Stress analysis method of permeable lining structure during water filling process of high-pressure tunnel

Abstract

The present invention discloses a stress analysis method for a permeable lining structure during a high-pressure tunnel water filling process, that is, using equal-amplitude step-by-step pressurized water filling to simulate the continuous water filling process of a high-pressure tunnel, and simulating the cracking of the lining under the internal water pressure by presetting virtual cracks; during the step-by-step water filling process, the internal and external water pressures on the lining structure are considered as surface forces, the internal water pressure is applied to the inner side of the lining and the lining cracks respectively, and the external water pressure is applied to the outer side of the lining; after the lining cracks, the internal water seeps into the surrounding rock, and the water load on the surrounding rock is considered as body force. The stress-seepage coupling method is used to analyze the infiltration process of the internal water in the surrounding rock, and the zero-thickness contact surface unit is used to simulate the mutual separation of the lining and the surrounding rock caused by the internal water seepage. Compared with the traditional lining structure stress analysis method, the present invention accurately reflects the operating mechanism of the lining structure, simplifies the analysis of the internal water seepage process after the lining cracks, significantly improves the calculation efficiency of the lining structure stress analysis, and solves the problem of low calculation efficiency of the traditional analysis method.

Description

Technical Field

[0001] The present invention relates to a method for analyzing the stress of a permeable lining structure during the water filling process of a high-pressure tunnel, and specifically, to a method for analyzing the stress of a permeable lining structure during the water filling process of a high-pressure tunnel based on a simplified numerical simulation method combining surface force and body force. The present invention belongs to the technical field of design of reinforced concrete lining structures of high-pressure tunnels in water conservancy and hydropower engineering. Background Art

[0002] As the backbone of clean energy and national grid regulation, pumped storage has been vigorously developed. High-pressure tunnels are important water supply systems for pumped storage power stations to divert water for power generation. During operation, they will be subjected to high head pressure, which generally exceeds 500m. Therefore, the selection and design of high-pressure tunnel lining structures is a key task in the construction of pumped storage power stations.

[0003] Reinforced concrete lining is the preferred lining structure design type in high-pressure tunnel design and has been widely used in engineering. A large number of existing engineering practices have shown that during the water filling process of high-pressure tunnels, as the internal water pressure continues to increase, the reinforced concrete lining will inevitably be tensilely cracked, causing the internal water to seep out along the lining cracks. Therefore, this type of lining structure is also called a permeable lining structure. Moreover, through the monitoring data feedback during the water filling process of the existing projects, it is found that after the lining structure of the high-pressure tunnel cracks, the internal water seeps into the surrounding rock. Under the action of high water pressure, the lining and the surrounding rock will be separated from each other. The displacement continuity condition is no longer satisfied between the two, but the hydraulic continuity condition is satisfied. Therefore, the water filling process of the high-pressure tunnel is a complex hydraulic coupling process.

[0004] In order to meet the needs of engineering design, in view of the complex hydraulic coupling process in the high-pressure tunnel filling process, technical personnel in this field, when designing the high-pressure tunnel lining structure, respectively adopted the cohesive force unit with seepage function and the pore / fracture seepage-stress coupling theory to propose different high-pressure tunnel filling process analysis methods for the stress analysis and reinforcement calculation of the lining structure.

[0005] Although these analysis methods can more accurately reflect the operating mechanism of the high-pressure tunnel filling process, they need to deal with the complex hydraulic coupling behavior of the internal water seepage after the lining cracks when calculating the stress of the permeable lining structure. As a result, when calculating the stress of the lining structure based on these analysis methods, the calculation process is more complicated, the calculation time is longer, the stability is poor, and the efficiency is low, which makes it difficult to meet the needs of rapid engineering analysis.

[0006] Therefore, there is currently a lack of a simple, efficient and stable analysis method for the stress analysis of permeable lining structures during the water filling process of high-pressure tunnels. Summary of the invention

[0007] In view of the above reasons, the purpose of the present invention is to provide a method for analyzing the stress of a permeable lining structure during the water filling process of a high-pressure tunnel. According to the method for analyzing the stress of a permeable lining structure disclosed in the present invention, the stress of the lining structure is calculated with high efficiency, short calculation time and high accuracy.

