A Design and Analysis Method for Inclined Advance Support Anchor Bolt System in Drill-and-Blast Tunnel

Abstract

This invention discloses a design and analysis method for an inclined pre-support anchor system in a drill-and-blast tunnel, comprising: statistically analyzing the mechanical parameters of the surrounding rock to obtain the initial stress field of the surrounding rock; simulating excavation of the tunnel surrounding rock using different construction methods and support systems to calculate the excavation stress field formed after excavation disturbance; calculating the inclined pre-support anchor support stress field; analyzing the characteristics of the range of the support stress field changing with the excavation method, the tunnel face advance distance, and the parameters of the inclined pre-support anchor, determining the optimal design parameters of the inclined pre-support anchor under each excavation method, and increasing the surrounding rock parameters within the influence range by one order of magnitude, recalculating the excavation stress field and displacement field of the surrounding rock; comparing and correcting until the calculated excavation stress field and displacement field roughly match the measured values. This invention achieves a quantitative description of the influence range of the inclined anchor and effectively simulates the anchor's support effect on the surrounding rock, providing a theoretical basis for the design and construction of pre-support.

Description

Technical Field

[0001] This invention relates to the field of tunnel and underground engineering construction technology, specifically to a design and analysis method for an inclined pre-support anchor system for drill-and-blast tunnels. Background Technology

[0002] The stress field is a core issue in studying the deformation and failure of tunnel surrounding rock and the interaction between the surrounding rock and the support structure. Disasters such as tunnel face extrusion deformation, arch collapse, and steel arch deformation are all closely related to the stress field of the surrounding rock. Only by fully understanding the spatiotemporal distribution characteristics of the tunnel stress field, and analyzing the initial stress field, excavation stress field, and support stress field of the surrounding rock, can we conduct a reasonable and realistic analysis of the deformation and failure of the surrounding rock and the interaction between the surrounding rock and the support structure, and thus propose reasonable support design and deformation control measures. The initial stress field refers to the initial stress present in the tunnel surrounding rock under undisturbed conditions. The excavation stress field refers to the stress field that appears due to the redistribution of stress in the surrounding rock caused by the forward excavation of the tunnel face. The excavation stress field has a certain spatial distribution range and changes continuously with the advancement of the tunnel face and the passage of time. The support stress field appears around the surrounding rock in contact with the support; it has a smaller spatial distribution range and changes with the progress of excavation activities and the passage of time. These three stress fields constitute the comprehensive stress field of the surrounding rock.

[0003] Rock bolts are one of the most widely used support structures in tunnel engineering, and their reinforcement effect has been proven by numerous engineering practices. Currently, radial rock bolts are widely used for surrounding rock reinforcement, but mostly as an auxiliary reinforcement method after excavation. In tunnel face pre-support, pre-reinforcement is mostly done using pre-construction pipes or pipe roofs; the use of inclined rock bolts for pre-reinforcement has not been widely applied, and related research is limited. Therefore, establishing a quantitative evaluation and parameter optimization method for inclined pre-support rock bolt systems is of great significance for effectively evaluating the reinforcement range of inclined rock bolts, optimizing corresponding parameters, and guiding on-site pre-support construction.

[0004] However, as a strong support for support design, how to effectively reflect the reinforcement effect of anchor bolts on surrounding rock using scientific methods remains a hot topic that needs extensive discussion and research. Usually, two methods are used to evaluate the reinforcement effect of anchor bolts: analytical solution and numerical simulation. (1) Establish the constitutive relationship of the anchored rock mass, such as establishing analytical constitutive equations for the anchor bolt and the grouting body or rock mass in coupled and uncoupled states. Although this method can better reflect the interaction between the surrounding rock and the anchor bolt, its calculation mechanism is too complicated. (2) Use numerical simulation method to treat the conventional anchor bolt element model as a cable element. Although this simulation method can obtain the axial force of the anchor bolt more accurately, it does not consider the joint action between the anchor bolt and the rock mass. Therefore, the calculated support effect of the anchor bolt on the surrounding rock is very small and cannot reflect the strong support effect of the anchor bolt revealed by a large number of engineering practices. Therefore, current numerical simulation studies generally employ two methods to demonstrate the support effect of rock bolts on the surrounding rock: ① Increasing the surrounding rock parameters (elastic modulus, cohesion, and internal friction angle, etc.) in the area where the rock bolts act, which can better simulate the rock bolts' control over surrounding rock deformation and stress release; ② Treating the force exerted by the rock bolts on the pad as an equivalent force evenly distributed on the tunnel wall (Smeared approach), thereby demonstrating the combined support effect of the rock bolts on the surrounding rock.

