CN217111752U - Novel loading device for shield tunnel model test - Google Patents

Abstract

The utility model discloses a novel loading device for shield tunnel model test. The novel loading device comprises a reaction force frame part, a base part and a loading part; Reaction force, the base is used to place the model and the end of the loading part. The loading part applies the load through the spring, constrains the deformation and provides the formation resistance. Compared with the prior art, the device has the advantages of simple operation, easy purchase of the required components, convenient processing and low cost; the loading component adopts the method of multiple springs in parallel, and by adjusting the spring stiffness and compression amount, the tunnel models of different sizes can be multiplied. The repeated test of these working conditions solves the problems of poor repeatability and high complexity caused by the model embedded in the soil.

Description

A Novel Loading Device for Shield Tunnel Model Test

technical field

The utility model relates to the technical field of auxiliary tools for engineering structure testing, in particular to a novel loading device for shield tunnel model testing.

Background technique

As a special structure in underground engineering, shield tunnel has large scale and long service time, and plays an extremely important role in the field of urban rail transportation. If the structure is damaged or collapsed, it will inevitably cause major accidents. casualties and property damage. Therefore, how to ensure the safety of shield tunnels in the whole life cycle is one of the key contents of current research in the fields of design, construction and structural health monitoring.

Considering the diversity and complexity of the underground environment, combined with the particularity of the structure of the shield tunnel itself, it is difficult to obtain the force and boundary conditions of this type of structure clearly and accurately, even if the large-scale finite element method greatly reduces the structure. The difficulty of calculation is limited by the progress of theoretical research. The existing physical models and mechanical mechanisms are also derived on the basis of many assumptions and simplifications. The calculation results cannot accurately reflect the state response of the actual structure. As an important way and method to reflect the structural response mechanism, the model test can provide a solid foundation for the theoretical study of shield tunneling mechanics and health inspection because of its own intuition and controllability.

Most of the existing shield tunnel test methods are prototype tests or model tests embedded in soil, which have defects such as excessive scale, high cost, long cycle, and complicated operation. It greatly limits the diversity of research contents, and the sensors used are mostly point sensors such as earth pressure gauges, strain gauges, displacement gauges, etc., which are complicated in operation, easily interfered with signals, and cannot well detect the distribution of structural responses. state. Therefore, a new type of device is urgently needed for auxiliary testing.

Utility model content

The purpose of this utility model is to provide a new type of loading device for shield tunnel model test, which is simple to operate, easy to purchase, convenient to process and low cost; The tunnel model is subjected to repeated tests under various working conditions.

In order to achieve the above purpose, the present application proposes a novel loading device for shield tunnel model testing, including a loading component for applying loads, constraining the deformation of the tunnel model and providing formation resistance, the loading components include hexagonal nuts B, hexagonal Nut C, Hexagonal Nut D, Screw, Thin Hexagonal Nut, Small Diameter Flat Head Rivet, Large Diameter Flat Head Rivet, Steel Plate with Holes, Steel Plate, Small Stiffness Loading Spring, Large Stiffness Formation Spring, Rubber Connection Block, Square Plastic Rod, Round Magnet, pressure sensor and variable diameter adapter, the hexagonal nut B is fixed to the end of the screw rod by welding, the hexagonal nut C and the hexagonal nut D can rotate freely on the screw rod, the hexagonal nut C is located outside the rectangular square tube , used to tighten the screw on the rectangular square tube after the load is applied in place, the hexagonal nut D is located on the outside of the steel plate with holes, used to adjust the position of the steel plate with holes, and its function is equivalent to the fixed end of the soil spring; The perforated steel plate is penetrated to the screw rod through a drill hole with the same diameter as the screw rod at the center position, and the oppositely arranged perforated steel plate and the inner circumference of the steel plate are fixed with large-diameter flat head rivets by welding, and two large-diameter flat head rivets arranged opposite to each other are fixed by welding. A formation spring is sleeved between them, a rubber connecting block is fixed on the outside of the steel plate by gluing, and a pressure sensor is adsorbed on the inside through a circular magnet. The other end of the head rivet passes through the variable diameter adapter, the small diameter flat head rivet and the thin hexagonal nut are fixed together by welding, and the thin hexagonal nut is tightened on the other end of the screw rod.