[0008] To achieve the above object, the present invention adopts the following technical solution: a method for analyzing the stress of a permeable lining structure during water filling of a high-pressure tunnel, namely:

[0009] Using preset virtual cracks in the lining structure to simulate the cracking of the lining structure under the water pressure in the high-pressure tunnel;

[0010] A layer of zero-thickness contact surface unit is set between the lining structure and the surrounding rock. The zero-thickness contact surface unit is used to simulate the separation of the lining structure and the surrounding rock caused by the infiltration of internal water. The infiltration process of internal water in the surrounding rock is analyzed by the stress-seepage coupling method.

[0011] Formulate a step-by-step water filling scheme with equal amplitude to simulate the continuous water filling process of high-pressure tunnels;

[0012] During the step-by-step water filling process of the high-pressure tunnel, the internal and external water pressures on the lining structure are considered as surface forces. According to the water filling pressure of each level, the force boundary conditions of the lining structure at each level of water filling are determined. The internal water pressure is applied to the inner side of the lining and the lining cracks in the form of surface force, and the external water pressure is applied to the outer side of the lining structure in the form of surface force, which is used as the boundary condition for the force calculation of the lining structure.

[0013] During the process of equal-amplitude step-by-step water filling in high-pressure tunnels, the internal water seeps outward and contacts the inner side of the surrounding rock. The water load on the surrounding rock is considered based on physical strength, and the initial seepage boundary conditions of the surrounding rock are determined based on the water pressure on the outer side of the lining during each stage of water filling.

[0014] Furthermore, the method for presetting virtual cracks in the lining structure is: determining the setting position and number of virtual cracks according to the type of high-pressure tunnel geostress field; when the initial geostress field of the high-pressure tunnel is a vertical deadweight stress field, the virtual cracks are set at the top or bottom position of the lining structure, the number of the virtual cracks is 1 or 2, and there is a zero-thickness contact surface unit between the virtual cracks and the lining structure; when the initial geostress field of the high-pressure tunnel is a horizontal tectonic stress field, the virtual cracks are set at the horizontal waist position of the lining structure, the number of the virtual cracks is 1 or 2, and there is a zero-thickness contact surface unit between the virtual cracks and the lining structure.

[0015] Furthermore, the method for formulating the equal-amplitude step-by-step pressurization water filling scheme for simulating the continuous water filling process of the high-pressure tunnel is as follows:

[0016] S3.1. Determine the initial water filling pressure head of the step-by-step water filling scheme based on the standard value of the axial tensile strength of the concrete used for the lining;

[0017] Initial filling water pressure head pp initial The calculation formula is;

[0018] pp initial =ασ ftk (1)

[0019] Where: pp initial is the initial water filling pressure head, unit is MPa; α is the correction coefficient, the value is 1.5; σ ftk is the standard value of concrete axial tensile strength, unit: MPa;

[0020] S3.2. Determine the total number of water filling steps S for the step-by-step water filling scheme based on the initial water filling pressure head and the operating pressure head of the high-pressure tunnel. n , the calculation formula is:

[0021]

[0022] Where: pp final is the operating pressure head of the high-pressure tunnel, in MPa; pp initial is the initial water filling pressure head, unit MPa; Δp is the amplitude of step-by-step pressurization, unit MPa, and its value is 0.25MPa;

[0023] S3.3, determine the time step of the high-pressure tunnel with equal amplitude and step-by-step water filling;

[0024] T fluid =t|max(σ ratio )≤1.0e-5 (3)

[0025] Where: T fluid is the time step of equal-amplitude step-by-step water filling, max(σ ratio ) is the maximum unbalanced force.

[0026] Furthermore, the specific method for determining the stress boundary conditions of the lining structure is:

[0027] S4.1. Simulate the continuous water filling process of high-pressure tunnel according to the equal-amplitude step-by-step pressurization water filling scheme;

[0028] S4.2. When each stage of the high-pressure tunnel is filled with water, the water pressure inside the tunnel is evenly distributed and applied to the inner side of the lining and the lining cracks in the form of surface force according to the water filling pressure, and the water pressure outside the tunnel is applied to the outer side of the lining structure;

[0029] The water pressure value at each point inside the lining is the same and equal to the water pressure value at each level;

[0030] S4.3. When each stage of the high-pressure tunnel is filled with water, the external water pressure on the outside of the lining is determined according to the distribution of the external water pressure. The external water pressure of the tunnel is applied to the outside of the lining in the form of surface force;

[0031] If the external water pressure on the outside of the lining is applied in a linear distribution, the external water pressure decreases linearly from the crack position to the relative position of the crack according to the distance. The external water pressure p at each point on the outside of the lining from the crack position to the relative position of the crack is ext Calculate according to the following formula;