[0005] However, both methods mentioned above have significant problems. Method ① lacks a quantitative analysis of the anchor bolt reinforcement range. Many studies roughly use the anchor bolt length or anchoring section length as the reference, without any theoretical basis to explain the value of the reinforcement range. In fact, the anchor bolt's effective range is the result of the interaction between the surrounding rock and the anchor bolt support stress field. It is influenced by parameters such as excavation method, face advance distance, anchor bolt length, and angle. It is a comprehensive function with multiple variables, including time, space, construction method parameters, and anchor bolt design parameters, rather than a fixed single numerical function. Method ② yields a very small surface force value after conversion. Unless this surface force value is increased exponentially, the anchor bolt's support effect on the surrounding rock remains insignificant. This results in an excessively large axial force value required to achieve the desired effect, far exceeding the anchor bolt's design tensile strength. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a design and analysis method for inclined pre-support anchor systems in drill-and-blast tunnels. Based on the analysis of the evolution of the surrounding rock stress field caused by tunnel face excavation, it obtains the inclined pre-support stress field through numerical simulation analysis and comparison of the surrounding rock excavation stress field under different support conditions. This achieves a quantitative description of the influence (reinforcement) range of the inclined anchors. By improving the surrounding rock parameters within this range, the effective simulation of the anchor's support effect on the surrounding rock is realized. Simultaneously, the stress field is inverted based on field measurement information, and the calculation results are corrected. This method enhances the study of the evolution characteristics of the support stress field under different construction methods, tunnel face advance distances, and anchor parameters, providing a theoretical basis for the design and construction of pre-support systems.

[0007] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0008] A design and analysis method for an inclined pre-support anchor system in a drill-and-blast tunnel includes the following steps:

[0009] S1. Statistical analysis of the physical and mechanical parameters of the tunnel in the surrounding rock, the magnitude and direction of the geostress field, and the lithological occurrence information of the strata;

[0010] S2. The initial stress field of the surrounding rock is obtained by numerical simulation.

[0011] S3. Simulated excavation of the tunnel surrounding rock using different construction methods was conducted, and the excavation stress field σ formed after excavation disturbance was calculated when the tunnel did not use an inclined pre-anchor support system. 开挖2 ;

[0012] S4. Simulate excavation of the tunnel surrounding rock using the same construction method, and calculate the excavation stress field σ formed after excavation disturbance when the tunnel adopts an inclined advanced anchor support system. 开挖1 ;

[0013] S5. Analyze the evolution characteristics of the excavation stress field, calculate the stress concentration ratio of the surrounding rock, and analyze the improvement effect of advanced support on the stress concentration of the surrounding rock.

[0014] S6. Calculate the support stress field formed by the inclined advance anchor bolts and analyze the evolution characteristics of the support stress field;

[0015] σ 支护 =σ 开挖1 -σ 开挖2 (4)

[0016] In the formula: σ 支护 σ is the additional stress field formed by the inclined advanced anchor bolt support. 开挖1 σ represents the stress field formed during excavation of the surrounding rock when there is inclined pre-anchor support. 开挖2 This refers to the stress field formed during unsupported excavation of the surrounding rock.

[0017] S7. Use Tecplot software to draw contour lines for the inclined pre-anchor support stress field obtained in step S6, and take the 0.1 MPa contour line as the boundary of the influence range of the inclined anchor.

[0018] S8. Determine the reinforcement range of anchor bolts for a specific cross-section based on the construction excavation method, the advance distance of the tunnel face, and the anchor bolt design parameters.