Further, it also includes a reaction frame member used to support the loading member and bear the load and the resistance of the formation, the reaction frame member includes a rectangular square tube, a hexagonal nut and a regular polygon frame, and the two regular polygon frames are evenly welded. A rectangular square tube, the midpoint of the long side of the cross section of the rectangular square tube is aligned with the midpoint of the side length of the regular polygon frame, a plurality of drill holes are arranged on the rectangular square tube, and the distances between adjacent drill holes are equal. A hexagonal nut A is welded at each drilled hole, and the diameter of the hexagonal nut A is equal to the diameter of the drilled hole.

Further, it also includes a base part for placing the head of the loading part and the tunnel model, the base part includes a steel frame and a wooden board, the wooden board is fixed to the steel frame by gluing, and the length and width of the wooden board are based on the tunnel model. The diameter of the board and the length of the head of the loading part are determined, and the thickness of the board ensures that the axial direction of the loading spring and the ground spring placed on it is parallel to the axial direction of the screw.

Further, the central axis of the base member coincides with the central axis of the reaction frame member.

Further, the loading member is mounted on the rectangular square tube of the reaction frame member through a screw rod; the head of the loading member is supported on the wooden board of the base member through a square plastic rod, so as to ensure that the axis direction of the loading spring and the formation spring is consistent with the screw rod. The axis directions are parallel to each other.

Further, the square plastic rod is fixed to the steel plate with holes by gluing.

Furthermore, the loading spring is in an active state with the small-diameter flat head rivet, the pressure sensor and the variable-diameter adapter, and the formation spring and the large-diameter flat head rivet can slide with each other, so as to simulate that the soil is only affected by Compression and not tension characteristics.

Further, a single soil spring is equivalent to five parallel springs, specifically set as one loading spring and four formation springs; the sum of the stiffness of the loading spring and the stiffness of the formation spring is equal to the stiffness of the soil spring, and the stiffness of the loading spring is equal to that of the soil spring. The stiffness of the spring is not necessarily equal to that of the formation spring; the loading spring is used not only to apply external loads, but also to provide the formation resistance due to structural deformation in the test, and the formation spring is only used to provide the resistance caused by the structural deformation in the test. Ground resistance.

The above technical solution adopted by the present utility model has the advantages that: the novel loading device includes a reaction force frame part, a base part and a loading part; Place the model and the end of the loading part, which is loaded by springs, constrains deformation, and provides formation resistance. Compared with the prior art, the components required by the device are easy to purchase, convenient to process, and low cost; the loading components adopt the method of multiple springs in parallel, and by adjusting the spring stiffness and the compression amount, various working conditions can be performed on tunnel models of different sizes. It solves the problems of poor repeatability and high complexity caused by the model embedded in the soil.

Description of drawings

Figure 1 is a front view of a new loading device for shield tunnel model testing.

Figure 2 is a top view of the new loading device used for the shield tunnel model test.

FIG. 3 is a three-dimensional schematic diagram of the reaction frame components.

FIG. 4 is a front view of the reaction frame member.

FIG. 5 is a plan view of the reaction frame member.

Figure 6 is a front view of the base member.

Figure 7 is a bottom view of the base member.

Figure 8 is a three-dimensional schematic view of the loading part.

Figure 9 is a front view of the loading member.

Figure 10 is a side view of the loading member.

Figure 11 is an exploded schematic view of the loading part.

Figure 12 is a top view of the new loading device applied to the three-ring model test of the shield tunnel.

Figure 13 is a cross-sectional view of the new loading device applied to the three-ring model test of the shield tunnel.

Fig. 14 is a schematic diagram of the strain data collected by the optical fiber sensor along the circumference when the tunnel model is in a healthy state and a damaged state, respectively.

Description of the serial numbers in the figure: 1. Equilateral angle steel, 2. Rectangular square tube, 3A-3D, hexagonal nut, 4. Regular polygon frame, 5. Steel frame, 6. Wooden board, 7. Screw, 8. Thin hexagonal nut, 9 , small diameter flat head rivets, 10, large diameter flat head rivets, 11, steel plate with holes, 12, steel plate, 13, loading spring, 14, formation spring, 15, rubber connecting block, 16, square plastic rod, 17, round Shaped magnet, 18, pressure sensor, 19, variable diameter adapter, 20, demodulator and supporting data acquisition computer, 21, connecting jumper, 22, model damage point, 23, bridge box, 24, NI acquisition board , 25, NI data acquisition computer, 26, strain fiber, 27, temperature fiber, 28, tunnel model.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present application more clearly understood, the present application will be described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, but not to limit the present application, that is, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application generally described and illustrated in the drawings herein may be arranged and designed in a variety of different configurations.

