A method and device for designing primary support structure of tunnel with unequal thickness

Abstract

The present invention discloses a method and device for designing a tunnel unequal thickness primary support structure, including: in a target construction scenario of an equal thickness primary support structure, determining the minimum external insertion angle of the rock drill according to the distance from the rock drill to the excavation contour line around the tunnel, the thickness of the rock drill, the fixed initial support thickness, the reserved distance from the tunnel face to the rock drill, the drill rod radius, and the exposed drill rod length; determining the minimum initial support thickness value in the unequal thickness primary support structure based on the fixed initial support thickness; taking the initial excavation position of the rock drill in each cycle as the minimum initial support position, taking the tunnel face of the rock drill in each cycle as the maximum initial support position, and setting steel arches at equal intervals from the initial excavation position to the tunnel face; determining the maximum initial support thickness value according to the minimum external insertion angle and the minimum initial support thickness value, and obtaining the target unequal thickness primary support structure. This method can not only meet the requirements of surrounding rock stability and support structure safety, but also effectively reduce the serious problem of over-excavation and backfilling caused by the large external insertion angle of the rock drill.

Description

Technical Field

[0001] The invention relates to the technical field of mechanized tunnel construction, and in particular to a method and device for designing a tunnel primary support structure with unequal thickness. Background Art

[0002] Most mountain tunnels are excavated using the drill and blast method, which results in serious over-excavation. The over-excavation needs to be backfilled with shotcrete. When drilling with a rock drill, the over-excavation value is even greater. In order to save construction costs and speed up construction, it is necessary to consider unequal thickness initial support for the tunnel during excavation. The unequal thickness initial support structure of the tunnel divides the entire initial support structure into multiple cycles according to the time sequence before and after construction. Within the excavation length of each cycle, excavation and support are carried out according to the advance required by the design. The starting point and end point of the cycle are a continuous structure, and each cycle uses unequal thickness gradient initial support according to the actual situation.

[0003] With the rapid development of the road traffic industry, tunnel construction is gradually moving towards mechanization and intelligence. In order to ensure the safe, fast and efficient completion of tunnel construction, large-scale mechanized supporting construction is the inevitable choice of the construction party. Among them, the use of three-arm rock drills is the most representative. The excavation operation using three-arm rock drills has gradually replaced the traditional manual excavation operation. Through theoretical analysis and on-site practice of the three-arm rock drill, researchers found that the system external insertion angle of the three-arm rock drill excavation is relatively large, and the over-excavation is serious after blasting excavation.

[0004] Therefore, we need a design scheme for the initial support structure of tunnels with unequal thickness, which can not only meet the requirements of surrounding rock stability and support structure safety, but also effectively reduce the serious problem of over-excavation and backfilling caused by the large external insertion angle of the rock drill. Summary of the invention

[0005] The present invention provides a method and device for designing a tunnel primary support structure of unequal thickness, which can not only meet the requirements of surrounding rock stability and support structure safety, but also effectively reduce the serious problem of over-excavation and backfilling caused by a large external insertion angle of a rock drill.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme:

[0007] In a first aspect, the present invention provides a method for designing a tunnel primary support structure of unequal thickness, the method comprising:

[0008] In the target construction scenario of the equal-thickness primary support structure, the minimum external insertion angle of the rock drill in the target construction scenario is determined according to the distance from the rock drill to the excavation contour line around the tunnel, the thickness of the rock drill, the thickness of the fixed primary support, the reserved distance from the tunnel face to the rock drill, the drill rod radius and the exposed drill rod length; the exposed drill rod length is the length of the drill rod extending out of the excavation contour line around the tunnel;

[0009] Determine the minimum primary support thickness value of the target construction scenario in the unequal thickness primary support structure according to the product of the fixed primary support thickness and a first preset value; the first preset value is ≥ 0.6;

[0010] The initial excavation position of the rock drill in each cycle is taken as the minimum initial support position, the tunnel face of the rock drill in each cycle is taken as the maximum initial support position, and a plurality of steel arch frames are arranged at equal intervals from the initial excavation position to the tunnel face;

[0011] Based on trigonometric functions, the maximum primary support thickness value is determined according to the minimum external interpolation angle and the minimum primary support thickness value to obtain a target unequal thickness primary support structure; the primary support thickness value increases proportionally from the initial excavation position to the tunnel face.

[0012] In a possible implementation, in a target construction scenario of an equal-thickness primary support structure, the minimum external insertion angle of the rock drill in the target construction scenario is determined according to the distance from the rock drill to the excavation contour line around the tunnel, the thickness of the rock drill, the thickness of the fixed primary support, the reserved distance from the tunnel face to the rock drill, the drill rod radius, and the exposed drill rod length, specifically including:

[0013] In the target construction scenario of the equal thickness primary support structure, when the reserved distance from the face to the rock drill is greater than the length of the exposed drill rod, the minimum external insertion angle of the rock drill in the target construction scenario is determined according to the distance from the rock drill to the excavation contour line around the tunnel, the thickness of the rock drill, the thickness of the fixed primary support and the reserved distance from the face to the rock drill;

[0014] In the target construction scenario of the equal-thickness primary support structure, when the reserved distance from the tunnel face to the rock drill is less than the exposed drill rod length, the minimum external insertion angle of the rock drill in the target construction scenario is determined according to the acquired drill rod radius, the fixed primary support thickness and the reserved distance from the tunnel face to the rock drill.

