A roadway anchor rod supporting quantitative design method based on cross-section steel ratio reinforcement effect

Abstract

The application discloses a kind of roadway anchor rod supporting quantitative design method based on section steel ratio strengthening effect, comprising: obtaining the parameters of roadway periphery;Obtain rock sample uniaxial compressive strength, elastic stage stiffness and elastic modulus;Obtain the initial shear strength parameters of the surrounding rock of the roadway to be designed, carry out constant normal stiffness direct shear test on unanchored rock sample, obtain the initial cohesion and initial internal friction angle of rock sample;Obtain the rock mass structure parameters of the roadway to be designed;Obtain the equivalent strength parameters of the unanchored rock mass of the roadway to be designed;Obtain the apparent cohesion, apparent internal friction angle and apparent stiffness of the anchored rock mass under different section steel ratio conditions, and establish a functional relationship;Based on the functional relationship, combined with the actual maximum principal stress of the main bearing area, judge whether the surrounding rock of the main bearing area meets the stability requirements;According to the judgment result of the stability of the surrounding rock of the main bearing area, obtain the anchor rod supporting parameters.The application can solve the problem that the design result is difficult to accurately evaluate.

Description

Technical Field

[0001] This invention belongs to the field of underground engineering surrounding rock support design technology, and particularly relates to a quantitative design method for roadway anchor support based on the steel content ratio strengthening effect of the cross section. Background Technology

[0002] Rock bolt support is one of the most widely used methods for controlling surrounding rock in coal mine roadways, tunnels, and underground caverns. Existing rock bolt support design methods mainly include engineering analogy, empirical formulas, and numerical simulation trial methods. Engineering analogy and empirical formulas rely on existing engineering experience and are difficult to accurately reflect the support effect under different surrounding rock structures, stress environments, and rock bolt parameters. Although numerical simulation trial methods can analyze the deformation and plastic zone changes of surrounding rock, they usually treat rock bolts as independent structural units or reduce or increase rock mass parameters through empirical parameters, making it difficult to directly establish a quantitative relationship between rock bolt diameter, spacing, and density and the increase in anchored rock mass strength.

[0003] In practical engineering, rock bolt support does not only constrain local blocks but also forms a reinforced anchoring ring of a certain thickness around the roadway. This reinforced anchoring ring, together with the surrounding rock, forms a load-bearing system, providing a certain confining pressure to the deep main load-bearing zone, thereby improving the triaxial stress state of the surrounding rock and enhancing the bearing capacity of the main load-bearing zone. However, existing technologies lack a method that can quantitatively describe the influence of cross-sectional steel content on the apparent strength parameters of the anchored rock mass based on experiments, and further be used for back-calculation of roadway support parameters.

[0004] Therefore, it is necessary to propose a new quantitative design method for roadway anchor bolt support, which links anchor bolt support parameters, anchor rock strength enhancement, anchor reinforcement ring bearing capacity and surrounding rock stability in the main bearing area, so as to achieve quantitative determination of anchor bolt support parameters. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a quantitative design method for roadway anchor bolt support based on the strengthening effect of cross-sectional steel content. This method can solve the problems of existing anchor bolt support designs relying on experience, lack of quantitative correlation between support parameters and surrounding rock strengthening effect, and difficulty in accurately evaluating design results.

