Method for determining influence of shield tunnel holing on mechanical characteristics of main body structure

Abstract

The invention relates to the technical field of tunnel engineering, in particular to a method for determining the influence of shield tunnel holing on mechanical characteristics of a main body structure. Comprising the following steps: S1, constructing a three-dimensional numerical calculation model of a shield tunnel; wherein the three-dimensional numerical calculation model is composed of a stratum model and a shield tunnel model arranged in the stratum model; s2, calculating the initial ground stress of the stratum model in the three-dimensional numerical calculation model; s3, calculating deformation and stress of a shield tunnel model without holes in the three-dimensional numerical calculation model under the action of surrounding stratum load; s4, calculating the structural mechanical characteristics of the shield tunnel model after holing in the three-dimensional numerical calculation model under the action of a peripheral external load; according to the method, the problem that the relation between the structural analysis result of the shield tunnel holing working condition and the structural safety risk cannot be determined by an existing method is solved, and the structural safety risk after shield tunnel holing can be known more visually.

Description

Technical Field

[0001] The invention relates to the technical field of shield tunnel engineering, and in particular to a method for determining the influence of a shield tunnel opening on the mechanical characteristics of a main structure. Background Art

[0002] With the continuous development of my country's economy, the high-speed railway network, expressway network, urban road network, and urban rail transit network have been further improved, and more and more shield tunnel projects have emerged. However, tunnel projects are narrow and long structures with closed internal environments and few entrances and exits, which makes evacuation and rescue in disasters more difficult. In addition, the closed and narrow tunnel structure is not well connected with the ground transportation network and underground space infrastructure, and the underground space cannot be effectively utilized.

[0003] Therefore, it is necessary to open holes in the shield tunnel to connect the shield tunnel with other underground spaces. The conditions where holes need to be opened in the shield tunnel include horizontal holes to build cross passages, vertical holes to build municipal wells, vertical holes to build drainage pump houses, and diagonal holes to build road ramps. At the same time, the shield tunnel itself is an assembled structure with weak structural stability. Opening holes in the shield tunnel breaks the integrity of the structure, and its structural safety performance is even more difficult to guarantee.

[0004] At present, there are some literatures that study the mechanical response of the main structure of the cross channel constructed by shield tunnel opening. For example, Pang Kang et al. (2021) established a three-dimensional finite element model to analyze the stress and deformation of the structure. However, the disadvantage of this numerical model is that the segments involved in the opening are simplified as a whole, which is inconsistent with the assembly state of the segment lining near the actual shield tunnel opening. It fails to effectively simulate the discontinuous characteristics of the lining joints near the opening, and the structural stress concentration results are different from the actual situation. It is also impossible to simulate the force transmission effect of the joints near the opening and the opening deformation characteristics of the joints, and it is impossible to effectively reveal the structural safety risks. For example, Chen Rendong (2022) explored the influence of shield tunnel opening on structural stress and deformation by conducting centrifugal model tests, but the centrifugal model test is costly and difficult. It is very expensive to conduct an in-depth analysis of this problem by means of centrifugal model tests, and it is generally used as a verification of the numerical analysis results.

[0005] It can be seen from this that the existing methods fail to effectively analyze the impact of shield tunnel opening on structural safety performance, cannot accurately reveal the structural safety risks that may be induced by shield tunnel opening, and thus cannot provide scientific guidance for the design of actual construction safety control measures.