Thus, the following detailed description of the embodiments of the application provided in the accompanying drawings is not intended to limit the scope of the application as claimed, but is merely representative of selected embodiments of the application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

Example 1

Figures 1 and 2 show the overall schematic diagram of the new loading device used for the shield tunnel model test. The new loading device includes three parts: the reaction frame part, the base part and the loading part. The reaction frame parts include rectangular square tube 2, hexagonal nut 3A and regular polygon frame 4, the base part includes steel frame 5 and wooden board 6, the loading part includes hexagonal nuts 3B, 3C, 3D, screw 7, thin hexagonal nut 8, small diameter flat Head rivet 9, large diameter flat head rivet 10, steel plate with holes 11, steel plate 12, small stiffness loading spring 13, large stiffness formation spring 14, rubber connecting block 15, square plastic rod 16, round magnet 17, pressure sensor 18 and Variable diameter adapter 19. Among them, the reaction frame part is used to support the loaded part and bear the reaction force of the load and formation resistance; the base part is used to place the head of the loaded part and the tunnel model; the loading part is used to apply the load, constrain the deformation of the model and provide the formation resistance; The central axis of the component coincides with the central axis of the reaction frame member; the loading member is mounted on the rectangular square tube 2 of the reaction frame member through the screw 7; the head of the loading member includes a rubber connecting block 15, a high-rigidity formation spring 14, a small The stiffness loading spring 13, steel plate 12, perforated steel plate 11, large-diameter flat head rivet 10, etc., are supported on the wooden board 6 of the base member through the square plastic rod 16, so as to ensure that the axial direction of the loading spring 13 and the formation spring 14 is consistent with the screw 7 The axis directions are parallel to each other.

Figures 3 to 5 show schematic structural diagrams of the reaction frame components. In the figure, the regular polygon frame 4 is made by cutting and welding the equilateral angle steel 1; The position of the midpoint, and according to the characteristics of the shield tunnel model, the distances between the multiple drill holes are equal; the diameter of the hexagonal nut 3A is equal to the diameter of the drill hole, and is fixed to the rectangular square tube 2 by welding; the rectangular square tube 2 The midpoint of the long side of the cross section is aligned with the midpoint of the side length of the regular polygon frame 4, and is fixed to the regular polygon frame 4 by welding.

6 to 7 show the schematic structural diagrams of the base member. In the figure, the steel frame 5 is made by welding a square tube; the wooden board 6 is fixed on the steel frame 5 by gluing, and the length and width of the wooden board 6 are determined according to the diameter of the shield tunnel model and the length of the head of the loading part, and the wooden board 6 The thickness of the screw should be able to ensure that the axial direction of the loading spring 13 and the ground spring 14 placed thereon is parallel and consistent with the axial direction of the screw 7 .

8 to 11 are schematic diagrams showing the structure of the loading part. In the figure, the hexagonal nut 3B is fixed to the end of the screw rod 7 by welding, and the hexagonal nuts 3C and 3D can freely rotate and move on the screw rod 7. On the pipe 2, the position of the steel plate 11 with holes can be adjusted through the hexagonal nut 3D. The function of the hexagonal nut 3D is equivalent to the fixed end of the soil spring; the steel plate 11 with holes is passed through a hole with the same diameter as the screw rod 7 in the center position to the screw rod. 7; the large diameter flat head rivet 10 is fixed to the perforated steel plate 11 by welding, and the square plastic rod 16 is fixed to the perforated steel plate 11 by gluing; the thin hexagonal nut 8 and the small diameter flat head rivet 9 are fixed together by welding , tighten the thin hexagonal nut 8 on the other end of the screw 7; the large-diameter flat head rivet 10 is fixed on the steel plate 12 by welding, the rubber connecting block 15 is fixed on the steel plate 12 by gluing, and the pressure sensor 18 is adsorbed by the circular magnet 17 On the steel plate 12, the variable diameter adapter 19 is installed on the pressure sensor 18; the diameter of the small-diameter flat head rivet 9 is slightly smaller than the inner diameter of the loading spring 13, and the diameter of the large-diameter flat head rivet 10 is slightly smaller than the inner diameter of the formation spring 14. One end of the spring 13 passes through the small diameter flat head rivet 9, and the other end passes through the variable diameter adapter 19 installed on the pressure sensor 18; the loading spring 13 and the small diameter flat head rivet 9, the pressure sensor 18 and the variable diameter adapter 19 In the active state, the formation spring 14 and the large-diameter flat head rivet 10 can slide with each other, so as to simulate the characteristics of soil only under compression and not under tension.

