Test device and method for exploring deformation and bearing capacity of shield tunnel under load effect

Abstract

The invention relates to a test device and method for exploring deformation and bearing capacity of a shield tunnel under a load effect, and the device comprises a bottom plate, the front side surface of the bottom plate is fixedly provided with an annular counterforce ring, and the inner periphery and the outer periphery of the counterforce ring are fixedly provided with supporting arms; a plurality of loading units are mounted on the inner circumference of the counter-force ring, and the loading units are distributed in a central symmetry manner by taking the circle center of the counter-force ring as the center; the loading unit comprises a hydraulic device, a hard cushion block and a soft cushion block; and an elastic base is arranged between the hydraulic device and the counter-force ring. The device of the invention accommodates an upright lining ring to take into account the effect of gravity. A hard cushion block and a soft cushion block are arranged on the loading unit, so that load concentration is avoided; the elastic base is installed between the bottom of the hydraulic device and the counter-force ring, forced displacement of the lining ring caused by loads can be avoided, and it can be guaranteed that the force line of the hydraulic device is stable. According to the invention, the whole lining ring can be subjected to load-deformation relation exploration, the shape of the lining ring is fitted, multiple stress factors are considered, and the experiment accuracy is improved.

Description

Technical Field

[0001] The invention relates to the field of shield tunnel testing, and in particular to a test device and method for exploring the deformation and bearing capacity of a shield tunnel under load. Background Art

[0002] Due to the safety and high degree of mechanization of shield tunnel construction, it has been widely used in the field of tunnel engineering. Shield excavation will break the stress distribution of the surrounding rock, release the stress of the surrounding rock in the excavation area, and transfer it to the tunnel lining in the form of convergent deformation. The tunnel lining stress caused by excavation is the main load form of the shield tunnel. Reasonable evaluation of the deformation and bearing capacity of the shield tunnel under the excavation load is of great significance for guiding the design and construction of the shield tunnel.

[0003] In the laboratory testing phase, the field often relies on civil engineering test equipment to test tunnel linings, but tunnel linings are usually circular or quasi-circular in cross-section, which makes it difficult to fix tunnel linings to existing civil engineering test equipment, and the directions of loading forces in existing civil engineering test equipment are different, making it difficult to fit the tunnel lining structure for loading. According to the research on the surrounding rock stress of shield tunnels, the outer surface of the tunnel lining is mainly subjected to the pressure of the surrounding rock, which is dispersed on the tunnel lining, rather than a concentrated force with a specific action position.

[0004] Patent CN211784219U mentions a large-section horseshoe-shaped segment stress characteristics and structural bearing capacity test device. The test device applies loads to the tunnel segments through a series of steel strands. As the load on the steel strands increases, the tunnel segments will produce forced displacements in the direction of the load. However, under the pressure of the surrounding rock, the tunnel will also provide a reaction force to the surrounding rock, causing the tunnel to produce displacements in the opposite direction of the pressure. This existing solution does not match the actual stress conditions of the tunnel, and the stress simulation is not realistic, resulting in inaccurate test results. In addition, the device of this solution is in a flat state, which makes it difficult to simulate the gravity effect of a real tunnel.

[0005] Patent CN118670890A provides a device and method for testing the bending bearing capacity of segment joints under different axial forces. The device is specifically used to test segment joints, and can only explore the stress conditions of the joints at the top of the tunnel. It is unable to explore the overall stress conditions of the entire lining ring in the surrounding rock. The lining ring is not only subjected to the vertical pressure given by the surrounding rock, but also to the tangential force at the waist of the lining ring, the gravity on the top of the lining ring, and the reaction force provided by the bottom of the lining ring. Therefore, the stress conditions and bearing capacity of the lining ring at different parts of the surrounding rock are different. Therefore, the device cannot simulate the stress conditions of the entire lining ring, and the test results of the segment joints are relatively isolated. In addition, the action points for applying loads to the segments are relatively concentrated, resulting in smaller test result data.

