Joint structure between rings of segment and design method of joint structure between rings

Abstract

To provide joint structure between rings of a segment that can clarify required properties of a joint between rings in the state that a tunnel is deformed largely and restrain risk of tunnel collapse with low cost.SOLUTION: The present invention relates to joint structure between rings of a segment connecting tunnel rings that connect segments constituting a shield tunnel by segment joints in a tunnel circumferential direction to each other by a joint between rings in a tunnel axial direction. Maximum strength of a segment body is defined to be larger than maximum strength of the joint between rings.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an inter-ring joint structure of a segment and a method for designing an inter-ring joint structure. [Background technology]

[0002] Earthquakes of a magnitude beyond what was previously assumed have occurred, raising interest in the seismic resistance of the segments used in shield tunnels. Generally, shield tunnels deform in response to ground deformation, so when earthquake loads act on the tunnel, it deforms in a transverse direction, becoming elliptical. This damages the tunnel lining and reduces the structural safety of the tunnel.

[0003] Furthermore, even if an unexpected earthquake occurs and the tunnel deforms more than expected, the tunnel lining must be able to prevent collapse from the perspective of protecting human lives. The following methods are known to reduce the risk of tunnel lining collapse during such deformation. For example, one method is to increase the thickness of the tunnel lining to improve the lining strength. Another method is to improve the strength of the inter-ring joints by taking advantage of the splice effect. Conventionally, inter-ring joints are generally designed to have the same diameter as the segment joints or one size smaller.

[0004] Furthermore, as a rational design method for inter-ring joints, for example, as shown in Patent Document 1, a method is known in which joints that have previously been modeled linearly in a beam-spring model are modeled as segment joints with nonlinear rotational springs and inter-ring joints with nonlinear shear springs. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-32692 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the above-mentioned conventional method has the following problems. In other words, when the thickness of the tunnel lining is increased, the outer diameter of the tunnel and the weight of the segments also increase, which poses a problem of increased costs. Furthermore, although the design method for ring-to-ring joints described in Patent Document 1 can keep costs lower compared to increasing the thickness of the tunnel lining as described above, it merely determines whether the components are within a set stress level (allowable stress level, etc.) when a certain external force is applied, and the standards required for ring-to-ring joints when considering the destruction of the tunnel are unclear, which could result in over- or under-specified specifications. Therefore, there is a demand for a ring-to-ring joint structure with a more reliable design that keeps costs down, and there is room for improvement in this regard.

[0007] The present invention has been made in consideration of the above-mentioned problems, and aims to provide an inter-ring joint structure for segments and a design method for an inter-ring joint structure that can clarify the required performance of an inter-ring joint in a situation where a tunnel undergoes large deformation and can reduce the risk of tunnel collapse at low cost. [Means for solving the problem]

[0008] (1) Aspect 1 of the segment inter-ring joint structure according to the present invention is a segment inter-ring joint structure in which tunnel rings, each formed by connecting segments constituting a shield tunnel in the tunnel circumferential direction by segment joints, are connected in the tunnel axial direction by inter-ring joints, and is characterized in that the maximum strength of the main body of the segment is set to be greater than the maximum strength of the inter-ring joint.

[0009] In the present invention, the structure is such that, in the failure mode of the tunnel ring, failure of the segment body precedes fracture of the inter-ring joints. In other words, by improving the strength of the inter-ring joints, the failure mode of the tunnel lining is such that bending failure of the segment body precedes fracture of the inter-ring joints, thereby reducing the risk of collapse of the tunnel lining, including the segments. In this way, in the present invention, the maximum shear strength required for the inter-ring joints can be determined based on the maximum bending strength of the segment body.

[0010] (2) Aspect 2 of the present invention is a segment inter-ring joint structure according to aspect 1, in which the maximum strength of the inter-ring joint is M r_max , the maximum strength of the segment body is M b_max When set as above, it is preferable to satisfy the formula (1).

[0011]

number

[0012] In this case, the risk of the failure mode not being as expected due to variations in the material can be reduced.