[0032]

[0033] In the formula, Indicates the external water pressure at the lining crack. is the external water pressure at the relative position of the lining crack, k is the ratio coefficient of the external water pressure at the lining outer crack to the relative position of the crack, which is 0.9, D is the tunnel diameter, and z is the vertical distance from the lining crack position to the relative position of the crack;

[0034] If the water pressure on the outside of the lining is applied uniformly, the same external water pressure is applied at different positions on the outside of the lining in the form of surface force. The external water pressure p at any point on the outside of the lining is ext Calculated as follows:

[0035]

[0036] In the formula, p ext Indicates the external water pressure value at a certain point outside the lining. Indicates the external water pressure value at the lining crack;

[0037] S4.4, when each stage of high-pressure tunnel is filled with water, water pressure is applied to the lining cracks in a surface force manner according to the water filling pressure value of each stage;

[0038] The water pressure at the lining crack decreases linearly from the inside to the outside of the lining. The water pressure p at any position on the lining crack is car Determined by the following formula:

[0039]

[0040]

[0041] In the formula, p car Indicates the water pressure at a certain point on the lining crack, is the water pressure on the inner side of the lining crack, which is equal to the water filling pressure value of each level. is the external water pressure at the lining crack, l is the crack length, z' is the distance from the crack outside the lining, and β is the reduction coefficient of the water pressure on the crack, which is taken as 0.95.

[0042] Furthermore, when the number of preset cracks in the lining is single, the water pressure outside the tunnel is applied to the outside of the lining in a uniform or linear manner; when the number of preset cracks in the lining is two, the water pressure outside the tunnel needs to be applied to the outside of the lining in a uniform manner.

[0043] Furthermore, the method for determining the initial seepage boundary condition of the surrounding rock is:

[0044] During the calculation and analysis of each level of water filling, the internal water seeps out and contacts the inner side of the surrounding rock. According to the balance relationship between the external water pressure applied to the outer side of the lining and the water pressure applied to the inner side of the lining, the water pressure value p applied on the inner boundary of the surrounding rock during each level of water filling in the high-pressure tunnel is SR The same as the external water pressure value on the outside of the lining at the same position, that is, it satisfies the following formula:

[0045] p SR =p ext (9)

[0046] In the formula, p SR is the water pressure at a certain point inside the surrounding rock, p ext It is the external water pressure on the outside of the lining.

[0047] The present invention considers the operating mechanism of the permeable lining structure and uses a simplified numerical simulation method combining surface force and body force to analyze the stress of the lining structure during the water filling process of the high-pressure tunnel and after the lining structure cracks, thereby significantly improving the calculation efficiency of the force analysis of the permeable lining structure and solving the problem of low calculation efficiency of traditional analysis methods.

[0048] Compared with the traditional pore / fracture seepage-stress coupling analysis method, the present invention can determine the lining cracking position according to the ground stress type. At the same time, the external water pressure on the outside of the lining can consider two distribution types: uniform and linear. The stress condition of the lining structure is analyzed, which is closer to the actual engineering situation and the analysis result is more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 A schematic diagram of the force on the permeable lining structure during the water filling process of a high-pressure tunnel analyzed by the present invention;

[0050] Figure 2 A flow chart of a method for analyzing the stress of a permeable lining structure during a high-pressure tunnel filling process according to the present invention;

[0051] Figure 3A A schematic diagram of a single virtual crack established for the present invention;

[0052] Figure 3B for Figure 3A A local magnified image of a virtual crack;

[0053] Figure 4A Schematic diagram of two virtual cracks established for the present invention;

[0054] Figure 4B for Figure 4A A local magnified image of a virtual crack;

[0055] Figure 5A It is a schematic diagram of the three-dimensional structure of the surrounding rock and lining structure of the present invention;

[0056] Figure 5B for Figure 5A The three-dimensional diagram of the zero-thickness contact surface unit between the lining and the surrounding rock established in the paper;

[0057] Figure 6 A schematic diagram of a steel bar structure unit established for the present invention;

[0058] Figure 7 This is a schematic diagram of the step-by-step pressurization and water filling process of the present invention;

[0059] Fig. 8A It is a schematic diagram of the water pressure application method inside the lining of the present invention;

[0060] Figure 8B This is a diagram of the linear application of water pressure on the outer side of the lining of the present invention;

[0061] Figure 8C This is a diagram showing a method for uniformly applying water pressure on the outer side of the lining of the present invention;

[0062] Fig.8D It is a schematic diagram of the water pressure application method at the lining crack of the present invention;

[0063] Fig. 9 This is a diagram of the method of applying water pressure inside the surrounding rock according to the present invention.