[0019] S9. Improve the surrounding rock parameters within the influence range of the anchor bolt;

[0020] S10. Recalculate the tunnel surrounding rock excavation stress field and excavation displacement field after the parameters within the reinforcement range are improved under the action of inclined advanced support anchor bolts.

[0021] S11. Based on the optimized anchor bolt design parameters, feedback is given to the construction site for further optimization of the anchor bolt parameters.

[0022] S12. Based on the measured disturbance stress around the tunnel and the monitored displacement data at the tunnel construction site, the surrounding rock stress field is inferred and compared with the calculated excavation stress field and displacement field. The calculation parameters are corrected and steps S1-S11 are repeated to recalculate until the calculated excavation stress field and displacement field are approximately consistent with the measured values.

[0023] Preferably, in steps S2, S3, and S4, FLAC is used. 3D Perform the calculation.

[0024] Furthermore, in step S3, the different construction methods include two-step and three-step construction methods.

[0025] Furthermore, in step S5, the method for calculating the stress concentration ratio of the surrounding rock is as follows:

[0026]

[0027]

[0028]

[0029] In the formula: λ x , λ y , λ z σ represents the stress concentration ratio in the x, y, and z directions of the surrounding rock element, respectively. x σ y σ z σ represents the stress under the excavation stress field in the x, y, and z directions of the surrounding rock unit, respectively. x0 σ y0 σ z0 These represent the initial stresses in the x, y, and z directions of the surrounding rock unit, respectively.

[0030] Furthermore, in step S7, the area with a pressure greater than or equal to 0.1 MPa is the influence range of the inclined forward anchor bolt, and the area with a pressure less than 0.1 MPa is the non-influence range of the inclined forward anchor bolt.

[0031] Furthermore, in step S8, the method for determining the excavation method is as follows: draw the influence range diagram of the inclined advanced anchor support stress field under different construction methods, analyze the evolution characteristics of the inclined advanced anchor support stress field under the two-step and three-step construction methods, compare the differences in the influence range under different construction methods, and obtain the excavation method that can best play the role of inclined advanced anchor support.

[0032] Furthermore, in step S8, the method for determining the tunnel face advance distance is as follows: draw an evolution diagram of the influence range of the inclined advanced anchor support stress field as the tunnel face advances, analyze the evolution characteristics of the inclined advanced anchor support stress field as the tunnel face advances, and obtain the spatiotemporal distribution characteristics of the inclined advanced anchor support stress field.

[0033] Furthermore, in step S8, the method for determining the anchor bolt design parameters is as follows: by changing the anchor bolt design parameters, the length, angle, installation range, and other key design parameters that best exert the function of the inclined pre-support anchor bolt are obtained; the influence range diagram of the stress field of the inclined pre-support anchor bolt as the anchor bolt parameters change is plotted; the evolution characteristics of the stress field of the inclined pre-support anchor bolt under the change of the inclined pre-support anchor bolt parameters are analyzed; and the length, angle, installation range, and other key design parameters that best exert the function of the inclined pre-support anchor bolt are obtained.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] This invention is based on the evolution of the stress field in the surrounding rock of a tunnel caused by face excavation, and integrates the spatiotemporal evolution analysis of the stress field into the entire process of support system design. Through numerical simulation analysis and comparison of the stress field of the surrounding rock under different support conditions, the stress field of inclined pre-support is obtained, achieving a quantitative description of the influence range of the inclined anchor. By improving the surrounding rock parameters within this range, the effective simulation of the anchor's support effect on the surrounding rock is achieved. Simultaneously, the stress field is inverted based on field measurement information, and the calculation results are corrected. This invention studies the evolution characteristics of the support stress field under different construction methods, face advance distances, and anchor parameters, providing a theoretical basis for the design and construction of pre-support systems. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the method flow of the present invention;

[0038] Figure 2(a) shows the design diagram of the inclined advanced support anchor system;

[0039] Figure 2(b) shows the numerical simulation model of the inclined advanced support anchor system;