[0006] Based on this, the present invention provides a method for determining the influence of shield tunnel opening on the mechanical characteristics of the main structure to solve the technical problems raised above! Summary of the invention

[0007] The purpose of the present invention is to provide a method for determining the influence of shield tunnel opening on the mechanical characteristics of the main structure, so as to solve the problem that the existing methods fail to clearly define the relationship between the structural analysis results of the shield tunnel opening working condition and the structural safety risk.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] The present invention provides a method for determining the influence of shield tunnel opening on the mechanical characteristics of the main structure, comprising the following steps:

[0010] S1. Construct a three-dimensional numerical calculation model of the shield tunnel;

[0011] The three-dimensional numerical calculation model is composed of a stratum model and a shield tunnel model arranged in the stratum model, and the shield tunnel model is composed of ordinary segment lining, segment lining to be broken, and segment lining outside the portion to be broken;

[0012] S2, calculating the initial geostress of the formation model in the three-dimensional numerical calculation model;

[0013] S3. Calculate the deformation and stress of the shield tunnel model without opening in the three-dimensional numerical calculation model under the action of the surrounding stratum load;

[0014] S4. Calculate the structural mechanical characteristics of the shield tunnel model after opening the hole in the three-dimensional numerical calculation model under the action of surrounding external loads.

[0015] The present invention is further configured as follows: in step S1, each of the segment linings is an elastic unit.

[0016] The present invention is further configured as follows: the elastic unit is a mechanical characteristic unit used in a shield tunnel model to simulate the interaction between segments and their joints, soil layers and structures.

[0017] The present invention is further configured as follows: in step S1, shear-resistant, tensile-resistant and elastic joints are provided between the segment linings, and the joints are spring units.

[0018] The present invention is further configured as follows: the spring unit is a three-dimensional numerical calculation model unit used to simulate the mechanical behavior of the joint when subjected to force.

[0019] The present invention is further configured as follows: in the step S1, a binding constraint is set between the segment lining to be broken and the segment lining outside the portion to be broken.

[0020] The present invention is further configured as follows: in the step S1, it also includes reasonably cutting the segment lining to be broken and the segment lining outside the portion to be broken, and dividing the segment lining to be broken and the segment lining outside the portion to be broken into hexahedrons.

[0021] The present invention is further configured as follows: in step S1, the boundary conditions of the three-dimensional numerical calculation model are:

[0022] The sides of the formation model are normal constraints;

[0023] The bottom of the stratum model is a fixed constraint;

[0024] The top of the stratigraphic model is the free surface;

[0025] The normal preload is set in the longitudinal direction of the segment lining.

[0026] The present invention is further configured as follows: the selection formula of the normal preload force is:

[0027] Where p is the normal preload, F is the resultant water and soil pressure in front of the shield tunnel excavation face, S is the shield lining annular joint contact area, and α is the lining annular joint stress relaxation coefficient.

[0028] The present invention is further configured as follows: in step S3, the opening shape of the shield tunnel model is square or circular.

[0029] The present invention is further configured as follows: in step S4, the calculation formula for the number of longitudinal lining rings of the shield tunnel model at the opening is:

[0030] N = n + 2 × (m + 2), where N is the number of longitudinal rings of the shield tunnel model, n is the number of lining rings involved in the opening, m is the range of the non-affected area on both sides of the opening, and m ≥ 5.

[0031] The present invention is further configured as follows: in step S4, when the state of the segment lining to be broken changes under the action of the surrounding external load, the states of all the contact and spring units related thereto are updated, the contact between the segment lining to be broken and the adjacent segment lining to be broken is set to an inactive state, the outer surface of the segment lining having a contact relationship with the formation model is updated so that it is only included in the active state in the current analysis step, and the spring unit having a connection relationship with the segment lining to be broken is killed.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The present invention provides a numerical modeling scheme for conveniently and effectively calculating the influence of shield tunnel opening on structural safety. The stratum model and the shield tunnel model in the numerical model are both solid units. By providing a setting method for contact and spring units in a key analysis step, the accuracy and convergence of the numerical calculation are improved. The provided method for determining the influence of the shield tunnel opening on the mechanical characteristics of the main structure, and the obtained numerical calculation results can be used to judge whether the stress safety of the shield tunnel model, the stress safety of the joints, the waterproof safety of the joints, and the structural deformation meet the requirements of the specifications, thereby providing a basis for the formulation of a safety guarantee measure plan. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The numerical calculation model of the shield tunnel opening with a rectangular opening in Example 1;