[0006] To achieve the above objectives, this invention provides a quantitative design method for roadway anchor bolt support based on the strengthening effect of cross-sectional steel content, comprising: S1: Determine the original rock stress state and actual stress of the main bearing area of ​​the roadway to be designed: Use in-situ geostress testing to obtain the three-dimensional stress tensor of the original rock in the area where the roadway to be designed is located. Based on the original rock three-dimensional stress tensor, determine the maximum principal stress, intermediate principal stress, minimum principal stress and the direction of each principal stress. Combined with the axial orientation, cross-sectional shape and cross-sectional dimensions of the roadway to be designed, use analytical calculation and / or numerical calculation to obtain the stress distribution of the surrounding rock after the roadway is excavated, determine the location of the main bearing area and the actual maximum principal stress of the main bearing area, and use the actual maximum principal stress of the main bearing area as the engineering load parameter for subsequent stability judgment of the main bearing area. S2: Determine the initial compressive mechanical parameters of the intact rock surrounding the roadway to be designed: Collect rock samples of the roadway surrounding rock corresponding to the in-situ stress test area described in S1, prepare rock samples of predetermined size and conduct uniaxial compression tests to obtain the uniaxial compressive strength, axial stiffness in the elastic stage, and elastic modulus of the rock samples; wherein, the axial stiffness in the elastic stage of the rock samples is calculated based on the load increment and axial displacement increment in the elastic stage of the rock samples, and the axial stiffness in the elastic stage is used as the normal constraint stiffness of the constant normal stiffness direct shear test in S3 and S6, the uniaxial compressive strength is used as the intact rock uniaxial compressive strength for determining the equivalent strength parameters of the unanchored rock mass in S5, and the elastic modulus is used as the unanchored reference parameter for evaluating the stiffness strengthening effect of the anchored rock samples in S6. S3: Determine the initial shear strength parameters of the unanchored rock samples: Using multiple groups of unanchored rock samples from the same sampling area, with the same lithology and size as in S2, set the axial stiffness of the rock sample obtained in S2 to the normal constraint stiffness of the constant normal stiffness direct shear test, and apply different initial normal forces to each group of unanchored rock samples. Conduct constant normal stiffness direct shear tests under the same normal constraint stiffness and different initial normal forces. Based on the initial normal force, normal displacement during the shearing process, and the normal constraint stiffness of each group of unanchored rock samples, determine the real-time normal force and real-time normal stress during the shearing process, and obtain the peak shear stress of each group of tests and the corresponding real-time normal stress when the peak shear stress is reached. Perform strength fitting based on the peak shear stress of each group of tests and its corresponding real-time normal stress to obtain the initial cohesion and initial internal friction angle of the unanchored rock samples, and use the initial cohesion and initial internal friction angle as the unanchored reference parameters for evaluating the steel content strengthening effect of the section in step S6. S4: Determine the rock mass structural parameters and Hoek-Brown calculation parameters for the roadway to be designed: Through on-site geological surveys and rock mass quality evaluation, obtain the structural plane spacing, structural plane attitude, structural plane filling status, rock mass integrity, geological strength index GSI, and disturbance coefficient D of the surrounding rock of the roadway to be designed. Then, determine the intact rock material constant m by fitting the rock triaxial compression test or based on the corresponding lithology. iThe geological strength index GSI, disturbance coefficient D, and intact rock material constant m are used to determine the geological strength index GSI, disturbance coefficient D, and intact rock material constant m. i As input parameters for converting the complete rock mechanics parameters obtained in S2 into equivalent rock mechanics parameters of the unanchored rock mass in the field in S5; S5: Determine the equivalent initial mechanical parameters of the unanchored rock mass in the tunnel to be designed: Combine the uniaxial compressive strength of intact rock obtained in S2 with the geological strength index GSI, disturbance coefficient D, and intact rock material constant m obtained in S4. i Substituting the Hoek-Brown strength criterion, the Hoek-Brown strength parameters and nonlinear strength envelope of the unanchored rock mass in the roadway to be designed are determined. Based on the stress range of the main bearing area determined in S1, the nonlinear strength envelope is equivalently transformed to obtain the equivalent cohesion, equivalent internal friction angle, and uniaxial compressive strength of the unanchored rock mass in the roadway to be designed. Combined with the complete rock elastic modulus obtained in S2 and the rock mass structure parameters obtained in S4, the equivalent elastic modulus of the unanchored rock mass is obtained. The equivalent cohesion, equivalent internal friction angle, and equivalent elastic modulus of the unanchored rock mass are used as the rock mass-scale reference parameters for calculating the apparent mechanical parameters of the anchored rock mass in S6. S6: Establish the functional relationship between the steel content of the cross section and the apparent mechanical parameters of the anchored rock mass in the field: Use rock samples with the same sampling area, lithology, size and initial conditions as S2 and S3, and set different diameters and / or different numbers of anchor rods in the rock samples to form multiple anchored rock samples with different cross section steel contents; S7: Set the axial stiffness of the rock sample in the elastic stage obtained in S2 as the normal constraint stiffness of the direct shear test of the constant normal stiffness of each group of anchored rock samples, and use the same initial normal force classification as in S3. Under the same normal constraint stiffness, the same initial normal force classification and different steel ratios of the cross sections, carry out the direct shear test of the constant normal stiffness of each group of anchored rock samples. S8: Based on the peak shear stress of each group of anchored rock samples and the real-time normal stress corresponding to the peak shear stress, obtain the apparent cohesion and apparent internal friction angle of anchored rock samples under different steel ratios of cross sections, and obtain the apparent stiffness or apparent elastic modulus of anchored rock samples based on the load-displacement relationship before and / or during the shearing process. S9: Using the initial cohesion and initial internal friction angle of the unanchored rock sample obtained in S3 and the elastic modulus of the unanchored rock sample obtained in S2 as the benchmarks for indoor tests, determine the relationship between the cohesion strengthening function, the internal friction angle strengthening function, the elastic modulus strengthening function and the steel content of the section. S10: Apply the cohesion strengthening function, internal friction angle strengthening function, and elastic modulus strengthening function to the equivalent cohesion, equivalent internal friction angle, and equivalent elastic modulus of the unanchored rock mass obtained in S5, respectively, to establish the functional relationship between the apparent cohesion, apparent internal friction angle, and apparent elastic modulus of the anchored rock mass and the equivalent initial mechanical parameters and cross-sectional steel ratio of the unanchored rock mass.

