A method for evaluating the toughness of shield segment lining based on joint stress characteristics

Abstract

The present invention discloses a method for evaluating the toughness of a shield segment lining based on the stress characteristics of joints: Step 1, establish a three-dimensional finite element model of the shield lining according to the design scheme of the shield lining structure; Step 2, determine the load system acting on the shield lining in combination with the burial depth and geological conditions of the shield lining; Step 3, apply the load system in the finite element model; Step 4, continuously increase the top load from p until a predetermined condition is reached, which is p + Δp1 at this time; Step 5, define the initial performance of the lining structure before overloading; Step 6, when the surface overloading value is Δp, increase the load from p to p + Δp; Step 7, repeat Step 4, increase the load from p + Δp to p + Δp + Δp2; Step 8, define the performance of the lining structure after overloading; Step 9, determine the steel plate reinforcement scheme after the action of overloading Δp; Step 10, repeat Step 4, increase the pressure from p + Δp to p + Δp + Δp3; Step 11, define the performance recovery of the reinforced lining structure; Step 12, calculate the toughness of the lining structure.

Description

Technical Field

[0001] The invention relates to the field of shield segment lining toughness assessment, and in particular to a shield segment lining toughness assessment method based on joint stress characteristics. Background Art

[0002] The shield lining is assembled from prefabricated segments, and there are a large number of joints in the lining structure. Due to the existence of joints, which is a weak link, the lining structure is very likely to suffer from excessive longitudinal differential settlement, water leakage, concrete cracking and other diseases when the surrounding load of the tunnel changes due to surface overload, resulting in the performance degradation of the lining structure. Therefore, it is crucial to scientifically and rationally evaluate the status of the shield lining structure when the surface is overloaded for the safe operation of the tunnel.

[0003] At present, when evaluating the performance of shield linings, the risk matrix method, Monte Carlo method, hierarchical analysis method, etc. are often used to construct a tunnel performance evaluation index system, and then combined with the convergence deformation value of the lining structure, the local joint deformation value and the concrete crack width value and other indicators to give suggestions on whether the tunnel is currently in need of repair, regular inspection or no maintenance. This type of evaluation method can only evaluate the state of the lining structure when the load around the tunnel changes. In actual engineering, an evaluation method is needed that can comprehensively consider the performance degradation of the tunnel structure when the surface is overloaded and the performance recovery after reinforcement, that is, to evaluate the entire performance evolution process.

[0004] Based on the concept of toughness, a shield lining structure toughness assessment method and a corresponding index system are constructed, which can effectively assess the real-time status of the shield lining structure and the recovery of the structural performance after reinforcement. In recent years, the toughness assessment method of shield lining has been applied, but the convergence deformation is used as a variable when calculating the performance of the lining structure. There are the following problems: (1) The damage of the shield lining starts from the joints. When the convergence deformation is used as a variable to calculate the performance of the lining structure, it cannot truly reflect the performance of the lining structure; (2) After the shield lining is reinforced and repaired by using technologies such as built-in steel plates, the convergence deformation of the lining structure is difficult to recover, but its performance has actually been enhanced. If the convergence deformation is used as a variable to calculate the performance of the lining structure, the performance will not be improved, which is inconsistent with the actual situation. Summary of the invention

[0005] The present invention is made to solve the above-mentioned problems, and aims to provide a shield segment lining toughness evaluation method based on joint stress characteristics.