[0064] Among them, p int represents the internal water pressure on the lining structure, p ext represents the external water pressure on the lining structure, p lin Represents the seepage phenomenon of water in the lining structure, p SR' Indicates the seepage phenomenon of water in the surrounding rock; p car It represents the water pressure on the crack after the lining structure cracks, p SR Indicates the water pressure on the surrounding rock; 1- lining structure, 2- virtual crack, 3- surrounding rock, 4- zero thickness contact surface unit between lining and surrounding rock, 5- steel structure unit. DETAILED DESCRIPTION

[0065] The structure and features of the present invention are described in detail below in conjunction with the accompanying drawings and embodiments. It should be noted that various modifications can be made to the embodiments disclosed herein, and therefore, the embodiments disclosed in the specification should not be regarded as limiting the present invention, but are merely examples of embodiments, the purpose of which is to make the features of the present invention obvious.

[0066] When designing the lining structure of a high-pressure tunnel, technicians in this field usually use a cohesive force unit with a seepage function based on the pore / crack seepage-stress coupling theory, and establish a three-dimensional finite difference numerical calculation model of a high-pressure tunnel containing a lining structure to calculate the hoop stress and radial stress, steel bar stress and crack width of the lining structure during the water filling process of the high-pressure tunnel. However, as the internal water pressure of the high-pressure tunnel continues to increase during the water filling process, the lining structure will inevitably be tensilely cracked, causing the internal water to seep out along the lining cracks and penetrate into the surrounding rock. The forces of the lining structure itself, the surrounding rock itself, and the forces between the lining and the surrounding rock all change, making the force analysis and calculation process of the lining structure complicated, the calculation time prolonged, and the calculation efficiency low.

[0067] In order to solve the problem of complex force analysis and low calculation efficiency of permeable lining structure in the process of high-pressure tunnel water filling in the traditional process, the present invention proposes a new force analysis method for lining structure in the process of high-pressure tunnel water filling. According to the force analysis method for lining structure, the force of lining structure is calculated by the three-dimensional finite difference numerical calculation model of high-pressure tunnel, which has high calculation efficiency and accuracy. Figure 1 As shown, when analyzing the stress of the permeable lining structure during the high-pressure tunnel filling process, the present invention first uses a preset virtual crack 2 in the lining structure 1 to simulate the cracking of the lining structure under the water pressure in the high-pressure tunnel; a zero-thickness contact surface unit 4 is set between the lining and the surrounding rock, and the zero-thickness contact surface unit is used to simulate the separation of the lining structure 1 and the surrounding rock 3 caused by the seepage of water in the tunnel after the lining structure cracks, and the stress-seepage coupling method is used to analyze the penetration process of the internal water in the surrounding rock; then, an equal-amplitude step-by-step pressurized water filling method is used to simulate the continuous water filling process of the high-pressure tunnel; according to the formulated equal-amplitude step-by-step pressurized water filling method, the water in the surrounding rock is analyzed. In the process of equal-amplitude step-by-step water filling of high-pressure tunnels, the internal and external water pressures on the lining structure are considered as surface forces. According to the water filling pressure of each stage, the force boundary conditions of the lining structure at each stage of water filling are determined, in which the internal water pressure is applied to the inner side of the lining and the lining cracks in the form of surface force, and the external water pressure is applied to the outer side of the lining structure in the form of surface force, which is used as the boundary condition for the force calculation of the lining structure; in the process of equal-amplitude step-by-step water filling of high-pressure tunnels, the internal water seeps out and contacts the inner side of the surrounding rock. The water load on the surrounding rock is considered as body force, and the initial seepage boundary conditions of the surrounding rock are determined according to the water pressure on the outer side of the lining at each stage of water filling.

[0068] The stress boundary conditions of the lining structure and the initial seepage boundary conditions of the surrounding rock are input into the three-dimensional finite difference numerical calculation model of the high-pressure tunnel to calculate the annular stress and radial stress of the lining structure, the steel bar stress and the crack width during the water filling process of the high-pressure tunnel.

[0069] like Figure 2 As shown, the method for analyzing the stress of the permeable lining structure during the high-pressure tunnel filling process of the present invention is:

[0070] S1. First, virtual cracks are preset in the lining structure to simulate the cracking of the lining structure under the water pressure in the high-pressure tunnel.

