Drilling and blasting method mechanized tunnel surrounding rock pressure arch evolution and pressure calculation method

Abstract

The invention provides a drilling and blasting method mechanized tunnel surrounding rock pressure arch evolution and pressure calculation method, which specifically comprises the following steps: constructing a mechanized tunnel finite difference calculation model, and setting tunnel engineering calculation parameters; determining surrounding rock pressure arch inner and outer boundaries based on change characteristics of surrounding rock stress before and after excavation; automatically monitoring the stress change in the surrounding rock excavation process through Flac3D software, storing a calculation model of each excavation stage, and automatically calculating the upper and lower boundaries of a pressure arch of the model of each stage; performing curve fitting and correction on the key points of the upper and lower boundaries of the pressure arch to obtain a calculation formula of the pressure arch of each excavation construction method; and respectively calculating the internal loosening pressure of the surrounding rock pressure arch and the external deformation pressure of the pressure arch to obtain a mechanical tunnel surrounding rock pressure calculation formula. According to the method, the pressure arch range formed by mechanical tunnel construction disturbance is determined more accurately, quantitative evaluation of the mechanical tunnel construction disturbance range is achieved, and a basis is provided for feasibility of large-section and long-footage construction of mechanical tunnel surrounding rock.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel and underground engineering construction, and in particular to a method for calculating pressure arch evolution and pressure of surrounding rock in a mechanized tunnel using a drilling and blasting method. Background Art

[0002] Surrounding rock pressure refers to the force that causes deformation or destruction of the rock mass and support around the underground excavation space. It includes the surrounding rock force caused by ground stress and the force acting on the support structure due to the obstruction of surrounding rock deformation. The tunnel surrounding rock pressure arch plays an important role in analyzing the stability of the tunnel surrounding rock. During the excavation of the tunnel, the stress will be redistributed. The surrounding rock pressure problem is related to the stability of the surrounding rock. The better the stability of the surrounding rock, the smaller the surrounding rock pressure generated. There are many factors that affect the surrounding rock pressure, which can usually be divided into two categories: one is geological factors, which include the original stress state, rock mechanical properties, rock structure surface, etc.; the other is engineering factors, which include construction methods, support setting time, support stiffness, tunnel shape, etc. The surrounding rock pressure action mode and calculation method are directly related to the selection of support type and the determination of support parameters.

[0003] The methods for determining surrounding rock pressure generally include: on-site measurement method, theoretical calculation method, statistical method, etc. The measurement method is to use instruments to measure the size of surrounding rock pressure on site, which is the most convincing, but due to the influence of measurement technology, the measurement results often cannot fully reflect the actual situation. Theoretical calculation is to use some mature calculation theories to calculate the surrounding rock pressure under the conditions of making some simplified assumptions about the surrounding rock and geological environment of the cavern, but due to the complex and changeable geological conditions of the surrounding rock, the various parameters used in the calculation are inevitably inconsistent with the actual situation. It is necessary to propose a calculation method that can more accurately determine the surrounding rock pressure of mechanized tunnels. Summary of the invention

[0004] In order to solve the deficiencies in the above-mentioned prior art, the present invention provides a method for calculating the pressure arch evolution and pressure of a mechanized tunnel surrounding rock using a drilling and blasting method, which can more accurately determine the range of the pressure arch formed by the disturbance of the mechanized tunnel construction, realize the quantitative evaluation of the disturbance range of the mechanized tunnel construction, and provide a basis for the feasibility of large-section and long-footage construction of mechanized tunnel surrounding rock; a method for calculating the surrounding rock pressure of a mechanized tunnel based on the pressure arch range is obtained, so that the design of the tunnel excavation method and support is more reasonable, and it is convenient to more accurately evaluate the safety of the support structure.

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

[0006] The method for calculating the pressure arch evolution and pressure of the surrounding rock of a mechanized tunnel using the drilling and blasting method includes the following steps:

[0007] S1. Statistics of tunnel engineering calculation parameters, including but not limited to the magnitude and direction of the geostress field, physical and mechanical parameters of the surrounding rock, support scheme, and excavation method;

[0008] S2, using finite difference software Flac 3D Save and write out the initial stress field of surrounding rock;

[0009] S3, simulate excavation of tunnel surrounding rock using step method and full section method, through Flac 3D Save and write out the excavation stress field formed after excavation disturbance;

[0010] S4. Analyze the evolution characteristics of the stress field before and after excavation to determine the inner boundary of the surrounding rock pressure arch; analyze the degree of deviation of the maximum principal stress vector from the vertical direction to determine the outer boundary of the surrounding rock pressure arch;