[0013] (3) A third aspect of the present invention may be characterized in that in the segment-ring joint structure of the first or second aspect, the segments are composite segments.

[0014] In this case, by using composite segments with high bending strength in the segment body, it is possible to prevent the inter-ring joints from being under-specified, which has the advantage of making the above-mentioned effects more pronounced.

[0015] (4) A fourth aspect of the present invention is characterized in that, in the inter-ring joint structure of any one of the segments of the first to third aspects, the maximum shear strength Sr of the inter-ring joint satisfies the formula (2).

[0016]

number

[0017] The present invention makes it possible to more clearly define the required performance of the ring-to-ring joint, thereby reducing the risk of tunnel collapse and providing optimal performance at low cost.

[0018] (5) A fifth aspect of the design method for a ring-to-ring joint structure according to the present invention is a design method for a ring-to-ring joint structure in which tunnel rings, each formed by connecting segments constituting a shield tunnel in the tunnel circumferential direction by segment joints, are connected in the tunnel axial direction by inter-ring joints, characterized in that the maximum strength of the main body of the segment is set to be greater than the maximum strength of the inter-ring joint.

[0019] In the present invention, the structure is such that, in the failure mode of the tunnel ring, failure of the segment body precedes fracture of the inter-ring joints. In other words, by improving the strength of the inter-ring joints, the failure mode of the tunnel lining is such that bending failure of the segment body precedes fracture of the inter-ring joints, thereby reducing the risk of collapse of the tunnel lining, including the segments. In this way, in the present invention, the maximum shear strength required for the inter-ring joints can be determined based on the maximum bending strength of the segment body.

[0020] (6) A sixth aspect of the present invention is a method for designing an inter-ring joint structure according to the fifth aspect, wherein the maximum strength of the inter-ring joint is M r_max , the maximum strength of the segment body is M b_max When set as above, it is preferable to satisfy the formula (1).

[0021]

number

[0022] In this case, the risk of the failure mode not being as expected due to variations in the material can be reduced.

[0023] (7) A seventh aspect of the present invention may be characterized in that, in the design method for an inter-ring joint structure according to the fifth or sixth aspect, the segments are composite segments.

[0024] In this case, by using composite segments with high bending strength in the segment body, it is possible to prevent the inter-ring joints from being under-specified, which has the advantage of making the above-mentioned effects more pronounced.

[0025] (8) Aspect 8 of the present invention is characterized in that, in the design method for a ring-to-ring joint structure according to any one of aspects 5 to 7, the maximum shear strength Sr of the ring-to-ring joint satisfies formula (2).

[0026]

number

[0027] The present invention makes it possible to more clearly define the required performance of the ring-to-ring joint, thereby reducing the risk of tunnel collapse and providing optimal performance at low cost.

[0028] (9) A ninth aspect of the design method for an inter-ring joint structure according to the present invention is a design method for an inter-ring joint structure according to the eighth aspect, characterized in that it comprises the following steps: a first step of setting an initial value for said formula (2); a second step of using said formula (2) to determine the bending moment generated in the segment body, the bending moment generated in the segment joint, and the shear force generated in the inter-ring joint based on the initial value; a third step of determining whether or not a break point at which stiffness changes has been reached in at least one of said segment body, said segment joint, and said inter-ring joint determined in said second step; a fourth step of determining whether or not the segment joint or the inter-ring joint has reached a break point in stiffness and changing the material setting; a fifth step of changing the material setting when it is determined that the strength is not maximum when the segment body has reached a break point in stiffness and terminating the design flow when it is determined that the strength is maximum; and a sixth step of setting a material for the inter-ring joint based on the shear strength of the inter-ring joint at the end of step five.