[0040] Figure 3(a) shows the initial stress field of the surrounding rock in the numerical simulation of the stress field of the tunnel surrounding rock;

[0041] Figure 3(b) shows the excavation stress field of the surrounding rock in the numerical simulation of the stress field of the tunnel surrounding rock;

[0042] Figure 3(c) shows the stress concentration ratio (tangential) of the surrounding rock in the numerical simulation of the stress field of the tunnel surrounding rock;

[0043] Figure 3(d) shows the stress field of the surrounding rock support in the numerical simulation of the stress field of the tunnel surrounding rock;

[0044] Figure 4(a) shows the influence range of the inclined advanced support anchor bolt;

[0045] Figure 4(b) shows the influence range of the inclined advanced anchor bolt support in the two-step construction method;

[0046] Figure 4(c) shows the evolution characteristics of the influence range of the inclined advance anchor bolt along the longitudinal direction of the tunnel;

[0047] Figure 4(d) is a three-dimensional diagram of the support range of the inclined advanced anchor bolt;

[0048] Figure 5(a) is a schematic diagram of the reinforcement range (red part) after the inclined advanced support anchor is reinforced;

[0049] Figure 5(b) shows the stress field of the surrounding rock after reinforcement by inclined pre-supported anchor bolts during excavation;

[0050] Figure 6(a) shows the dynamic inversion of the tunnel ground stress field;

[0051] Figure 6(b) is a statistical chart of the measured stress at the construction site. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0053] A design and analysis method for an inclined pre-support anchor system in drill-and-blast tunnels, such as Figure 1 As shown, the main steps include:

[0054] S1. Collect information on the physical and mechanical parameters of the tunnel in the surrounding rock, the magnitude and direction of the geostress field, and the lithological occurrence of the strata.

[0055] Information such as the physical and mechanical parameters of the surrounding rock under different levels and stress grades, the magnitude and direction of the stress field, and the lithological occurrence of the strata are of great significance for accurately simulating the stress field of the surrounding rock. At the same time, this information still needs to be dynamically corrected by using deformation and displacement monitoring data from the construction site.

[0056] S2. The initial stress field of the surrounding rock is obtained by numerical simulation calculation.

[0057] Different tunnels are located in areas with varying stress fields and geological conditions, corresponding to different surrounding rock classifications. Furthermore, some tunnels are situated in special geological sections, such as fault fracture zones. Numerical simulation methods like FLAC are used to address these differences. 3D The initial (original) stress field of the surrounding rock under different conditions was calculated, the initial (original) stress field was classified, and then analyzed using FLAC. 3D The stress field is saved and written using a self-developed Fish language. Figure 3(a) shows the use of FLAC. 3D The calculated initial (original) stress field of the surrounding rock is related to the stress field of the surrounding rock and its own geological conditions.

[0058] S3. Calculate the excavation stress field σ formed after excavation disturbance when the tunnel does not use an inclined advance anchor support system. 开挖2 .

[0059] For Class IV and V surrounding rock, two-stage and three-stage construction methods are commonly used. FLAC is applied to different construction methods. 3DSimulated excavation was conducted by first calculating the excavation stress field (stress field formed by excavation of surrounding rock without support) after excavation disturbance when the tunnel does not use an inclined pre-anchor support system. This was then analyzed using FLAC. 3D The stress field is saved and written using a self-developed Fish language. Figure 2 shows a schematic diagram of the inclined pre-support anchor bolts for the tunnel. Figure 2(a) shows the design diagram of the inclined pre-support anchor bolt system for the tunnel. The inclined pre-support anchor bolts are installed at an angle of 45° before the excavation of the tunnel face (with auxiliary pre-support small guide pipes if necessary, shown by the dashed lines in the figure). The prestressed system anchor bolts (vertical anchor bolts) together with shotcrete and steel supports form the initial support. Figure 2(b) shows the numerical model diagram of the inclined pre-support anchor bolt system for the tunnel. Figure 3(b) shows the stress field of the surrounding rock excavation.