[0035] Figure 2 A numerical calculation model for a shield tunnel opening of a rectangular opening for killing the segment lining to be broken in Example 1;

[0036] Figure 3 It is a schematic diagram of applying equal ground stress to the formation model in Example 1;

[0037] Figure 4 This is a schematic diagram of local stress concentration after the shield tunnel model in Example 1 is opened;

[0038] Figure 5 It is a schematic diagram of the joint state of the shield tunnel model after the hole is opened in Example 1;

[0039] Figure 6 Schematic diagram of the stress condition of the joint after the shield tunnel is opened in Example 1, where "×" is the position of the bolt joint and the number is the tension (kN) on the bolt;

[0040] Figure 7 The numerical model of the shield tunnel opening with a circular opening in Example 1;

[0041] Figure 8 This is an analysis diagram of Example 2 in which the rectangular opening is located at the upper layer;

[0042] Fig. 9 This is an analysis diagram of Example 2 in which the rectangular opening is located at the lower layer;

[0043] Fig.10 This is an analysis diagram of Example 2 in which the circular opening is located at the upper layer;

[0044] Fig.11 This is an analysis diagram of Example 2 in which the circular opening is located in the lower layer.

[0045] Legend: 1. Strata model; 2. Shield tunnel model; 21. Ordinary segment lining; 22. Segment lining to be broken; 23. Segment lining outside the part to be broken. DETAILED DESCRIPTION

[0046] The following will be combined with 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.

[0047] Embodiment 1:

[0048] like Figure 1-Figure 7 As shown, this embodiment provides a method for determining the influence of shield tunnel opening on the mechanical characteristics of the main structure, comprising the following steps:

[0049] S1. Construct a three-dimensional numerical calculation model of the shield tunnel.

[0050] The three-dimensional numerical calculation model is composed of a stratum model and a shield tunnel model 2 arranged in the stratum model 1. The shield tunnel model 2 is composed of an ordinary segment lining 21, a segment lining 22 to be broken, and a segment lining 23 outside the portion to be broken.

[0051] In addition, shear-resistant, tensile-resistant and elastic joints should be provided between the linings of each segment, and the joints are spring units.

[0052] The spring unit is a three-dimensional numerical calculation model used to simulate the mechanical behavior of the joint when it is subjected to force.

[0053] A binding constraint is set between the segment lining 22 to be broken and the segment lining 23 outside the portion to be broken.

[0054] At the same time, it also includes reasonably cutting the segment lining 22 to be broken and the segment lining 23 outside the to-be-broken portion, and dividing the segment lining 22 to be broken and the segment lining 23 outside the to-be-broken portion into hexahedrons.

[0055] Among them, the boundary conditions of the three-dimensional numerical calculation model are:

[0056] The side of the formation model 1 is normal constrained;

[0057] The bottom of the formation model 1 is a fixed constraint;

[0058] The top of the formation model 1 is a free surface;

[0059] The normal preload is set in the longitudinal direction of the segment lining.

[0060] Furthermore, the selection formula of normal preload is:

[0061] Where p is the normal preload, F is the resultant water and soil pressure in front of the shield tunnel excavation face, S is the shield lining annular joint contact area, and α is the lining annular joint stress relaxation coefficient.

[0062] In this embodiment, it should be noted that both the stratum model 1 and the shield tunnel model 2 are solid unit models (three-dimensional finite element units), and hard contact is adopted between the stratum model 1 and the shield tunnel model 2. Since the ordinary segment lining 21, the segment lining 22 to be broken, and the segment lining 23 outside the to-be-broken portion in the shield tunnel model 2 all adopt elastic units, the difficulty of model convergence can be reduced; at the same time, the segment lining 22 to be broken and the segment lining 23 outside the to-be-broken portion are combined and reasonably cut so that they can be divided into hexahedral units, thereby improving the calculation accuracy.