[0007] Compared with the prior art, the present invention has the following advantages and technical effects: 1. This invention transforms anchor support parameters into cross-sectional steel content indices and establishes a quantitative relationship between anchor diameter, spacing, row spacing and anchor rock mechanical parameters.

[0008] 2. This invention obtains the apparent strength parameters of the anchored rock mass through direct shear tests of the constant normal stiffness of anchored rock samples, avoiding the problem of relying on empirical values ​​in traditional anchor bolt support design.

[0009] 3. This invention equates the reinforcement range of the anchor bolts around the roadway to an anchor reinforcement ring, calculates the constraint pressure that the anchor reinforcement ring can provide to the main bearing area, and realizes the transformation of the anchor bolt support function from "local component function" to "surrounding rock reinforcement ring function".

[0010] 4. This invention substitutes the confining pressure provided by the anchor reinforcement ring into the Hoek-Brown strength criterion to determine the stability of the surrounding rock in the main bearing area, thereby achieving a unified evaluation among anchor bolt parameters, anchored rock mass strength, and surrounding rock stability.

[0011] 5. This invention can back-calculate the anchor bolt diameter, spacing, row spacing, and effective reinforcement length based on the stability of the main load-bearing area, thereby improving the scientific, quantitative, and reliable nature of roadway anchor bolt support design. Attached Figure Description

[0012] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a flowchart of a quantitative design method for roadway anchor bolt support based on the strengthening effect of cross-sectional steel content, according to an embodiment of the present invention. Figure 2 This is a schematic diagram of a direct shear test with constant normal stiffness of anchored rock samples according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of the roadway surrounding rock anchoring reinforcement ring and the main bearing area according to an embodiment of the present invention; Among them, 1. Tunnel excavation outline, 2. Anchor bolt, 3. Anchoring reinforcement ring, 4. Main bearing area, 5. Inner surface of anchoring reinforcement ring, 6. Outer surface of anchoring reinforcement ring, 7. Constraint pressure, 8. Cubic rock sample, 9. Shear surface, 10. Shear direction. Detailed Implementation

[0013] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0014] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0015] This embodiment proposes a quantitative design method for roadway anchor support based on the strengthening effect of cross-sectional steel content, such as... Figure 1 As shown, the specific steps include: Obtain the maximum principal stress, minimum principal stress, intermediate principal stress, and direction of principal stress around the roadway; Rock samples were collected from the surrounding rock of the tunnel and uniaxial compression tests were conducted to obtain the uniaxial compressive strength, elastic stage stiffness and elastic modulus of the rock samples; To obtain the initial shear strength parameters of the surrounding rock of the roadway to be designed, a direct shear test with constant normal stiffness was carried out on the unanchored rock sample to obtain the initial cohesion and initial internal friction angle of the rock sample. Obtain the rock mass structure parameters of the tunnel to be designed; The equivalent strength parameters of the unanchored rock mass in the roadway to be designed were obtained using the Hoek-Brown strength criterion. The apparent cohesion, apparent internal friction angle, and apparent stiffness of the anchored rock mass under different cross-sectional steel ratios were obtained, and the functional relationships between the apparent cohesion, apparent internal friction angle, and apparent stiffness of the anchored rock mass and the initial parameters of the rock mass and the cross-sectional steel ratio were established. Based on the aforementioned functional relationship, and in conjunction with the actual maximum principal stress in the main bearing area, it is determined whether the surrounding rock in the main bearing area meets the stability requirements. Based on the assessment results of the stability of the surrounding rock in the main bearing area, the anchor bolt support parameters are obtained.

[0016] Specifically, it mainly includes: S1, obtain the original rock stress parameters of the roadway to be designed, and obtain the maximum principal stress, minimum principal stress, intermediate principal stress and principal stress direction around the roadway through on-site in-situ stress test; S2, obtain the basic mechanical parameters of the surrounding rock of the roadway to be designed, collect rock samples of the surrounding rock of the roadway to be designed, prepare cubic rock samples with a size of 100mm×100mm×100mm, carry out uniaxial compression test, and obtain the uniaxial compressive strength, elastic stage stiffness and elastic modulus of the rock sample. S3, obtain the initial shear strength parameters of the surrounding rock of the roadway to be designed, carry out a direct shear test with constant normal stiffness on the unanchored rock sample, and obtain the initial cohesion c0 and initial internal friction angle φ0 of the rock sample based on the peak shear stress under different normal stress conditions. S4, obtain the rock mass structure parameters of the roadway to be designed, and obtain the rock mass structure plane spacing, structure plane attitude, rock mass integrity, GSI value and disturbance coefficient D through field investigation; S5. The equivalent strength parameters of the unanchored rock mass in the roadway to be designed are obtained by adopting the Hoek-Brown strength criterion, and the equivalent cohesion, equivalent internal friction angle and uniaxial compressive strength of the unanchored rock mass are calculated. S6. Establish a quantitative relationship between the cross-sectional steel content and the apparent strength parameters of the anchored rock mass. Anchors of different diameters are installed at the center of 100mm×100mm×100mm cubic rock samples, with the anchor axis perpendicular to the shear direction. Constant normal stiffness direct shear tests are conducted on anchored rock samples under different cross-sectional steel content conditions to obtain the apparent cohesion of the anchored rock mass under different cross-sectional steel content conditions. Apparent internal friction angle and apparent stiffness and establish , , The functional relationship between the rock mass initial parameters and the steel content η of the cross section; such as Figure 2 As shown, the specimen used in the direct shear test of the constant normal stiffness of the anchored rock sample is a cubic rock sample 8. The anchor rod 2 is installed in the cubic rock sample 8 and passes through the predetermined shear surface 9. The axis of the anchor rod 2 is perpendicular to the shear direction 10 so that the relative displacement formed during the shearing process is applied to the anchor rod 2, thereby reflecting the strengthening effect of the anchor rod 2 on the shear strength and shear deformation characteristics of the rock sample.