[0060] S4. The calculated excavation stress field σ formed after excavation disturbance when the tunnel adopts an inclined advanced anchor support system is obtained. 开挖1 .

[0061] The same construction method was used to simulate excavation of the surrounding rock of the tunnel. The tunnel adopted an inclined advanced anchor support system and was supported by FLAC. 3D The excavation stress field formed after excavation disturbance (stress field formed by excavation of surrounding rock with inclined pre-anchor support) was calculated and then processed using FLAC. 3D The stress field is saved and written using a self-developed Fish language;

[0062] S5. Analyze the evolution characteristics of the excavation stress field. Calculate the stress concentration ratio of the surrounding rock and analyze the improvement effect of advanced support on the stress concentration of the surrounding rock.

[0063] By comparing the stress field formed by the unsupported excavation of the surrounding rock obtained in step S3 or the stress field formed by the excavation of the surrounding rock with inclined pre-anchor support obtained in step S4 with the initial stress field of the surrounding rock, the stress concentration ratio of the surrounding rock is obtained, as shown in Figure 3(c). It reflects the ratio of the decrease or increase of the stress of the surrounding rock near the working face due to the stress redistribution caused by excavation. It is a quantity that can quantitatively evaluate the magnitude of the disturbance of the surrounding rock caused by excavation. The larger the stress concentration ratio, the greater the degree of disturbance of the surrounding rock caused by excavation.

[0064]

[0065]

[0066]

[0067] In the formula: λ x , λ y , λ z σ represents the stress concentration ratio in the x, y, and z directions of the surrounding rock element, respectively. x σ y σz σ represents the stress under the excavation stress field in the x, y, and z directions of the surrounding rock unit, respectively. x0 σ y0 σ z0 These represent the initial (original rock) stresses in the x, y, and z directions of the surrounding rock unit, respectively.

[0068] S6. Calculate the support stress field formed by the inclined advance anchor bolts and analyze the evolution characteristics of the support stress field.

[0069] The stress field σ formed by unsupported surrounding rock excavation obtained in step S3 开挖2 The stress field σ formed during excavation of the surrounding rock with inclined advance anchor bolt support, obtained in step S4. 开挖1 By comparing the differences, the additional stress field formed by the inclined advanced anchor bolt support is represented, which, for simplicity, is referred to as the support stress field.

[0070] σ 支护 =σ 开挖1 -σ 开挖2 (4)

[0071] In the formula: σ 支护 σ is the additional stress field formed by the inclined advanced anchor bolt support. 开挖1 σ represents the stress field formed during excavation of the surrounding rock when there is inclined pre-anchor support. 开挖2 Figure 3(d) shows the stress field formed during unsupported excavation of the surrounding rock. The stress field formed by inclined advanced anchor bolt support is shown in Figure 3(d).

[0072] S7. The stress field of the inclined advanced anchor bolt support obtained in step S6 is plotted using Tecplot software to draw contour lines. The 0.1 MPa contour line is taken as the boundary of the influence range of the inclined anchor bolt. The area greater than or equal to 0.1 MPa is taken as the influence range of the inclined anchor bolt, i.e. the reinforcement range. The area less than 0.1 MPa is taken as the non-influence range of the inclined anchor bolt. Figure 4(a) is the influence range diagram of the inclined advanced anchor bolt support.

[0073] S8. Determine the reinforcement range of anchor bolts for specific cross-sections based on different construction methods, tunnel face advance distance, and anchor bolt design parameters; including:

[0074] S81. Analyze the evolution characteristics of the stress field of inclined pre-anchor support under different excavation methods to obtain the excavation method that best utilizes the inclined pre-anchor support function; specifically, analyze the evolution characteristics of the stress field of inclined pre-anchor support under two-stage and three-stage excavation methods, draw the influence range diagram of inclined pre-anchor under different methods, compare the differences in influence range under different methods, and obtain the excavation method that best utilizes the inclined pre-anchor support function; Figure 4(b) shows the influence range diagram of inclined pre-anchor support under the two-stage excavation method. The influence range is closely related to the tunnel axial position and the tunnel perimeter position;