[0029] In the present invention, by taking into consideration the change in stiffness due to plasticization, it is possible to provide a ring-to-ring joint with more optimized performance. [Effects of the Invention]

[0030] According to the segment inter-ring joint structure and the design method for the inter-ring joint structure of the present invention, it is possible to clarify the required performance of the inter-ring joint in situations where the tunnel is subject to large deformation, and to reduce the risk of tunnel collapse at low cost. [Brief explanation of the drawings]

[0031] [Figure 1] FIG. 2 is a partially cutaway perspective view showing a main portion of a segment of a shield tunnel according to an embodiment of the present invention. [Figure 2] FIG. 2 is a perspective view showing the configuration of the segment shown in FIG. [Figure 3] FIG. 1 is a diagram showing the design concept of the inter-ring joint structure of the segment according to the present embodiment. [Figure 4] FIG. 1 is a diagram showing a design concept of a conventional inter-ring joint structure of segments. [Figure 5] FIG. 1 is a diagram showing an FEM analysis model that forms the basis of the design concept of the inter-ring joint structure. [Figure 6] FIG. 6 is a diagram showing the relationship between the ring reaction force and the amount of forced displacement in the analysis results of FIG. 5. [Figure 7] FIG. 6 is a diagram showing a contour diagram of strain distribution in the analysis results of FIG. 5. [Figure 8] FIG. 10 is a perspective view of a splice bending model that models an inter-ring joint structure. [Figure 9] FIG. 10 is a side view of a splice bending model that models an inter-ring joint structure. [Figure 10] FIG. 10 is a diagram showing an example of a design flow for an inter-ring joint structure. [Figure 11]Graphs showing a nonlinear material setting model, where (a) is a relationship diagram between shear force and shear displacement of a ring-to-ring joint, (b) is a relationship diagram between bending moment and curvature of a segment body, and (c) is a relationship diagram between bending moment and joint rotation angle of a segment joint. [Figure 12] 10A and 10B are diagrams showing a material setting model according to an embodiment, in which (a) is a diagram showing the relationship between shear force and shear displacement of a ring-to-ring joint, (b) is a diagram showing the relationship between bending moment and curvature of a segment body, and (c) is a diagram showing the relationship between bending moment and joint rotation angle of a segment joint. DETAILED DESCRIPTION OF THE INVENTION

[0032] Hereinafter, an inter-ring joint structure of a segment and a design method for an inter-ring joint structure according to an embodiment of the present invention will be described with reference to the drawings.

[0033] 1 and 2, the segment 10A according to this embodiment constitutes a tunnel ring including segment rings, which are structural members of a circular tunnel lining constructed on the inner wall of a hole excavated by the shield tunneling method, and is described as an example of a composite segment filled with concrete, with segment joint surfaces in the tunnel circumferential direction and inter-ring joint surfaces in the tunnel axial direction. Note that the segment 10A may also be a steel segment composed only of a steel shell portion without concrete filling, or a reinforced concrete segment made up of a combination of reinforcing steel and concrete.

[0034] Here, in the segment 10A, the arc direction is referred to as the tunnel circumferential direction X1, the short side direction perpendicular to the arc direction is referred to as the tunnel axial direction X2, and the height direction of the segment is referred to as the tunnel radial direction X3. In addition, the outer side of the tunnel radial direction X3 is referred to as the natural ground side (tunnel natural ground side), and the inner side is referred to as the inner space side (tunnel inner space side).

[0035] In the shield tunneling method, a plurality of segments 10A are connected in the tunnel circumferential direction X1 and the tunnel axial direction X2 along the inner wall of a tunnel excavated in the natural ground to form a cylindrical wall. The segments 10A are formed in the shape of an arc plate with a curvature approximately equal to the curvature of the inner surface of the tunnel excavation hole. In other words, the segments 10A have a hexahedral shape curved on an arc on the outer circumferential surface side of the tunnel.

[0036] The segments 10A are assembled in a staggered arrangement in which the joining positions of adjacent tunnel rings in the tunnel axial direction X2 in the tunnel circumferential direction X1 are shifted in the tunnel circumferential direction X1. In other words, of the adjacent rings, one first ring and the other second ring are alternately arranged in the tunnel axial direction X2.