[0017] During the experiment, a preset initial normal force was applied to the normal direction of the cubic rock sample 8, and the axial stiffness of the rock sample in the elastic stage obtained in step S2 was set as the normal constraint stiffness of the constant normal stiffness direct shear test. Subsequently, relative shear loads were applied to the rock sample portions on both sides of the shear surface 9 along the shear direction 10, causing relative displacement on both sides of the shear surface 9. During the shearing process, the normal force was adjusted in real time according to the normal displacement of the cubic rock sample 8 and the normal constraint stiffness to obtain the real-time normal stress, shear stress, and shear displacement during the shearing process.

[0018] By varying the diameter and / or number of anchor bolts 2, multiple sets of anchored rock samples with different cross-sectional steel ratios were obtained. Under the same rock sample size, initial normal force classification, and normal constraint stiffness, constant normal stiffness direct shear tests were conducted along the same shear direction 10. Based on the peak shear stress and corresponding real-time normal stress at which the cubic rock sample 8 under different cross-sectional steel ratios fails along the shear plane 9, the apparent cohesion and apparent internal friction angle of the anchored rock samples were obtained. The apparent stiffness of the anchored rock samples was then obtained based on the load-displacement relationship.

[0019] The direct shear test of the unanchored rock sample with constant normal stiffness in step S3 adopts the same method as... Figure 2 The test results showed the same rock sample size, shear plane 9, shear direction 10, initial normal force classification, and normal constraint stiffness. The difference was that the cubic rock sample 8 did not have anchor bolts 2 installed. This was used to obtain the initial shear strength parameters of the unanchored rock sample, which served as a benchmark for evaluating the strengthening effect of anchor bolts 2.

[0020] S7. Calculate the steel content η of the on-site section based on the anchor bolt diameter, spacing, and row spacing to be used at the engineering site. Substitute η into the functional relationship established in step S6 to obtain the apparent cohesion of the on-site anchored rock mass. Apparent internal friction angle and apparent stiffness ; S8, the effective reinforcement range of the anchor bolts around the roadway to be designed is equivalent to an anchoring reinforcement ring, based on... Apparent internal friction angle and apparent stiffness Calculate the bearing capacity of the anchoring reinforcement ring and determine the confining pressure that the anchoring reinforcement ring can provide to the outer main bearing zone under the condition that the stress on its inner surface does not exceed the uniaxial compressive strength of the anchored rock mass. ; S9 will constrain the confining pressure Substitute the Hoek-Brown strength criterion to calculate the ultimate strength of the surrounding rock in the main bearing area under the confined pressure condition, and determine whether the surrounding rock in the main bearing area is damaged based on the actual maximum principal stress in the main bearing area. S10: When the surrounding rock of the main bearing area meets the stability requirements, output the anchor bolt support parameters; when the surrounding rock of the main bearing area does not meet the stability requirements, adjust the anchor bolt diameter, spacing, row spacing or length, recalculate the steel content η of the on-site section and the bearing capacity of the anchor reinforcement ring, and repeat steps S7 to S9 until the surrounding rock of the main bearing area meets the stability requirements.

[0021] Furthermore, rock samples were collected from the surrounding rock of the tunnel, and 100mm×100mm×100mm cube rock samples were prepared. Uniaxial compression tests were conducted to obtain the stress-strain curves, uniaxial compressive strength, elastic stage stiffness, and elastic modulus of the rock samples.

[0022] Obtaining the elastic stage stiffness K0 and elastic modulus E0 includes: K0 = ΔP / Δu; E0 = K0L / A; Where ΔP is the load increment during the elastic stage of the rock sample, Δu is the axial displacement increment during the elastic stage of the rock sample, L is the height of the rock sample, and A is the pressure-bearing area of ​​the rock sample.

