A roadway side support design method based on shear failure theory

Abstract

This invention discloses a roadway sidewall support design method based on shear failure theory. Addressing the problem that existing suspension theories cannot explain the sidewall failure mechanism, it proposes that sidewall failure is essentially shear slip; by establishing shear angle... θ =45°- Φ / 2. Height of loose material in the tunnel roof h 1=( B +2 H tan θ ) / (2 f ), width of loose body in the side J = H tan θ, Determine the number of anchor bolts per row N = K ( G 1+ G 2) / ( T tan θ This method employs a core formula system to accurately calculate the number, spacing, and length of rock bolts in the ribbed wall. All parameters in this method are directly related to the mechanical properties of the surrounding rock. Through the principle of mechanical equilibrium, it accurately calculates the rock bolt support parameters for the roadway ribbed wall, conforming to the ribbed wall shear failure mechanism. The design results are consistent with engineering practice. This method not only explains the ribbed wall failure mechanism but also provides calculation results that are highly consistent with reality, demonstrating significant safety and economic benefits.

Description

Technical Field

[0001] This invention relates to the field of coal mine roadway support, and in particular to a roadway sidewall support design method based on shear failure theory. Background Technology

[0002] Roadways are the lifeline of a mine, undertaking critical tasks such as personnel movement, ventilation, and transportation. After roadway excavation, the surrounding rock transforms from its original stress state to a low-stress state, with the shallow surrounding rock becoming loose under low-stress conditions. For flat-roof, straight-wall roadways, the failure modes of the surrounding rock are typically roof tensile failure and sidewall shear failure. Existing technologies mainly suffer from the following problems: 1. Unreasonable theoretical basis: The design of side support in coal mine roadways in my country generally adopts the suspension theory formula. ( Q For anchor bolt anchoring force, K For safety reasons, H r The thickness of the loosened rock layer at the top. The formula for calculating the spacing between anchor bolts (based on the unit weight of the roof) is the same as the formula for calculating roof support. However, the side anchor bolts are not suspension bands, and the main failure mode of the side is shear slip rather than vertical collapse. Using the roof collapse height as a calculation parameter is seriously inconsistent with the actual situation in the project. 2. Unscientific design methods: Some mines directly select side support parameters using analogy or empirical methods, which lacks theoretical support, cannot explain the mechanical principles of side support, and is difficult to quantify based on specific geological conditions; 3. Insufficient safety: Existing design methods fail to accurately reflect the failure mechanism of the surrounding rock (shear shearing of the shoulder socket, bulging deformation of the side), resulting in unreasonable design of support parameters (especially the number, spacing and anchoring depth of anchor bolts), which poses safety hazards.

[0003] Therefore, it is urgent to establish a set of roadway sidewall support design theories and methods that conform to the sidewall shear failure mechanism, have reasonable parameter selection, and have a rigorous calculation process. Summary of the Invention

[0004] To overcome the irrationality of using suspension theory to design roadway sidewall support in existing technologies, and to solve the problem of lacking a reasonable theoretical formula for roadway sidewall support design by accurately calculating the roadway sidewall anchor support parameters through the principle of mechanical equilibrium, this application provides a roadway sidewall support design method based on shear failure theory.

[0005] This application provides a roadway sidewall support design method based on shear failure theory, employing the following technical solution: A roadway sidewall support design method based on shear failure theory includes the following steps: S1. Based on the internal friction angle of the surrounding rock of the side wall FDetermine the shear angle of the side i ,satisfy i =45°- F / 2; S2. Calculate the height of loose material in the roadway roof. h 1=( B +2 H tan i ) / (2 f ),in B The width of the alleyway, H The height of the tunnel, f The Protodextrin coefficient for the roof; S3. Calculate the width of the loose material above the side panel. J = H tan i ; S4. Calculate the total shear force of the loose mass. J 剪 =( G 1+ G 2) cos i ,in G 1 represents the weight of the loose material in the top plate above the side panel. G 2 represents the weight of the loose material in the side panel; S5. Calculate the reverse shear force of a single anchor bolt. J 反剪 = T sin i ,in T Design anchoring force for a single anchor bolt; S6. Determine the number of anchor bolts per row based on mechanical equilibrium. N = KJ 剪 / J 反剪 = K ( G 1+ G 2) / ( T tan i ), K For safety factor; S7. Calculate the spacing between and row spacing of the side anchor bolts; S8. Calculate the average loosening depth of the roadway sidewalls. = H tan i / 2 and determine the anchor bolt length L > L 1+ + L 3, of which L 1 represents the exposed length of the anchor bolt. L 3 represents the depth at which the anchor bolt is inserted into the stable coal and rock strata.