Figures 12 and 13 show a schematic diagram of the hoop strain detection test of a shield tunnel model based on a new loading device. This test method for circumferential strain detection of shield tunnel model based on the new loading device can adopt the following steps:

The first step is to obtain the size of the tunnel model 28, the size of the external load and the stratum resistance through the similarity theory, determine the number of loading points around the tunnel model, and determine the equilateral angle steel 1 to the variable diameter adapter 19 and other parts. size, specification and quantity;

The second step is to cut and weld the equilateral angle steel 1 to form two identical regular polygon frames 4, then cut and drill the rectangular square tube 2, and weld the hexagonal nut 3A to the drilled hole of the rectangular square tube 2 At the position, a plurality of rectangular square tubes 2 are evenly welded to the regular polygon frame 4;

The third step is to cut and weld the square tube to make the base steel frame 5, cut and process the wooden board 6, and glue the wooden board 6 to the steel frame 5. The size of the wooden board 6 should be able to put down the tunnel model and the end part of the loading part at the same time. ;

The fourth step, screw the hexagon nuts 3B and 3C along one end of the screw 7, fix the hexagon nut 3B on the end of the screw 7 by welding, and then rotate the screw 7 through the holes and hexagons on the rectangular square tube 2. Nut 3A, so that the screw 7 is installed on the reaction frame 4, and the hexagonal nut 3C is located between the hexagonal nut 3B and the rectangular square tube 2, so as to ensure that the screw 7 can be tightened and fixed on the rectangular square tube 2 after the load is applied in place. superior;

The fifth step is to drill a hole in the center of the steel plate 11 with holes, weld the small-diameter flat head rivet 9 to the thin hexagonal nut 8, weld the large-diameter flat head rivet 10 to the relative positions of the steel plates 11 and 12, and connect the pressure sensor. 18 is adsorbed to one side of the steel plate 12 by the circular magnet 17, then the variable diameter adapter 19 is installed on the pressure sensor 18, and then the rubber connecting block 15 is fixed to the other side of the steel plate 12 by gluing;

The sixth step, screw the hexagonal nut 3D from the other end of the screw 7, thread the steel plate 11 with holes on the screw 7, and then tighten the welded thin hexagonal nut 8 and the small-diameter flat head rivet 9 from the other end of the screw 7. , and then glue the square plastic rod 16 on the perforated steel plate 11. Note that the bonding position is symmetrical about the perforated steel plate 11 up and down, left and right, and finally install the loading spring 13 between the small diameter flat head rivet 9 and the variable diameter adapter 19. A formation spring 14 is installed between the large-diameter flat head rivets 10 to connect the perforated steel plate 11 and the steel plate 12;

The seventh step is to connect the connection jumper 21, the distributed strain optical fiber 26 and the distributed temperature optical fiber 27 in series by welding, paste the distributed strain optical fiber 26 and the distributed temperature optical fiber 27 on the inner surface of the tunnel model 28, and then connect the tunnel model 28. Placed in the center of the board 6;

In the eighth step, the pressure sensor 18 is connected to the NI acquisition board 24 through the bridge box 23, and the NI acquisition board 24 is connected to the NI data acquisition computer 25;

The ninth step, contact the rubber connecting block 15 in the loading device with the tunnel model 28, and adjust the positions of the screw 7, the thin hexagonal nut 8 and the small-diameter flat head rivet 9 by turning the hexagon nut 3B with a torque wrench, according to the NI data acquisition computer The result of the force sensor 18 output by 25 ensures that the loading spring 13 is in the initial critical state, and then turns the hexagon nut 3D with a wrench to adjust the position of the steel plate 11 with holes, and by measuring the distance between the steel plate 11 and the steel plate 12 with holes, to ensure the formation The spring 14 is in an initial critical state;

The tenth step, connect the connecting jumper 21 to the distributed optical fiber demodulator based on Brillouin scattering (BOTDA, BOFDA) and the supporting data acquisition computer 20, and measure the hoop strain of the model under the unloaded state as the initial value ;