[0011] S5, through Flac 3D The built-in Fish language automatically calculates the upper and lower boundaries of the pressure arch at each excavation stage, realizes the three-dimensional visualization of the surrounding rock pressure arch range, and picks up the position coordinates of the pressure arch at the key parts of the tunnel through the program to realize the automatic calculation and writing of the height and width of the pressure arch; monitors the temporal and spatial evolution of the surrounding rock pressure arch range;

[0012] S6. Curve fitting and correction are performed on the key points of the upper and lower boundaries of the pressure arch to obtain a calculation formula for the range of the pressure arch under different burial depths, different sections, different geology, and different excavation and support methods; the radial displacement of the top of the outer boundary of the pressure arch is automatically read;

[0013] S7. Calculate the loosening pressure inside the pressure arch and the deformation pressure outside the pressure arch respectively. The surrounding rock pressure = loosening pressure inside the pressure arch + deformation pressure outside the pressure arch. The calculation formula of the surrounding rock pressure of mechanized tunnels under different burial depths, different sections, different geology, and different excavation and support methods is obtained:

[0014] p=γh f +KΔ d

[0015] Where: γ-surrounding rock mass (kN / m 3 );h f -pressure arch height (m); K-elastic reaction coefficient of surrounding rock (kPa / m); Δ d -Radial displacement of surrounding rock in the bearing area after the support structure is constructed (m).

[0016] Further, in step S4, the method for determining the inner boundary of the pressure arch is as follows: for the horizontal stress increase area, if there is no horizontal stress reduction area near the tunnel wall, then the tunnel wall is the inner boundary of the pressure arch in this area; if there is a horizontal stress reduction area near the tunnel wall, then the surface where the horizontal stress does not increase or decrease is used as the inner boundary of the pressure arch in this part; for the vertical stress increase area, the maximum value of the maximum principal stress is distributed on the inner boundary of the pressure arch as a judgment method.

[0017] Furthermore, the excavation stress field obtained in step S3 is compared with the initial stress field obtained in step S2, and whether the difference between the two is a positive value is determined to determine whether the region is a stress increase region:

[0018] σ 差 =σ 开挖 -σ 初始 (1)

[0019] Where: 差 is the excavation stress difference, σ 开挖 is the stress field formed by surrounding rock excavation, σ 初始 It is the initial stress field of the surrounding rock before excavation.

[0020] Further, in step S4, the method for determining the outer boundary of the pressure arch is: for the formation where the vertical stress is the maximum principal stress, a relative deflection index δ is introduced to indicate the degree to which the maximum principal stress vector deviates from the vertical direction, which is defined as follows:

[0021]

[0022] In the formula, σ max is the maximum principal stress, σ zz is the vertical stress; when δ<5%, the direction of the maximum principal stress vector gradually returns to the vertical direction, and δ=5% is used as the judgment method for the outer boundary of the pressure arch.

[0023] The beneficial effects of the present invention are:

[0024] The present invention more accurately determines the range of pressure arches formed by disturbances in mechanized tunnel construction using the drilling and blasting method, realizes quantitative evaluation of the range of disturbances in mechanized tunnel construction, and provides a basis for the feasibility of large-section and long-footage construction of mechanized tunnel surrounding rocks; a method for calculating the surrounding rock pressure of mechanized tunnels based on the range of pressure arches is obtained, which makes the design of tunnel excavation methods and supports more reasonable and facilitates a more accurate evaluation of the safety of the support structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 It is the technical route of the present invention;

[0027] Figure 2(a) shows the initial stress field of the surrounding rock;

[0028] Figure 2(b) shows the stress field of surrounding rock excavation;

[0029] Figure 3 This is the cloud diagram of horizontal stress changes before and after surrounding rock excavation (the red area is the area of ​​increased horizontal stress);

[0030] Figure 4 This is a cloud diagram of vertical stress changes before and after surrounding rock excavation (the red area is the area of ​​increased vertical stress);

[0031] Figure 5 It is the boundary of the surrounding rock pressure arch (the red area includes the upper, lower, left and right boundaries of the pressure arch);

[0032] Figure 6 Visualize the 3D pressure arch of surrounding rock;

[0033] Figure 7 It is the fitting curve of surrounding rock pressure arch. DETAILED DESCRIPTION

[0034] To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. The components of the embodiments of the present application generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians of the art without making creative work are within the scope of protection of the present application.

[0035] The evolution and calculation method of surrounding rock pressure arch in mechanized tunnel using drilling and blasting method specifically includes: constructing a mechanized tunnel finite difference calculation model, setting model ground stress, physical and mechanical parameters, support parameters, excavation method, monitoring points and other information according to the site conditions of the tunnel engineering; determining the upper and lower boundaries of the surrounding rock pressure arch based on the changing characteristics of surrounding rock stress before and after excavation; and 3D The software automatically monitors the stress changes during the surrounding rock excavation process and saves the calculation models of each excavation stage; the upper and lower boundaries of the pressure arch of the model at each stage are automatically calculated through the Fish language, and the three-dimensional visualization of the pressure arch range is realized, and the height and thickness of the pressure arch are automatically written out; the key points of the upper and lower boundaries of the pressure arch are curve fitted and corrected to obtain the calculation formula of the pressure arch for each excavation method; the loosening pressure inside the pressure arch of the surrounding rock and the deformation pressure of the pressure arch are calculated separately, and the calculation formula for the surrounding rock pressure of mechanized tunnels under different burial depths, different sections, different geology, and different excavation and support methods is obtained.