[0063] In addition, it should be noted that the adjacent parts of the longitudinal seams and annular seams between all the segment linings in the shield tunnel model 2 adopt hard contact, which can simulate the opening and dislocation deformation trend of the segment lining at the joints, and the segment lining 22 to be broken is set as an independent component, wherein the independent component means that the part is set separately, which includes but is not limited to the following types: fixed constraints, contact constraints, hinge constraints, elastic constraints, so that the interaction relationship between the segment lining 22 to be broken and the surrounding structure under actual working conditions can be more accurately simulated, and the real distribution of stress and deformation during the demolition process can be reflected through the transmission effect of the binding constraint; binding constraints are set between the segment lining 22 to be broken and the segment lining 23 outside the to-be-broken part, and shear and tensile joints are set between the segment linings of the shield tunnel model 2, and the joints adopt spring units; by setting different degrees of freedom and different stiffness curves of the joints, the shear and tensile stiffness are simulated, and the stiffness curve can be set to be nonlinear.

[0064] S2. Calculate the initial geostress of the formation model 1 in the three-dimensional numerical calculation model.

[0065] In this embodiment, it should be noted that this analysis step only activates the stratum model 1 and does not activate the shield tunnel model 2, that is, only the stratum model 1 is used and the shield tunnel model 2 is not used.

[0066] S3. Calculate the deformation and stress of the shield tunnel model 2 without opening in the three-dimensional numerical calculation model under the action of the surrounding stratum load.

[0067] Among them, the opening shape of the shield tunnel model 2 is square or circular.

[0068] In this embodiment, it should be noted that in this step, the stratigraphic units within the outer contour of the shield tunnel model 2 will be killed (hidden or deleted), and the shield tunnel model 2 will be activated at the same time, and then the deformation and stress of the shield tunnel model 2 without a hole in the three-dimensional numerical calculation model under the action of the surrounding stratigraphic load will be calculated.

[0069] S4. Calculate the structural mechanical characteristics of the shield tunnel model 2 after the hole is opened in the three-dimensional numerical calculation model under the action of the surrounding external load.

[0070] Among them, the calculation formula for the number of longitudinal lining rings at the opening of shield tunnel model 2 is:

[0071] N = n + 2 × (m + 2), where N is the number of longitudinal rings of the shield tunnel model, n is the number of lining rings involved in the opening, m is the range of the non-affected area on both sides of the opening, and m ≥ 5.

[0072] In addition, when the state of the segment lining 22 to be broken changes under the action of the surrounding external load, the states of all the contact and spring units related to it shall be updated, the contact between the segment lining 22 to be broken and the adjacent segment lining 22 to be broken shall be set to an inactive state, the outer surface of the segment lining having a contact relationship with the formation model 1 shall be updated so that it is only included in the active state in the current analysis step, and the spring unit having a connection relationship with the segment lining 22 to be broken shall be killed.

[0073] In this embodiment, it should be noted that by killing the segment lining 22 to be broken, and applying equal ground stress to the stratum model 1 other than the segment lining 22 to be broken, the stability of the stratum model 1 is maintained, and then the structural mechanical characteristics of the shield tunnel model 2 after the hole is opened in the three-dimensional numerical calculation model under the surrounding external load are calculated. By setting under the surrounding external load, the problem of non-convergence of structural calculation caused by factors such as the non-existence of contact caused by the life and death state (hiding or deletion) between multiple ordinary segment linings 21, the segment lining 22 to be broken, and the segment lining 23 outside the part to be broken, and the distortion of the shield tunnel model 2 caused by the lack of spring constraints can be avoided.

[0074] Embodiment 2:

[0075] The three-dimensional numerical calculation model of this embodiment can open holes of different shapes, positions and angles in the simulated shield tunnel. The method is universal and the structural responses under different opening conditions can be compared and analyzed.