[0023] Furthermore, constant normal stiffness direct shear tests were conducted on unanchored rock samples to obtain the initial cohesion and initial internal friction angle of the rock samples, including: Based on the unanchored rock sample, a direct shear test with constant normal stiffness was carried out under different normal stress σ to obtain the peak shear stress τ corresponding to each normal stress. Based on the peak shear stress τ and normal stress σ, a linear fit is performed according to τ=c0+σtanφ0 to obtain the initial cohesion c0 and initial internal friction angle φ0 of the unanchored rock sample.

[0024] Specifically, constant normal stiffness direct shear tests were conducted on unanchored rock samples to obtain peak shear stresses under different normal stress conditions. The initial cohesion and initial internal friction angle of the unanchored rock samples were obtained by fitting the following formula: τ = c0 + σtanφ0; In the formula, τ is the peak shear stress, σ is the normal stress, c0 is the initial cohesion, and φ0 is the initial internal friction angle.

[0025] Obtaining rock mass structural parameters and determining the strength of unanchored rock mass includes: The spacing between rock mass structural planes, the orientation of the structural planes, the filling condition of the structural planes, the integrity of the rock mass, the GSI value, and the disturbance coefficient D were obtained through on-site geological surveys.

[0026] The Hoek-Brown strength criterion was used to determine the strength of unanchored rock mass: ; in: ; When the rock mass GSI ≥ 25, s = exp[(GSI – 100) / 9], a = 0.5; when the rock mass GSI < 25, s = 0, a = 0.65 – GSI / 200; In the formula, This represents the maximum principal stress at which the rock mass fails. For the minimum principal stress, The uniaxial compressive strength of intact rock. is the constant of the complete rock material, and mb, s, and a are the rock mass parameters.

[0027] Furthermore, establishing the functional relationships between the apparent cohesion, apparent internal friction angle, and apparent stiffness of the anchored rock mass and the initial parameters and steel content of the rock mass section includes: ; ; ; in, To enhance the apparent cohesion of the rock mass, To the apparent internal friction angle of the anchored rock mass, To increase the apparent elastic modulus of the anchored rock mass, This is the strengthening coefficient of the anchor bolt for the cohesion within the rock mass. is the strengthening coefficient of the friction angle between the anchor bolt and the rock mass. η is the reinforcement coefficient of the rock mass elastic modulus of the anchor bolt, which is dimensionless; η is the steel content of the rock mass section to which the anchor bolt is installed.

[0028] Specifically, establishing a cross-sectional steel ratio strengthening model includes: An anchor bolt was installed at the center of a 100mm×100mm×100mm cube rock sample, with the anchor bolt direction perpendicular to the shear direction. Multiple sets of anchored rock samples were prepared using anchor bolts of different diameters, so that each set of anchored rock samples had a different cross-sectional steel content.

[0029] The steel content of a cross section is defined as: ; Where: A = πd² / 4, ; In the formula, η is the steel content of the cross section, A is the cross-sectional area of ​​the anchor bolt, Aᵣ is the shear cross-sectional area of ​​the rock sample, and d is the diameter of the anchor bolt.

[0030] Direct shear tests with constant normal stiffness were conducted on anchored rock samples with different cross-sectional steel ratios to obtain the apparent cohesion of the anchored rock samples under different η conditions. Apparent internal friction angle and apparent stiffness .

[0031] Establish the following functional relationship: ; ; ; in, To enhance the apparent cohesion of the rock mass, To the apparent internal friction angle of the anchored rock mass, To increase the apparent elastic modulus of the anchored rock mass, This is the strengthening coefficient of the anchor bolt for the cohesion within the rock mass. is the strengthening coefficient of the friction angle between the anchor bolt and the rock mass. η is the reinforcement coefficient of the rock mass elastic modulus of the anchor bolt, which is dimensionless; η is the steel content of the rock mass section to which the anchor bolt is installed.

[0032] When the test results show that the internal friction angle decreases and the cohesion increases significantly after anchoring, Take a negative value; when the test results show that the internal friction angle increases after anchoring, Take the positive value.