[0006] Optionally, in S3, the weight of the loose material in the top plate above the side is... G 1= oh 1 HR tan i ,in a This refers to the spacing between the top slab anchor bolts. R This is the unit weight of the surrounding rock of the roof.

[0007] Optionally, in S3, the weight of the loose material in the side panel... G 2= aH 2 R 帮 tan i / 2, where R 帮 The unit weight of the surrounding rock is used to determine the density of the surrounding rock.

[0008] Optionally, in S5, the safety factor K The value is taken from 1.0 to 2.0, depending on the shear strength of the surrounding rock and the burial depth of the tunnel. The value is larger when the strength is low and the burial depth is high.

[0009] Optionally, in S6, one method for calculating the spacing between and row spacing of the side anchor bolts is: anchor bolt spacing b 帮 =( H - h u - h d ) / ( n -1), where h u This refers to the distance between the upper anchor bolt and the top plate. h d This refers to the distance between the lower anchor bolt and the bottom plate. n The actual number of anchor bolts to be installed and n ≥ N The anchor bolt spacing is taken as 1 meter.

[0010] Optionally, in S6, another method for calculating the spacing between anchor bolts and the row spacing is: [The remaining text appears to be incomplete and requires further context.] , R a The average unit weight of coal and rock; the anchor bolt row spacing is equal to the anchor bolt spacing.

[0011] Optionally, in S7, the anchor bolt is anchored into the stable rock layer to a certain depth. L 3. Not less than 0.7m, and not less than the length of two resin anchors.

[0012] In summary, this application includes at least one of the following beneficial technical effects: 1. All calculation parameters are directly related to the mechanical properties of the surrounding rock of the rib, including internal friction angle, unit weight, and roadway geometry, avoiding the use of irrelevant parameters such as roof fall height, and the design results are more in line with engineering reality; the system establishes a rib support design theory based on shear failure mechanism, correcting the long-standing industry misuse of suspension theory; 2. All parameters in this method are directly related to the mechanical properties of the surrounding rock. The number of anchor bolts is accurately calculated through the mechanical equilibrium equation. Compared with the empirical analogy method, the design results are consistent with the actual engineering situation. Under the premise of ensuring safety, over-support can be avoided, saving about 15% to 20% of the project cost. 3. The method in this application not only explains the failure mechanism of the rib but also the calculation results are very consistent with reality, and have significant safety and economic benefits; it is recommended that the anchoring depth into stable rock strata be ≥0.7m (not less than the length of two resin anchoring agents) to ensure that the anchoring force is fully realized and significantly reduce the rib breakage accident rate. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the shear failure mechanics model of the roadway sidewall in an embodiment of this application.

[0014] Figure 2 This is the design drawing of the support section of the 3402 transport roadway in the embodiment of this application. Detailed Implementation

[0015] The present application will be further described in detail below with reference to all the accompanying drawings.

[0016] This application discloses a roadway sidewall support design method based on shear failure theory.

[0017] Example Reference Figure 1 , S1. Determination of the shear angle of the side panel: The actual shear failure surface of the rib is less than 45°, and the shear angle is different from the internal friction angle of the surrounding rock of the rib. i The relationship is: i =45°- F / 2; In the formula: i —Shear angle of the side (°). F —Angle of friction within the surrounding rock of the side wall (°).

[0018] S2. Calculation of the height of loose material in the tunnel roof: h 1=( B +2 H tan i ) / (2 f ); In the formula: h1 — Height of loose material in the tunnel roof (m). B —Wide width of the alley (m) H —Tunnel height (m) f —Protodextrin coefficient of the roof.

[0019] S3. Width of loose material above the side J calculate: J = H tan i ; In the formula: J — Width of loose material above the side (m).

[0020] Loose body weight calculation: (1) Weight of loose material in the top plate above the side: G 1= oh 1 JR = oh 1 HR tan i ; In the formula: G 1 — Weight of loose material in the top plate above the side (kN). a — Spacing of anchor bolts in the top slab (m). R —Unit weight of surrounding rock in the roof (kN / m³) 3 ).

[0021] (2) Weight of loose material in the side panel: G 2= aH 2 R 帮 tan i / 2; In the formula: G 2 — Weight of loose material in the side panel (kN). R 帮 —Unit weight of surrounding rock in the rib area (kN / m³) 3 ) S4. Calculation of shear force and counter-shear force: Total shear force of loose body: J 剪 =( G 1+ G 2) cos i ; S5. The counter-shear force generated by a single anchor bolt: J 反剪 = T sin i ; In the formula:T —Design anchoring force of a single anchor bolt (kN). K —Safety factor (generally taken as 1.0~2, the value is determined according to the shear strength of the surrounding rock and the burial depth of the tunnel; the value is larger for lower strength and greater burial depth).