The eleventh step is to apply the load. First, use a wrench to control the hexagonal nut 3D not to rotate, so that the position with the holed steel plate 11 remains unchanged, and then use a torque wrench to turn the hexagonal nut 3B. The precession distance is used to control the compression amount of the loading spring 13 to achieve the purpose of applying the load. The specific value of the applied load is checked and adjusted through the output result of the force sensor 18;

In the twelfth step, the optical fiber demodulator and the supporting data acquisition computer 20 are used to collect the data of the distributed strain fiber 26 and the distributed temperature fiber 27 when the tunnel model 28 is in a healthy state and a damaged state respectively under different loads. By performing temperature compensation processing on the data under different working conditions, the strain data along the circumferential direction can be obtained after subtracting the initial value. According to the strain value corresponding to the damage point 22 of the model, the degree of damage can be qualitatively judged.

The above middle hexagon nuts 3A, 3B, 3C and 3D have the same specifications but different functions. The main function of the hexagonal nut 3A is to limit the movement of the screw 7; the hexagonal nut 3B provides a fulcrum for the torque wrench, and quantifies and controls the compression of the loading spring 13 through the number of rotations and the pitch of the screw 7; After the load is applied in place, the screw 7 is tightened and fixed to the rectangular square tube 2; the hexagonal nut 3D is used to adjust the position of the steel plate 11 before loading, so that the formation spring 14 is in a critical state, and its position remains unchanged during and after loading , used to simulate the fixed end of the soil spring.

The stiffness (unit: N/mm) of the loading spring 13 and the formation spring 14 can be obtained by the following formula:

K=k _r ×A

K'=K/C

K'=K ₀ +4K ₁

Wherein, k _r represents the formation resistance coefficient (unit: KN/m ³ ), which can be determined through empirical values or theoretical calculation formulas. A represents the contact area between the actual structure and the formation corresponding to the action range of a single loading component (unit: m ² ), and the action range is determined according to the number of loading components arranged in the circumferential direction of the model. If there are 12 loading parts, the action range of a single loading part is 30°. According to the radius of the actual shield ring, the chord length L corresponding to the range of 30° can be obtained, and then multiplied by the width B of the shield ring, that is, the actual The contact area between the structure and the formation is A=L×B. K represents the stiffness of a single soil spring on the actual structure, C represents the similarity ratio between the prototype and the model, K' represents the total spring stiffness of a single loaded component of the model structure calculated by the similarity ratio, and K ₀ represents the loaded spring in a single loaded component The stiffness of 13, 4K ₁ represents the stiffness of the four formation springs 14 in a single loaded part.

The number of turns required to turn the hexagon nut 3B in a single loading part can be obtained by the following formula:

F=ΔL×K ₀

ΔL=P×n

Among them, F represents the size of the required applied load (unit: N), ΔL represents the compressive deformation of the loading spring 13 (unit: mm), that is, the displacement of the screw 7, P represents the pitch of the screw 7, and n represents the hexagonal nut The number of rotations of 3B can be obtained by dividing the required load by the stiffness of the loading spring 13, and then dividing by the thread pitch.

In the present invention, a single soil spring is equivalent to five parallel springs, which are specifically set as one loading spring 13 and four ground springs 14; the sum of the stiffness of the loading spring 13 and the stiffness of the ground spring 14 is equal to the stiffness of the soil spring, but the The stiffness of the spring 13 and the stiffness of the formation spring 14 are not necessarily equal; the loading spring 13 is used not only to apply external loads, but also to provide formation resistance due to structural deformation, and the formation spring 14 is only used to provide The effect of formation resistance caused by structural deformation.

The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. These descriptions are not intended to limit the invention to the precise form disclosed, and obviously many changes and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described for the purpose of explaining certain principles of the invention and its practical applications, to thereby enable those skilled in the art to make and utilize various exemplary embodiments of the invention and various Different choices and changes. The scope of the present invention is intended to be defined by the claims and their equivalents.