[0015] In a possible implementation, when the reserved distance from the tunnel face to the rock drill is greater than the length of the exposed drill rod, the minimum external insertion angle of the rock drill in the target construction scene is determined according to a first formula, and the first formula is specifically:

[0016] ;

[0017] in, represents the minimum external insertion angle, Indicates the distance from the rock drill to the excavation contour line around the tunnel. Represents half the thickness of the rock drill, Indicates the fixed initial support thickness. Indicates the reserved distance from the tunnel face to the rock drill.

[0018] In a possible implementation, when the reserved distance from the tunnel face to the rock drill is less than the length of the exposed drill rod, the minimum external insertion angle of the rock drill in the target construction scene is determined according to a second formula, and the second formula is specifically:

[0019] ;

[0020] in, Indicates the drill pipe radius.

[0021] In a possible implementation manner, after obtaining the target unequal thickness primary support structure, the method further includes: performing safety verification on the target unequal thickness primary support structure.

[0022] In a possible implementation, safety verification is performed on the target unequal thickness primary support structure, specifically including:

[0023] According to the target construction scene, three-dimensional stratum models corresponding to the primary support structure of equal thickness and the target primary support structure of unequal thickness are respectively established;

[0024] By means of numerical simulation calculation, first measurement data of the fixed primary support in the primary support structure of equal thickness at the target position and second measurement data of each target primary support in the target primary support structure of unequal thickness at the target position are obtained respectively; the first measurement data and the second measurement data both include verification thickness, axial force, bending moment and safety factor;

[0025] When the error between the second measured data and the first measured data meets a preset simulation error threshold, the target unequal thickness primary support structure is considered to be a safe structure.

[0026] In a possible implementation manner, after determining that the target unequal thickness primary support structure is a safe structure, the safety verification of the target unequal thickness primary support structure further includes:

[0027] Long-term monitoring is performed on five monitoring items, namely, the arch crown and arch foot subsidence, horizontal displacement, surrounding rock and primary support contact pressure, steel arch frame stress, and primary support concrete stress value of the target monitoring point of the target construction scene with the target unequal thickness primary support structure, to obtain a curve of each monitoring item changing with time;

[0028] Determine the change amount of each monitoring item based on the curve corresponding to each monitoring item;

[0029] When the change amount of each of the monitoring items is less than the preset change threshold of the monitoring item, it is considered that the target unequal thickness primary support structure meets the safety requirements.

[0030] In a second aspect, the present invention provides a device for designing a tunnel primary support structure with unequal thickness, comprising:

[0031] The first processing unit is used to determine the minimum external insertion angle of the rock drill in the target construction scene of the equal-thickness primary support structure according to the acquired distance from the rock drill to the excavation contour line around the tunnel, the thickness of the rock drill, the thickness of the fixed primary support, the reserved distance from the tunnel face to the rock drill, the drill rod radius, and the exposed drill rod length in the target construction scene; the exposed drill rod length is the length of the drill rod extending from the excavation contour line around the tunnel;

[0032] A second processing unit is used to determine the minimum primary support thickness value of the target construction scene in the unequal thickness primary support structure according to the product of the fixed primary support thickness and a first preset value; the first preset value is ≥ 0.6;

[0033] The third processing unit is used to set a plurality of steel arches at equal intervals from the excavation initial position to the tunnel face, with the excavation initial position of the rock drill in each cycle as the minimum primary support and the tunnel face of the rock drill in each cycle as the maximum primary support;

[0034] The fourth processing unit is used to determine the maximum initial support thickness value based on the trigonometric function according to the minimum external interpolation angle and the minimum initial support thickness value to obtain a target unequal thickness initial support structure; the initial support thickness value increases proportionally from the initial excavation position to the tunnel face.

[0035] In a possible implementation manner, the first processing unit is specifically configured to execute:

[0036] In the target construction scenario of the equal thickness primary support structure, when the reserved distance from the face to the rock drill is greater than the length of the exposed drill rod, the minimum external insertion angle of the rock drill in the target construction scenario is determined according to the distance from the rock drill to the excavation contour line around the tunnel, the thickness of the rock drill, the thickness of the fixed primary support and the reserved distance from the face to the rock drill;

[0037] In the target construction scenario of the equal-thickness primary support structure, when the reserved distance from the tunnel face to the rock drill is less than the exposed drill rod length, the minimum external insertion angle of the rock drill in the target construction scenario is determined according to the acquired drill rod radius, the fixed primary support thickness and the reserved distance from the tunnel face to the rock drill.

[0038] In a possible implementation, when the reserved distance from the tunnel face to the rock drill is greater than the length of the exposed drill rod, the first processing unit is specifically configured to execute:

[0039] The minimum external interpolation angle of the rock drill in the target construction scene is determined according to a first formula, wherein the first formula is specifically:

[0040] ;

[0041] in, represents the minimum external insertion angle, Indicates the distance from the rock drill to the excavation contour line around the tunnel. Represents half the thickness of the rock drill, Indicates the fixed initial support thickness. Indicates the reserved distance from the tunnel face to the rock drill.

[0042] In a possible implementation, when the reserved distance from the tunnel face to the rock drill is less than the length of the exposed drill rod, the first processing unit is specifically configured to execute:

[0043] The minimum external interpolation angle of the rock drill in the target construction scene is determined according to the second formula, where the second formula is specifically:

[0044] ;

[0045] in, Indicates the drill pipe radius.

[0046] In a possible implementation, after obtaining the target unequal thickness primary support structure, the tunnel unequal thickness primary support structure design device further includes a fifth processing module; the fifth processing module is configured to execute:

[0047] The target unequal thickness primary support structure is safety verified.