[0022] S6. Calculation of the number of anchor bolts per row: N = KJ 剪 / J 反剪 = K ( G 1+ G 2) / ( T tan i ); In the formula: N —Number of anchor bolts per row; K —Safety factor (generally taken as 1.0~2, the value is determined according to the shear strength of the surrounding rock and the burial depth of the tunnel; the value is larger for lower strength and greater burial depth).

[0023] S7. Determination of the spacing and row spacing of the side anchor bolts: (1) Calculation method for the spacing between and row of anchor bolts in the side wall b 帮 =( H - h u - h d ) / ( n -1); In the formula: b 帮 — Anchor spacing (m) h u — Distance from the top anchor bolt to the top plate (m). h d — Distance from the lower anchor bolt to the bottom plate (m). n —Actual number of anchor bolts deployed ( n ≥ N ); The anchor bolt spacing is directly taken as 1 meter.

[0024] (2) Method 2 for calculating the spacing between and row of anchor bolts in the side wall ; In the formula: a 帮 — Spacing between and row of anchor bolts on the side (m). R a — Average bulk density of coal and rock (kN / m³) H s —Average loosening depth of roadway sidewalls (m); anchor bolt row spacing is equal to anchor bolt spacing.

[0025] Calculation of average loosening depth of roadway sidewalls: H s = H tan i / 2; In the formula: H s —Average loosening depth of the tunnel sidewalls (m).

[0026] S8. Anchor Bolt Length Determination L > L 1+ H s + L 3 In the formula: L —Total anchor length (m) L 1 — Exposed length of anchor bolt (generally 0.1m). L 3——Anchoring depth into stable rock strata (generally ≥0.7m, and not less than the length of two resin anchoring agents).

[0027] Reference Figure 1 and Figure 2 Taking the 3402 transport roadway of a mine in Shandong as an example, the engineering application effect of the present invention is verified.

[0028] (I) Project Overview Tunnel cross-section: rectangular, tunnel width B =5.5m, net width 5.2m; tunnel height H =3.2m, net height 3.0m.

[0029] Surrounding rock conditions: Protodyakonov coefficient of the roof f =4, unit weight of surrounding rock in the roof R =26.3kN / m³; the side is coal seam, and the friction angle of the surrounding rock in the side is... F =29.5°, unit weight of surrounding rock at the base R 帮 =13.2kN / m³.

[0030] Support material: MSGLD-400(X) high-strength threaded steel resin anchor rod, with a single anchor rod designed anchoring force T=80kN.

[0031] (II) Calculation process Step 1: Determine the shear angle of the side panel: i =45° - 29.5° / 2 = 30.25° Step 2: Calculate the height of loose material in the tunnel roof: h1=(5.5+2×3.2×tan30.25°) / (2×4)=1.14m Step 3: Calculate the width of the loose material above the side panel: J =3.2 × tan30.25° = 1.8m Step 4: Calculation of loose mass weight: Weight of loose material on top plate above the side G 1 = 1 × 1.14 × 1.8 × 26.3 = 54 kN Weight of loose body in the side G 2 = (1 × 3.2) 2 ×tan30.25°×13.2) / 2=38.3kN Step 5: Calculate the number of anchor bolts (take...) K =2): N = [2 × (54 + 38.3)] / (80 × tan30.25°) = 4 roots Step 6: Determine the spacing and row spacing of the side anchor bolts: Method 1: b 帮 =(3.2-0.2-0.3) / (4-1)=0.9m Method 2: a 帮 =[80tan30.25° / (2×0.92×19.75)] 1 / 2 =1.1m Based on calculations using both methods, the spacing between anchor bolts was determined to be 0.9m × 0.9m. Step 7: Determine the anchor bolt length: =(3.2×tan30.25°) / 2=0.91m L >0.1 + 0.91 + 0.7 = 1.71m Design anchor bolt length value L =1800mm.

[0032] (III) Comparison of Implementation Results (1) The present invention adopts shear theory, and the calculation parameters are directly related to the failure mode of the side, which is superior to the original suspension theory.

[0033] (2) The calculated anchor spacing of 900mm in this invention is completely consistent with the actual value. The original calculated anchor spacing was 1860mm, with a human intervention range of 52%, eliminating the arbitrariness of human data selection. The deformation of the sidewall during the roadway service period is reduced by more than 30%.