[0006] In summary, there is currently a lack of a laboratory test device in the field that can not only fit the shape of the tunnel lining ring, but also truly simulate the stress conditions of the entire lining ring and evenly distribute the load force of the lining ring. Summary of the invention

[0007] The purpose of this application is to provide a test device for exploring the deformation and bearing capacity of a shield tunnel under load, aiming to solve the problems existing in the prior art.

[0008] The embodiment of the present application provides a test device for exploring the deformation and bearing capacity of a shield tunnel under load, comprising a vertical bottom plate, a reaction ring in the shape of a circular ring is fixed to the front side of the bottom plate, and support arms are fixed to the inner and outer peripheries of the reaction ring; a plurality of loading units are installed on the inner periphery of the reaction ring, the number of the loading units is an even number, and the loading units are centrally symmetrically distributed with respect to the center of the reaction ring, the bases of the plurality of loading units are tangent to the inner peripheral surface of the reaction ring, the heads of the plurality of loading units extend along the radial direction of the reaction ring, and the heads of the plurality of loading units surround a circular experimental space, and the experimental space is used to place tunnel specimens;

[0009] The loading unit includes a hydraulic device, a hard pad and a soft pad; an elastic base is arranged between the hydraulic device and the reaction ring, the fixed part of the elastic base is fixedly connected to the reaction ring, and the movable part of the elastic base is fixedly connected to the hydraulic device; the hard pad is fixedly connected to the telescopic rod of the hydraulic device; the hard pad overlaps with the soft pad, and the length of the hard pad is not less than the thickness of the tunnel specimen.

[0010] Furthermore, the support arm is in the shape of a right-angled trapezoid, wherein one right-angled side is fixed to the circumferential surface of the reaction ring and extends along the axial direction of the reaction ring, and the other right-angled side is fixed to the base plate so that the support arm is perpendicular to the base plate; there are multiple support arms, and one support arm is arranged between two adjacent loading units.

[0011] Furthermore, the reaction ring is made of steel, the outer diameter of the reaction ring is 0.1 m larger than the inner diameter so that the reaction ring has a width, and the depth of the reaction ring is greater than the thickness of the tunnel specimen.

[0012] Furthermore, the hard pad is made of steel, the soft pad is made of rubber, the side of the soft pad facing the experimental space is a curved surface, and the center thickness of the soft pad is not less than 1 cm.

[0013] Furthermore, the elastic base includes a sleeve, a slider and a spring, two active ends of the spring are respectively fixed on the sleeve and the slider, one end of the slider extends from the sleeve, and the other end of the slider is limited in the sleeve.

[0014] A test method for exploring the deformation and bearing capacity of a shield tunnel under load is carried out on the test device. First, a bottom plate is fixed to a reaction wall by bolts, so that the entire device including a reaction ring and a loading unit is vertically installed on the reaction wall. When loading, the tunnel specimen is placed in the test space from the side of the reaction ring, and two loading units symmetrically distributed around the center of the reaction ring are used as a group to work synchronously to position the tunnel specimen. Among multiple groups of loading units, the loading unit group on the vertical axis is started first, followed by the loading units on both sides of the vertical axis, and finally the loading units on the horizontal axis. When all the loading units are against the tunnel specimen, the positioning and clamping of the tunnel specimen are completed. During the experiment, a stress sheet is attached to the tunnel specimen between two adjacent loading units, the loading unit at the bottom of the tunnel specimen maintains the current state, and other loading units simultaneously apply force to the tunnel specimen, and the reaction force value of the loading unit at the bottom of the tunnel specimen is detected, and the deformability and bearing capacity of the tunnel specimen are calculated through the stress value detected by the stress sheet and the reaction force value and pressure value detected at the loading unit.