[0071] Since the cracking position of the lining crack under the action of high internal water is consistent with the direction of the maximum principal stress, and in most cases the number of through cracks is 1 to 2, the present invention determines the location and number of virtual cracks according to the type of high-pressure tunnel geostress field. The specific principle is: when the initial geostress field of the high-pressure tunnel is a vertical self-weight stress field, such as Figure 3A and Figure 3B As shown in FIG. 1 , the virtual crack 2 is set at the top or bottom of the lining structure 1, and the virtual crack 2 and the lining structure 1 are zero-thickness contact surface units. When the initial geostress field of the high-pressure tunnel is a horizontal tectonic stress field, as shown in FIG. Figure 4A and Figure 4B As shown, the virtual crack 2 is set at the horizontal waist position of the lining structure 1, and there is a zero-thickness contact surface unit between the virtual crack and the lining structure.

[0072] S2. A layer of zero-thickness contact surface unit is set between the lining and the surrounding rock to simulate the separation between the lining and the surrounding rock after the lining structure cracks.

[0073] like Figure 5A and 5B As shown, in order to simulate the separation between the lining and the surrounding rock after the lining structure cracks, the present invention sets a layer of zero-thickness contact surface unit 4 between the lining structure 1 and the surrounding rock 3.

[0074] In order to calculate the stress of the lining structure, a steel structure unit 5 is designed in the lining structure 1, such as Figure 6 shown.

[0075] S3. According to the standard value of the axial tensile strength of the concrete used in the lining structure and the operating water head of the high-pressure tunnel, determine the equal-amplitude step-by-step pressurization water filling scheme for the high-pressure tunnel to simulate the continuous water filling process of the high-pressure tunnel.

[0076] The present invention adopts a step-by-step equal amplitude pressurized water filling method to simulate the high-pressure tunnel filling process, see Figure 7 As shown;

[0077] S3.1. Determine the initial water filling pressure head of the step-by-step water filling scheme based on the standard value of the axial tensile strength of the concrete used for the lining.

[0078] Initial filling water pressure head pp initial The calculation formula is;

[0079] pp initial =ασ ftk (1)

[0080] Where: pp initial is the initial water filling pressure head, unit is MPa; α is the correction coefficient, the value is 1.5; σ ftk It is the standard value of concrete axial tensile strength, unit is MPa, the value can be referred to Table 1:

[0081] Table 1 Standard values ​​of concrete axial tensile strength

[0082]

[0083] S3.2. Determine the total number of water filling steps S for the step-by-step water filling scheme based on the initial water filling pressure head and the operating pressure head of the high-pressure tunnel. n , the calculation formula is as follows:

[0084]

[0085] Where: pp final is the operating pressure head of the high-pressure tunnel, in MPa; pp initial is the initial water filling pressure head, unit is MPa; Δp is the amplitude of step-by-step pressurization, unit is MPa, and its value is usually 0.25MPa.

[0086] S3.3. Determine the time step for the step-by-step filling of the high-pressure tunnel with equal amplitude.

[0087] The present invention uses equal-amplitude step-by-step pressurized water filling to simulate the continuous water filling process of a high-pressure tunnel. In order to ensure numerical stability and computational efficiency, the seepage calculation time is the same at each level of water filling pressure, that is, the same step-by-step water filling time step is used. Whether the step-by-step water filling time step is determined rationally will affect the calculation time and calculation accuracy of the entire water filling process. If the water filling time step is too large, the calculation time of the entire water filling process will be too long; if the water filling time step is too small, the stress seepage calculation will not reach a state of equilibrium, and reliable simulation results cannot be obtained. When the stress seepage calculation reaches a state of equilibrium, when the imbalance in the seepage calculation is less than a certain threshold, the present invention uses an equal-amplitude step-by-step water filling time step, and the determination formula is as follows:

[0088] T fluid =t|max(σ ratio )≤1.0e-5 (3)

[0089] Where: T fluid is the time step of equal-amplitude step-by-step water filling, max(σratio ) is the maximum unbalanced force ratio.

[0090] The invention is the key to improving the efficiency of force analysis calculation of permeable lining structure in high-pressure tunnel water filling process, and determines the force boundary conditions of lining structure and the initial seepage boundary conditions of surrounding rock.