[0048] In a possible implementation, when performing safety verification on the target unequal thickness primary branch structure, the fifth processing module is specifically configured to execute:

[0049] According to the target construction scene, three-dimensional stratum models corresponding to the primary support structure of equal thickness and the target primary support structure of unequal thickness are respectively established;

[0050] By means of numerical simulation calculation, first measurement data of the fixed primary support in the primary support structure of equal thickness at the target position and second measurement data of each target primary support in the target primary support structure of unequal thickness at the target position are obtained respectively; the first measurement data and the second measurement data both include verification thickness, axial force, bending moment and safety factor;

[0051] When the error between the second measured data and the first measured data meets a preset simulation error threshold, the target unequal thickness primary support structure is considered to be a safe structure.

[0052] In a possible implementation, after determining that the target unequal thickness primary support structure is a safe structure, the fifth processing module is further configured to execute:

[0053] Long-term monitoring is performed on five monitoring items, namely, the arch crown and arch foot subsidence, horizontal displacement, surrounding rock and primary support contact pressure, steel arch frame stress, and primary support concrete stress value of the target monitoring point of the target construction scene with the target unequal thickness primary support structure, to obtain a curve of each monitoring item changing with time;

[0054] Determine the change amount of each monitoring item based on the curve corresponding to each monitoring item;

[0055] When the change amount of each of the monitoring items is less than the preset change threshold of the monitoring item, it is considered that the target unequal thickness primary support structure meets the safety requirements.

[0056] In practical applications, the method for designing tunnel unequal thickness primary support structures provided by an embodiment of the present invention first calculates the minimum external insertion angle of the target construction scenario under the equal thickness primary support structure; secondly, according to the fixed primary support thickness under the equal thickness primary support structure, the minimum primary support thickness value of the target construction scenario under the unequal thickness primary support structure is determined; thirdly, the initial excavation position of the rock drill in each cycle is taken as the minimum primary support position, and the tunnel face of the rock drill in each cycle is taken as the maximum primary support position, and a plurality of steel arch frames are arranged at equal intervals from the initial excavation position to the tunnel face; finally, the maximum primary support thickness value is determined according to the minimum external insertion angle and the minimum primary support thickness value by using trigonometric functions, and the primary support thickness value is proportionally increased from the initial excavation position to the tunnel face to obtain the target unequal thickness primary support structure; the tunnel unequal thickness primary support structure designed by this method can not only meet the requirements of surrounding rock stability and support structure safety, but also effectively reduce the serious problem of over-excavation and backfilling caused by the large external insertion angle of the rock drill. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 A flowchart of the steps of a method for designing a tunnel primary support structure of unequal thickness provided by an embodiment of the present invention;

[0058] Figure 2 A schematic diagram of a theoretical external insertion angle of a rock drill in a method for designing a primary support structure of unequal thickness in a tunnel provided by an embodiment of the present invention;

[0059] Figure 3 A schematic diagram of the external insertion angle of a rock drill when the reserved distance from the tunnel face to the rock drill is greater than the length of the exposed drill rod in a method for designing a primary support structure of unequal thickness of a tunnel provided by an embodiment of the present invention;

[0060] Figure 4 A schematic diagram of the external insertion angle of a rock drill when the reserved distance from the tunnel face to the rock drill is less than the length of the exposed drill rod in a method for designing a primary support structure of unequal thickness of a tunnel provided by an embodiment of the present invention;

[0061] Figure 5(a), (b), and (c) are respectively unequal thickness primary support structures when the target construction scenarios are type A lining, type C lining, and type D lining in a tunnel unequal thickness primary support structure design method provided in an embodiment of the present invention.

[0062] Figure 6 A structural block diagram of a tunnel unequal thickness primary support structure design device provided in an embodiment of the present invention.

[0063] Reference numerals and descriptions:

[0064] 11. Rock drill; 12. Drill rod; 13. Excavation contour line; 14. Head face; 15. Primary support structure of equal thickness; 16. Primary support structure of target unequal thickness; 17. Steel arch frame. DETAILED DESCRIPTION

[0065] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0066] In the following, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present disclosure, unless otherwise specified, "multiple" means two or more. In addition, the use of "based on" or "according to" means openness and inclusiveness, because the process, steps, calculations or other actions "based on" or "according to" one or more of the conditions or values ​​may be based on additional conditions or values ​​beyond the described values ​​in practice.

[0067] In order to ensure that the stability of the surrounding rock and the safety requirements of the support structure are met, the serious problem of over-excavation and backfilling caused by the large external insertion angle of the rock drill can be effectively reduced.

[0068] like Figure 1 As shown, in a first aspect, an embodiment of the present invention provides a method for designing a tunnel primary support structure with unequal thickness, the method comprising:

[0069] Step 101, in a target construction scenario of an equal-thickness primary support structure 15, determine the minimum external insertion angle of the rock drill 11 in the target construction scenario based on the acquired distance from the rock drill 11 to the tunnel excavation contour line 13, the rock drill thickness, the fixed primary support thickness, the reserved distance from the face to the rock drill, the drill rod radius, and the exposed drill rod length.

[0070] The exposed drill rod length is the length of the drill rod 12 extending from the excavation contour line 13 around the hole.

[0071] Specifically, the rock drill 11 is a three-arm rock drill trolley. The target construction scenario is that the tunnel passes through the Class IV surrounding rock formation. The three-arm rock drill trolley adopts a mechanized three-step method for excavation. The lining types of the target construction scenario include type A lining, type C lining and type D lining. In type A lining, type C lining and type D lining, the cycle footage of the three-arm rock drill trolley is 3.2m, 3.2m and 4m respectively.

