Design Methods of Tunnel Structures

Abstract

The present application provides a design method for a tunnel structure, which relates to the field of tunnel construction. The method includes: determining the basic load condition of the erection space, the basic load condition is used to indicate the vertical load condition and the horizontal load condition of the erection space, and the basic load condition corresponds to the surrounding rock grade of the erection space and the tunnel burial depth; based on the basic load condition and the preset sharing ratio, determining the erection thickness of the initial support structure, the preset sharing ratio is a ratio value greater than the required ratio condition, and the required ratio condition is used to indicate that the initial support structure is erected with a full load sharing condition; based on the initial support structure and the structural internal force conditions of the erection space, a secondary lining structure is erected on the basis of the initial support structure to obtain a tunnel structure in the erected space. The initial support structure is used to fully bear the surrounding rock load pressure, reduce the concrete thickness of the secondary lining structure, reduce the overall stiffness of the tunnel lining, and reduce the damage to the tunnel structure during an earthquake.

Description

Technical Field

[0001] The present application relates to the field of tunnel construction, and in particular to a design method for a tunnel structure. Background Art

[0002] The drilling and blasting tunnel is an economical and effective method for highways, railways, oil and gas pipelines and other projects to cross mountains and overcome height differences. It is widely used in relevant projects at home and abroad. In the 20th century, many earthquakes occurred around the world, causing varying degrees of damage to underground structures, thus providing a large amount of necessary and valuable data for in-depth research on the mechanism of tunnel earthquake damage.

[0003] In the current relevant tunnel design specifications, for tunnels with a magnitude of 7 or less, only the shallow entrance and exit sections are required to be seismically checked. For earthquake zones with a magnitude of 8 or 9, not only the shallow entrance sections are required to be seismically checked, but also the deep-buried fault fracture zones, weak and large deformation sections and other unfavorable geological sections are required to be seismically checked.

[0004] The seismic force of the structure is the main load for structural verification. If the current structural calculation method is used, the high-intensity earthquake zone will still be borne independently by the secondary lining structure, and the thickness of the secondary lining structure of the tunnel will be increased to meet the structural seismic requirements. However, from the above-mentioned earthquake influencing factors, the thicker the tunnel lining is, the greater its stiffness is, and the greater the impact of earthquake damage is, which is more unfavorable to the seismic effect of the tunnel structure. At the same time, increasing the thickness of the secondary lining to support seismic resistance has increased the project investment to a certain extent. Summary of the invention

[0005] The embodiment of the present application provides a design method for a tunnel structure. When designing the tunnel structure, the load sharing ratio of the initial support structure and the secondary lining structure is adjusted, and the initial support structure bears all the surrounding rock loads, thereby achieving the joint earthquake resistance effect of the initial support structure and the secondary lining structure, effectively saving engineering investment and reducing the damage to the tunnel structure during an earthquake to a certain extent. The technical solution is as follows:

[0006] According to one aspect of the present application, a method for designing a tunnel structure is provided, the method comprising:

[0007] Determine the basic load condition of the erection space, the basic load condition is used to indicate the vertical load condition and the horizontal load condition of the erection space, the basic load condition corresponds to the surrounding rock grade of the erection space and the tunnel burial depth, the surrounding rock grade is used to indicate that the erection space is a surrounding rock of grade V or above;

[0008] Determining the erection thickness of the initial support structure based on the basic load condition and a preset sharing ratio, wherein the preset sharing ratio is a ratio value greater than a required ratio condition, and the required ratio condition is used to indicate that the initial support structure is to be erected with a full load sharing condition;

[0009] Based on the initial support structure and the structural internal force conditions of the erection space, a secondary lining structure is erected on the basis of the initial support structure to obtain a tunnel structure in the erection space.

[0010] In an optional embodiment, determining the erection thickness of the initial support structure based on the basic load condition and the preset sharing ratio includes:

[0011] Determine the surrounding rock density, permanent load coefficient and surrounding rock collapse height of the frame space; determine the vertical load condition based on the product of the surrounding rock density, the permanent load coefficient and the surrounding rock collapse height;

[0012] determining an upper lateral pressure and a lower lateral pressure based on the vertical load condition;

[0013] The vertical load condition, the upper lateral pressure and the lower lateral pressure are applied to the erection space according to the preset sharing ratio to obtain the erection thickness of the initial support, which includes the thickness of the inner protective layer, the thickness of the outer protective layer, the thickness of the first shotcrete and the strength grade of the first shotcrete.

[0014] In an optional embodiment, before determining the vertical load condition based on the product of the surrounding rock density, the permanent load coefficient and the height of the surrounding rock collapse body, the method further includes:

[0015] Determine a first value of a first preset parameter after target power operation, and a product of the first value and a second preset parameter as the height of the surrounding rock collapse body, wherein the value of the target power corresponds to the surrounding rock grade.

[0016] In an optional embodiment, the basic load condition of the erection space further includes a basic ground motion peak acceleration;

[0017] The method further comprises: before erecting a secondary lining structure on the basis of the initial support structure and the structural internal force conditions of the erection space, the method further comprises:

[0018] Adjusting the basic earthquake peak acceleration according to a preset rule to obtain a reduced basic earthquake peak horizontal acceleration and a reduced basic earthquake peak vertical acceleration;

[0019] The structural internal force condition of the erection space is determined based on the reduced basic seismic peak horizontal acceleration and the reduced basic seismic peak vertical acceleration.

[0020] In an optional embodiment, adjusting the basic dynamic peak acceleration according to a preset rule to obtain a reduced basic earthquake motion peak horizontal acceleration and a reduced basic earthquake motion peak vertical acceleration includes:

[0021] Determine a depth reduction coefficient according to a preset rule, wherein the depth reduction coefficient is used to indicate the earthquake damage corresponding to different buried depths of the erection structure; determine the product of the depth reduction coefficient and the basic seismic peak acceleration as the reduced basic seismic peak horizontal acceleration;

[0022] The product of the reduced basic seismic peak horizontal acceleration and a third preset parameter is determined as the reduced basic seismic peak vertical acceleration.

[0023] In an optional embodiment, the method further includes:

[0024] Determining a structural internal force condition of the erection structure based on the reduced basic earthquake peak horizontal acceleration and the reduced basic earthquake peak vertical acceleration;

[0025] The cross-sectional axial force, cross-sectional shear force and cross-sectional bending moment of the secondary lining structure are obtained based on the structural internal force conditions.