[0091] During the high-pressure tunnel equal-amplitude step-by-step water filling process, the method for determining the stress boundary conditions of the lining structure is: according to the surface force of the internal and external water pressures on the lining structure, the internal water pressure is applied to the inside of the lining and the lining cracks, and the external water pressure is applied to the outside of the lining structure. The specific method is:

[0092] S4.1. According to the water filling scheme determined in step S3, equal amplitude step-by-step pressurization water filling is performed to simulate the continuous water filling process of the high-pressure tunnel.

[0093] In the present invention, the annular reinforcement in the lining is simulated using Cable structural units.

[0094] S4.2. When each stage of the high-pressure tunnel is filled with water, the pressure on the inner side of the lining structure and at the lining cracks is calculated based on the water filling pressure.

[0095] Depend on Figure 1 It can be seen that during the continuous water filling process of the high-pressure tunnel, the internal water pressure p in the tunnel is int The water pressure outside the tunnel is evenly distributed and applied to the inner side of the lining and the cracks of the lining in the form of surface force. ext Applied to the outside of the lining structure.

[0096] like Fig. 8A As shown, the water pressure inside the lining structure 1 is considered as surface force and is applied to the inside of the lining in a uniform distribution, that is, the water pressure values ​​at each point inside the lining are the same and equal to the water filling pressure value of each stage.

[0097] S4.3. Calculate the external water pressure on the outside of the lining structure when each stage of the high-pressure tunnel is filled with water.

[0098] In each level of water filling calculation, the external water pressure on the outside of the lining is determined according to the distribution form of the external water pressure. The external water pressure is applied to the outside of the lining in the form of surface force. When calculating the external water pressure on the outside of the lining, the surface force is considered. The external water pressure can be distributed in a linear manner (such as Figure 8B ) and uniform distribution (as shown in Figure 8C Two distribution types (as shown) are applied to the outside of the lining.

[0099] Furthermore, when the number of preset cracks in the lining is single, the external water pressure can be applied to the outside of the lining in a uniform or linear manner; when the number of preset cracks in the lining is two, the external water pressure needs to be applied to the outside of the lining in a uniform manner.

[0100] like Figure 8B If the external water pressure on the outside of the lining is applied in a linear distribution, the external water pressure decreases linearly according to the distance from the crack position to the relative position of the crack. The external water pressure p at each point on the outside of the lining from the crack position to the relative position of the crack ext Calculate according to the following formula;

[0101]

[0102] In the formula, Indicates the external water pressure at the lining crack, is the external water pressure at the relative position of the lining crack, k is the ratio coefficient of the external water pressure at the crack on the outside of the lining to the relative position of the crack, which is taken as 0.9, D is the tunnel diameter, and z is the vertical distance from the lining crack position to the relative position of the crack.

[0103] like Figure 8C If the water pressure on the outside of the lining is applied uniformly, the same external water pressure is applied at different positions on the outside of the lining in the form of surface force. The external water pressure p at any point on the outside of the lining ext Calculated as follows:

[0104]

[0105] In the formula, p ext Indicates the external water pressure value at a certain point outside the lining. Indicates the external water pressure value at the lining crack.

[0106] S4.4. In the calculation of each level of water filling, water pressure is applied to the lining cracks in a surface force manner based on the water filling pressure value of each level and the external water pressure at the lining cracks.

[0107] In the present invention, the water pressure at the lining crack is distributed in a linear decreasing manner from the inside to the outside of the lining. Fig.8D As shown in the figure, the water pressure p at any position on the lining crack is car Determined by the following formula:

[0108]

[0109] In the formula, p car Indicates the water pressure at a certain point on the lining crack, is the water pressure on the inner side of the lining crack, which is equal to the water filling pressure value of each level. is the external water pressure at the lining crack, l is the crack length, z' is the distance from the crack outside the lining, and β is the reduction coefficient of the water pressure on the crack, which is taken as 0.95.

[0110] During the process of equal-amplitude step-by-step water filling in a high-pressure tunnel, when the lining structure cracks, the internal water seeps into the surrounding rock. The method for determining the initial seepage boundary conditions of the surrounding rock is as follows: the water load on the surrounding rock is considered as body force, the stress-seepage coupling method is used to analyze the infiltration process of the internal water in the surrounding rock, the zero-thickness contact surface unit is used to simulate the separation of the lining structure and the surrounding rock caused by the infiltration of the internal water, and the initial seepage boundary conditions of the surrounding rock are calculated.