[0072] When the external insertion angle of the rock drill 11 is calculated theoretically, the thickness of the supporting layer is not considered, that is, the primary support structure is not considered. Figure 2 As shown, the calculation formula of the theoretical external insertion angle θ of the rock drill 11 is as follows:

[0073] ;

[0074] in, is the distance from the rock drill 11 to the excavation contour line 13 around the hole, Half the thickness of the rock drill, It is the reserved distance from the tunnel face 14 to the rock drill 11.

[0075] In actual engineering construction, steel frames, anchors, meshes and shotcrete supports are designed. They need to be supported in time after excavation. Continuous blasting and bare rock construction are not allowed. Therefore, in actual engineering, when calculating the external insertion angle of the rock drill 11, the influence of the initial support thickness needs to be considered. According to the size of the reserved distance from the face to the rock drill, it can be divided into two application scenarios: the reserved distance from the face to the rock drill is greater than the exposed drill rod length, and the reserved distance from the face to the rock drill is less than the exposed drill rod length.

[0076] Furthermore, in the target construction scene of the equal-thickness primary support structure 15, the minimum external insertion angle of the rock drill 11 in the target construction scene is determined according to the obtained distance from the rock drill 11 to the tunnel perimeter excavation contour line 13, the rock drill thickness, the fixed primary support thickness, the reserved distance from the tunnel face to the rock drill, the drill rod radius, and the exposed drill rod length, specifically including:

[0077] In the target construction scenario of the equal-thickness primary support structure 15, when the reserved distance from the face to the rock drill is greater than the exposed drill rod length, the minimum external insertion angle of the rock drill 11 in the target construction scenario is determined based on the obtained distance from the rock drill 11 to the tunnel excavation contour line 13, the rock drill thickness, the fixed primary support thickness and the reserved distance from the face to the rock drill.

[0078] like Figure 3 As shown, further, when the reserved distance from the tunnel face to the rock drill is greater than the length of the exposed drill rod 12, the minimum external insertion angle of the rock drill 11 in the target construction scene is determined according to the first formula, and the first formula is specifically:

[0079] ;

[0080] in, represents the minimum external insertion angle, represents the distance from the rock drill 11 to the excavation contour line 13 around the hole, Represents half the thickness of the rock drill, Indicates the fixed initial support thickness. Indicates the reserved distance from the tunnel face to the rock drill.

[0081] In the embodiment of the present invention, when the reserved distance from the face to the rock drill is greater than the length of the exposed drill rod 12, the calculated external insertion angles under the three linings of type A lining, type C lining and type D lining are shown in Table 1:

[0082] Table 1 Minimum external insertion angle when the reserved distance from the tunnel face to the rock drill is greater than the length of the exposed drill rod 12

[0083]

[0084] In the target construction scenario of the equal-thickness primary support structure 15, when the reserved distance from the face to the rock drill is less than the length of the exposed drill rod 12, the minimum external insertion angle of the rock drill 11 in the target construction scenario is determined according to the obtained drill rod radius, the fixed primary support thickness and the reserved distance from the face to the rock drill.

[0085] like Figure 4 As shown, further, when the reserved distance from the face to the rock drill is less than the exposed drill rod length, the minimum external insertion angle of the rock drill 11 in the target construction scene is determined according to the second formula, and the second formula is specifically:

[0086] ;

[0087] in, Indicates the drill pipe radius.

[0088] In the embodiment of the present invention, when the reserved distance from the face to the rock drill is less than the length of the exposed drill rod, the calculated external insertion angles under the three linings of type A lining, type C lining and type D lining are shown in Table 2:

[0089] Table 2 Minimum external insertion angle when the reserved distance from the face to the rock drill is less than the length of the exposed drill rod 12

[0090]

[0091] In this embodiment, by comparing Table 1 and Table 2, taking into account factors such as the surrounding rock advance pre-reinforcement cycle length and effective overlap, the relationship between the surrounding rock stability and the tunnel face 14, and the control of the external insertion angle, in the actual construction process, the cycle footage, reserved length of the tunnel face, and actual external insertion angle control values ​​of the surrounding rock mechanized construction type A lining, type C lining, and type D lining are shown in Table 3:

[0092] Table 3 Mechanized construction parameters of surrounding rock and control values ​​of external insertion angle

[0093]

[0094] Step 102: Determine the minimum initial support thickness value of the target construction scenario in the unequal thickness initial support structure 1615 according to the product of the fixed initial support thickness and the first preset value.

[0095] Among them, the first preset value is ≥0.6.

[0096] Specifically, according to the highway engineering quality assessment standard for civil engineering projects, the average thickness of the sprayed layer is required to be no less than 0.6 times the design thickness of the design sprayed layer. Therefore, when determining the minimum initial support thickness value, it is necessary to calculate the product of the fixed initial support thickness and the first preset value.

[0097] Combining Table 2, Table 3 and Table 4, we can calculate that the minimum initial support thickness values ​​of type A lining, type C lining and type D lining are 17cm, 16cm and 16cm respectively.

[0098] Step 103, taking the initial excavation position of the rock drill 11 in each cycle as the minimum initial support, taking the tunnel face 14 of the rock drill 11 in each cycle as the maximum initial support, and arranging multiple steel arch frames 17 at equal intervals from the initial excavation position to the tunnel face 14.

[0099] Specifically, in each excavation cycle of the rock drill 11, the thickness of the shotcrete at the initial excavation position is the minimum value, i.e., the minimum initial support, and the thickness of the shotcrete at the tunnel face 14 is the maximum value, i.e., the maximum initial support. Before shotcrete is sprayed, a plurality of steel arches 17 are arranged at equal intervals from the initial excavation position to the tunnel face 14 for support.