[0006] The present invention provides a shield segment lining toughness assessment method based on joint stress characteristics, which has the following characteristics and comprises the following steps: step 1, establishing a three-dimensional finite element model of the shield lining according to the design scheme of the shield lining structure; step 2, determining the load system acting on the shield lining structure in combination with the buried depth and geological conditions of the shield lining structure, wherein the parameters of the load system at least include the vertical earth pressure at the top of the tunnel; step 3, applying the load system in the three-dimensional finite element model and analyzing the mechanical response of the shield lining structure; step 4, continuously increasing the vertical earth pressure at the top of the tunnel from p, analyzing the mechanical response of the shield lining structure, until a predetermined condition is reached, at which time the vertical earth pressure at the top of the tunnel increases to p+Δp1; step 5, defining the initial performance value of the shield lining structure before overloading; step 6, when the surface overload value is Δp, increasing the vertical earth pressure at the top of the tunnel by Δp on the basis of step 3. Increase from p to p+Δp, and analyze the mechanical response of the shield lining structure; step 7, continuously increase the vertical soil pressure on the top of the tunnel from p+Δp, and analyze the mechanical response of the shield lining structure until the predetermined condition is met, at which time the vertical soil pressure on the top of the tunnel increases to p+Δp+Δp2; step 8, define the performance value of the shield lining structure after surface overload; step 9, determine the steel plate reinforcement scheme for the shield lining after the ground overload Δp, and based on the calculation in step 6, paste the steel plate inside the shield lining structure; step 10, continuously increase the vertical soil pressure on the top of the tunnel from p+Δp, and analyze the mechanical response of the shield lining structure until the predetermined condition is met, at which time the vertical soil pressure on the top of the tunnel increases to p+Δp+Δp3; step 11, define the performance recovery value of the reinforced shield lining structure; step 12, calculate the toughness of the shield lining structure according to the toughness assessment model.

[0007] The shield segment lining toughness assessment method based on joint stress characteristics provided by the present invention may also have the following features: wherein, in step 1, the three-dimensional finite element model includes segments and bolts.

[0008] The shield segment lining toughness assessment method based on joint stress characteristics provided by the present invention may also have the following features: wherein, in step 2, the parameters of the load system also include the tunnel bottom reaction force p k , lateral earth pressure at the top of the tunnel q1, lateral earth pressure at the bottom of the tunnel q2, lining deadweight g, normal foundation spring F n and the tangential foundation spring F s .

[0009] The shield segment lining toughness assessment method based on joint stress characteristics provided by the present invention may also have the following feature: wherein, in step 4, the predetermined condition is that the maximum stress value of a joint bolt in all joints reaches the bolt yield stress or the maximum opening value of a joint reaches the joint opening limit.

[0010] The shield segment lining toughness assessment method based on joint stress characteristics provided by the present invention may also have the following feature: wherein, in step 5, the initial performance value is Q0=100%.

[0011] The shield segment lining toughness assessment method based on joint stress characteristics provided by the present invention may also have the following feature: wherein, in step 8, the performance value of the shield lining structure after surface overload is Q1=Δp2 / Δp1.

[0012] The shield segment lining toughness assessment method based on joint stress characteristics provided by the present invention may also have the following feature: wherein, in step 11, the performance recovery value of the reinforced shield lining structure is Q2=Δp3 / Δp1.

[0013] The shield segment lining toughness evaluation method based on joint stress characteristics provided by the present invention may also have the following characteristics: wherein, in step 12, the toughness of the shield lining structure is R e =[Q1*(t2-t1)+Q2*(t3-t2)] / [Q0*(t3-t1)], where t1 is the time point of surface overload, t2 is the time point when the performance of the reinforced shield lining recovers to Q2, and t3-t1 is the time for toughness assessment.