[0076] As an implementation method of this embodiment, Figure 8-Figure 11As shown in the figure, the distribution curve of the lateral displacement of the arch waist on the opening side along the tunnel axis is roughly "M" shaped, that is, the center of the opening is horizontally displaced toward the inside of the tunnel, and the two sides of the opening are horizontally displaced toward the outside of the tunnel. For assembled linings, the bending of the structure may cause the joints in the tensioned parts to open. In addition, it can be found that the circular opening ( Fig.10 and Fig.11 ) compared to the rectangular opening ( Figure 8 and Fig. 9 ), the range of displacement of the main tunnel structure and the degree of curve bending are also larger.

[0077] As for the lateral displacement of the arch waist on the opposite side of the opening, the three working conditions of the circular opening are generally smaller than those of the three working conditions of the rectangular opening. This may be because the unclosed ring in the middle of the circular opening has no direct effect of external soil load on the opening side, so the displacement of the lining ring toward the opposite side of the opening is relatively small. In addition, for the same circular or rectangular opening, the opening is located on the upper layer. Figure 8 and Fig.10 The outward horizontal displacement of the arch waist on the opposite side of the opening is greater. This is because the stiffness of the upper half of the lining structure is greatly weakened. Under the direct action of the overlying load, the lining structure has a more obvious "flattening" deformation trend, resulting in an increase in the horizontal displacement of the arch waist on the opposite side of the lining ring where the opening is located toward the outside of the tunnel.

[0078] Since the size of the circular opening is larger than that of the rectangular opening, the overall vertical settlement of the vault in the circular opening condition is greater than that in the rectangular opening condition. The distribution curve of the vertical displacement of the lining vault in different rectangular opening conditions along the tunnel axis is roughly "U"-shaped, and the vertical settlement of the lining ring vault at the opening is the largest. The distribution curve of the vertical displacement of the lining ring vault in different circular opening conditions along the tunnel axis is roughly "V"-shaped, and the vertical settlement of the lining ring vault at the opening is the largest. This is because the circular opening is larger and the middle is an unclosed ring, so the sudden change trend of the vertical deformation of the middle ring is greater. For the three rectangular opening conditions, under the combined influence of the weakening of the structural stiffness and the disappearance of the external load of the lining at the opening, the vault settlement of the condition where the opening is located in the upper layer is the largest, followed by the condition where it is located at the bottom of the vault. For the two circular opening conditions, the middle part of the opening is an unclosed ring with low stiffness, which is the main influencing factor of the lining ring deformation. The opening is located in the upper layer. Fig.10 The vault settlement is the largest.

[0079] The influence of the opening position on the convergence deformation of the structure is relatively complex. On the one hand, the opening will cause the weakening of the structural stiffness, and the degree of weakening of the structural stiffness varies with the opening shapes; on the other hand, the initial load on the lining ring at the opening disappears, and the stress state of the structure changes. In addition, the assembly point of the lining ring may also affect the structural deformation. At different assembly points, the positions of the joints and seams between the segment rings near the opening may be different. Therefore, the influence of the opening position on the convergence deformation of the lining structure is complex, but for the same size of opening conditions, the overall difference in the vertical convergence rate of the main tunnel is small: the difference in deformation rate of different conditions for rectangular openings is less than 0.67%, and the difference in deformation rate of different conditions for circular openings is less than 1.15%.

[0080] The main results of the calculation and analysis output of the present invention include deformation, stress and contact status. By analyzing the deformation of the lining, it can be determined whether the opening of the shield tunnel may cause excessive structural deformation, exceeding the limit of the specification; by analyzing the stress of the lining, it can be determined whether the local stress concentration of the structure caused by the opening of the shield tunnel model exceeds the bearing capacity limit of the material; by analyzing the stress of the joint, the safety state of the joint is determined in combination with the tensile or shear bearing capacity of the joint; by analyzing the contact state of the segment lining joint, including the opening amount and slippage, combined with the requirements of the joint waterproofing specification, the safety of the segment joint waterproofing is determined. Then, according to the different adverse response characteristics of the shield tunnel model, a targeted structural safety assurance strategy is formulated.