[0100] Step 104 , based on trigonometric functions, determine the maximum initial support thickness value according to the minimum external interpolation angle and the minimum initial support thickness value, and obtain the target unequal thickness initial support structure 16 .

[0101] Among them, the initial support thickness value increases proportionally from the initial position of excavation to the tunnel face 14, that is, the thickness of the shotcrete increases gradually from the initial position of excavation to the tunnel face 14.

[0102] Specifically, under the premise that the external insertion angle of the rock drill is determined, the excavation length of each cycle is determined, the reserved distance from the tunnel face to the rock drill in each cycle is determined, and the minimum initial support thickness value is determined, the maximum initial support thickness value can be calculated according to the trigonometric function.

[0103] In this embodiment, the maximum initial support thickness values ​​of type A lining, type C lining and type D lining are calculated to be 70 cm, 67 cm and 81 cm respectively.

[0104] like Figure 5 As shown, in Figure 5 In the type a lining in (a) above, the target unequal thickness primary support structure is as follows: the length of one excavation cycle of the rock drill is 3.2m, the setting interval of the steel arch frame in each cycle is 80cm, the reserved distance from the heading to the rock drill is 240cm, the minimum external insertion angle is 10.62°, the minimum primary support thickness is 17cm, and the maximum primary support thickness is 70cm.

[0105] exist Figure 5 In the C-type lining in (b), the target unequal thickness primary support structure is as follows: the length of one excavation cycle of the rock drill is 3.2m, the setting interval of the steel arch frame in each cycle is 80cm, the reserved distance from the heading to the rock drill is 160cm, the minimum external insertion angle is 10.02°, the minimum primary support thickness is 16cm, and the maximum primary support thickness is 67cm.

[0106] exist Figure 5 In the type D lining in (c) above, the target unequal thickness primary support structure is as follows: the length of one excavation cycle of the rock drill is 4m, the setting interval of the steel arch frame in each cycle is 100cm, the reserved distance from the heading to the rock drill is 300cm, the minimum external insertion angle is 8.15°, the minimum primary support thickness is 16cm, and the maximum primary support thickness is 81cm.

[0107] Furthermore, after obtaining the target unequal thickness primary support structure, the tunnel unequal thickness primary support structure design method further includes: performing safety verification on the target unequal thickness primary support structure.

[0108] Specifically, in order to ensure the safety and stability of the designed target unequal thickness primary support structure, it is necessary to perform safety verification on the target unequal thickness primary support structure. In this embodiment, the safety verification includes two types: numerical simulation verification and on-site monitoring verification.

[0109] Furthermore, the safety verification of the target unequal thickness primary support structure is carried out, including:

[0110] According to the target construction scenario, three-dimensional stratum models corresponding to the primary support structure of equal thickness and the target primary support structure of unequal thickness are established respectively.

[0111] Through the method of numerical simulation calculation, the first measurement data of the fixed primary support in the equal-thickness primary support structure at the target position and the second measurement data of each target primary support in the target unequal-thickness primary support structure at the target position are obtained respectively.

[0112] Wherein, the first calculated data and the second calculated data both include the calculated thickness, axial force, bending moment and safety factor;

[0113] When the error between the second measured data and the first measured data meets a preset simulation error threshold, the target unequal thickness primary support structure is considered to be a safe structure.

[0114] In this embodiment, FLAC3D 5.0 ​​finite element software is used. Taking the cross section of the tunnel in the embodiment of the present invention as an example, a three-dimensional stratum structure model is established. The mechanized three-step method is used for excavation, and the equal-thickness initial support structure and the target unequal-thickness initial support structure under the support parameters of type C lining and type D lining are respectively verified for safety. Among them, the initial support thickness of the target unequal-thickness initial support structure in the type C lining is 16~67cm; the initial support thickness of the target unequal-thickness initial support structure in the type D lining is 16~81cm. When calculating the thickness, axial force, bending moment and safety factor of the target unequal-thickness initial support structure, it is necessary to calculate each steel arch position in the cycle. The calculation results of the target unequal-thickness initial support structure and the equal-thickness initial support structure are shown in Table 4:

[0115] Table 4 Comparison of calculation results of equal thickness primary support structure and target unequal thickness primary support structure

[0116]

[0117] Note: The fourth steel arch frame of the target unequal thickness primary support structure is the connection between the thickest and thinnest primary support, so the verification thickness is converted to the median value of 43.60cm.

[0118] According to Table 4, the target unequal thickness primary support structure is divided into four frames for calculation. The target unequal thickness primary support structure in the C-type lining has a maximum axial force of -2731.45 kN, a maximum bending moment of -24.15 kN·m, and a minimum safety factor of 2.91 at the right arch foot of the third steel arch frame; the original design of the equal thickness primary support structure has a maximum axial force of -1360.29 kN, a maximum bending moment of -3.34 kN·m, and a minimum safety factor of 3.06 at the left arch foot. The target unequal thickness primary support structure in the D-type lining has a maximum axial force of -2875.82 kN, a maximum bending moment of -28.60 kN·m and a minimum safety factor of 2.31 at the right arch foot of the third steel arch frame; the original design of the equal thickness primary support structure has a maximum axial force of -1350.91 kN, a maximum bending moment of -2.38 kN·m and a minimum safety factor of 3.12 at the right arch foot. The safety factors are all greater than the requirements of the specifications.