[0015] The beneficial effects of the present invention are:

[0016] 1. The device of the present invention can simulate the stress condition of the entire lining ring more realistically: In terms of gravity, the device of the present invention accommodates an upright lining ring to take into account the gravity effect on the bottom of the lining ring. In terms of surrounding rock load, the load of the surrounding rock on the circumferential surface of the lining ring is simulated by evenly distributed loading units, and the loading unit is provided with a hard pad with the same thickness as the lining ring, so that the load is evenly distributed in the thickness direction of the lining ring to avoid load concentration; on top of this, the soft pad can not only fit the lining rings with different surface curvatures, but also further distribute the load evenly, so that the stress on the surface of the lining ring can be evenly distributed without being affected by the action site; in addition, an elastic base is installed between the bottom of the hydraulic device and the reaction ring to avoid forced displacement of the load on the lining ring, and the installation position of the elastic base can ensure the stability of the force line of the hydraulic device and is not easy to deviate, so that the load output by the loading unit is more stable.

[0017] 2. The loading units of the present invention are evenly distributed around the lining ring. After starting, the two centrally symmetrical loading units are started together, which can realize rapid clamping and positioning of the lining ring and ensure that the position of the lining ring tends to the middle of the reaction ring, so that the elongation length of the hydraulic device of each loading unit is uniform, avoiding the problem of unstable clamping caused by the excessive extension length of some hydraulic devices, ensuring that the force on the lining ring is uniform and stable, thereby ensuring the accuracy of the test.

[0018] In summary, the present invention can explore the load-deformation relationship of the entire lining ring, fit the shape of the lining ring, and consider multiple stress factors to improve the accuracy of the experiment. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0020] Figure 2 It is a schematic diagram of the front structure of the present invention.

[0021] Figure 3 It is a schematic structural diagram of the loading unit of the present invention.

[0022] Figure 4 It is a structural schematic diagram of the elastic base.

[0023] Figure 5 It is a displacement cloud diagram of the hard pad form (without soft pad) of the device of the present invention.

[0024] Figure 6 It is a stress cloud diagram of the hard pad form (without soft pad) of the device of the present invention.

[0025] Figure 7 It is a stress cloud diagram under the combined action of the hard pad and the soft pad of the device of the present invention.

[0026] In the figure:

[0027] 1. Base plate; 2. Screw hole; 3. Reaction ring; 4. Support arm; 5. Tunnel specimen; 6. Loading unit; 7. Hydraulic device; 8. Hard pad; 9. Soft pad; 10. Elastic base; 11. Sleeve; 12. Slider; 13. Spring; 14. Ring. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] like Figure 1-Figure 2 A test device for exploring the deformation and bearing capacity of a shield tunnel under load is shown, comprising a vertical bottom plate 1, and a plurality of screw holes 2 are arranged along the periphery of the bottom plate 1, so as to facilitate driving bolts to install the bottom plate 1 on a reaction wall. The reaction wall is a reaction wall commonly used in civil engineering tests. A circular reaction ring 3 is fixed to the front side of the bottom plate 1, and support arms 4 are fixed to the inner and outer peripheries of the reaction ring 3. The reaction ring 3 is made of steel, and the outer diameter of the reaction ring 3 is 0.1m larger than the inner diameter so that the reaction ring 3 has a width. Usually, the outer diameter of the reaction ring 3 is 1.5m, the inner diameter is 1.4m, and the depth is 0.5m. The depth of the reaction ring 3 is greater than the thickness of the tunnel specimen 5. The diameter of the tunnel specimen 5 is not less than 0.7m.

[0030] The support arm 4 is made of steel and is fixed to the reaction ring 3 by welding, which can improve the rigidity and shear resistance of the reaction ring 3. The support arm 4 is in a right-angled trapezoid, one of the right-angled sides is fixed to the circumference of the reaction ring 3 and extends along the axial direction of the reaction ring 3, and the other right-angled side is fixed to the bottom plate 1, so that the support arm 4 is perpendicular to the bottom plate 1; there are multiple support arms 4, and one support arm 4 is arranged between two adjacent loading units 6.