[0014] Functions and Effects of the Invention

[0015] According to the shield segment lining toughness assessment method based on joint stress characteristics involved in the present invention, the specific process is as follows: step 1, according to the design scheme of the shield lining structure, a three-dimensional finite element model of the shield lining is established; step 2, in combination with the buried depth and geological conditions of the shield lining structure, the load system acting on the shield lining structure is determined, and the parameters of the load system at least include the vertical soil pressure at the top of the tunnel; step 3, applying the load system in the three-dimensional finite element model to analyze the mechanical response of the shield lining structure; step 4, continuously increasing the vertical soil pressure at the top of the tunnel from p, analyzing the mechanical response of the shield lining structure, until the predetermined condition is reached, at which time the vertical soil pressure at the top of the tunnel increases to p+Δp1; step 5, defining the initial performance value of the shield lining structure before overloading; step 6, when the surface overload value is Δp, on the basis of step 3, the vertical soil pressure at the top of the tunnel is increased from p to p+Δp1. The maximum value is p+Δp, and the mechanical response of the shield lining structure is analyzed; step 7, the vertical soil pressure on the top of the tunnel is continuously increased from p+Δp, and the mechanical response of the shield lining structure is analyzed until the predetermined condition is met, at which time the vertical soil pressure on the top of the tunnel is increased to p+Δp+Δp2; step 8, the performance value of the shield lining structure after surface overload is defined; step 9, the steel plate reinforcement scheme of the shield lining after the ground overload Δp is determined, and on the basis of the calculation in step 6, the steel plate is pasted inside the shield lining structure; step 10, the vertical soil pressure on the top of the tunnel is continuously increased from p+Δp, and the mechanical response of the shield lining structure is analyzed until the predetermined condition is met, at which time the vertical soil pressure on the top of the tunnel is increased to p+Δp+Δp3; step 11, the performance recovery value of the reinforced shield lining structure is defined; step 12, the toughness of the shield lining structure is calculated according to the toughness evaluation model.

[0016] Therefore, the present invention uses the opening amount of local joints of the lining structure and the bolt stress as indicators to analyze the performance evolution of the lining structure, and then calculates the tunnel toughness value in combination with the performance recovery during surface overload and after reinforcement, so as to realize accurate evaluation of the toughness of the shield lining. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic flow chart of a shield segment lining toughness evaluation method based on joint stress characteristics in an embodiment of the present invention;

[0018] Figure 2 is a schematic diagram of a finite element model of a shield lining structure in an embodiment of the present invention;

[0019] Figure 3 is a schematic diagram of water and soil loads around a tunnel in an embodiment of the present invention;

[0020] Figure 4 is the shield lining joint opening and bolt stress state before overloading in the embodiment of the present invention (unit: MPa);

[0021] Figure 5 is the joint opening and bolt stress state when the shield lining bolt yields without steel plate in the embodiment of the present invention (unit: MPa);

[0022] Figure 6 It is the shield lining joint opening and bolt stress state after overloading 90 kPa in the embodiment of the present invention (unit: MPa);

[0023] Figure 7 is a schematic diagram of a finite element model of a shield lining structure with added steel plates in an embodiment of the present invention;

[0024] Figure 8 is the joint opening and bolt stress state when the shield lining bolts to which the steel plate is applied yield in the embodiment of the present invention (unit: MPa); and

[0025] Fig. 9 It is a schematic diagram of a toughness assessment model for a shield lining structure in an embodiment of the present invention. DETAILED DESCRIPTION

[0026] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the following embodiments and the accompanying drawings specifically illustrate a shield segment lining toughness assessment method based on joint stress characteristics of the present invention.

[0027] There are many situations in which the load around the shield lining changes, such as surface overload, surface unloading, tunnel lateral unloading, etc. This embodiment takes tunnel surface overload as the background and provides a shield segment lining toughness assessment method based on joint stress characteristics.

[0028] Figure 1 It is a flow chart of a shield segment lining toughness assessment method based on joint stress characteristics in an embodiment of the present invention.

[0029] like Figure 1 As shown, the shield segment lining toughness assessment method based on joint stress characteristics involved in this embodiment includes the following steps:

[0030] Step S1, according to the design scheme of the shield lining structure, a three-dimensional finite element model of the shield lining is established, and the model includes segments and bolts.

[0031] Figure 2 It is a schematic diagram of a finite element model of a shield lining structure in an embodiment of the present invention.