[0026] In an optional embodiment, the method further includes:

[0027] The thickness of the secondary lining structure and the second shotcrete strength grade are determined based on the cross-sectional axial force, the cross-sectional shear force, the cross-sectional bending moment and the initial support structure.

[0028] In an optional embodiment, the method further includes:

[0029] A waterproof layer is laid between the primary supporting structure and the secondary lining structure.

[0030] In an optional embodiment, the structural internal force conditions of the initial support structure and the erection space, before erecting the secondary lining structure on the basis of the initial support structure, further include:

[0031] Determine the shotcrete cross-sectional area and the secondary lining cross-sectional area of ​​the erection space; determine the sum of the shotcrete cross-sectional area and the secondary lining cross-sectional area as the structural calculation cross-sectional area;

[0032] Determine the shotcrete moment of inertia and the secondary lining moment of inertia of the erection space, and determine the shotcrete moment of inertia and the secondary lining moment of inertia as the structural calculation moment of inertia;

[0033] The structural internal force condition is determined based on the structural calculated cross-sectional area and the structural calculated moment of inertia.

[0034] In an optional embodiment, the structural internal force conditions of the initial support structure and the erection space, before erecting the secondary lining structure on the basis of the initial support structure, further include:

[0035] No waterproof layer is laid between the primary support structure and the secondary lining structure;

[0036] Determining a calculated cross-sectional area for the structure based on the shotcrete cross-sectional area and the secondary lining cross-sectional area;

[0037] Determine the distance from the centroid of the shotcrete section to the centroid of the secondary lining section to obtain the first distance;

[0038] Determine the calculated moment of inertia of the structure according to a preset formula based on the shotcrete cross-sectional area, the secondary lining cross-sectional area and the first distance;

[0039] The structural internal force condition is determined based on the structural calculated cross-sectional area and the structural calculated moment of inertia.

[0040] The beneficial effects brought by the technical solution provided by the embodiment of the present application include at least:

[0041] Based on the basic load conditions of the erection space and the preset sharing ratio, the initial support structure is determined, and the secondary lining structure is determined based on the initial support structure and the structural internal force conditions of the erection space, and finally the tunnel structure is obtained. The initial support structure bears all the surrounding rock load pressure, reduces the thickness of the secondary lining concrete, reduces the overall stiffness of the tunnel lining, and achieves the joint earthquake resistance effect of the initial structure and the secondary lining structure, which reduces the damage to the tunnel structure during an earthquake to a certain extent and saves engineering investment. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0043] Figure 1 is a structural schematic diagram of a mounting space provided by an exemplary embodiment of the present application;

[0044] Figure 2 is a flow chart of a design method for a tunnel structure provided by an exemplary embodiment of the present application;

[0045] Figure 3 is a flow chart of a method for designing a tunnel structure provided by another embodiment;

[0046] Figure 4 is based on Figure 3 Schematic diagram of all-directional seismic forces in the erection space provided in the embodiment;

[0047] Figure 5 is a flow chart of a method for designing a tunnel structure provided by another embodiment;

[0048] Figure 6 It is a flow chart of a method for verifying a tunnel structure provided by another embodiment. DETAILED DESCRIPTION

[0049] In order to make the objectives, technical solutions and advantages of the present application more clear, the present application is further described in detail below in conjunction with the accompanying drawings.

[0050] First, the application scenarios involved in the embodiments of the present application are introduced.

[0051] In the current high-intensity earthquake zones, the destructive force is stronger on the surface and weaker underground. When designing earthquake-resistant tunnels in high-intensity earthquake zones of level V and above, the design and calculation of the tunnel seismic structure should specify an appropriate release load sharing ratio so that the support structure and surrounding rock are combined into a joint force-bearing whole and jointly bear the effect of the release load. The release load sharing ratio is used to indicate the proportion of the release load borne by the support structure (initial support structure and secondary lining structure) and the surrounding rock in the total release load after the tunnel structure is determined and excavation is carried out.

[0052] Considering the stress conditions during the construction and excavation process, in order to ensure the need for safe construction, it is particularly important to ensure the safety of the secondary lining structure before the construction of the primary support structure. For tunnel structures built in grade V surrounding rock and above, the load release ratio of the surrounding rock and the primary support structure reaches about 60%-80%. Considering the permanent safety of the primary support structure, the sharing ratio of the secondary lining structure should reach 60%-80%. The former is used when the rock quality is good, and the latter is used when the rock quality is poor. The conventional calculation of the load release coefficient of each level of surrounding rock can be determined by referring to Table 1.

[0053] Table 1 Sharing ratio

[0054] Surrounding rock grade The ratio of initial support structure to surrounding rock support bearing capacity Secondary lining load ratio Ⅱ 100 Safety Reserve Ⅲ 100 Safety Reserve Ⅳ ≥70 ≥40 Ⅴ1 ≥50 ≥60 Ⅴ2 ≥40 ≥70 Ⅵ ≥30 ≥80 Shallow buried area ≥50 ≥60

[0055] It can be seen that in the prior art, the primary support structure and the surrounding rock support combination bear the main release load. If the secondary lining structure independently bears most of the load according to the structural calculation method, the seismic requirements of the tunnel structure can only be met by increasing the thickness of the secondary lining structure of the tunnel. In this case, the thicker the secondary lining thickness of the tunnel structure, the greater the required rigidity of the structure, and the greater the impact of earthquake damage. The design of the II and III surrounding rocks shown in the above table is that the initial support structure and the surrounding rock support bear 100% of the release load, and the secondary lining is used as a safety reserve. This is mainly because the II and III surrounding rocks themselves have good stability and high strength, and basically no support is required to ensure safe operation. In actual projects, II and III surrounding rocks are rarely encountered.

[0056] This creates a contradiction in the seismic structure design of tunnels in high-intensity areas. In the embodiment of the present application, the initial support bears all the loads for seismic design, thins the thickness of the secondary lining structure of the tunnel structure, reduces the impact of earthquakes on the tunnel structure, meets the seismic construction requirements of the tunnel, and further ensures the structural safety of the tunnel structure when it is damaged by an earthquake.