[0033] Furthermore, based on the aforementioned functional relationship, determining whether the surrounding rock in the main bearing area meets the stability requirements, combined with the actual maximum principal stress in the main bearing area, includes: Based on the aforementioned functional relationship, the steel content of the on-site section is calculated according to the anchor bolt diameter, spacing, and row spacing to be used in the engineering site, thereby obtaining the apparent cohesion, apparent internal friction angle, and apparent stiffness of the on-site anchored rock mass. Based on the apparent cohesion, apparent internal friction angle, and apparent stiffness of the anchored rock mass at the site, the effective reinforcement range of the anchor bolts around the roadway is equivalent to an anchoring reinforcement ring. The confining pressure that this anchoring reinforcement ring can provide to the outer main bearing area under the condition that the stress on its inner surface does not exceed the uniaxial compressive strength of the anchored rock mass is calculated. Figure 3 As shown, the tunnel excavation forms a tunnel excavation outline 1. Multiple anchor bolts 2 are arranged in the surrounding rock around the tunnel excavation outline 1. The multiple anchor bolts 2 reinforce the surrounding rock within their effective reinforcement range, forming an anchoring reinforcement ring 3 around the tunnel excavation outline 1. The anchoring reinforcement ring 3 is bounded by the inner surface 5 of the inner anchoring reinforcement ring and the outer surface 6 of the outer anchoring reinforcement ring. The inner surface 5 of the anchoring reinforcement ring corresponds to the tunnel excavation outline 1, and the outer surface 6 of the anchoring reinforcement ring is determined according to the effective reinforcement length of the anchor bolts 2.

[0034] The surrounding rock outside the anchoring reinforcement ring 3 constitutes the main bearing zone 4. The steel content of the on-site section is calculated based on the diameter, spacing, and row spacing of the on-site anchor bolts 2. This on-site steel content is then substituted into the functional relationship established in step S6 to obtain the apparent cohesion, apparent internal friction angle, and apparent elastic modulus of the anchoring reinforcement ring 3. The bearing capacity of the anchoring reinforcement ring 3 is then calculated based on the inner surface 5, the outer surface 6, and the apparent mechanical parameters of the anchoring reinforcement ring 3.

[0035] The anchoring reinforcement ring 3 transmits radial constraint to the outer main load-bearing area 4 through its outer surface 6. This radial constraint is equivalent to the confining pressure 7. The confining pressure 7 characterizes the lateral constraint provided by the anchoring reinforcement ring 3 to the main load-bearing area 4 and serves as the minimum principal stress in the ultimate strength calculation of the main load-bearing area 4. Substituting the confining pressure 7 into the Hoek-Brown strength criterion, the ultimate strength of the main load-bearing area 4 under the confining pressure 7 condition is obtained. This ultimate strength is then compared with the actual maximum principal stress of the main load-bearing area 4 determined in step S1 to determine whether the main load-bearing area 4 meets the stability requirements.

[0036] Substitute the confining pressure into the Hoek-Brown strength criterion to calculate the ultimate strength of the surrounding rock in the main bearing area under the confining pressure condition, and determine whether the surrounding rock in the main bearing area meets the stability requirements based on the actual maximum principal stress in the main bearing area.

[0037] Furthermore, based on the aforementioned functional relationship, the steel content of the on-site section is calculated according to the anchor bolt diameter, spacing, and row spacing to be used at the engineering site, thereby obtaining the apparent cohesion, apparent internal friction angle, and apparent stiffness of the on-site anchored rock mass, including: Calculate the steel content of the on-site section based on the anchor diameter, anchor spacing, and anchor row spacing at the engineering site; Substituting the steel content of the on-site section into the aforementioned functional relationship, the apparent cohesion, apparent internal friction angle, and apparent stiffness of the on-site anchored rock mass are obtained.

[0038] Furthermore, calculating the confining pressure that the anchoring reinforcement ring can provide to the outer main load-bearing zone under the condition that the stress on its inner surface does not exceed the uniaxial compressive strength of the anchoring rock mass includes: Calculate the inner radius of the anchor reinforcement ring based on the cross-sectional area of ​​the tunnel excavation, and calculate the outer radius of the anchor reinforcement ring based on the effective reinforcement length of the anchor bolt. Calculate the uniaxial compressive strength of the anchored rock mass based on the apparent cohesion and apparent internal friction angle of the anchored rock mass at the site. Based on the uniaxial compressive strength of the anchored rock mass, the inner and outer radii of the anchor reinforcement ring, and the safety factor of the anchor reinforcement ring, calculate the maximum confining pressure that the anchor reinforcement ring can provide to the main bearing area.

[0039] Furthermore, based on the assessment results of the stability of the surrounding rock in the main load-bearing area, the anchor bolt support parameters are obtained as follows: When the surrounding rock in the main load-bearing zone meets the stability requirements, the anchor bolt support parameters are output. When the stability requirements are not met, the anchor bolt diameter, spacing, row spacing or length are adjusted and the steel content of the on-site section and the bearing capacity of the anchor reinforcement ring are recalculated until the surrounding rock in the main load-bearing zone meets the stability requirements.

[0040] Specifically, the steel content of the on-site section is calculated based on the diameter, spacing, and row spacing of the anchor bolts at the engineering site: ; in: ; In the formula, S is the anchor bolt spacing, and P is the anchor bolt row spacing. Let be the diameter of the i-th anchor rod. It is the sum of the cross-sectional areas of all anchor bolts within a support unit.