[0036] Technical route such as Figure 1 As shown, the specific steps are as follows:

[0037] S1. Statistics of tunnel engineering calculation parameters: including but not limited to the magnitude and direction of the geostress field, physical and mechanical parameters of the surrounding rock, support scheme, excavation method and other information; the tunnel is a deep buried tunnel with a burial depth of H d , height H t Large-scale mechanized supporting construction is adopted, and the excavation method is the step method and the full section method. The control parameters of the construction method are mainly: excavation footage l f , Upper step height H u and the upper step length S l wait.

[0038] S2, using finite difference software Flac 3D The initial stress field of the surrounding rock under different levels and different ground stress levels is calculated and the Flac 3D The initial stress field is saved and written using the self-written Fish language. Figure 2(a) is a cloud diagram of the initial stress field of the surrounding rock.

[0039] S3, simulate excavation of tunnel surrounding rock using step method and full section method, through Flac 3D The excavation stress field formed after excavation disturbance is calculated and the excavation stress field is obtained by using Flac 3D The self-written Fish language is used to save and write the excavation stress field. Figure 2(b) is a cloud diagram of the surrounding rock excavation stress field.

[0040] S4. Analyze the evolution characteristics of the stress field before and after excavation to determine the inner boundary of the surrounding rock pressure arch; analyze the degree of deviation of the maximum principal stress vector from the vertical direction to determine the outer boundary of the surrounding rock pressure arch. Specifically:

[0041] For the determination of the inner boundary of the pressure arch, the following method is used: for the horizontal stress increase area, such as Figure 3 If there is no horizontal stress reduction zone near the tunnel wall, the tunnel wall is the inner boundary of the pressure arch in this area. If there is a horizontal stress reduction zone near the tunnel wall, the surface where the horizontal stress does not increase or decrease is the inner boundary of the pressure arch in this area. For the vertical stress increase zone, such as Figure 4 , the maximum value of the maximum principal stress is distributed on the inner boundary of the pressure arch as a discrimination method. The evolution characteristics of the stress field before and after excavation are analyzed, and the excavation stress field obtained in step S3 is compared with the initial stress field obtained in step S2. According to whether the difference between the two is a positive value, it can be judged whether the area is a stress increase area:

[0042] σ 差 =σ 开挖 -σ 初始 (1)

[0043] Where: 差 is the excavation stress difference, σ 开挖 is the stress field formed by surrounding rock excavation, σ 初始 It is the initial stress field of the surrounding rock before excavation.

[0044] The following method is used to determine the outer boundary of the pressure arch: For the stratum where the vertical stress is the maximum principal stress, such as Figure 5 , the relative deflection index δ is introduced to indicate the degree to which the maximum principal stress vector deviates from the vertical direction, which is defined as follows:

[0045]

[0046] In the formula, σ max is the maximum principal stress, σ zz When δ<5%, the direction of the maximum principal stress vector gradually returns to the vertical direction, and δ=5% is used as the judgment method for the outer boundary of the pressure arch.

[0047] S5, through Flac 3D The built-in Fish language automatically calculates the upper and lower boundaries of the pressure arch at each excavation stage, realizing 3D visualization of the surrounding rock pressure arch range, such as Figure 6 The program picks up the position coordinates of the pressure arch at the key part of the tunnel, and realizes the automatic calculation and writing of the height and width of the pressure arch.

[0048] During the simulation, the middle part of the model (Y = 30m) was selected as the monitoring section, and the distance change between the monitoring section and the excavation surface was used to reflect the spatiotemporal effect of the evolution of the three-dimensional pressure arch after tunnel excavation. 3DThe model information is used to analyze the evolution of the pressure arch distribution range of the monitoring section as the excavation face advances, and the evolution law of the pressure arch range of the tunnel surrounding rock during the construction process is obtained.

[0049] S6. Perform curve fitting and correction on the key points of the upper and lower boundaries of the pressure arch, such as Figure 7 , obtain the calculation formula of the pressure arch range under different burial depths, different sections, different geology, and different excavation and support methods; automatically read the radial displacement of the arch top position at the outer boundary of the pressure arch.