[0057] Figure 1 It is a schematic diagram of the structure of the installation space provided by the embodiment shown in this application.

[0058] The embodiment of the present application is applicable to surrounding rocks of level V or above in high-intensity earthquake zones. First, Figure 1 The reference numerals shown are explained:

[0059] 1-primary support structure, 2-secondary lining structure;

[0060] 11-First shotcrete;

[0061] 21- Second shotcrete.

[0062] Secondly, Figure 1 The erection space shown is described in detail:

[0063] The erection space is composed of an initial support structure 1 and a secondary lining structure 2. The thickness of the initial support structure 1 and the number of required longitudinal frames are determined. The thickness and the number of required longitudinal frames are calculated by the design method provided in the embodiment of the present application. When the initial support structure 1 is erected in the erection space, the thickness of the initial support structure 1 is formed by spraying the first shotcrete 11. The specific construction process is not specifically limited in this application. The thickness of the secondary lining structure 2 is further determined according to the thickness of the initial support structure 1. The secondary lining structure 2 is formed by spraying the second shotcrete 21, which may also include secondary lining steel bars ( Figure 1(not shown in the figure), when the secondary lining structure 2 is formed by spraying the second shotcrete 21, the secondary lining steel bars are laid in the secondary lining structure 2, and then the second shotcrete 21 is sprayed to cover the secondary lining structure 2, so as to achieve the effect that the secondary lining steel bars are interspersed in the secondary lining structure 2. The initial support structure 1 and the secondary lining structure 2 together form a tunnel structure.

[0064] Optionally, a waterproof layer is laid in the initial support structure 1 and the secondary lining structure 2 ( Figure 1 The waterproof layer is used to assist the initial support structure 1 and the secondary lining structure 2 to enhance the waterproofness of the tunnel structure and make the tunnel structure impermeable and impermeable.

[0065] It should be noted that Figure 1 The tunnel structure shown can be constructed based on the design method of the tunnel structure provided in this application. The design method of the tunnel structure is described in detail as follows:

[0066] For details, please see Figure 2 A flowchart of a method for designing a tunnel structure is shown.

[0067] Step 201, determine the basic load condition of the erection space, the basic load condition is used to indicate the vertical load condition and horizontal load condition of the erection space, the basic load condition corresponds to the surrounding rock grade of the erection space and the tunnel burial depth, the surrounding rock grade is used to indicate that the erection space is of grade V or above surrounding rock.

[0068] The basic load condition is used to indicate the bearing capacity of the erection space, which is determined by the surrounding rock grade of the erection space, the tunnel burial depth and the tunnel cross-sectional dimensions. The basic load condition includes vertical load conditions and horizontal load conditions. The horizontal load condition includes upper lateral pressure and lower lateral pressure.

[0069] The vertical load condition is used to indicate the deadweight of the structure in the erection space and is perpendicular to the horizontal plane and downward. It is determined by the surrounding rock density, permanent load coefficient and the height of the surrounding rock collapse in the erection space. i The product of the height h of the surrounding rock collapse is taken as the vertical load. For details, please refer to Formula 1:

[0070] Formula 1: q v =γ*h*γ i

[0071] In formula 1: q v -vertical load condition, unit: kPa; γ-surrounding rock density, unit: kN / m 3 ; γ i- permanent load coefficient; h-height of surrounding rock collapse, unit: m; according to relevant specifications, the permanent load coefficient γ corresponding to surrounding rock grade V can be obtained i is 1.2.

[0072] The surrounding rock bulk density can be directly obtained according to Table 2 below. The surrounding rock grade involved in the embodiment of the present application is Grade V, and the corresponding surrounding rock bulk density is 17 kN / m 3 -20kN / m 3 In the present embodiment, 20 kN / m 3 Perform subsequent calculations.

[0073] Table 2 Correspondence between surrounding rock grade and surrounding rock bulk density

[0074] Surrounding rock level <![CDATA[Unit weight of surrounding rock γ (kN / m 3 )]]> Ⅰ 26-28 Ⅱ 25-27 Ⅲ 23-25 Ⅳ 20-23 Ⅴ 17-20 Ⅵ 15-17

[0075] The height of the surrounding rock collapse body is mainly determined by the surrounding rock grade, specifically, the first value of the first preset parameter after the target power operation is determined, and the product of the first value and the second preset parameter is determined as the surrounding rock collapse body height h, in meters, where the value of the target power corresponds to the surrounding rock grade; in this embodiment, the first preset parameter is taken as 0.41, the second preset parameter is taken as 1.79, the surrounding rock grade is grade V, and the corresponding target power value is 5; for the specific calculation formula, please refer to Formula 2:

[0076] Formula 2: h = 0.41 * 1.79 S

[0077] In Formula 2: h is the height of the surrounding rock collapse, unit: m; S is the surrounding rock grade, which is determined by engineering geological survey data and is divided into grades I to VI. Grade V is used in the embodiment of the present application.

[0078] After obtaining the vertical load conditions, the upper lateral pressure and the lower lateral pressure are determined based on the vertical load conditions. Before determining the upper lateral pressure and the lower lateral pressure, the lateral pressure coefficient must be determined. The lateral pressure coefficient includes the upper lateral pressure coefficient and the lower lateral pressure coefficient, and the lateral pressure coefficient is determined by the surrounding rock conditions of the erected structure.

[0079] Step 202, based on the basic load condition and the preset sharing ratio, determine the erection thickness of the initial support structure, the preset sharing ratio is a ratio value greater than the required ratio condition, and the required ratio condition is used to indicate that the initial support structure is erected under full load sharing conditions.

[0080] The vertical load, upper lateral pressure and lower lateral pressure are applied to the erection structure according to a preset sharing ratio, and the steel arch frame support shotcrete required for the initial support structure of the erection structure is structurally calculated to obtain the thickness of the initial support structure. The thickness of the initial support structure includes the thickness of the inner protective layer, the thickness of the outer protective layer, the thickness of the first shotcrete and the strength grade of the first shotcrete.