Claims (8)

1. a novel loading device for shield tunnel model test, it is characterized in that, for applying load, restraining tunnel model deformation and providing the loading member of formation resistance, described loading member comprises hexagonal nut B (3B), hexagonal Nut C (3C), Hexagon Nut D (3D), Screw (7), Thin Hexagon Nut (8), Small Diameter Flat Head Rivet (9), Large Diameter Flat Head Rivet (10), Steel Plate with Holes (11), Steel plate (12), small stiffness loading spring (13), high stiffness formation spring (14), rubber connecting block (15), square plastic rod (16), round magnet (17), pressure sensor (18) and variable diameter The adapter (19), the hexagon nut B (3B) is fixed to the end of the screw rod (7) by welding, the hexagon nut C (3C) and the hexagon nut D (3D) can freely rotate and move on the screw rod (7), The hexagonal nut C (3C) is located on the outside of the rectangular square tube, and is used to tighten the screw (7) on the rectangular square tube (2) after the load is applied in place, and the hexagonal nut D (3D) is located on the steel plate with holes (11) The outer side is used to adjust the position of the steel plate with holes (11), and its function is equivalent to the fixed end of the soil spring; the steel plate with holes (11) is drilled through a hole with the same diameter as the screw (7) at the center position. On the screw (7), a large-diameter flat head rivet (10) is fixed by welding on the inner periphery of the oppositely arranged perforated steel plate (11) and the steel plate (12), and the two oppositely arranged large-diameter flat head rivets are sleeved. There is a formation spring (14), a rubber connecting block is fixed on the outside of the steel plate (12) by gluing, and a pressure sensor (18) is adsorbed on the inside through a circular magnet (17), and a variable diameter is installed on the pressure sensor (18). An adapter (19), one end of the loading spring (13) passes through the small diameter flat head rivet (9), and the other end passes through the variable diameter adapter (19), the small diameter flat head rivet (9) and the thin hexagonal nut ( 8) Fastened together by welding, tighten the thin hex nut (8) on the other end of the threaded rod (7). 2. A novel loading device for shield tunnel model test according to claim 1, characterized in that, further comprising a reaction force frame part for supporting the loading part and bearing load and formation resistance, the reaction force frame The components include a rectangular square tube (2), a hexagonal nut A (3A) and a regular polygonal frame (4), and a plurality of rectangular square tubes (2) are uniformly welded between the two regular polygonal frames (4). 2) The midpoint of the long side of the cross section is aligned with the midpoint of the side length of the regular polygon frame (4). A plurality of drill holes are arranged on the rectangular square tube (2), and the distances between adjacent drill holes are equal. A hexagonal nut A (3A) is welded at the hole, and the diameter of the hexagonal nut A (3A) is equal to the diameter of the drilled hole. 3. a kind of novel loading device for shield tunnel model test according to claim 1, is characterized in that, also comprises the base part for placing loading part head and tunnel model, and described base part comprises steel frame ( 5) and a wooden board (6), the wooden board (6) is fixed on the steel frame (5) by gluing, the length and width of the wooden board (6) are determined according to the diameter of the tunnel model and the length of the head of the loading part, and the wooden board (6) is The thickness of (6) ensures that the axial directions of the loading spring (13) and the formation spring (14) placed thereon are parallel and consistent with the axial direction of the screw (7). 4 . The novel loading device for shield tunnel model test according to claim 3 , wherein the central axis of the base member and the central axis of the reaction force frame member coincide. 5 . 5. A novel loading device for shield tunnel model test according to claim 1, characterized in that, the loading member is mounted on the rectangular square tube (2) of the reaction force frame member through a screw (7); The head of the loading part is supported on the wooden board (6) of the base part through a square plastic rod (16), so as to ensure that the axial directions of the loading spring (13) and the ground spring (14) are parallel and consistent with the axial direction of the screw (7). 6 . The novel loading device for shield tunnel model test according to claim 5 , wherein the square plastic rod ( 16 ) is fixed to the perforated steel plate ( 11 ) by gluing. 7 . 7. A novel loading device for shield tunnel model test according to claim 1, characterized in that the loading spring (13) is connected to a small-diameter flat head rivet (9), a pressure sensor (18) and a variable The diameter adapters (19) are in an active state, and the formation springs (14) and the large-diameter flat head rivets (10) can slide with each other, so as to simulate the characteristics of soil only under compression and not under tension. 8. A novel loading device for shield tunnel model test according to claim 1, characterized in that a single soil spring is equivalent to five parallel springs, specifically set as one loading spring (13) and four strata Spring (14); the sum of the stiffness of the loading spring (13) and the stiffness of the ground spring (14) is equal to the stiffness of the soil spring, but the stiffness of the loading spring (13) and the stiffness of the ground spring (14) are not necessarily equal; The loading spring (13) is used not only to apply external loads, but also to provide the formation resistance effect caused by the structural deformation in the test, and the formation spring (14) is only used to provide the formation resistance effect caused by the structural deformation in the test .

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