[0119] At the same time, it can be seen that the safety factor of the unequal thickness primary support structure is not higher as the thickness increases, because the internal force gradually increases with the thickness of the primary support sprayed mix. Compared with the calculation results of the equal thickness primary support structure, the main characteristics are: the internal force of each section of the equal thickness primary support structure is evenly distributed, while the distribution of the internal force of the unequal thickness primary support section changes with the thickness of the concrete sprayed mix.

[0120] According to the above analysis of internal forces and safety factors, the target unequal thickness primary support structure of the present invention meets the force requirements of tunnel construction. The specific reasons are as follows:

[0121] (1) The unequal thickness primary support structure is an integral load-bearing unit, and local weak points cannot affect the stability of the overall structure.

[0122] (2) Although the thickness of local sprayed concrete is reduced, the cross-section of the thicker sprayed concrete has greater stiffness and smaller deformation, and the load it bears will also be greater.

[0123] (3) The starting point and end point of each excavation cycle of the rock drill are a continuous structure, not completely independent. Therefore, the section with a large spray mix thickness at the starting point will compensate for the section with a small spray mix thickness and form an overall force-bearing structure.

[0124] Furthermore, after determining that the target unequal thickness primary support structure is a safe structure, safety verification of the target unequal thickness primary support structure also includes:

[0125] Long-term monitoring is carried out on five monitoring items, including the arch crown and arch foot subsidence, horizontal displacement, contact pressure between surrounding rock and primary support, steel arch frame stress and primary support concrete stress of the target monitoring points in the target construction scenario of the target unequal thickness primary support structure, and a curve of each monitoring item changing with time is obtained.

[0126] Based on the curve corresponding to each monitoring item, the change amount of each monitoring item is determined.

[0127] When the change amount of each monitoring item is less than the preset change threshold of the monitoring item, it is considered that the target unequal thickness primary support structure meets the safety requirements.

[0128] In the embodiment of the present invention, 7 measuring points are arranged in each section for displacement around each tunnel, and 5 measuring points are arranged in each section for stress and strain of initial support. The monitoring data obtained from the monitoring section are statistically analyzed, and the curves of the settlement of the arch crown and arch foot, horizontal displacement, contact pressure value between surrounding rock and initial support, stress of steel arch frame and stress value of initial support concrete over time are drawn. The test results of each monitoring item are summarized as shown in Table 5:

[0129] Table 5 Summary of monitoring results

[0130]

[0131] According to Table 5, the maximum cumulative settlement of the arch crown of the test section of the target unequal thickness primary support structure on the left line of the tunnel is 7.60mm, which is only 7.6% of the designed reserved deformation (10cm), and the overall settlement of each measuring point is small; the maximum horizontal displacement is 8.20mm, which is only 8.2% of the designed reserved deformation (10cm), and the overall displacement of each measuring point is small; the maximum contact pressure between the surrounding rock and the primary support is 96.00kPa, and it can be seen from the time-history curve that the pressure values ​​at the symmetrical positions on both sides of the tunnel are roughly the same, indicating that there is no bias; the maximum compressive stress of the steel arch frame is 56.89MPa, reaching 24.2% of the yield strength of the steel, and the maximum tensile stress is 70.83MPa, reaching 30.1% of the yield strength of the steel, and the stress of the steel arch frame at other measuring points is relatively small; the maximum compressive stress of the initial support concrete is 6.55MPa, reaching 33.2% of the design value, and the maximum tensile stress is 1.39MPa, reaching 63.2% of the design strength, and the pressure values ​​of the initial support concrete at other measuring points are small.

[0132] Therefore, the sinking of the arch crown and arch foot, horizontal displacement, contact pressure between the primary support and the surrounding rock, stress of the steel arch frame and the primary support concrete stress of the unequal thickness primary support test section on the left line of the tunnel exit are all far less than the control values. The surrounding rock has good self-stability when it is moderately weathered, has relatively developed joints and fissures, and is locally broken. The surrounding rock stress after initial support mainly comes from the stress generated by the deadweight of the surrounding rock, and the safety reserve is sufficient, meeting the safety requirements of construction and support structure. Therefore, the optimized unequal thickness primary support was used for support verification of the Class IV surrounding rock section on the left line of the tunnel exit section, which is safe.

[0133] In practical applications, the method for designing tunnel unequal thickness primary support structures provided by an embodiment of the present invention first calculates the minimum external interpolation angle of the target construction scenario under the equal thickness primary support structure; secondly, according to the fixed primary support thickness under the equal thickness primary support structure, the minimum primary support thickness value of the target construction scenario under the unequal thickness primary support structure is determined; thirdly, the initial excavation position of the rock drill in each cycle is taken as the minimum primary support position, and the tunnel face of the rock drill in each cycle is taken as the maximum primary support position, and multiple steel arch frames are arranged at equal intervals from the initial excavation position to the tunnel face; finally, using trigonometric functions, according to the minimum external interpolation angle and the minimum primary support thickness value, the maximum primary support thickness value is determined, and the primary support thickness values ​​are proportionally increased from the initial excavation position to the tunnel face to obtain the target unequal thickness primary support structure.

[0134] The tunnel unequal thickness primary support structure designed by this method can not only meet the requirements of surrounding rock stability and support structure safety, but also effectively reduce the serious problem of over-excavation and backfilling caused by the large external insertion angle of the drilling rig.