[0081] For the surrounding rock section with grade V stability deviation in this embodiment, a steel arch frame is generally required inside the first shotcrete layer. At this time, the thickness of the first shotcrete can reach 18cm-30cm, which is used to indicate that the corresponding erection structure has a strong bearing capacity. When calculating, the first shotcrete and the steel arch frame should be regarded as a whole for calculation to further determine the basic load conditions. Optionally, the steel arch frame can be made by steel bar welding or directly made of I-beam and other steel. The thickness of the first shotcrete is determined with the height of the steel arch frame to ensure that the thickness of its outer protective layer is not less than 40mm and the thickness of the inner protective layer is not less than 20mm.

[0082] Optionally, when calculating the thickness of the initial support knot, the parameters used in the calculation should also be based on the actual implementation situation on site; or, they should be determined and adjusted based on changes in parameters such as the cross-sectional conditions of the erected structure, geological conditions, and surrounding rock grade.

[0083] The preset sharing ratio is specifically a ratio value greater than the required ratio condition, and the required ratio condition is used to indicate that the initial support structure is erected with a full load sharing condition. Optionally, the required ratio condition is used to indicate that the initial support structure is erected with a ratio value greater than 90%. In this embodiment, the initial support is erected with a full load sharing condition with a required ratio value of 100%. Specifically, the vertical load condition, the upper lateral pressure, and the lower lateral pressure are applied to the erection structure at a distribution ratio of 100%.

[0084] Step 203, based on the initial support structure and the structural internal force conditions of the erection space, a secondary lining structure is erected on the basis of the initial support structure to obtain a tunnel structure in the erection space.

[0085] Based on the aforementioned inner protective layer thickness, outer protective layer thickness, first shotcrete thickness and first shotcrete strength grade, the structural internal force conditions of the erection structure containing the initial support structure are determined, and the structural internal force conditions include section axial force, section shear force and section bending moment.

[0086] Based on the aforementioned cross-sectional axial force, cross-sectional shear force and cross-sectional bending moment, a secondary lining structure is determined, wherein the secondary lining structure includes a thickness of the secondary lining structure and a second shotcrete grade.

[0087] In summary, the method provided in this embodiment determines the initial support structure based on the basic load conditions of the erection space and the preset sharing ratio, determines the secondary lining structure based on the initial support structure and the structural internal force conditions of the erection space, and finally obtains the tunnel structure. The initial support structure bears all the surrounding rock load pressure, reduces the thickness of the secondary lining concrete, reduces the overall stiffness of the tunnel lining, and achieves the joint earthquake resistance effect of the initial structure and the secondary lining structure, which reduces the damage to the tunnel structure during an earthquake to a certain extent and saves engineering investment.

[0088] Figure 3 A flowchart of a tunnel structure design method provided by another embodiment of the present application is shown.

[0089] Step 301, determining the design basic earthquake peak acceleration of the erection space.

[0090] In the current relevant tunnel specifications, for tunnels in low-intensity areas, only the shallow buried entrance and exit sections are required to be seismically calculated. For high-intensity earthquake areas (eight and nine degrees), not only the shallow buried section of the tunnel entrance is required to be seismically calculated, but also the deeply buried fault fracture zone, weak large deformation and other unfavorable geological sections are required to be seismically calculated.

[0091] According to relevant regulations, the basic seismic peak acceleration is determined as 1 / 2.5 times the maximum value of the regularized seismic peak acceleration response spectrum with a damping ratio of 5%, and is divided into zones of 0.05g, 0.10g, 0.15g, 0.20g, 0.30g and 0.40g. The range of basic seismic peak acceleration in each zone is shown in Table 3 below, and the corresponding relationship between the seismic fortification intensity and the basic seismic peak acceleration value is shown in Table 4 below.

[0092] Table 3. Peak ground acceleration α max Partition value

[0093] <![CDATA[Peak acceleration of basic ground motion α max Zoning value]]> <![CDATA[Peak ground acceleration α max Range]]> 0.05g <![CDATA[0.01g≤α max <0.09g]]> 0.10g <![CDATA[0.09g≤α max <0.14g]]> 0.15g <![CDATA[0.14g≤α max <0.19g]]> 0.20g <![CDATA[0.19g≤α max <0.28g]]> 0.30g <![CDATA[0.28g≤α max <0.38g]]> 0.40g <h2 style=";text-align:left;direction:ltr"><![CDATA[0.38g≤α <h2 style=";text-align:left;direction:ltr"> max <h2 style=";text-align:left;direction:ltr"> <0.75g]]><h2 style=";text-align:left;direction:ltr">

[0094] Table 4 Correspondence between seismic fortification intensity and design basic ground motion peak acceleration

[0095]

[0096] In this embodiment, after the initial support structure is determined, the peak acceleration of the earthquake motion is adjusted, and the adjustment rule is specifically determined according to the burial depth of the erection structure.

[0097] Before adjusting the basic seismic peak acceleration, determine the depth reduction factor β, which is used to indicate the corresponding earthquake damage under different buried depths of the erection structure. When the tunnel structure is in a high-intensity earthquake zone and has a buried depth, if the buried depth is higher, the earthquake damage is smaller, and if the buried depth is lower, the earthquake damage is greater. Based on the buried depth of the tunnel structure, this embodiment adjusts the basic seismic peak acceleration according to a preset rule to obtain a reduced seismic peak horizontal acceleration and a reduced seismic peak vertical acceleration.

[0098] According to the buried depth of the erected structure, the depth reduction coefficient is determined according to the preset rules. When the buried depth of the erected structure cave top is 0m, β is 1.0; when the buried depth of the erected structure cave top is 50m, β is 0.5; when the buried depth of the erected space cave top is 200m, β is 0.25; the rest of the cave top buried depth is calculated according to linear interpolation. For example, when the buried depth of the erected structure cave top is 80m, the linear interpolation rule is selected for calculation. For the specific calculation process, please refer to Formula 3:

[0099] Formula 3:

[0100] In formula 3, β is the depth reduction coefficient.

[0101] After the depth reduction factor is determined, the product of the depth reduction factor and the basic ground motion peak acceleration is determined as the reduced basic ground motion peak horizontal acceleration. For details, please refer to Formula 4:

[0102] Formula 4:

[0103] In formula 4, β is the depth reduction coefficient; α is d - Basic ground motion peak acceleration; - Reduce the basic ground motion peak horizontal acceleration.

