:

[0120]

[0121] Support stress in the limit equilibrium zone:

[0122]

[0123] The immediate top boundary bears the reaction load F of the key block B M :

[0124]

[0125] Horizontal thrust T AB :

[0126]

[0127] When the key block B and the key block C do not suffer from extrusion failure at the hinge, the horizontal thrust is greater than the shear force;

[0128]

[0129] At this time, the support resistance of the filling body beside the roadway is f d1 :

[0130]

[0131] When the key block B and the key block C do not suffer from extrusion failure at the hinge, the horizontal thrust is less than the shear force. At this time, the support resistance f of the backfill body beside the roadway is d2 :

[0132]

[0133] Substituting the known parameters into the above formula, we can get:d1 = 17.78 MN / m, f d1 = 1.96 MN / m. The stability of key block B is controlled by key block A and key block C. During the basic roof breaking stage of gob-side entry retaining, the support resistance of the gob-side filling body corresponds to the maximum values of f d1 and f d2 . It should not only meet the requirement of preventing the sliding instability when the rotation angle of key block B is small, but also meet the requirement of preventing the extrusion deformation instability when the rotation angle increases, which conforms to the "R-S" stability theory of the masonry beam structure;

[0134] The support resistance f of the gob-side filling body dm2 :

[0135] f dm2 = max(f d1 , f d2 ) = 17.78 MN / m

[0136]

[0137] Study the relationship between the roof cutting resistance, support strength of the gob-side filling body and the width of the gob-side filling body under the engineering geological conditions of this working face. Take the width b range of the gob-side filling body from 0 to 3 m, and calculate the relationship curve between the roof cutting resistance support strength of the gob-side filling body and the width of the gob-side filling body;

[0138] According to the relationship curve, fit the support strength σ of the gob-side filling body F and the width b of the gob-side filling body to obtain the fitting curve:

[0139] σ F = 7.54 - 6.99ln(b - 0.01), R 2 = 0.987

[0140] According to the fitting curve of σ F and b, when 0.1 < b < 2, as the width of the gob-side filling body decreases, the strength required for the gob-side filling body increases rapidly; when b > 2, as the width of the gob-side filling body decreases, the strength required for the gob-side filling body decreases slowly. Considering the cost of the gob-side filling body and the support material comprehensively, the minimum width b of the gob-side filling body min is 2 m. To ensure the stability of the gob-side entry retaining roof structure, the minimum support strength σ of the gob-side filling body min is 9.82 MPa;

[0141] When the minimum width b of the gob-side filling body min is 2 m and the minimum support strength σ of the gob-side filling body required to be achieved min is 9.82 MPa, a certain safety factor k0 needs to be considered in on-site construction. Then, the support strength σ0 of the gob-side filling body for gob-side entry retaining and the width b0 of the gob-side filling body are:

[0142] b0=k0b min =2.4m (23)

[0143] σ0=k0σ min =11.78MPa (24)

[0144] Taking the safety factor k0=1.2, the width b0 of the side filling body of the gob-side tunneling and the strength σ0 of the side filling body are calculated. When the width b0 of the side filling body of the gob-side tunneling is 2.4m and the strength σ0 of the side filling body is 11.78MPa, the roof structure of the gob-side tunneling can be guaranteed to be stable and meet the requirements of the gob-side tunneling.

[0145] The method has a simple operation process, strong reliability, and quantitative description of mechanical parameters. It is suitable for determining the width and support strength of the filling body beside the gob-retained tunnel under different engineering geological conditions, solving the problem that the existing technical methods are difficult to determine the width and strength of the filling body beside the gob-retained tunnel.

[0146] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as those generally understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless defined as herein.

[0147] The above embodiments are only for explaining the technical idea of ​​the present invention, and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention shall fall within the protection scope of the present invention. The above embodiments of the present invention are described in detail, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A method for determining the width and strength of the filling body beside the gob-side entry retaining, characterized in that: The steps include: S1. Construct the key block structure of gob-side entry retention: divide the blocks formed after the arc-shaped triangular block at the end of the working face is broken into key blocks A, B and C. Under the support of the direct roof, caving gangue, roadside filling and solid coal seam, and the active support of anchors (cables) in the roadway and filling area, key block B forms the key block structure of gob-side entry retention with key blocks A and C. When key block B is in a stable state, the surrounding rock deformation of the gob-side entry retention under the support structure is small, and the stability of the surrounding rock structure of the entry retention depends on the stability of key block B. S2. Establishment of the mechanical model for stability analysis of key block B: Based on the key block structure constructed in S1, simplify the key block B, caving gangue, roadside filling, solid coal sill and direct roof, generate the mechanical model diagram for stability analysis of key block B, and perform the following steps: S2.

1. Calculate the geometric parameters of key block B, including the breaking length L in the advancing direction of the working face and the lateral breaking length L2. Use the relevant data of the return air chute of the coal mine working face on the mechanical model of key block B stability analysis to solve L and L2; The calculation formulas for the working face periodic pressure step distance L and the roof lateral breaking length L2 are as follows: Where h is the thickness of the basic top rock layer; R T is the tensile strength of the basic top rock layer; L s is the inclined length of the working face; S2.