[0031] The inner circumference of the reaction ring 3 is equipped with a plurality of loading units 6, the number of the loading units 6 is an even number, and the loading units 6 are centrally symmetrically distributed with respect to the center of the reaction ring 3, the bases of the plurality of loading units 6 are tangent to the inner circumferential surface of the reaction ring 3, the heads of the plurality of loading units 6 extend along the radial direction of the reaction ring 3, and the heads of the plurality of loading units 6 form a circular experimental space, and the experimental space is used to place the tunnel specimen 5. The reaction ring 3 is in the shape of a perfect circle, and the inner circumference has a uniform curvature, so that the contact surfaces between each loading unit 6 and the reaction ring 3 are tangent, so as to facilitate the control of the uniformity of the plurality of loading units 6, and the base of the loading unit 6 is stable, so that the entire loading unit 6 can be stably connected to the tunnel specimen 5.

[0032] Specific as Figure 3 As shown, the loading unit 6 includes a hydraulic device 7, a hard pad 8 and a soft pad 9. The hard pad 8 is fixedly connected to the telescopic rod of the hydraulic device 7; the hard pad 8 overlaps with the soft pad 9, and the length of the hard pad 8 is not less than the thickness of the tunnel specimen 5. The hydraulic device 7 can use a jack with a pressure gauge, and the display screen of the pressure gauge is used to display the output of the hydraulic device 7. The material of the hard pad 8 is steel, the width is preferably 6cm, the length is not more than 0.5m, and the thickness is not less than 3cm. The material of the soft pad 9 is rubber, and the side of the soft pad 9 facing the experimental space is a curved surface to fit the outer peripheral surface of the tunnel specimen 5, and the center thickness of the soft pad 9 is not less than 1cm. The material of the soft pad 9 is relatively soft and deformable, so when the tunnel specimen 5 is not a perfect circle, it can also fit the surface well.

[0033] An elastic base 10 is provided between the hydraulic device 7 and the reaction ring 3. Figure 4 As shown, the elastic base 10 includes a sleeve 11, a slider 12 and a spring 13. The two active ends of the spring 13 are respectively fixed on the sleeve 11 and the slider 12. One end of the slider 12 extends out of the sleeve 11, and the other end of the slider 12 is limited in the sleeve 11. The slider 12 is limited in the sleeve 11 by screwing a collar 14 on the end of the sleeve 11. The sleeve 11 is fixedly connected to the reaction ring 3, and the slider 12 is fixedly connected to the hydraulic device 7. The diameter of the spring 13 is slightly smaller than the inner diameter of the sleeve 11, so that the spring 13 can remain stable during the stretching process to prevent the spring 13 from twisting.

[0034] like Figure 6-Figure 7 As shown, the device of the present invention can make the stress of the lining ring more uniform, rather than concentrated locally, so that the stress distribution of the tunnel lining ring as a whole is more uniform, and the stress data detected by the stress sheet pasted at the non-load action site is representative.

[0035] The test method for using the aforementioned test device to explore the deformation and bearing capacity of the shield tunnel under load is as follows: first, the base plate 1 is fixed to the reaction wall by bolts, so that the entire device including the reaction ring 3 and the loading unit 6 is vertically installed on the reaction wall.

[0036] When loading, the tunnel specimen 5 is placed in the experimental space from the side of the reaction ring 3, and two loading units 6 symmetrically distributed around the center of the reaction ring 3 are used as a group to work synchronously to position the tunnel specimen 5. Among the multiple groups of loading units 6, the loading units 6 on the vertical axis are started first, followed by the loading units 6 on both sides of the vertical axis, and finally the loading units 6 on the horizontal axis. In this way, it can be ensured that the force on the tunnel specimen 5 is symmetrical, the tunnel specimen 5 can be quickly fixed in the reaction ring 3, and the position of the auxiliary tunnel specimen 5 in the reaction ring 3 tends to be centered, so that the extended length of the piston rod of the hydraulic device 7 in each loading unit 6 is within a reasonable range, thereby stabilizing the loading force of the loading unit 6 on the tunnel specimen 5 and improving the accuracy of the test data. When all the loading units 6 are against the tunnel specimen 5, the positioning and clamping of the tunnel specimen 5 are completed.