[0037] Inside the concrete of segment 10A, multiple main reinforcing bars extending in an arc in the tunnel circumferential direction X1 are arranged on the inner space side and the natural ground side, and reinforcing ribs are arranged as needed. The size of segment 10A can be changed as appropriate depending on transportability, assembly, etc. The curvature of the arc shape of segment 10A is determined as appropriate depending on the cross section of the tunnel to be excavated.

[0038] The segment 10A includes a pair of main girders 11, 11 facing each other in the tunnel axial direction X2, a skin plate 12 arranged on the tunnel natural ground side, and a pair of joint plates 13, 13 provided at the ends of the pair of main girders 11, 11 and the skin plate 12 in the tunnel circumferential direction X1. The segment 10A is configured in a substantially arc-shaped plate shape by having the skin plate 12, formed by curving a thin rectangular steel plate into an arc-shaped surface, arranged on the natural ground side of the tunnel, and having fill concrete 14 filled in the area surrounded by the pair of steel main girders 11, 11, the pair of steel joint plates 13, 13, and the skin plate 12.

[0039] The pair of main girders 11, 11 are arranged parallel to each other at a distance in the tunnel axis direction X2, and the ends of each main girder 11, 11 in the tunnel circumferential direction X1 are connected by joint plates 13. Skin plates 12 are welded to the ground-side peripheral edges of the pair of main girders 11, 11 and the pair of joint plates 13, 13. In other words, the segment 10A forms a steel shell framed by the pair of main girders 11, 11, the pair of joint plates 13, 13, and the skin plates 12. Filling concrete 14 is filled inside this steel shell.

[0040] The main girder 11 is provided with inter-ring joints 20 for connecting with other adjacent segments 10A in the tunnel axis direction X2. Three to eight inter-ring joints 20 are provided on each face of the main girder 11 at equal intervals in the tunnel axis direction X2. Well-known joints such as bolt joints, pin joints, interlocking joints, or mechanical joints are used as the inter-ring joints 20.

[0041] As described above, the skin plate 12 is provided on the ground side of the segment 10A. The skin plate 12 is made of steel plate and is arranged to cover the ground-side opening between the pair of main girders 11, 11 and the pair of joint plates 13, 13, which are assembled in a frame shape. The skin plate 12 is fixed to the ground-side peripheral edges of the main girders 11 and the joint plates 13 by welding. The skin plate 12 prevents the outflow of the fill concrete 14 to the outside and prevents water and soil from the ground from infiltrating into the steel shell. It can also be used as a formwork when pouring the fill concrete 14.

[0042] The filler concrete 14 is filled in the steel shell so that it is flush with the inner end face, as shown in Figure 2. The filler concrete 14 is selected appropriately from among ordinary concrete, high-strength concrete, high-fluidity concrete, fiber-reinforced concrete, etc., depending on, for example, the stress acting on the tunnel lining and the cross-sectional shape of the tunnel.

[0043] The joint plates 13 are provided at both ends in the tunnel circumferential direction X1 and are equipped with segment joints 15, which correspond to inter-piece joints that abut the segment joint surfaces 13a of the joint plates 13 of other segments 10A adjacent in the tunnel circumferential direction X1. The segment joints 15 are located approximately in the center of the joint plates 13 in the height direction X3. The segment joints 15 are configured such that, for example, a male joint is provided in one joint plate 13 in the tunnel circumferential direction X1 (e.g., reference numeral 13A shown in FIG. 1) and a female joint is provided in the other joint plate (e.g., reference numeral 13B shown in FIG. 1), and these joints are fitted with the female joint and male joint of the adjacent segment 10A, respectively. As such segment joints 15, well-known joints such as bolt joints, pin joints, or mechanical joints are used.