[0135] like Figure 6 As shown, in a second aspect, an embodiment of the present invention further provides a device for designing a tunnel primary support structure of unequal thickness, the device comprising:

[0136] The first processing unit 201 is used to determine the minimum external insertion angle of the rock drill in the target construction scene in the target construction scene of the equal-thickness primary support structure according to the acquired distance from the rock drill to the excavation contour line around the tunnel, the thickness of the rock drill, the thickness of the fixed primary support, the reserved distance from the tunnel face to the rock drill, the radius of the drill rod, and the exposed drill rod length; the exposed drill rod length is the length of the drill rod extending out of the excavation contour line around the tunnel;

[0137] The second processing unit 202 is used to determine the minimum primary support thickness value of the target construction scene in the unequal thickness primary support structure according to the product of the fixed primary support thickness and the first preset value; the first preset value is ≥ 0.6;

[0138] The third processing unit 203 is used to set a plurality of steel arches at equal intervals from the excavation initial position to the tunnel face, with the excavation initial position of the rock drill in each cycle as the minimum primary support position and the tunnel face of the rock drill in each cycle as the maximum primary support position;

[0139] The fourth processing unit 204 is used to determine the maximum primary support thickness value based on the minimum external interpolation angle and the minimum primary support thickness value based on trigonometric functions to obtain a target unequal thickness primary support structure; the primary support thickness value increases proportionally from the initial excavation position to the tunnel face.

[0140] Furthermore, the first processing unit 201 is specifically configured to execute:

[0141] In the target construction scenario of the equal-thickness primary support structure, when the reserved distance from the face to the rock drill is greater than the length of the exposed drill rod, the minimum external insertion angle of the rock drill in the target construction scenario is determined based on the distance from the rock drill to the excavation contour line around the tunnel, the thickness of the rock drill, the thickness of the fixed primary support, and the reserved distance from the face to the rock drill.

[0142] In the target construction scenario of the equal-thickness primary support structure, when the reserved distance from the tunnel face to the rock drill is less than the exposed drill rod length, the minimum external insertion angle of the rock drill in the target construction scenario is determined according to the obtained drill rod radius, the fixed primary support thickness and the reserved distance from the tunnel face to the rock drill.

[0143] Further, when the reserved distance from the tunnel face to the rock drill is greater than the length of the exposed drill rod, the first processing unit 201 is specifically configured to execute:

[0144] The minimum external interpolation angle of the rock drill in the target construction scene is determined according to the first formula, and the first formula is specifically:

[0145] ;

[0146] in, represents the minimum external insertion angle, Indicates the distance from the rock drill to the excavation contour line around the tunnel. Represents half the thickness of the rock drill, Indicates the fixed initial support thickness. Indicates the reserved distance from the tunnel face to the rock drill.

[0147] Further, when the reserved distance from the tunnel face to the rock drill is less than the length of the exposed drill rod, the first processing unit 201 is specifically configured to execute:

[0148] The minimum external interpolation angle of the rock drill in the target construction scene is determined according to the second formula, and the second formula is specifically:

[0149]

[0150] in, Indicates the drill pipe radius.

[0151] Furthermore, after obtaining the target unequal thickness primary support structure, the tunnel unequal thickness primary support structure design device further includes a fifth processing module; the fifth processing module is configured to execute:

[0152] Conduct safety verification on target unequal thickness primary support structures.

[0153] Furthermore, when performing safety verification on the target unequal thickness primary support structure, the fifth processing module is specifically configured to execute:

[0154] According to the target construction scenario, three-dimensional stratum models corresponding to the primary support structure of equal thickness and the target primary support structure of unequal thickness are established respectively;

[0155] By means of numerical simulation calculation, the first measurement data of the fixed primary support in the equal thickness primary support structure at the target position and the second measurement data of each target primary support in the target unequal thickness primary support structure at the target position are obtained respectively; the first measurement data and the second measurement data both include the verification thickness, axial force, bending moment and safety factor;

[0156] When the error between the second measured data and the first measured data meets a preset simulation error threshold, the target unequal thickness primary support structure is considered to be a safe structure.

[0157] Further, after determining that the target unequal thickness primary support structure is a safe structure, the fifth processing module is further configured to execute:

[0158] Long-term monitoring is carried out on five monitoring items, namely, the arch crown and arch foot subsidence, horizontal displacement, contact pressure between surrounding rock and primary support, steel arch frame stress, and primary support concrete stress of the target monitoring points of the target construction scene with the target unequal thickness primary support structure, to obtain the curve of each monitoring item changing with time;

[0159] Based on the curve corresponding to each monitoring item, determine the change amount of each monitoring item;

[0160] When the change amount of each monitoring item is less than the preset change threshold of the monitoring item, it is considered that the target unequal thickness primary support structure meets the safety requirements.