[0081] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0082] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for determining the influence of shield tunnel opening on the mechanical characteristics of the main structure, characterized in that: The following steps are involved: S1. Construct a three-dimensional numerical calculation model of the shield tunnel; The three-dimensional numerical calculation model is composed of a stratum model and a shield tunnel model arranged in the stratum model, and the shield tunnel model is composed of ordinary segment lining, segment lining to be broken, and segment lining outside the portion to be broken; S2, calculating the initial geostress of the formation model in the three-dimensional numerical calculation model; S3. Calculate the deformation and stress of the shield tunnel model without opening in the three-dimensional numerical calculation model under the action of the surrounding stratum load; S4. Calculate the structural mechanical characteristics of the shield tunnel model after opening the hole in the three-dimensional numerical calculation model under the action of surrounding external loads.

2. A method for determining the influence of shield tunnel opening on the mechanical characteristics of the main structure according to claim 1, characterized in that: In the step S1, each of the segment linings is an elastic unit.

3. The method for determining the influence of shield tunnel opening on the mechanical characteristics of the main structure according to claim 1 is characterized in that: In the step S1, shear-resistant, tensile-resistant and elastic joints are provided between the segment linings, and the joints are spring units.

4. The method for determining the influence of shield tunnel opening on the mechanical characteristics of the main structure according to claim 1 is characterized in that: In the step S1, a binding constraint is set between the segment lining to be broken and the segment lining outside the portion to be broken.

5. The method for determining the influence of shield tunnel opening on the mechanical characteristics of the main structure according to claim 1 is characterized in that: In the step S1, it also includes reasonably cutting the segment lining to be broken and the segment lining outside the portion to be broken, and dividing the segment lining to be broken and the segment lining outside the portion to be broken into hexahedrons.

6. The method for determining the influence of shield tunnel opening on the mechanical characteristics of the main structure according to claim 1 is characterized in that: In step S1, the boundary conditions of the three-dimensional numerical calculation model are: The sides of the formation model are normal constraints; The bottom of the stratum model is a fixed constraint; The top of the stratigraphic model is the free surface; The normal preload is set in the longitudinal direction of the segment lining.

7. The method for determining the influence of shield tunnel opening on the mechanical characteristics of the main structure according to claim 1 is characterized in that: The selection formula of the normal preload force is: Where p is the normal preload, F is the resultant water and soil pressure in front of the shield tunnel excavation face, S is the shield lining annular joint contact area, and α is the lining annular joint stress relaxation coefficient.

8. The method for determining the influence of shield tunnel opening on the mechanical characteristics of the main structure according to claim 1 is characterized in that: In step S3, the opening shape of the shield tunnel model is square or circular.

9. The method for determining the influence of shield tunnel opening on the mechanical characteristics of the main structure according to claim 1, characterized in that: In step S4, the calculation formula for the number of longitudinal lining rings of the shield tunnel model at the opening is: N = n + 2 × (m + 2), where N is the number of longitudinal rings of the shield tunnel model, n is the number of lining rings involved in the opening, m is the range of the non-affected area on both sides of the opening, and m ≥ 5.

10. The method for determining the influence of shield tunnel opening on the mechanical characteristics of the main structure according to claim 1, characterized in that: In step S4, when the state of the segment lining to be broken changes under the action of the surrounding external load, the states of all the contact and spring units related to it are updated, the contact between the segment lining to be broken and the adjacent segment lining to be broken is set to an inactive state, the outer surface of the segment lining that has a contact relationship with the formation model is updated so that it is only included in the active state in the current analysis step, and the spring unit that has a connection relationship with the segment lining to be broken is killed.

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