[0044] FIG. 3 is a diagram showing the design concept of the inter-ring joint structure 1 of the segment 10A according to this embodiment. FIG. 3 shows the behavior of the segment main body and the inter-ring joint when the horizontal axis is strain ε and the vertical axis is generated stress σ. FIG. 4 is a diagram showing the design concept of the inter-ring joint structure of a segment according to a comparative example (conventional method). FIG. 4 shows the behavior of the segment main body and the inter-ring joint when the horizontal axis is strain ε and the vertical axis is generated stress σ. In FIGS. 3 and 4, σb is the maximum stress intensity of the segment main body, and σr is the maximum stress intensity of the inter-ring joint. As shown in FIG. 4, in the comparative example, the materials of the segment main body and the inter-ring joint are designed so that the respective maximum stress intensities σb and σr are equal to or less than the allowable stress intensity.

[0045] In contrast, in the inter-ring joint structure 1 of the segment 10A according to this embodiment, which connects the tunnel rings 1A to each other in the tunnel extension direction by the inter-ring joints 20, as shown in Figure 3, the maximum strength of the segment main body 10 is greater than the maximum strength of the inter-ring joints 20, and therefore the timing at which the stress intensity generated in the segment 10A reaches the maximum stress intensity σb is earlier than the maximum stress intensity σr of the inter-ring joints 20, and the fracture of the segment main body 10 precedes the fracture of the inter-ring joints 20 in the fracture mode of the tunnel ring 1A. The technical basis for this is the large deformation analysis of tunnels shown below.

[0046] To confirm the failure mode of the tunnel, a large deformation analysis was carried out on Tunnel Ring 1A. Specifically, the FEM analysis model shown in Figure 5 was created, and a gradually increasing forced displacement F was applied to the top of this model. In the analysis model, Tunnel Ring 1A consists of two rings. The inner diameter d of Tunnel Ring 1A is 6,400 mm, the segment thickness t is 250 mm, the segment width D is 500 mm, and the distributed load on the tunnel natural ground side is 0.1 MPa.

[0047] Two analysis cases (Case 1 and Case 2) were conducted in which the performance of the inter-ring joints 20 was changed. In Case 1, the performance of the inter-ring joints was low (low shear strength), the maximum bending strength of the segment body was set to 1218 kNm, and M24 10.9 high-strength bolts were used for the segment joints and inter-ring joints. In Case 2, the performance of the inter-ring joints was high (high shear strength), the maximum bending strength of the segment body was set to 1218 kNm, and M24 segment joints and M48 inter-ring joints were used, both with 10.9 high-strength bolts.

[0048] Figure 6 shows the relationship between the ring reaction force and the forced displacement as a result of the analysis. In Figure 6, "△" indicates the timing of fracture of the inter-ring joint, and "▲" indicates the timing of fracture of the segment joint. As shown in Figure 6, in Case 1, where the inter-ring joints had low performance (low shear strength), it was confirmed that the reaction force of the lining dropped suddenly after the inter-ring joints broke. On the other hand, in Case 2, where the inter-ring joints had high performance (high shear strength), bending failure of the segment body preceded the fracture, and no inter-ring joint breakage was observed, nor was there any noticeable drop in reaction force.

[0049] Therefore, in order for the tunnel lining to exhibit resilient behavior, it is preferable that the failure mode be one in which failure of the segment body precedes failure of the inter-ring joints, and as described above, it is desirable to design the inter-ring joint structure 1 so that the maximum strength of the segment body 10 is greater than the maximum strength of the inter-ring joints 20, and so that in the failure mode of the tunnel ring 1A, failure of the segment body 10 precedes failure of the inter-ring joints 20.

[0050] Next, a method using specific mathematical expressions will be described as a design method for the above-mentioned inter-ring joint structure 1. In the inter-ring joint structure 1, the maximum strength of the inter-ring joint 20 is M r_max_ , the maximum strength of the segment body 10 is M b_max When the equation (1) is satisfied, it is preferable that the equation (1) is satisfied. m is a material coefficient and 1≦γ m ≦1.2, for example, M r_max is the maximum shear strength Sr of the inter-ring joint × the spacing between the inter-ring joints. Preferably, the material coefficient γ m is 1≦γ m The value must satisfy the condition of ≦1.05. Material coefficient γ m Regarding the upper limit of γ, the material coefficient for seismic design in "Tunnel Library No. 23 Segment Design" is set at 1.05 for steel and 1.2 for concrete, taking into account variations. m ≦1.2. Furthermore, when the inter-ring joints 20 are installed at unequal intervals, it is desirable to calculate the inter-ring joint interval based on the smallest inter-ring joint interval in the tunnel ring 1A.