[0161] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0162] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for designing a tunnel primary support structure with unequal thickness, characterized in that: include: In the target construction scenario of the equal-thickness primary support structure, the minimum external insertion angle of the rock drill in the target construction scenario is determined according to the distance from the rock drill to the excavation contour line around the tunnel, the thickness of the rock drill, the thickness of the fixed primary support, the reserved distance from the tunnel face to the rock drill, the drill rod radius and the exposed drill rod length; the exposed drill rod length is the length of the drill rod extending out of the excavation contour line around the tunnel; Determine the minimum primary support thickness value of the target construction scenario in the unequal thickness primary support structure according to the product of the fixed primary support thickness and the first preset value; The first preset value is ≥ 0.6; The initial excavation position of the rock drill in each cycle is taken as the minimum initial support position, the tunnel face of the rock drill in each cycle is taken as the maximum initial support position, and a plurality of steel arch frames are arranged at equal intervals from the initial excavation position to the tunnel face; Based on trigonometric functions, the maximum primary support thickness value is determined according to the minimum external interpolation angle and the minimum primary support thickness value, and a target unequal thickness primary support structure is obtained; the primary support thickness value increases proportionally from the initial excavation position to the tunnel face; In the target construction scenario of the equal thickness primary support structure, when the reserved distance from the face to the rock drill is greater than the length of the exposed drill rod, the minimum external insertion angle of the rock drill in the target construction scenario is determined according to the distance from the rock drill to the excavation contour line around the tunnel, the thickness of the rock drill, the thickness of the fixed primary support and the reserved distance from the face to the rock drill; In a target construction scenario of an equal-thickness primary support structure, when the reserved distance from the face to the rock drill is less than the exposed drill rod length, the minimum external insertion angle of the rock drill in the target construction scenario is determined according to the obtained drill rod radius, the fixed primary support thickness, and the reserved distance from the face to the rock drill; When the reserved distance from the tunnel face to the rock drill is greater than the length of the exposed drill rod, the minimum external insertion angle of the rock drill in the target construction scene is determined according to the first formula, and the first formula is specifically: Among them, represents the minimum external insertion angle, represents the distance from the rock drill to the excavation contour line around the tunnel, represents half of the thickness of the rock drill, represents the fixed primary support thickness, and represents the reserved distance from the tunnel face to the rock drill; When the reserved distance from the tunnel face to the rock drill is less than the length of the exposed drill rod, the minimum external insertion angle of the rock drill in the target construction scene is determined according to the second formula, and the second formula is specifically: Where, represents the drill pipe radius.

2. The method for designing a tunnel primary support structure with unequal thickness according to claim 1 is characterized in that: After obtaining the target unequal thickness primary support structure, the method further includes: performing safety verification on the target unequal thickness primary support structure.

3. The method for designing a tunnel primary support structure with unequal thickness according to claim 2 is characterized in that: The safety verification of the target unequal thickness primary support structure is carried out, including: According to the target construction scene, three-dimensional stratum models corresponding to the primary support structure of equal thickness and the target primary support structure of unequal thickness are respectively established; By means of numerical simulation calculation, first measurement data of the fixed primary support in the primary support structure of equal thickness at the target position and second measurement data of each target primary support in the target primary support structure of unequal thickness at the target position are obtained respectively; the first measurement data and the second measurement data both include verification thickness, axial force, bending moment and safety factor; When the error between the second measured data and the first measured data meets a preset simulation error threshold, the target unequal thickness primary support structure is considered to be a safe structure.

4. The method for designing a tunnel primary support structure with unequal thickness according to claim 3 is characterized in that: After determining that the target unequal thickness primary support structure is a safe structure, the safety verification of the target unequal thickness primary support structure further includes: Long-term monitoring is performed on five monitoring items, namely, the arch crown and arch foot subsidence, horizontal displacement, surrounding rock and primary support contact pressure, steel arch frame stress, and primary support concrete stress value of the target monitoring point of the target construction scene with the target unequal thickness primary support structure, to obtain a curve of each monitoring item changing with time; Determine the change amount of each monitoring item based on the curve corresponding to each monitoring item; When the change amount of each of the monitoring items is less than the preset change threshold of the monitoring item, it is considered that the target unequal thickness primary support structure meets the safety requirements.

5. A device for designing primary support structures of unequal thickness in tunnels, characterized in that: include: The first processing unit is used to determine the minimum external insertion angle of the rock drill in the target construction scene of the equal-thickness primary support structure according to the acquired distance from the rock drill to the excavation contour line around the tunnel, the thickness of the rock drill, the thickness of the fixed primary support, the reserved distance from the tunnel face to the rock drill, the drill rod radius, and the exposed drill rod length in the target construction scene; the exposed drill rod length is the length of the drill rod extending from the excavation contour line around the tunnel; A second processing unit is used to determine a minimum primary support thickness value of the target construction scene in the unequal thickness primary support structure according to the product of the fixed primary support thickness and the first preset value; The first preset value is ≥ 0.6; The third processing unit is used to set a plurality of steel arches at equal intervals from the excavation initial position to the tunnel face, with the excavation initial position of the rock drill in each cycle as the minimum primary support and the tunnel face of the rock drill in each cycle as the maximum primary support; The fourth processing unit is used to determine the maximum primary support thickness value based on the minimum external interpolation angle and the minimum primary support thickness value based on trigonometric functions to obtain a target unequal thickness primary support structure; the primary support thickness value increases proportionally from the initial excavation position to the tunnel face; The first processing unit is specifically configured to perform: In the target construction scenario of the equal thickness primary support structure, when the reserved distance from the face to the rock drill is greater than the length of the exposed drill rod, the minimum external insertion angle of the rock drill in the target construction scenario is determined according to the distance from the rock drill to the excavation contour line around the tunnel, the thickness of the rock drill, the thickness of the fixed primary support and the reserved distance from the face to the rock drill; In a target construction scenario of an equal-thickness primary support structure, when the reserved distance from the face to the rock drill is less than the exposed drill rod length, the minimum external insertion angle of the rock drill in the target construction scenario is determined according to the obtained drill rod radius, the fixed primary support thickness, and the reserved distance from the face to the rock drill; When the reserved distance from the tunnel face to the rock drill is greater than the length of the exposed drill rod, the minimum external insertion angle of the rock drill in the target construction scene is determined according to the first formula, and the first formula is specifically: Among them, represents the minimum external insertion angle, represents the distance from the rock drill to the excavation contour line around the tunnel, represents half of the thickness of the rock drill, represents the fixed primary support thickness, and represents the reserved distance from the tunnel face to the rock drill; When the reserved distance from the tunnel face to the rock drill is less than the length of the exposed drill rod, the minimum external insertion angle of the rock drill in the target construction scene is determined according to the second formula, and the second formula is specifically: Where, represents the drill pipe radius.

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