[0041] The apparent parameters of the rock mass to be anchored in the field were obtained, including: Substituting η into the cross-sectional steel ratio strengthening model, the apparent cohesion of the anchored rock mass in the field is obtained. Apparent internal friction angle and apparent stiffness .

[0042] Establishing the bearing capacity model of the anchorage reinforcement ring includes: The effective reinforcement range of the anchor bolts around the roadway is equivalent to an anchoring reinforcement ring, with an inner radius of [missing information]. The outer radius is .

[0043] For non-circular tunnels, the equivalent circle radius is used to represent the tunnel cross-section: , In the formula, The cross-sectional area of ​​the tunnel excavation. This refers to the effective reinforcement length of the anchor bolt.

[0044] Calculate the uniaxial compressive strength of the anchored rock mass based on the apparent cohesion and apparent internal friction angle of the anchored rock mass at the site: ; The equivalent circumferential compressive stress on the inner surface of the anchoring reinforcement ring is: ; In the formula, The constraint pressure provided by the outer surface of the anchoring reinforcement ring to the main load-bearing area. To anchor and strengthen the surface support reaction force of the ring or the reaction force of the tunnel wall.

[0045] To ensure that the anchoring reinforcement ring itself does not crush, the following conditions must be met: ; In the formula, The safety factor is the anchorage reinforcement ring.

[0046] Therefore, the maximum confining pressure that the anchoring reinforcement ring can provide to the outer main load-bearing zone can be obtained: ; When the reaction force on the inner wall of the tunnel is not considered... ,but: ; Determining the stability of the surrounding rock in the main load-bearing zone includes: The confining pressure provided by the anchoring reinforcement ring to the main load-bearing area Substituting the Hoek-Brown strength criterion, the ultimate strength of the surrounding rock in the main load-bearing zone under confined pressure is calculated: ; When the actual maximum principal stress in the main load-bearing area satisfy: At that time, the surrounding rock in the main bearing area was determined to be stable.

[0047] when At that time, it was determined that the surrounding rock in the main bearing area was unstable or at risk of damage.

[0048] In the formula, γ is the safety factor of the main load-bearing area.

[0049] The back-calculated anchor support parameters include: When the main load-bearing area is unstable, the steel content of the cross section or the load-bearing capacity of the anchor reinforcement ring can be increased by at least one of the following methods: increasing the diameter of the anchor bolt; decreasing the spacing between anchor bolts; decreasing the row spacing of anchor bolts; increasing the effective reinforcement length of the anchor bolts; increasing the preload of the anchor bolts; or using shear-resistant anchor bolts or anchor cables.

[0050] Recalculate after adjustment and This continues until the surrounding rock in the main bearing area meets the stability requirements.

[0051] Numerical simulation verification includes: After completing the theoretical calculations, a numerical model of the surrounding rock of the tunnel was established. The rock mass parameters within the anchoring reinforcement zone were replaced with... , and The rock mass parameters of the main bearing area outside the anchoring reinforcement ring are set to those of the unanchored rock mass, and the deformation, plastic zone range, and stress distribution of the surrounding rock in the roadway are calculated. If the numerical simulation results show that the deformation or plastic zone range of the surrounding rock in the roadway does not meet the engineering requirements, the support parameters are adjusted.