[0051]

number

[0052] Furthermore, in the ring-to-ring joint structure 1, the maximum shear strength Sr of the ring-to-ring joint is set so as to satisfy the formula (2).

[0053]

number

[0054] Figure 7 is a contour diagram of the strain distribution, which is the analysis result of the FEM analysis model shown in Figure 5. There is symmetry near the region marked with symbol X where the strain is greatest. Therefore, formula (2) is obtained using the splice bending model shown in Figures 8 and 9, which models the inter-ring joint structure (region marked with symbol X). That is, from the splice bending model shown in Figures 8 and 9, theoretical formulas for the beam representing the segment body 10, the spring in the tunnel radial direction X3 representing the inter-ring joint 20, and the rotational spring representing the segment joint 15 are obtained, and the maximum bending strength M of the segment body 10 is calculated. b_max and the maximum shear strength S of the joint 20 between the rings r_max The following relational expression can be obtained. α is the maximum bending strength of the segment body M b_max and the maximum bending strength M of the segment joint s_max The ratio of (=(M s_max / 2) / M b_max ) and a value between 0.1 and 0.4 is desirable.

[0055] FIG. 10 is a design flow diagram showing the procedure for designing the ring-to-ring joint structure 1 using the formula (2) with a nonlinear material model. 10, the design flow for the inter-ring joint structure 1 begins with setting an initial value for formula (2) in step S1. Next, in step S2, formula (2) is used to calculate the bending moment generated in the segment body 10, the bending moment generated in the segment joint 15, and the shear force generated in the inter-ring joint 20 based on the initial values.

[0056] Thereafter, it is determined whether or not a break point where the rigidity changes has been reached, as shown in FIGS. 11(a) to 11(c), in at least one of the segment body 10, segment joint 15, and inter-ring joint 20 determined in step S2 (step S3). In this design flow, it is determined whether or not a break point in rigidity has been reached in the order of the inter-ring joint 20, the segment body 10, and the segment joint 15. That is, first, in step S31, it is determined whether or not a break point in rigidity has been reached in the inter-ring joint 20, and if not (step S31: No), the process proceeds to step S32. In step S32, it is determined whether or not a break point in rigidity has been reached in the segment body 10, and if not (step S32: No), the process proceeds to step S33. Furthermore, in step S33, it is determined whether or not a break point in rigidity has been reached in the segment joint 15, and if not (step S31: No), the process returns to step S2. If the bending point of the stiffness is reached in any of steps S31, S32, and S33 (steps S31, S32, and S33: Yes), the process proceeds to steps S4 and S5.

[0057] Then, in step S4, when the segment joint 15 or the inter-ring joint 20 reaches a bending point in stiffness, it is determined whether or not it is at its maximum strength, and if it is not at its maximum strength, the material settings are changed. That is, if the segment joint 15 or the inter-ring joint 20 is not at its maximum strength (steps S41, S43: No), the stiffness and bending point are updated. If the segment joint 15 or the inter-ring joint 20 is at its maximum strength (steps S41, S43: Yes), the physical property values ​​of each joint are changed, and the process returns to step S1.

[0058] Also, in step S5, when the segment body 10 reaches the breaking point of rigidity, if it is determined that it is not at its maximum strength (step S5: No), the material settings are changed, and if it is determined that it is at its maximum strength (step S5: Yes), the design flow ends. Then, the material of the inter-ring joint 20 is set based on the shear strength of the inter-ring joint 20 at the end of step S5 (step S6). That is, the design is such that the segment body 10 reaches the maximum strength first.