[0104] The product of the reduced basic earthquake peak horizontal acceleration and the third preset parameter is determined as the reduced basic earthquake peak vertical acceleration, wherein the third preset parameter is used to indicate the prescribed vertical earthquake acceleration reduction factor. In this embodiment, the third preset parameter is taken as 0.65. For details, please refer to Formula 5:

[0105] Formula 5:

[0106] In formula 5, - Reduced basic ground motion peak horizontal acceleration; - Reduce the basic ground motion peak vertical acceleration.

[0107] Step 302, determining the structural internal force conditions of the erection space.

[0108] According to the reduced basic earthquake peak horizontal acceleration and reduced basic earthquake peak vertical acceleration calculated in step 302, the structural internal force conditions of the erection space are calculated. The structural internal force conditions are used to indicate the earthquake forces (load forces) in all directions of the erection space. For details, please refer to Figure 4 A schematic diagram showing the various directions of earthquake forces in the erection space.

[0109] The structural internal force conditions include the horizontal seismic load of the erection space, the vertical seismic load of the erection space, the horizontal seismic earth pressure of the side wall, the horizontal seismic force generated by the cave roof surrounding rock, and the vertical seismic force generated by the cave roof surrounding rock. The above parameters are used to calculate the structure of the erection structure using the quasi-static method. The seismic load is calculated according to the following formulas 6 to 12, where the seismic action partial coefficient is taken as 1.3 in accordance with relevant regulations. Since the parameters contained in the above structural internal force conditions can all be replaced by the finished product program for calculation, this embodiment will not be described in detail, but only a brief calculation formula is provided. The specific formula is as follows:

[0110] Horizontal seismic loads of erection space:

[0111] Formula 6:

[0112] Vertical seismic load of erection space:

[0113] Formula 7:

[0114] In formulas 6 to 7: C i - Importance correction factor, take 1.0; C z -Site influence coefficient; - Reduced basic ground motion peak horizontal acceleration; - Reduced basic ground motion peak vertical acceleration; G is -Calculate the gravity of the structure at the point, unit: Kn; E ih -Horizontal seismic load of the erection space; E iv -Vertical seismic loads in erection spaces.

[0115] Seismic horizontal earth pressure on side wall:

[0116] Formula 8: Δe e =1.3C i C z q(λ′-λ)

[0117] Formula 9:

[0118] Formula 10:

[0119] In formulas 8 to 9: θ-seismic angle; φ c - natural angle of repose of surrounding rock; Ci - Importance correction factor, take 1.0; C z -Site influence coefficient; Δe e - Seismic horizontal earth pressure on side walls.

[0120] Horizontal seismic force generated by the surrounding rock of the cave roof:

[0121] Formula 11:

[0122] Vertical seismic force generated by the surrounding rock of the cave roof:

[0123] Formula 12:

[0124] In formulas 11 to 12: C i - Importance correction factor, take 1.0; C z -Site influence coefficient; - Reduced basic ground motion peak horizontal acceleration; - Reduced basic ground motion peak vertical acceleration; q v -vertical load condition; q he -Horizontal seismic force generated by the surrounding rock of the cave roof; q ve -Vertical seismic force generated by the surrounding rock of the cave roof.

[0125] Step 303, erecting a secondary lining structure in the erection space.

[0126] The structural internal force conditions obtained in the above step 302 are used to obtain the cross-sectional shear force, cross-sectional axial force and cross-sectional bending moment of the erection space according to the finished product program.

[0127] In summary, the method provided in the embodiment of the present application determines the initial support structure based on the basic load conditions of the erection space and the preset sharing ratio, determines the secondary lining structure based on the initial support structure and the structural internal force conditions of the erection space, and finally obtains the tunnel structure. The initial support structure bears all the surrounding rock load pressure, reduces the thickness of the secondary lining concrete, reduces the overall stiffness of the tunnel lining, and achieves the joint earthquake resistance effect of the initial structure and the secondary lining structure, which reduces the damage to the tunnel structure during an earthquake to a certain extent and saves engineering investment.

[0128] Figure 5 A flowchart of a tunnel structure design method provided by another embodiment of the present application is shown.

[0129] Step 501, determine the initial support structure of the erection space.

[0130] Determine the basic load condition of the erection space, and apply the vertical load condition, upper lateral pressure and lower lateral pressure in the basic load condition to the erection structure at a distribution ratio of 100%. For the specific implementation process, please refer to the above steps 201 to 202.

[0131] Step 502: laying a waterproof layer between the initial support structure and the secondary lining structure, and determining the structural internal force conditions of the erection space.

[0132] When designing the seismic structure of the tunnel, after obtaining the initial support structure, the initial support structure and the secondary lining structure are considered to bear the same responsibility during the seismic design of the secondary lining structure. Among them, the initial support structure is mainly formed by the first shotcrete spraying. In order to ensure the waterproofness of the seismic structure, a waterproof layer will be laid on the basis of the initial support structure when the secondary lining structure is erected. When calculating, the stiffness conversion problem of the initial support structure and the secondary lining structure will be considered.

[0133] When the waterproof layer is laid, the present embodiment adopts the superimposed structure mode to calculate the structural internal force conditions of the erection space. That is, when the waterproof layer is laid, only pressure can be transmitted between the initial support structure and the secondary lining structure.

[0134] Determine the shotcrete cross-sectional area and secondary lining cross-sectional area of ​​the erection space, and determine the sum of the shotcrete cross-sectional area and the secondary lining cross-sectional area as the structural calculation cross-sectional area. For details, please refer to Formula 13:

[0135] Formula 13: A Z =A c +A e

[0136] In formula 13: A Z -Structural calculation cross-sectional area, unit: m 2 ; A c - Cross-sectional area of ​​shotcrete, unit: m 2 ; A e -Secondary lining cross-sectional area, unit: m 2 .

[0137] Determine the shotcrete moment of inertia and the secondary lining moment of inertia of the erection space, and determine the sum of the shotcrete moment of inertia and the secondary lining moment of inertia as the structural calculation moment of inertia. For details, please refer to Formula 14:

[0138] Formula 14: I Z =I c +I e

[0139] In formula 14: I Z - Structural calculation moment of inertia, unit: m 2 ;Ic - Moment of inertia of shotcrete, unit: m 2 ;I e -Secondary lining moment of inertia, unit: m 2 .