[0037] During the experiment, a stress plate is attached to the tunnel specimen 5 between two adjacent loading units 6. The loading unit 6 at the bottom of the tunnel specimen 5 maintains the current state, and other loading units 6 simultaneously apply force to the tunnel specimen 5. The reaction force value of the loading unit 6 at the bottom of the tunnel specimen 5 is detected, and the deformation-load relationship and failure law of the tunnel specimen 5 are calculated through the stress value detected by the stress plate and the reaction force value and pressure value detected at the loading unit 6.

[0038] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered as exemplary and non-restrictive in all respects.

Claims

1. A test device for exploring the deformation and bearing capacity of a shield tunnel under load, characterized in that: It comprises a vertical bottom plate, a reaction ring in the shape of a ring is fixed on the front side of the bottom plate, and support arms are fixed on the inner and outer peripheries of the reaction ring; a plurality of loading units are installed on the inner periphery of the reaction ring, the number of the loading units is an even number, and the loading units are centrally symmetrically distributed with respect to the center of the reaction ring, the bases of the plurality of loading units are tangent to the inner peripheral surface of the reaction ring, the heads of the plurality of loading units extend along the radial direction of the reaction ring, and the heads of the plurality of loading units surround a circular experimental space, and the experimental space is used to place tunnel specimens; The loading unit includes a hydraulic device, a hard pad and a soft pad; an elastic base is arranged between the hydraulic device and the reaction ring, the fixed part of the elastic base is fixedly connected to the reaction ring, and the movable part of the elastic base is fixedly connected to the hydraulic device; the hard pad is fixedly connected to the telescopic rod of the hydraulic device; the hard pad overlaps with the soft pad, and the length of the hard pad is not less than the thickness of the tunnel specimen.

2. The test device for exploring the deformation and bearing capacity of a shield tunnel under load according to claim 1 is characterized in that: The support arm is in the shape of a right-angled trapezoid, wherein one right-angled side is fixed to the circumferential surface of the reaction ring and extends along the axial direction of the reaction ring, and the other right-angled side is fixed to the base plate so that the support arm is perpendicular to the base plate; there are multiple support arms, and one support arm is arranged between two adjacent loading units.

3. The test device for exploring the deformation and bearing capacity of a shield tunnel under load according to claim 1 is characterized in that: The reaction ring is made of steel, the outer diameter of the reaction ring is 0.1m larger than the inner diameter so that the reaction ring has a width, and the depth of the reaction ring is greater than the thickness of the tunnel specimen.

4. The test device for exploring the deformation and bearing capacity of a shield tunnel under load according to claim 1 is characterized in that: The material of the hard pad is steel, the material of the soft pad is rubber, the side of the soft pad facing the experimental space is a curved surface, and the center thickness of the soft pad is not less than 1 cm.

5. The test device for exploring the deformation and bearing capacity of a shield tunnel under load according to claim 1 is characterized in that: The elastic base comprises a sleeve, a slider and a spring. Two action ends of the spring are respectively fixed on the sleeve and the slider. One end of the slider extends out of the sleeve, and the other end of the slider is limited in the sleeve.

6. A test method for exploring the deformation and bearing capacity of a shield tunnel under load, characterized in that: The test is carried out on the test device described in any one of claims 1 to 5. First, the bottom plate is fixed to the reaction wall by bolts, so that the entire device including the reaction ring and the loading unit is vertically installed on the reaction wall; when loading, the tunnel specimen is placed in the experimental space from the side of the reaction ring, and two loading units symmetrically distributed around the center of the reaction ring are used as a group to work synchronously to position the tunnel specimen. Among the multiple groups of loading units, the loading unit group on the vertical axis is started first, followed by the loading units on both sides of the vertical axis, and finally the loading units on the horizontal axis; when all the loading units are against the tunnel specimen, the positioning and clamping of the tunnel specimen are completed; during the experiment, a stress plate is attached to the tunnel specimen between two adjacent loading units, the loading unit at the bottom of the tunnel specimen maintains the current state, and other loading units simultaneously apply force to the tunnel specimen, and the reaction force value of the loading unit at the bottom of the tunnel specimen is detected, and the deformability and bearing capacity of the tunnel specimen are calculated by the stress value detected by the stress plate and the reaction force value and pressure value detected at the loading unit.

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