2. Calculate the roof fracture position and the supporting force of the solid coal wall σ y The width of the limit equilibrium zone of the elastic-plastic interface of the coal body x0: Based on the mechanical model of stability analysis of the key block B, the relevant data of the return air chute of the coal mine working face are used to solve σ y and x0; Roof fracture position and support force of solid coal wallσ y The calculation formula for the width x0 of the limit equilibrium zone of the elastic-plastic interface with the coal body is as follows: In the formula, h c is the height of gob-side entry; c0 is the cohesion of the interface between coal and rock; k is the stress concentration coefficient; λ represents the lateral pressure coefficient; H is the burial depth of the coal seam; P x is the support strength of the solid coal seam; α is the inclination of the coal seam; S3. Establish a mechanical analysis model of the stability of the immediate roof to solve the supporting force of the immediate roof: Ignore the influence of the broken angle of the immediate roof, set the right side of the immediate roof as fixed support, and its left boundary as a free end, simplify the supporting structure of the immediate roof, the backfill body beside the roadway and the solid coal seam into a mechanical analysis model of the stability of the immediate roof, and solve the supporting force of the immediate roof by performing the following steps: S3.

1. Force analysis of the direct roof mechanical model: including obtaining the reaction load F of the key block B on the direct roof upper boundary M , the lower boundary is subject to the resistance of the tunnel support f s , the supporting stress σ provided by the solid coal wall to the direct roof y , roadside support resistance f d and the supporting stress F provided by the falling gangue to the key block B g ; S3.2 Derivation and M o : and F M 、f s , σ y 、f d and F g The moment corresponding to the solid coal support point O, M o is the direct top bending moment, and M o The expression is: Where a is the width of the gob-side entry; b is the width of the filling body beside the entry; γ is the bulk density of the overlying rock layer; h1 is the thickness of the immediate top rock layer; σ t is the tensile strength of the direct top; S3.

3. Further solution and F M :According to the moment balance equation, the following formula is derived: S4. Establish the mechanical criterion for the stability of key block B: When key block B is rotating, the horizontal thrust on both sides is equal, that is, it satisfies T AB =T CB (13) The calculation formula of the occlusal contact length s of key block A and key block C to key block B is as follows: Where, θ is the rotation and sinking angle of key block B; When the key block B is stressed at point A, the total bending moment is 0, that is, ΣM A = 0, horizontal thrust T CB The calculation formula is as follows: Where Δ is the rotational sinking amount of the key block B; q is the load transferred by the upper weak rock layer and its deadweight borne by the basic top rock layer; According to formula (12), formula (13) and formula (14), the horizontal thrust T is obtained AB The calculation formula is as follows: S5. Determine the magnitude of horizontal thrust and shear force: When there is no extrusion failure at the hinge between key block B and key block C, the following expression is used: Where ψ is the contact friction coefficient between key block B and key block C; σ c is the compressive strength of key block B; When the horizontal thrust and shear force satisfy the judgment condition of formula (17), the support resistance calculation f of the roadside filling body is d1 The formula is as follows: Otherwise, the support resistance f of the backfill body beside the roadway d2 The calculation formula is as follows: In the formula, is the internal friction angle of the interface between coal and rock; S6. The calculation formula for the supporting resistance of the backfill body beside the roadway corresponding to the stability of the key block B of the gob-side roadway retention is: f dm2 =max(f d1 ,f d2 ) (20) S7. Calculate the strength of the backfill beside the roadway σ F , σ F The calculation formula is as follows: S8. According to equations (19), (20) and (21), the relationship curve between the support resistance and strength of the roadside filling body and the width of the roadside filling body is drawn. According to the relationship curve, the strength σ of the roadside filling body is fitted. F and the width b of the backfill beside the roadway, the fitting curve σ F The expression is: σ F =V-Iln(bO),R 2 =P (22) In the formula, V, I, and O are fitting coefficients; R 2 is the correlation coefficient; S9, according to σ F The fitting curve of the minimum lane filling width b is obtained min , and meet the minimum lane filling width b min The minimum strength of the filling body beside the road is min .

2. A method for determining the width and strength of the filling body beside a gob-side entry retaining according to claim 1, characterized in that: In the calculation of b min and σ min After that, the width and strength of the backfill beside the roadway are appropriately enhanced during on-site construction. When the width and support of the backfill beside the roadway along the gob-retained roadway reach σ0 and b0, the requirements of the gob-retained roadway can be met. The expressions of σ0 and b0 are: b0=k0b min (23) σ0=k0σ min (24) In the formula, k0 is the safety factor, and k0>1.

3. The method for determining the width and strength of the filling body beside the gob-side entry retaining according to claim 1 is characterized in that: In S1, when the key block B is in a stable state, the deformation of the surrounding rock of the gob-side entry below the support structure is small, and the stability of the surrounding rock structure of the entry depends on the stability of the key block B.

4. A method for determining the width and strength of the filling body beside a gob-side entry retaining according to claim 1, characterized in that: In S2.1, the calculation formulas for the working face periodic pressure step L and the roof lateral breaking length L2 are as follows: Where h is the thickness of the basic top rock layer; R T is the tensile strength of the basic top rock layer; L s is the inclination length of the working face.

5. The method for determining the width and strength of the filling body beside the gob-side entry retaining according to claim 1 is characterized in that: In S2.2, the roof fracture position and the supporting force of the solid coal wall σ y The calculation formula for the width x0 of the limit equilibrium zone of the elastic-plastic interface with the coal body is as follows: In the formula, h c is the height of gob-side entry; c0 is the cohesion of the interface between coal and rock; k is the stress concentration coefficient; λ represents the lateral pressure coefficient; H is the burial depth of the coal seam; P x is the support strength of the solid coal seam; α is the inclination of the coal seam.

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