[0032] like Figure 2As shown, in this embodiment, the outer diameter of the shield segment lining is 6.4m, the thickness is 0.3m, and the ring width is 1.2m. Each ring is assembled from a capping block, two adjacent blocks and three standard blocks. The central angle corresponding to the capping block is 22.5°, and the central angles corresponding to the adjacent blocks and the standard blocks are both 67.5°. The segments are connected by two bent bolts with a yield strength of 500MPa, and the opening limit of the joints between the segments is 6mm.

[0033] Step S2, determining the load system acting on the shield lining structure in combination with the buried depth and geological conditions of the shield lining structure.

[0034] Figure 3 Schematic diagram of water and soil loads around a tunnel in an embodiment of the present invention.

[0035] like Figure 3 As shown in the figure, p is the vertical soil pressure at the top of the tunnel, p k is the reaction force at the bottom of the tunnel, q1 is the lateral earth pressure at the top of the tunnel, q2 is the lateral earth pressure at the bottom of the tunnel, g is the deadweight of the lining, and F n is the normal foundation spring, F s It is a tangential foundation spring.

[0036] In this embodiment, the applied load system is: p = 410 kPa, p k =433kPa, q1=265kPa, q2=355kPa, g=24kN / m 3 , F n =15000kN / m 3 , F s =5000kN / m 3 .

[0037] Step S3, Figure 2 The three-dimensional finite element model shown in Figure 3 The load system shown is used to analyze the mechanical response of the shield lining structure.

[0038] Figure 4 It is the shield lining joint opening and bolt stress state before overloading in the embodiment of the present invention (unit: MPa).

[0039] At this time, the shield lining joints open and the bolt stress is as follows: Figure 4 shown.

[0040] Step S4, continuously increase the vertical earth pressure at the top of the tunnel from p, and analyze the mechanical response of the shield lining structure until the maximum stress of a joint bolt in all joints reaches the bolt yield stress or the maximum opening amount of a joint reaches the joint opening limit. At this time, the vertical earth pressure at the top of the tunnel increases to p+Δp1.

[0041] Figure 5 It is the joint opening and bolt stress state (unit: MPa) of the shield lining bolts when yielding without steel plate in the embodiment of the present invention.

[0042] In this embodiment, the vertical soil pressure at the top of the tunnel is continuously increased. When Δp1=228 kPa, the bolt stress reaches the yield stress of 500 MPa. Figure 5 shown.

[0043] Step S5, defining the initial performance value Q0 of the shield lining structure before overloading = 100%.

[0044] Step S6, when the surface overload value is Δp, based on step S3, the vertical earth pressure at the top of the tunnel is increased from p to p+Δp, and the mechanical response of the shield lining structure is analyzed.

[0045] Figure 6 It is the shield lining joint opening and bolt stress state after overload of 90kPa in the embodiment of the present invention (unit: MPa).

[0046] In this embodiment, when the ground overload Δp = 90 kPa, the shield lining joints open and the bolt stress is as follows: Figure 6 shown.

[0047] Step S7, based on step S6, the vertical earth pressure at the top of the tunnel is continuously increased from p+Δp, and the mechanical response of the shield lining structure is analyzed until the maximum stress of a joint bolt in all joints reaches the bolt yield stress or the maximum opening amount of a joint reaches the joint opening limit. At this time, the vertical earth pressure at the top of the tunnel increases to p+Δp+Δp2.

[0048] In this embodiment, the vertical soil pressure at the top of the tunnel is continuously increased. When Δp2 = 138 kPa, the bolt stress reaches the yield stress of 500 MPa. Figure 5 shown.

[0049] Step S8, defining the performance value Q1=Δp2 / Δp1 of the shield lining structure after the surface overload.

[0050] Step S9, determine the steel plate reinforcement scheme for the shield lining after the ground overload Δp acts. Based on the calculation in step 6, a steel plate is pasted inside the shield lining structure, such as Figure 7 shown.

[0051] Figure 7 It is a schematic diagram of a finite element model of a shield lining structure with added steel plates in an embodiment of the present invention.