[0075] S82. Analyze the evolution characteristics of the stress field of the inclined advanced anchor bolt support as the tunnel face advances, and obtain the spatiotemporal distribution characteristics of the stress field of the inclined advanced anchor bolt support. As the tunnel face advances, the evolution of the stress field of the inclined advanced anchor bolt support exhibits different spatiotemporal distribution characteristics. Draw the influence range evolution diagram as the tunnel face advances, and obtain the spatiotemporal distribution law of the stress field of the inclined advanced anchor bolt support; Figure 4(c) shows the evolution characteristics of the stress field of the inclined advanced anchor bolt support along the longitudinal direction of the tunnel as the tunnel face advances.

[0076] S83. Analyze the evolution characteristics of the stress field of the inclined pre-support anchor bolts under changes in parameters such as length, angle, installation range, position, and spacing, to obtain key design parameters such as length, angle, and installation range that best utilize the support function of the inclined pre-support anchor bolts. The evolution of the stress field of the inclined pre-support anchor bolts will exhibit different characteristics when these parameters change. By changing the parameters, the key design parameters such as length, angle, and installation range that best utilize the support function of the inclined pre-support anchor bolts are obtained, and the influence range diagram of the anchor bolt parameter changes is drawn. Figure 4(d) is a three-dimensional diagram of the support range of the inclined pre-support anchor bolts when the installation angle and position along the longitudinal direction of the tunnel change.

[0077] S9. Improve the surrounding rock parameters within the influence range of the anchor bolt, such as elastic modulus, cohesion and internal friction angle; improve by at least one order of magnitude, such as improving the V1 level parameter to the IV2 level parameter. Figure 5(a) is a schematic diagram of strengthening the surrounding rock parameters within the influence range of the anchor bolt.

[0078] S10. Recalculate the excavation stress field and excavation displacement field of the tunnel surrounding rock under the action of the inclined pre-supported anchor (after the parameters within the reinforcement range are increased). Figure 5(b) shows the excavation stress field of the surrounding rock after recalculation. Only by increasing the surrounding rock parameters within the anchorage range by one order of magnitude can an excavation stress field that matches the actual situation on site be obtained.

[0079] S11. Based on the optimized anchor bolt design parameters, feedback is given to the construction site for further optimization of the anchor bolt parameters.

[0080] S12. Based on the measured disturbance stress around the tunnel and the monitored displacement data at the tunnel construction site, the surrounding rock stress field is inferred and compared with the calculated excavation stress field and displacement field. The calculation parameters are corrected, and steps S1-S10 are repeated to recalculate until the calculated excavation stress field and displacement field roughly match the measured values. Figure 6(a) is a schematic diagram of inferring the surrounding rock stress field based on the measured disturbance stress and displacement around the tunnel at the tunnel construction site. The corrected surrounding rock stress field and the recalculated excavation stress field are shown in Figure 5(b). Figure 6(a) is a statistical chart of the measured stress at the construction site.

[0081] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.