[0052] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A quantitative design method for roadway anchor bolt support based on the strengthening effect of cross-sectional steel ratio, characterized in that, include: S1: Determine the original rock stress state and the actual load-bearing zone of the roadway to be designed. Stress: The three-dimensional stress tensor of the original rock in the area where the roadway to be designed is located is obtained by in-situ stress testing. The maximum principal stress, intermediate principal stress, minimum principal stress and the direction of each principal stress are determined based on the three-dimensional stress tensor of the original rock. Combined with the axial orientation, cross-sectional shape and cross-sectional dimensions of the roadway to be designed, the stress distribution of the surrounding rock after the roadway is excavated is obtained by analytical calculation and / or numerical calculation. The location of the main bearing area and the actual maximum principal stress of the main bearing area are determined. The actual maximum principal stress of the main bearing area is used as the engineering load parameter for subsequent stability judgment of the main bearing area. S2: Determine the initial compressive mechanical parameters of intact rock surrounding the roadway to be designed: Collect rock samples of the roadway surrounding rock corresponding to the in-situ stress test area of ​​S1, prepare rock samples of predetermined size and carry out uniaxial compression tests to obtain the uniaxial compressive strength, axial stiffness of the elastic stage and elastic modulus of the rock samples; Among them, the axial stiffness of the elastic stage of the rock samples is calculated based on the load increment and axial displacement increment of the rock samples in the elastic stage, and the axial stiffness of the elastic stage is used as the normal constraint stiffness of the constant normal stiffness direct shear test in S3 and S6, the uniaxial compressive strength is used as the intact rock uniaxial compressive strength to determine the equivalent strength parameters of the unanchored rock mass in S5, and the elastic modulus is used as the unanchored reference parameter for evaluating the stiffness strengthening effect of the anchored rock samples in S6. S3: Determine the initial shear strength parameters of the unanchored rock samples: Using multiple groups of unanchored rock samples from the same sampling area, with the same lithology and size as in S2, the axial stiffness of the rock samples obtained in S2 during the elastic stage is set as the normal constraint stiffness for the constant normal stiffness direct shear test. Different initial normal forces are applied to each group of unanchored rock samples, and constant normal stiffness direct shear tests are carried out under the same normal constraint stiffness and different initial normal forces. Based on the initial normal force, normal displacement during the shearing process, and normal constraint stiffness of each group of unanchored rock samples, the real-time normal force and real-time normal stress during the shearing process are determined, and the peak shear stress of each group of tests and the corresponding real-time normal stress at the peak shear stress are obtained. Strength fitting is performed based on the peak shear stress of each group of tests and its corresponding real-time normal stress to obtain the initial cohesion and initial internal friction angle of the unanchored rock samples. The initial cohesion and initial internal friction angle are used as the unanchored reference parameters for evaluating the steel content strengthening effect of the section in step S6. S4: Determine the rock mass structural parameters and Hoek-Brown calculation parameters for the roadway to be designed: Through on-site geological surveys and rock mass quality evaluation, obtain the structural plane spacing, structural plane attitude, structural plane filling status, rock mass integrity, geological strength index GSI, and disturbance coefficient D of the surrounding rock of the roadway to be designed. Then, determine the intact rock material constant m by fitting the rock triaxial compression test or based on the corresponding lithology. i The geological strength index GSI, disturbance coefficient D, and intact rock material constant m are used to determine the geological strength index GSI, disturbance coefficient D, and intact rock material constant m. i As input parameters for converting the complete rock mechanics parameters obtained in S2 into equivalent rock mechanics parameters of the unanchored rock mass in the field in S5; S5: Determine the equivalent initial mechanical parameters of the unanchored rock mass in the tunnel to be designed: Combine the uniaxial compressive strength of intact rock obtained in S2 with the geological strength index GSI, disturbance coefficient D, and intact rock material constant m obtained in S4. i Substituting the Hoek-Brown strength criterion, the Hoek-Brown strength parameters and nonlinear strength envelope of the unanchored rock mass in the roadway to be designed are determined. Based on the stress range of the main bearing zone determined in S1, the nonlinear strength envelope is equivalently transformed to obtain the equivalent cohesion, equivalent internal friction angle, and uniaxial compressive strength of the unanchored rock mass in the roadway to be designed. Combined with the complete rock elastic modulus obtained in S2 and the rock mass structure parameters obtained in S4, the equivalent elastic modulus of the unanchored rock mass is obtained. The equivalent cohesion, equivalent internal friction angle, and equivalent elastic modulus of the unanchored rock mass are used as the rock mass-scale reference parameters for calculating the apparent mechanical parameters of the anchored rock mass in S6. S6: Establish the functional relationship between the steel content of the cross section and the apparent mechanical parameters of the anchored rock mass in the field: Use rock samples with the same sampling area, lithology, size and initial conditions as S2 and S3, and set different diameters and / or different numbers of anchor rods in the rock samples to form multiple anchored rock samples with different cross section steel contents; S7: Set the axial stiffness of the rock sample in the elastic stage obtained in S2 as the normal constraint stiffness of the direct shear test of the constant normal stiffness of each group of anchored rock samples, and use the same initial normal force classification as in S3. Under the same normal constraint stiffness, the same initial normal force classification and different steel ratios of the cross sections, carry out the direct shear test of the constant normal stiffness of each group of anchored rock samples. S8: Based on the peak shear stress of each group of anchored rock samples and the real-time normal stress corresponding to the peak shear stress, obtain the apparent cohesion and apparent internal friction angle of anchored rock samples under different steel ratios of cross sections, and obtain the apparent stiffness or apparent elastic modulus of anchored rock samples based on the load-displacement relationship before and / or during the shearing process. S9: Using the initial cohesion and initial internal friction angle of the unanchored rock sample obtained in S3 and the elastic modulus of the unanchored rock sample obtained in S2 as the benchmarks for indoor tests, determine the relationship between the cohesion strengthening function, the internal friction angle strengthening function, the elastic modulus strengthening function and the steel content of the section. S10: Apply the cohesion strengthening function, internal friction angle strengthening function, and elastic modulus strengthening function to the equivalent cohesion, equivalent internal friction angle, and equivalent elastic modulus of the unanchored rock mass obtained in S5, respectively, to establish the functional relationship between the apparent cohesion, apparent internal friction angle, and apparent elastic modulus of the anchored rock mass in the field and the equivalent initial mechanical parameters and cross-sectional steel ratio of the unanchored rock mass.

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