[0052] In this embodiment, when the ground overload Δp = 90 kPa, a steel plate is applied inside the shield lining, the shield lining joint is opened and the bolt stress remains unchanged, such as Figure 6 shown.

[0053] Step S10, based on step S9, continuously increase the vertical earth pressure on the top of the tunnel from p+Δp, and analyze the mechanical response of the shield lining structure until the maximum stress of a joint bolt in all joints reaches the bolt yield stress or the maximum opening amount of a joint reaches the joint opening limit. At this time, the vertical earth pressure on the top of the tunnel increases to p+Δp+Δp3.

[0054] Figure 8 It is the joint opening and bolt stress state when the shield lining bolts applied with steel plates yield in the embodiment of the present invention (unit: MPa).

[0055] In this embodiment, the vertical soil pressure at the top of the tunnel is continuously increased. When Δp3 = 171 kPa, the bolt stress reaches the yield stress of 500 MPa. Figure 8 shown.

[0056] Step S11, defining the performance recovery value Q2=Δp3 / Δp1 of the reinforced shield lining structure.

[0057] Step S12, calculating the toughness of the shield lining structure according to the toughness assessment model.

[0058] Fig. 9 It is a schematic diagram of a toughness assessment model for a shield lining structure in an embodiment of the present invention.

[0059] like Fig. 9 As shown in Figure 2, the toughness of the shield lining structure is:

[0060] R e =(S BGHC +S DHIE ) / S AGIF =[Q1*(t2-t1)+Q2*(t3-t2)] / [Q0*(t3-t1)].

[0061] Among them, t1 is the time point of surface overload, t2 is the time point when the performance of the shield lining recovers to Q2 after reinforcement, and t3-t1 is the time for toughness assessment.

[0062] According to the above calculation results, Q1 = Δp2 / Δp1 = 0.61, Q2 = Δp3 / Δp1 = 0.75. Assuming t3-t2 = t2-t1, then R e =[Q1*(t2-t1)+Q2*(t3-t2)] / [Q0*(t3-t1)]=0.68.

[0063] Functions and Effects of the Embodiments

[0064] According to the shield segment lining toughness assessment method based on joint stress characteristics involved in this embodiment, the specific process is as follows: Step 1, according to the design scheme of the shield lining structure, a three-dimensional finite element model of the shield lining is established; Step 2, in combination with the buried depth and geological conditions of the shield lining structure, the load system acting on the shield lining structure is determined, and the parameters of the load system at least include the vertical earth pressure at the top of the tunnel; Step 3, applying the load system in the three-dimensional finite element model to analyze the mechanical response of the shield lining structure; Step 4, continuously increasing the vertical earth pressure at the top of the tunnel from p, analyzing the mechanical response of the shield lining structure, until the predetermined condition is reached, at which time the vertical earth pressure at the top of the tunnel increases to p+Δp1; Step 5, defining the initial performance value of the shield lining structure before overloading; Step 6, when the surface overload value is Δp, on the basis of Step 3, the vertical earth pressure at the top of the tunnel is increased from p to p+Δp1. The maximum value is p+Δp, and the mechanical response of the shield lining structure is analyzed; step 7, the vertical soil pressure on the top of the tunnel is continuously increased from p+Δp, and the mechanical response of the shield lining structure is analyzed until the predetermined condition is met, at which time the vertical soil pressure on the top of the tunnel is increased to p+Δp+Δp2; step 8, the performance value of the shield lining structure after surface overload is defined; step 9, the steel plate reinforcement scheme of the shield lining after the ground overload Δp is determined, and on the basis of the calculation in step 6, the steel plate is pasted inside the shield lining structure; step 10, the vertical soil pressure on the top of the tunnel is continuously increased from p+Δp, and the mechanical response of the shield lining structure is analyzed until the predetermined condition is met, at which time the vertical soil pressure on the top of the tunnel is increased to p+Δp+Δp3; step 11, the performance recovery value of the reinforced shield lining structure is defined; step 12, the toughness of the shield lining structure is calculated according to the toughness evaluation model.