[0111] The present invention simplifies the lining cracking process. The initial water filling pressure value in the step-by-step water filling pressure scheme exceeds the tensile strength of the lining. During the water filling process, the lining cracks are always in a cracking state. After the lining cracks and the internal water seeps out, the water load on the surrounding rock is considered as physical strength. By applying water pressure on the inner side of the surrounding rock, the stress-seepage coupling method is used to analyze the infiltration process of the internal water in the surrounding rock. Fig. 9 As shown in the figure, according to the balance of forces, in each level of water filling calculation, the water pressure value p applied on the inner boundary of the surrounding rock is SR The same as the external water pressure value on the outside of the lining at the same position, that is, it satisfies the following formula:

[0112] p SR =p ext (9)

[0113] In the formula, p SR is the water pressure at a certain point inside the surrounding rock, p ext It is the external water pressure on the outside of the lining.

[0114] When the high-pressure tunnel is filled with water at each stage, the stress boundary conditions of the lining structure and the initial seepage boundary conditions of the surrounding rock are input into the three-dimensional finite difference numerical calculation model of the high-pressure tunnel. According to the equal-amplitude step-by-step water filling scheme, the water filling process is continuously simulated until the total number of steps of step-by-step pressurized water filling is reached. According to the monitoring results during the step-by-step water filling process, the circumferential stress and radial stress of the lining structure, the steel bar stress and crack width during the high-pressure tunnel water filling process can be calculated.

[0115] Compared with the traditional force analysis method of permeable lining structure, the present invention analyzes the force boundary conditions of the permeable lining structure and surrounding rock during the high-pressure tunnel filling process based on a simplified numerical simulation method combining surface force and body force, while accurately reflecting the operating mechanism of the permeable lining. This significantly improves the force calculation efficiency of the lining structure and solves the problem of low calculation efficiency of the traditional method.

[0116] Finally, it should be noted that the above-described embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for analyzing the stress of a permeable lining structure during water filling of a high-pressure tunnel, characterized in that: Using preset virtual cracks in the lining structure to simulate the cracking of the lining structure under the water pressure in the high-pressure tunnel; A layer of zero-thickness contact surface unit is set between the lining structure and the surrounding rock. The zero-thickness contact surface unit is used to simulate the separation of the lining structure and the surrounding rock caused by the infiltration of internal water. The infiltration process of internal water in the surrounding rock is analyzed by the stress-seepage coupling method. Formulate a step-by-step water filling scheme with equal amplitude to simulate the continuous water filling process of high-pressure tunnels; During the step-by-step water filling process of the high-pressure tunnel, the internal and external water pressures on the lining structure are considered as surface forces. According to the water filling pressure of each level, the force boundary conditions of the lining structure at each level of water filling are determined. The internal water pressure is applied to the inner side of the lining and the lining cracks in the form of surface force, and the external water pressure is applied to the outer side of the lining structure in the form of surface force, which is used as the boundary condition for the force calculation of the lining structure. During the process of equal-amplitude step-by-step water filling in high-pressure tunnels, the internal water seeps outward and contacts the inner side of the surrounding rock. The water load on the surrounding rock is considered based on physical strength, and the initial seepage boundary conditions of the surrounding rock are determined based on the water pressure on the outer side of the lining during each stage of water filling.

2. The method for analyzing the stress of a permeable lining structure during water filling of a high-pressure tunnel according to claim 1 is characterized by: The method for presetting virtual cracks in the lining structure is: determining the setting positions and number of virtual cracks according to the type of the high-pressure tunnel ground stress field; When the initial geostress field of the high-pressure tunnel is a vertical self-weight stress field, the virtual crack is set at the top or bottom of the lining structure, the number of the virtual cracks is 1 or 2, and the virtual crack and the lining structure are zero-thickness contact surface units; When the initial geostress field of the high-pressure tunnel is a horizontal tectonic stress field, the virtual crack is set at the horizontal waist position of the lining structure, the number of the virtual cracks is 1 or 2, and there is a zero-thickness contact surface unit between the virtual crack and the lining structure.

3. The method for analyzing the stress of a permeable lining structure during water filling of a high-pressure tunnel according to claim 2 is characterized by: The method for formulating the equal-amplitude step-by-step pressurization water filling scheme for simulating the continuous water filling process of the high-pressure tunnel is as follows: S3.

1. Determine the initial water filling pressure head of the step-by-step water filling scheme based on the standard value of the axial tensile strength of the concrete used for the lining; Initial filling water pressure head pp initial The calculation formula is; pp initial =as ftk (1) Where: pp initial is the initial water filling pressure head, unit is MPa; α is the correction coefficient, the value is 1.5; σ ftk is the standard value of concrete axial tensile strength, unit: MPa; S3.