[0140] According to the above formula, the structural calculation cross-sectional area and structural calculation inertia moment of the erection space are determined to determine the structural internal force conditions of the erection space. The specific structural internal force conditions can be calculated using the finished product program, which will not be described in detail in this embodiment.

[0141] Step 503: No waterproof layer is laid between the initial support structure and the secondary lining structure, and the structural internal force conditions of the erection space are determined.

[0142] In the absence of a waterproof layer, the isotropic stresses generated between the initial support structure and the secondary lining structure are continuous. Please refer to the following formula for the specific calculation process.

[0143] Based on the cross-sectional area of ​​shotcrete and the cross-sectional area of ​​secondary lining, the structural calculation cross-sectional area is determined. For the specific formula, please refer to the above formula 12;

[0144] Determine the distance from the centroid of the shotcrete section to the centroid of the secondary lining section to obtain the first distance;

[0145] According to the cross-sectional area of ​​shotcrete, the cross-sectional area of ​​secondary lining and the first distance, the structural calculation moment of inertia is determined according to the preset formula; please refer to the following formula for details:

[0146] Formula 15:

[0147] Formula 16:

[0148] Formula 17:

[0149] In formulas 15 to 17: I Z - Structural calculation moment of inertia, unit: m 2 ; Y c - Distance from the centroid of the shotcrete section to the centroid of the composite section Unit: m; Y e - The distance from the centroid of the secondary lining concrete section to the centroid of the composite section, unit: m; D - The distance from the centroid of the shotcrete section to the centroid of the secondary lining section, unit: m; A c - Cross-sectional area of ​​shotcrete, unit: m 2 ; A e -Secondary lining cross-sectional area, unit: m 2 .

[0150] According to the above formula, the structural calculation cross-sectional area and structural calculation inertia moment of the erection space are determined to determine the structural internal force conditions of the erection space. The specific structural internal force conditions can be calculated using the finished product program, which will not be described in detail in this embodiment.

[0151] Step 504, determine the secondary lining structure of the hypothetical space to obtain the tunnel structure.

[0152] Based on the structural internal force conditions calculated in step 503 above, a secondary lining structure is erected on the basis of the initial support structure to obtain a tunnel structure within the erection space. For the specific process, please refer to step 203.

[0153] In summary, the method provided in the embodiment of the present application determines the initial support structure based on the basic load conditions of the erection space and the preset sharing ratio, determines the secondary lining structure based on the initial support structure and the structural internal force conditions of the erection space, and finally obtains the tunnel structure. The initial support structure bears all the surrounding rock load pressure, reduces the thickness of the secondary lining concrete, reduces the overall stiffness of the tunnel lining, and achieves the joint earthquake resistance effect of the initial structure and the secondary lining structure, which reduces the damage to the tunnel structure during an earthquake to a certain extent and saves engineering investment.

[0154] The design method of the tunnel structure involved in the present application can also be used in the seismic verification of the tunnel structure. The following scheme will provide a specific tunnel structure, and the method involved in the present application will be used to perform seismic verification on the tunnel structure.

[0155] The basic design conditions provided in this embodiment are that the design net section of tunnel A is 4.5m×4.5m, located in a 9-degree earthquake intensity zone, and the design basic ground motion peak acceleration is 0.6g. There is a 50m long fault fracture zone starting from K0+800m, the fault fracture zone is buried 80m deep, and the V-level surrounding rock, mudstone, is developed in groundwater. The seismic calculation of the tunnel is carried out according to the method provided in the previous application.

[0156] For details, please see Figure 6 , Figure 6 A flow chart of a tunnel structure verification method provided by another embodiment is shown.

[0157] Step 601, calculation of basic load of tunnel structure.

[0158] According to the basic data of tunnel A (section size, surrounding rock grade and tunnel depth), the basic vertical load and horizontal load of the tunnel structure are calculated using formulas 1 and 2, where the permanent load factor γ is determined according to relevant specifications. i is 1.2, and the surrounding rock bulk density γ is 20. For the specific calculation process, please refer to formulas 1 to 2:

[0159] h=0.41*1.79S =0.41×1.79 5 =7.53m

[0160] q v =γ i *h*γ=1.2×7.53×20=180kPa

[0161] Where:

[0162] q v -vertical load condition, unit: KPa; γ-surrounding rock density, unit: kN / m 3 ; γ i -permanent load coefficient, which is taken as 1.2 in this embodiment; h-height of surrounding rock collapse, unit: m; S-surrounding rock grade, which is taken as 5 in this embodiment.

[0163] According to the vertical load and the gypsum content of the stratum, the lateral pressure coefficient is determined to be 0.5, and the upper lateral pressure q is obtained. h1 =90kPa and lower lateral pressure q h2 =110kPa.

[0164] Step 602, calculation of the initial tunnel support structure.

[0165] The vertical load of the surrounding rock on the tunnel top is q v =150kPa, lateral pressure on the upper part of the cave side q h1 =90kPa and lower lateral pressure q h2 =110kPa acts on the tunnel structure at a distribution ratio of 100%, and the initial support structure calculation of the steel arch support shotcrete is carried out.

[0166] Calculation and practice show that the steel arch frame is made on-site using I14 I-steel, with a spacing of 1.0 meter, material Q235, inner protective layer thickness of 40mm, outer protective layer thickness of 40mm, first shotcrete thickness of 220mm, and first shotcrete grade of C25.

[0167] Step 603, calculation of seismic load of tunnel structure.

[0168] The design basic seismic peak acceleration is adjusted. According to the basic parameter information of tunnel A, it can be concluded from the relevant specifications that the design basic seismic peak acceleration is 0.6g. The depth reduction factor is adjusted according to the aforementioned preset rules to obtain the design basic seismic peak horizontal acceleration and the design basic seismic peak vertical acceleration. The specific calculation process is as follows, see formulas 3 to 5:

[0169]

[0170]

[0171]

[0172] Where: α d - Design basic ground motion peak acceleration (m / s 2 );β-design basic ground motion peak acceleration surrounding rock depth reduction factor; - Design basic ground motion peak horizontal acceleration after depth reduction (m / s 2 ); - Design basic ground motion peak vertical acceleration after depth reduction (m / s 2 ).