[0034] (3) The present invention is designed with an anchoring depth of 0.7m to ensure the anchoring force is achieved, while the original design is only 0.3m, which improves the anchoring reliability by 133%.

[0035] The implementation principle of a roadway sidewall support design method based on shear failure theory in this application embodiment is as follows: by establishing the shear angle i =45°- F / 2. Height of loose material in the tunnel roof h 1=( B +2 H tan i ) / (2 f ), width of loose body above the side =Htanθ、 Determine the number of anchor bolts per row N = K ( G 1+ G 2) / ( T tan i This method utilizes core theoretical calculation formulas to accurately calculate the number, spacing, row spacing, and length of rock face anchors. All parameters in this method are directly related to the mechanical properties of the surrounding rock. Through the principle of mechanical equilibrium, it accurately calculates the rock face anchor support parameters, and the design results conform to engineering realities. In contrast, the currently used suspension calculation method cannot explain the rock face failure mechanism, and the calculated results are several times higher than the actual values, thus failing to provide guidance. This proposed method not only explains the rock face failure mechanism but also provides calculation results that are highly consistent with reality, demonstrating significant safety and economic benefits.

[0036] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A roadway sidewall support design method based on shear failure theory, characterized in that, Includes the following steps: S1. Based on the internal friction angle of the surrounding rock of the side wall Φ Determine the shear angle of the side θ ,satisfy θ =45°- Φ / 2; S2. Calculate the height of loose material in the roadway roof. h 1=( B +2 H tan θ ) / (2 f ),in B The width of the alleyway, H The height of the tunnel, f The Protodextrin coefficient for the roof; S3. Calculate the width of the loose material above the side panel. J = H tan θ ; S4. Calculate the total shear force of the loose mass. J 剪 =( G 1+ G 2) cos θ ,in G 1 represents the weight of the loose material in the top plate above the side panel. G 2 represents the weight of the loose material in the side panel; S5. Calculate the reverse shear force of a single anchor bolt. J 反剪 = T sin θ ,in T Design anchoring force for a single anchor bolt; S6. Determine the number of anchor bolts per row based on mechanical equilibrium. N = KJ 剪 / J 反剪 = K ( G 1+ G 2) / ( T tan θ ), K For safety factor; S7. Calculate the spacing between and row spacing of the side anchor bolts; S8. Calculate the average loosening depth of the roadway sidewalls. = H tan θ / 2 and determine the anchor bolt length L > L 1+ + L 3, of which L 1 represents the exposed length of the anchor bolt. L 3 represents the depth at which the anchor bolt is inserted into the stable coal and rock strata.

2. The roadway side support design method based on shear failure theory according to claim 1, characterized in that: In S3, the weight of the loose material in the top plate above the side is... G 1= ah 1 HR tan θ ,in a This refers to the spacing between the top slab anchor bolts. R This is the unit weight of the surrounding rock of the roof.

3. The roadway sidewall support design method based on shear failure theory according to claim 1, characterized in that: In S3, the weight of the loose material in the side panel G 2= aH 2 R 帮 tan θ / 2, where R 帮 The unit weight of the surrounding rock is used to determine the density of the surrounding rock.

4. The roadway side support design method based on shear failure theory according to claim 1, characterized in that: In S5, the safety factor K The value is taken from 1.0 to 2.0, depending on the shear strength of the surrounding rock and the burial depth of the tunnel. The value is larger when the strength is low and the burial depth is high.

5. The roadway sidewall support design method based on shear failure theory according to claim 1, characterized in that: In S6, one method for calculating the spacing between and row spacing of the side anchor bolts is: anchor bolt spacing b 帮 =( H - h u - h d ) / ( n -1), where h u This refers to the distance between the upper anchor bolt and the top plate. h d This refers to the distance between the lower anchor bolt and the bottom plate. n The actual number of anchor bolts to be installed and n ≥ N The anchor bolt spacing is taken as 1 meter.

6. The roadway sidewall support design method based on shear failure theory according to claim 1, characterized in that: In S6, another method for calculating the spacing between and row spacing of the side anchor bolts is: spacing between and row spacing of anchor bolts , R a The average unit weight of coal and rock; the anchor bolt row spacing is equal to the anchor bolt spacing.

7. The roadway side support design method based on shear failure theory according to claim 1, characterized in that: In step S7, the anchor bolt is anchored into the stable rock layer to a certain depth. L 3. Not less than 0.7m, and not less than the length of two resin anchors.

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