[0050] S7. Calculate the loosening pressure inside the pressure arch of the surrounding rock and the deformation pressure outside the pressure arch respectively. The surrounding rock pressure is the sum of the loosening pressure inside the pressure arch (calculated using the height of the pressure arch in step S6) and the deformation pressure outside the pressure arch (Formula 3). Through a large number of calculations, a calculation formula for the surrounding rock pressure of a mechanized tunnel under different burial depths, different sections, different geology, and different excavation and support methods is obtained.

[0051] p=γh f +KΔ d (3)

[0052] Where: γ-surrounding rock mass (kN / m 3 );h f -pressure arch height (m); K-elastic reaction coefficient of surrounding rock (kPa / m); Δ d -Radial displacement of surrounding rock in the bearing area after the support structure is constructed (m).

[0053] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, technicians familiar with the field may make various corresponding changes and deformations based on the present invention, but these corresponding changes and deformations should all fall within the scope of protection of the claims attached to the present invention.

Claims

1. The method for calculating the pressure arch evolution and pressure of the surrounding rock of a mechanized tunnel using the drilling and blasting method is characterized by: The following steps are involved: S1. Statistics of tunnel engineering calculation parameters, including but not limited to the magnitude and direction of the geostress field, physical and mechanical parameters of the surrounding rock, support scheme, and excavation method; S2, using finite difference software Flac 3D Save and write out the initial stress field of surrounding rock; S3, simulate excavation of tunnel surrounding rock using step method and full section method, through Flac 3D Save and write out the excavation stress field formed after excavation disturbance; S4. Analyze the evolution characteristics of the stress field before and after excavation to determine the inner boundary of the surrounding rock pressure arch; analyze the degree of deviation of the maximum principal stress vector from the vertical direction to determine the outer boundary of the surrounding rock pressure arch; S5, through Flac 3D The built-in Fish language automatically calculates the upper and lower boundaries of the pressure arch at each excavation stage, realizes the three-dimensional visualization of the surrounding rock pressure arch range, and picks up the position coordinates of the pressure arch at the key parts of the tunnel through the program to realize the automatic calculation and writing of the height and width of the pressure arch; monitors the temporal and spatial evolution of the surrounding rock pressure arch range; S6. Curve fitting and correction are performed on the key points of the upper and lower boundaries of the pressure arch to obtain a calculation formula for the range of the pressure arch under different burial depths, different sections, different geology, and different excavation and support methods; the radial displacement of the top of the outer boundary of the pressure arch is automatically read; S7. Calculate the loosening pressure inside the pressure arch and the deformation pressure outside the pressure arch respectively. The surrounding rock pressure = loosening pressure inside the pressure arch + deformation pressure outside the pressure arch. The calculation formula of the surrounding rock pressure of mechanized tunnels under different burial depths, different sections, different geology, and different excavation and support methods is obtained: p❝γh f +KΔ d Where: γ-surrounding rock mass (kN / m 3 );h f -pressure arch height (m); K-elastic reaction coefficient of surrounding rock (kPa / m); Δ d -Radial displacement of surrounding rock in the bearing area after the support structure is constructed (m).

2. The method for calculating the pressure arch evolution and pressure of surrounding rock in a mechanized tunnel using the drilling and blasting method according to claim 1 is characterized by: In step S4, the method for determining the inner boundary of the pressure arch is as follows: for the horizontal stress increase area, if there is no horizontal stress reduction area near the tunnel wall, then the tunnel wall is the inner boundary of the pressure arch in this area; if there is a horizontal stress reduction area near the tunnel wall, then the surface where the horizontal stress does not increase or decrease is used as the inner boundary of the pressure arch at this location; for the vertical stress increase area, the maximum value of the maximum principal stress is distributed on the inner boundary of the pressure arch as a judgment method.

3. The method for calculating the pressure arch evolution and pressure of surrounding rock in a mechanized tunnel using the drilling and blasting method according to claim 2 is characterized by: The excavation stress field obtained in step S3 is compared with the initial stress field obtained in step S2, and whether the difference between the two is a positive value is determined to determine whether the area is a stress increase area: s 差 =s 开挖 -s 初始 (1) Where: 差 is the excavation stress difference, σ 开挖 is the stress field formed by surrounding rock excavation, σ 初始 It is the initial stress field of the surrounding rock before excavation.

4. The method for calculating the pressure arch evolution and pressure of surrounding rock in a mechanized tunnel using the drilling and blasting method according to claim 1 is characterized by: In step S4, the method for determining the outer boundary of the pressure arch is as follows: for a formation where the vertical stress is the maximum principal stress, a relative deflection index δ is introduced to indicate the degree to which the maximum principal stress vector deviates from the vertical direction, which is defined as follows: In the formula, σ max is the maximum principal stress, σ zz is the vertical stress; when δ<5%, the direction of the maximum principal stress vector gradually returns to the vertical direction, and δ=5% is used as the judgment method for the outer boundary of the pressure arch.

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