[0173] In the known and Under the premise of , various seismic forces are calculated according to the relevant standard formulas. For details, please refer to Figure 4 The tunnel seismic force diagram is shown in Figure 1. The calculation results are as follows. Please refer to formulas 6 to 12 for details:

[0174] Horizontal seismic loads on structures:

[0175]

[0176] Vertical seismic loads on the structure:

[0177]

[0178] Where: C i - Importance correction factor, take 1.0; C z -Site influence coefficient, take 1.0; - horizontal seismic coefficient; -Vertical seismic coefficient; G is -Calculate the gravity of the structure at the point, unit: kN; take the lining unit length as 0.5m, width as 1m; lining weight as 25kN / m 3 , that is, when the thickness is 0.47m, G is =1×0.5×0.47×25=5.88kN;

[0179] Seismic horizontal earth pressure on side wall:

[0180] Δe e =1.3×1.0×1.0×150×(0.28-0.22)=11.7kPa

[0181]

[0182]

[0183] Horizontal seismic force generated by the surrounding rock of the cave roof:

[0184]

[0185] Vertical seismic force generated by the surrounding rock of the cave roof:

[0186]

[0187] Step 604, calculating the internal force of the tunnel structure.

[0188] The various loads calculated in step 603 above are applied to calculate the internal forces on the tunnel structure.

[0189] The internal forces involved in this embodiment are mainly the cross-sectional axial force, cross-sectional shear force and cross-sectional bending moment, and these three parameters can be calculated by the finished product program, so they are not elaborated in this embodiment. The cross-sectional axial force is finally obtained to be 427.1 kN; the cross-sectional shear force is 183.2 kN; and the cross-sectional bending moment is 185.3 kN·m.

[0190] Step 605: verifying the seismic structure of the tunnel.

[0191] According to the various load conditions of the tunnel structure obtained in the above steps 601 to 604, a structural resistance calculation diagram of the tunnel structure support structure (initial support structure and secondary lining structure) is obtained, wherein the initial support structure is designed with C25 strength grade, and the secondary lining structure is designed with C35 strength grade. The compression reinforcement is calculated as one I14 I-beam, of which It is used to indicate that 6 steel bars with a diameter of 20 mm are required per meter of the tension zone.

[0192] According to Article 6.5.10 of the Technical Specification for Seismic Resistance of Oil and Gas Pipeline Engineering (GBT 50470-2017), the general verification criteria are as follows:

[0193] Formula 18:

[0194] In formula 18: S-design value of structural internal force; R-design value of structural bearing capacity; y RE -Seismic adjustment coefficient, according to Article 6.5.10 of the Technical Specification for Seismic Engineering of Oil and Gas Pipeline Lines (GBT 50470-2017), RE Take 0.85.

[0195] Verify the cross-sectional bending moment calculated in step 604:

[0196] According to Article 6.2.10 and Article 6.2.14 of the Code for Design of Concrete Structures (GB 50010-2010), the height x of the compression zone can be calculated by the formulas shown in Formulas 19 to 21. In this embodiment, x is calculated to be 220 mm:

[0197] Formula 19: α1f c bx=f y A s -f y 'A' s

[0198] Formula 20: x≤ξ b h0

[0199] Formula 21: x≥2a′ s

[0200] After calculating the height x of the compression zone, verify the section bending moment M. For the specific verification process, please refer to 22 to 23:

[0201] Formula 22:

[0202] Formula 23: M≤f v A s (ha s -a′ s )

[0203] The maximum cross-sectional bending moment obtained by calculation is 247.4 kN·m. In the above step 604, the cross-sectional bending moment of the tunnel structure provided in this embodiment is obtained to be 185.3 kN·m, and the cross-sectional bending moment meets the seismic requirements.

[0204] In formulas 19 to 23: M-section bending moment; α1-coefficient, take 1.0; f c -Design value of concrete axial compressive strength, C25 is 11.9N / mm 2 , C35 takes 16.7N / mm 2 ;f y -The design value of longitudinal reinforcement tensile strength is 360N / mm 2 ;f y ′-design value of steel arch compressive strength, take 215N / mm2; A s - The cross-sectional area of ​​the longitudinal reinforcement in the tension zone is 1884 mm 2 ; A′ s - The cross-sectional area of ​​the steel arch in the compression zone is 2150mm 2 ; b-section width, take 1000mm; h-section height, take 470mm; h0-section effective height, take 420mm; a s - The distance from the combined force point of the longitudinal reinforcement in the tension zone to the tension edge of the section is 50 mm; a′s -The distance from the combined force point of the steel arch in the compression zone to the compression edge of the section is 110mm. b - relative limit compression zone height, 0.55; x- compression zone height, take 2a′ s , take 220mm.

[0205] Verify the cross-sectional axial force obtained in step 603:

[0206] According to Article 6.2.15 of the Code for Design of Concrete Structures (GB 50010-2010), the maximum cross-sectional axial force N is calculated. max , please refer to Formula 24 for the specific calculation process:

[0207] Formula 24:

[0208] The maximum cross-sectional axial force obtained from the above formula 24 is 1147.3 kN, and the cross-sectional axial force obtained in step 603 is 427.1 kN. The cross-sectional axial force meets the seismic requirements.

[0209] In formula 24: N-section axial force; -The stability factor of reinforced concrete components is taken as 1.0; f c -Design value of concrete axial compressive strength, C25 is 11.9N / mm 2 , C35 takes 16.7N / mm 2 ; A-member cross-sectional area, (2.2+2.5)×105mm 2 ;f y 'Design value of longitudinal steel compressive strength, steel arch frame takes 215N / mm 2 , steel bar takes 360N / mm 2 ; A′ s - The total longitudinal steel cross-sectional area, steel arch frame takes 2150mm 2 , steel bar takes 1884mm 2 .

[0210] Verify the cross-sectional shear force obtained in step 603:

[0211] According to Article 6.3.1 of the Code for Design of Concrete Structures (GB 50010-2010), the maximum cross-sectional shear force V is calculated as max , please refer to Formula 25 for the specific calculation process:

[0212] Formula 25: V≤0.25β c f c bh0

[0213] The maximum cross-sectional shear force obtained from the above formula 25 is 2824.5 kN, and the cross-sectional shear force obtained in step 603 is 183.2 kN. The cross-sectional shear force meets the seismic requirements.