Claims

1. A design and analysis method for an inclined pre-support anchor system in a drill-and-blast tunnel, characterized in that: Includes the following steps: S1. Statistical analysis of the physical and mechanical parameters of the tunnel in the surrounding rock, the magnitude and direction of the geostress field, and the lithological occurrence information of the strata; S2. The initial stress field of the surrounding rock is obtained by numerical simulation. S3. Simulate excavation of the tunnel surrounding rock using different construction methods, and calculate the excavation stress field formed after excavation disturbance when the tunnel does not use an inclined pre-anchor support system. ; S4. Simulate excavation of the tunnel surrounding rock using the same construction method, and calculate the excavation stress field formed after excavation disturbance when the tunnel adopts an inclined advanced anchor support system. ; S5. Analyze the evolution characteristics of the excavation stress field, calculate the stress concentration ratio of the surrounding rock, and analyze the improvement effect of advanced support on the stress concentration of the surrounding rock. S6. Calculate the support stress field formed by the inclined advance anchor bolts and analyze the evolution characteristics of the support stress field; (4) In the formula: This is due to the additional stress field formed by the inclined advanced anchor bolt support. This refers to the stress field formed during excavation of the surrounding rock when there is inclined advanced anchor support. This refers to the stress field formed during unsupported excavation of the surrounding rock. S7. Use Tecplot software to draw contour lines for the inclined pre-anchor support stress field obtained in step S6, and take the 0.1 MPa contour line as the boundary of the influence range of the inclined anchor. S8. Determine the reinforcement range of anchor bolts for a specific cross-section based on the construction excavation method, the advance distance of the tunnel face, and the anchor bolt design parameters. S9. Improve the surrounding rock parameters within the influence range of the anchor bolt; S10. Recalculate the tunnel surrounding rock excavation stress field and excavation displacement field after the parameters within the reinforcement range are improved under the action of inclined advanced support anchor bolts. S11. Based on the optimized anchor bolt design parameters, feedback is given to the construction site for further optimization of the anchor bolt parameters. S12. Based on the measured disturbance stress around the tunnel and the monitored displacement data at the tunnel construction site, the surrounding rock stress field is inferred and compared with the calculated excavation stress field and displacement field. The calculation parameters are corrected and steps S1-S11 are repeated to recalculate until the calculated excavation stress field and displacement field match the measured values.

2. The design and analysis method for the inclined pre-support anchor system of the drill-and-blast tunnel according to claim 1, characterized in that: In steps S2, S3, and S4, FLAC is used. 3D Perform the calculation.

3. The design and analysis method for the inclined pre-support anchor system of the drill-and-blast tunnel according to claim 1, characterized in that: In step S3, the different construction methods include two-step and three-step construction methods.

4. The design and analysis method for the inclined pre-support anchor system of the drill-and-blast tunnel according to claim 1, characterized in that: In step S5, the method for calculating the stress concentration ratio of the surrounding rock is as follows: (1) (2) (3) In the formula: , These represent the stress concentration ratios in the x, y, and z directions of the surrounding rock unit, respectively. , These represent the stresses under the excavation stress field in the x, y, and z directions of the surrounding rock unit, respectively. , These represent the initial stresses in the x, y, and z directions of the surrounding rock unit, respectively.

5. The design and analysis method for the inclined pre-support anchor system of the drill-and-blast tunnel according to claim 1, characterized in that: In step S7, the area with a pressure greater than or equal to 0.1 MPa is the influence range of the inclined forward anchor bolt, and the area with a pressure less than 0.1 MPa is the non-influence range of the inclined forward anchor bolt.

6. The design and analysis method for the inclined pre-support anchor system of the drill-and-blast tunnel according to claim 1, characterized in that: In step S8, the method for determining the excavation method is as follows: draw the influence range diagram of the inclined advanced anchor support stress field under different construction methods, analyze the evolution characteristics of the inclined advanced anchor support stress field under the two-step and three-step construction methods, compare the differences in the influence range under different construction methods, and obtain the excavation method that can best play the role of inclined advanced anchor support.

7. The design and analysis method for the inclined pre-support anchor system of the drill-and-blast tunnel according to claim 1, characterized in that: In step S8, the method for determining the tunnel face advance distance is as follows: draw an evolution diagram of the influence range of the inclined advanced anchor support stress field as the tunnel face advances, analyze the evolution characteristics of the inclined advanced anchor support stress field as the tunnel face advances, and obtain the spatiotemporal distribution characteristics of the inclined advanced anchor support stress field.

8. The design and analysis method for the inclined pre-support anchor system of the drill-and-blast tunnel according to claim 1, characterized in that: In step S8, the method for determining the anchor bolt design parameters is as follows: by changing the anchor bolt design parameters, the length, angle, and installation range that best exert the inclined pre-support function of the anchor bolt are obtained; the influence range diagram of the inclined pre-support stress field with the change of anchor bolt parameters is plotted; the evolution characteristics of the inclined pre-support stress field under the change of inclined pre-support anchor bolt parameters are analyzed; and the length, angle, and installation range that best exert the inclined pre-support function of the anchor bolt are obtained.

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