[0059] According to the segment inter-ring joint structure 1 described above, the tunnel rings 1A, each of which is formed by connecting the segment bodies 10 constituting the shield tunnel in the tunnel circumferential direction by segment joints 15, are connected to each other in the tunnel axial direction X2 by inter-ring joints 20. In the segment inter-ring joint structure 1, the maximum bearing strength of the segment bodies 10 is set to be greater than the maximum bearing strength of the inter-ring joints 20.

[0060] Therefore, in this embodiment, the tunnel ring 1A has a structure in which failure of the segment main body 10 precedes fracture of the inter-ring joints 20 in its failure mode. In other words, by improving the strength of the inter-ring joints 20, the failure mode of the tunnel lining can be changed so that bending failure of the segment main body 10 precedes fracture of the inter-ring joints 20, thereby reducing the risk of tunnel collapse. In this way, in this embodiment, the maximum shear strength required for the inter-ring joints 20 can be determined based on the maximum bending strength of the segment main body 10.

[0061] In this embodiment, the maximum strength of the inter-ring joint 20 is M r_max_ , the maximum strength of the segment body 10 is M b_max This satisfies the above formula (1). This reduces the risk that the failure mode will not be as expected due to variations in the material.

[0062] Furthermore, in this embodiment, by using a composite segment having a high bending strength for the segment body 10, there is an advantage that the above effect becomes more pronounced.

[0063] In this embodiment, the maximum shear strength S of the inter-ring joint 20 r_max By satisfying the above-mentioned formula (2), the necessary performance of the ring-to-ring joint 20 can be further clarified, and optimal performance can be provided at low cost while reducing the risk of tunnel collapse.

[0064] Furthermore, the design method for the inter-ring joint structure of a segment according to this embodiment includes the following steps: a first step of setting an initial value for Equation (2); a second step of using Equation (2) to determine the bending moment generated in the segment body, the bending moment generated in the segment joint, and the shear force generated in the inter-ring joint based on the initial value; a third step of determining whether or not a break point at which the rigidity changes has been reached in at least one of the segment body, segment joint, and inter-ring joint determined in Step 2; a fourth step of determining whether or not the segment joint or the inter-ring joint has reached its break point in rigidity and changing the material settings; a fifth step of changing the material settings when it is determined that the strength is not maximum when the segment body has reached its break point in rigidity, and ending the design flow if it is determined that the strength is maximum; and a sixth step of setting the material of the inter-ring joint based on the shear strength of the inter-ring joint at the end of Step 5. In this case, by taking into account the change in stiffness due to plasticization, it is possible to provide a ring-to-ring joint with more optimized performance.

[0065] As described above, the segment inter-ring joint structure and the design method for the inter-ring joint structure according to this embodiment can clarify the necessary performance of the inter-ring joint 20 in situations where the tunnel undergoes large deformation, and can reduce the risk of tunnel collapse at low cost.

[0066] Next, an example will be described below that was carried out to verify the effects of the inter-segment ring joint structure 1 according to the embodiment described above.

[0067] (Example) In the examples, the above design formula was applied to a full-scale model for comparison. The specifications of the segment body, segment joints, and inter-ring joints are shown in Table 1. As shown in Table 1, the bending strength of the segment joints was set to 20% of that of the segment body, and the outer diameter of the inter-ring joints was set to the same diameter as the segment joints.

[0068] [Table 1]

[0069] As shown in Figures 12(a) to 12(c), the material settings for the segment body, segment joints, and inter-ring joints are modeled bilinearly to take plasticity into account. In Figure 12(a), the horizontal axis for the inter-ring joints is shear displacement δ (mm), and the vertical axis is shear strength per joint (kN). In Figure 12(b), the horizontal axis for the segment body is curvature φ (1 / m), and the vertical axis is bending moment (kNm). In Figure 12(c), the horizontal axis for the segment joints is joint rotation angle θ, and the vertical axis is bending moment (kNm).