2. Determine the total number of water filling steps S for the step-by-step water filling scheme based on the initial water filling pressure head and the operating pressure head of the high-pressure tunnel. n , the calculation formula is: Where: pp final is the operating pressure head of the high-pressure tunnel, in MPa; pp initial is the initial water filling pressure head, unit: MPa; Δp is the amplitude of step-by-step pressurization, unit: MPa, and its value is 0.25MPa; S3.3, determine the time step of the high-pressure tunnel with equal amplitude and step-by-step water filling; T fluid =t|max(σ ratio )≤1.0e-5 (3) Where: T fluid is the time step of equal-amplitude step-by-step water filling, max(σ ratio ) is the maximum unbalanced force.

4. The method for analyzing the stress of a permeable lining structure during water filling of a high-pressure tunnel according to claim 3 is characterized by: The specific method for determining the stress boundary conditions of the lining structure is: S4.

1. Simulate the continuous water filling process of high-pressure tunnel according to the equal-amplitude step-by-step pressurization water filling scheme; S4.

2. When each stage of the high-pressure tunnel is filled with water, the water pressure inside the tunnel is evenly distributed and applied to the inner side of the lining and the lining cracks in the form of surface force according to the water filling pressure, and the water pressure outside the tunnel is applied to the outer side of the lining structure; The water pressure value at each point inside the lining is the same and equal to the water pressure value at each level; S4.

3. When each stage of the high-pressure tunnel is filled with water, the external water pressure on the outside of the lining is determined according to the distribution of the external water pressure. The external water pressure of the tunnel is applied to the outside of the lining in the form of surface force; If the external water pressure on the outside of the lining is applied in a linear distribution, the external water pressure decreases linearly from the crack position to the relative position of the crack according to the distance. The external water pressure p at each point on the outside of the lining from the crack position to the relative position of the crack is ext Calculate according to the following formula; In the formula, Indicates the external water pressure at the lining crack. is the external water pressure at the relative position of the lining crack, k is the ratio coefficient of the external water pressure at the lining outer crack to the relative position of the crack, which is 0.9, D is the tunnel diameter, and z is the vertical distance from the lining crack position to the relative position of the crack; If the water pressure on the outside of the lining is applied uniformly, the same external water pressure is applied at different positions on the outside of the lining in the form of surface force. The external water pressure p at any point on the outside of the lining is ext Calculated as follows: In the formula, p ext Indicates the external water pressure value at a certain point outside the lining. Indicates the external water pressure value at the lining crack; S4.4, when each stage of high-pressure tunnel is filled with water, water pressure is applied to the lining cracks in a surface force manner according to the water filling pressure value of each stage; The water pressure at the lining crack decreases linearly from the inside to the outside of the lining. The water pressure p at any position on the lining crack is car Determined by the following formula: In the formula, p car Indicates the water pressure at a certain point on the lining crack, is the water pressure on the inner side of the lining crack, which is equal to the water filling pressure value of each level. is the external water pressure at the lining crack, l is the crack length, z' is the distance from the crack outside the lining, and β is the reduction coefficient of the water pressure on the crack, which is taken as 0.

95.

5. The method for analyzing the stress of a permeable lining structure during water filling of a high-pressure tunnel according to claim 4 is characterized in that: When the number of preset cracks in the lining is single, the external water pressure of the tunnel is applied to the outside of the lining in a uniform or linear manner; when the number of preset cracks in the lining is two, the external water pressure of the tunnel needs to be applied to the outside of the lining in a uniform manner.

6. The method for analyzing the stress of a permeable lining structure during water filling of a high-pressure tunnel according to claim 4 or 5, characterized in that: The method for determining the initial seepage boundary conditions of surrounding rock is: During the calculation and analysis of each level of water filling, the internal water seeps out and contacts the inner side of the surrounding rock. According to the balance relationship between the external water pressure applied to the outer side of the lining and the water pressure applied to the inner side of the lining, the water pressure value p applied on the inner boundary of the surrounding rock during each level of water filling in the high-pressure tunnel is SR The same as the external water pressure value on the outside of the lining at the same position, that is, it satisfies the following formula: p SR =p ext (9) In the formula, p SR is the water pressure at a certain point inside the surrounding rock, p ext It is the external water pressure on the outside of the lining.

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