[0214] In formula 25: V-section shear force; β c -Concrete strength influence coefficient, take 1.0; f c -Design value of concrete axial compressive strength, C25 is 11.9N / mm 2 , C35 takes 16.7N / mm 2 ; b- width of the section, take 1000mm; h0- effective height of the section, take 420mm.

[0215] If the secondary lining structure bears all or most of the load according to conventional seismic requirements, the cross-sectional axial force of the tunnel structure provided by this embodiment obtained in the above step 603 is 937.5 kN, the cross-sectional shear force is 273.9 kN, and the cross-sectional bending moment is 220.9 kN·m. From the data, it can be concluded that the secondary lining structure of the tunnel is the only seismic structure, and the seismic effect of the initial support structure is not considered. The concrete thickness required for the secondary lining structure is 47 cm, the tensile steel bars are 6￠18 steel bars, and the compressive steel bars are 6￠14 steel bars, where 6￠18 is used to indicate that 6 steel bars with a diameter of 18 mm are required for every meter of the tensile zone, and 6￠14 is used to indicate that 6 steel bars with a diameter of 14 mm are required for every meter of the compressive zone.

[0216] It can be clearly concluded that the model under normal conditions does not convert the basic seismic peak acceleration according to the tunnel burial depth and tunnel depth, and the seismic force in the calculated theoretical value is relatively large. At the same time, the influence of the initial support structure is ignored in the seismic calculation, and the seismic force is borne entirely by the secondary lining structure. The combined effect of the above two factors causes the concrete thickness and stiffness required for the secondary lining structure to be thick, which is not conducive to seismic resistance. The design method of the tunnel structure provided in this application can reduce the concrete thickness required for the secondary lining structure to a certain extent, reduce the overall stiffness of the tunnel structure lining, and reduce the damage to the tunnel structure when it is damaged by earthquakes.

[0217] A person of ordinary skill in the art can understand that all or part of the steps of implementing the above-mentioned embodiment can be completed by a human subject. In another embodiment, all or part of the steps of the above-mentioned embodiment are completed by hardware devices, or can be completed by controlling related hardware devices through a program. The program can be stored in a computer-readable storage medium, and the above-mentioned storage medium can be a read-only memory, a disk or an optical disk, etc.

[0218] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the invention disclosed herein. The present application is intended to cover any modification, use or adaptation of the present application, which follows the general principles of the present application and includes common knowledge or customary techniques in the art that are not disclosed in the present application. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present application are indicated by the following claims.

[0219] It should be understood that the present application is not limited to the precise structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present application is limited only by the appended claims.

Claims

1. A method for designing a tunnel structure, characterized in that: The method comprises: Determine the basic load condition of the erection space, the basic load condition is used to indicate the vertical load condition and the horizontal load condition of the erection space, the basic load condition corresponds to the surrounding rock grade of the erection space and the tunnel burial depth, the surrounding rock grade is used to indicate that the erection space is a surrounding rock of grade V or above; Determining the erection thickness of the initial support structure based on the basic load condition and a preset sharing ratio, wherein the preset sharing ratio is a ratio value greater than a required ratio condition, and the required ratio condition is used to indicate that the initial support structure is to be erected with a full load sharing condition; Based on the initial support structure and the structural internal force conditions of the erection space, a secondary lining structure is erected on the basis of the initial support structure to obtain a tunnel structure in the erection space; Wherein, the basic load condition of the erection space also includes basic ground motion peak acceleration; The method further comprises: before erecting a secondary lining structure on the basis of the initial support structure and the structural internal force conditions of the erection space, the method further comprises: Adjusting the basic earthquake peak acceleration according to a preset rule to obtain a reduced basic earthquake peak horizontal acceleration and a reduced basic earthquake peak vertical acceleration; Determining the structural internal force condition of the erection space based on the reduced basic earthquake peak horizontal acceleration and the reduced basic earthquake peak vertical acceleration; The step of adjusting the basic earthquake peak acceleration according to a preset rule to obtain a reduced basic earthquake peak horizontal acceleration and a reduced basic earthquake peak vertical acceleration includes: Determine a depth reduction coefficient according to a preset rule, wherein the depth reduction coefficient is used to indicate the earthquake damage corresponding to different buried depths of the installation space; determine the product of the depth reduction coefficient and the basic seismic peak acceleration as the reduced basic seismic peak horizontal acceleration; The product of the reduced basic seismic peak horizontal acceleration and a third preset parameter is determined as the reduced basic seismic peak vertical acceleration.

2. The method according to claim 1, characterized in that The step of determining the erection thickness of the initial support structure based on the basic load condition and the preset sharing ratio includes: Determine the surrounding rock density, permanent load coefficient and surrounding rock collapse height of the erection space; determine the vertical load condition based on the product of the surrounding rock density, the permanent load coefficient and the surrounding rock collapse height; determining an upper lateral pressure and a lower lateral pressure based on the vertical load condition; The vertical load condition, the upper lateral pressure and the lower lateral pressure are applied to the erection space according to the preset sharing ratio to obtain the erection thickness of the initial support, which includes the thickness of the inner protective layer, the thickness of the outer protective layer, the thickness of the first shotcrete and the strength grade of the first shotcrete.

3. The method according to claim 2, characterized in that Before determining the vertical load condition based on the product of the surrounding rock density, the permanent load coefficient and the height of the surrounding rock collapse body, the method further includes: Determine a first value of a first preset parameter after target power operation, and a product of the first value and a second preset parameter as the height of the surrounding rock collapse body, wherein the value of the target power corresponds to the surrounding rock grade.

4. The method according to claim 1, characterized in that: The method further comprises: Determining the structural internal force conditions of the erection space based on the reduced basic earthquake peak horizontal acceleration and the reduced basic earthquake peak vertical acceleration; The cross-sectional axial force, cross-sectional shear force and cross-sectional bending moment of the secondary lining structure are obtained based on the structural internal force conditions.

5. The method according to claim 4, characterized in that The method further comprises: The thickness of the secondary lining structure and the second shotcrete strength grade are determined based on the cross-sectional axial force, the cross-sectional shear force, the cross-sectional bending moment and the initial support structure.

6. The method according to any one of claims 1 to 5, characterized in that: The method further comprises: A waterproof layer is laid between the primary supporting structure and the secondary lining structure.

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