[0070] Calculations based on the above parameters show that the fracture of the inter-ring joints occurs first in the set model. Therefore, when calculations were performed using the design formula, it was found that in order to change the fracture mode to one in which bending fracture of the segment body occurs first, it was necessary to change the bolt diameter of the inter-ring joints from 39 mm to 61 mm.

[0071] The above describes embodiments of the inter-ring joint structure of a segment and the design method of an inter-ring joint structure according to the present invention. However, the present invention is not limited to the above embodiments and can be modified as appropriate within the scope of the invention.

[0072] For example, in the above-described embodiment, a method for designing an inter-ring joint structure is shown using the above-described formula (1) and formula (2), but the method is not limited to using formula (1) and formula (2).

[0073] In addition, although the present embodiment is directed to composite segments as segments, it can also be applied to concrete segments and steel segments.

[0074] Furthermore, although this embodiment is directed to a joint in which inter-ring joints are discretely arranged, it can also be applied to a continuous interfitting joint.

[0075] Furthermore, within the scope of the present invention, the components in the above-described embodiments can be replaced with well-known components as appropriate. [Explanation of symbols]

[0076] 1. Ring-to-ring joint structure 1A Tunnel Ring 10A segment 10 segment body 11 Main girder 13 Joint plate 13a Segment joint surface 14 Concrete 15 Segment joint 20 Ring-to-ring joint X1 Tunnel circumferential direction X2 Tunnel axis direction X3 Tunnel Radial Direction

Claims

1. A segment inter-ring joint structure in which tunnel rings, each formed by connecting segments constituting a shield tunnel in the tunnel circumferential direction by segment joints, are connected in the tunnel extension direction by inter-ring joints, A segment inter-ring joint structure, characterized in that the maximum strength of the segment body is set to be greater than the maximum strength of the inter-ring joint.

2. The maximum strength of the inter-ring joint is M ｒ_ｍａｘ , the maximum strength of the segment body is M ｂ_ｍａｘ Then, the formula (1) is satisfied. The segment-to-ring joint structure according to claim 1 . [Equation 1]

3. The segment is a synthetic segment. The segment-to-ring joint structure according to claim 2 .

4. The maximum shear strength Sr of the inter-ring joint satisfies formula (2), The segment-to-ring joint structure according to claim 1 . [Equation 2]

5. A design method for an inter-ring joint structure in which tunnel rings, each formed by connecting segments constituting a shield tunnel in the tunnel circumferential direction by segment joints, are connected to each other in the tunnel extension direction by inter-ring joints, A design method for an inter-ring joint structure, characterized in that the maximum strength of the main body of the segment is set to be greater than the maximum strength of the inter-ring joint.

6. The maximum strength of the inter-ring joint is M ｒ_ｍａｘ_ , the maximum strength of the segment body is M ｂ_ｍａｘ Then, the formula (1) is satisfied. The method for designing an inter-ring joint structure according to claim 5. [Equation 3]

7. The segment is a synthetic segment. The method for designing an inter-ring joint structure according to claim 6.

8. The maximum shear strength Sr of the inter-ring joint satisfies formula (2), The method for designing an inter-ring joint structure according to claim 5. [Equation 4]

9. a first step of setting an initial value of the formula (2); a second step of calculating the bending moment generated in the segment body, the bending moment generated in the segment joint, and the shear force generated in the inter-ring joint based on the initial value using the formula (2); a third step of determining whether or not a bending point at which rigidity changes has been reached in at least one of the segment body, the segment joint, and the inter-ring joint determined in the second step; a fourth step of determining whether the segment joint or the inter-ring joint has reached a bending point in rigidity and changing the material setting; a fifth step of changing the material setting when it is determined that the segment body does not have the maximum strength when it reaches a bending point in rigidity, and terminating the design flow when it is determined that the segment body has the maximum strength; a sixth step of determining a material for the inter-ring joint based on the shear strength of the inter-ring joint at the end of the fifth step; The method for designing an inter-ring joint structure according to claim 8, comprising:

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