[0065] Therefore, this embodiment uses the opening amount of local joints of the lining structure and the bolt stress as indicators to analyze the performance evolution of the lining structure, and then calculates the tunnel toughness value in combination with the performance recovery during surface overload and after reinforcement, so as to achieve an accurate assessment of the toughness of the shield lining.

[0066] The above-mentioned embodiments are preferred examples of the present invention and are not intended to limit the protection scope of the present invention.

Claims

1. A shield segment lining toughness assessment method based on joint stress characteristics, characterized in that: The following steps are involved: Step 1: Establish a three-dimensional finite element model of the shield lining according to the design scheme of the shield lining structure; Step 2, determining a load system acting on the shield lining structure in combination with the buried depth and geological conditions of the shield lining structure, wherein the parameters of the load system at least include the vertical earth pressure at the top of the tunnel; Step 3, applying the load system in the three-dimensional finite element model to analyze the mechanical response of the shield lining structure; Step 4, continuously increasing the vertical soil pressure at the top of the tunnel from p, analyzing the mechanical response of the shield lining structure, until a predetermined condition is reached, at which time the vertical soil pressure at the top of the tunnel increases to p+Δp1; Step 5, defining the initial performance value of the shield lining structure before overloading; Step 6, when the surface overload value is Δp, based on step 3, the vertical earth pressure on the top of the tunnel is increased from p to p+Δp, and the mechanical response of the shield lining structure is analyzed; Step 7, continuously increasing the vertical earth pressure at the top of the tunnel from p+Δp, analyzing the mechanical response of the shield lining structure, until the predetermined condition is reached, at which time the vertical earth pressure at the top of the tunnel increases to p+Δp+Δp2; Step 8, defining the performance value of the shield lining structure after the surface is overloaded; Step 9, determining a steel plate reinforcement scheme for the shield lining after the ground overload Δp acts, and based on the calculation in step 6, pasting a steel plate inside the shield lining structure; Step 10, continuously increasing the vertical soil pressure at the top of the tunnel from p+Δp, analyzing the mechanical response of the shield lining structure, until the predetermined condition is met, at which time the vertical soil pressure at the top of the tunnel increases to p+Δp+Δp3; Step 11, defining the performance recovery value of the reinforced shield lining structure; Step 12, calculating the toughness of the shield lining structure according to the toughness assessment model, Wherein, in step 12, the toughness of the shield lining structure is: <h2 style=";text-align:left;direction:ltr">R<h2 style=";text-align:left;direction:ltr"> e <h2 style=";text-align:left;direction:ltr"> ([Q1*(t2-t1)+Q2*(t3-t2)] / [Q0*(t3-t1)]) Where t1 is the time point of surface overload, t2 is the time point when the performance of the reinforced shield lining recovers to Q2, and t3-t1 is the time for toughness assessment. The initial performance value is Q0=100%, The performance value of the shield lining structure after the surface overload is Q1 = Δp2 / Δp1, The performance recovery value of the reinforced shield lining structure is Q2=Δp3 / Δp1.

2. The shield segment lining toughness assessment method based on joint stress characteristics according to claim 1 is characterized in that: in, In step 1, the three-dimensional finite element model includes segments and bolts.

3. The shield segment lining toughness assessment method based on joint stress characteristics according to claim 1 is characterized in that: in, In step 2, the parameters of the load system also include the tunnel bottom reaction force p k , lateral earth pressure at the top of the tunnel q1, lateral earth pressure at the bottom of the tunnel q2, lining deadweight g, normal foundation spring F n and the tangential foundation spring F s .

4. The shield segment lining toughness assessment method based on joint stress characteristics according to claim 1 is characterized in that: in, In step 4, the predetermined condition is that the maximum stress value of a joint bolt in all joints reaches the bolt yield stress or the maximum opening value of a joint reaches the joint opening limit.

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