A device and method for testing the impermeability of a secondary lining joint of an assembled tunnel considering initial defects

Abstract

The application provides a kind of assembled tunnel second lining joint impermeability test device and method considering initial defect, the device includes two test pieces, two test pieces are butted by shear key and slot, water-swelling adhesive strip is arranged in the joint of two test pieces, a rectangular water tank is arranged in the middle of the top surface of two test pieces, the bottom of two test pieces is supported respectively, a cushion beam is arranged on the top surface of each test piece outside the water tank along the direction parallel to the joint, two compression beams are arranged on two cushion beams along the direction perpendicular to the joint, a screw rod is arranged between the two ends of each compression beam and the end of two test pieces away from the joint respectively, and adjusting nut is screwed on the two ends of each screw rod;A cover plate is fixedly installed on the water tank, and a water injection hole, an exhaust hole and a pressure gauge connection hole are arranged on the cover plate. During the test, the initial defect angle of two test pieces is generated by tightening the adjusting nut, water is injected into the water tank through the water injection hole to test the influence of initial angle defect on the impermeability of the joint. The application can truly reflect the impermeability of the joint of tunnel second lining under actual construction error.

Description

Technical Field

[0001] This invention belongs to the field of tunnel construction technology and relates to a test of the impermeability of prefabricated tunnel secondary lining structure, specifically to a test device and method for the impermeability of prefabricated tunnel secondary lining joint considering initial defects. Background Technology

[0002] Prefabricated tunnel lining structures are assembled from multiple precast components, with circumferential or longitudinal joints between them. These joints are not only crucial for stress transfer between components but also the weakest points where groundwater leakage is most likely to occur. Shear keys or tongue-and-groove joints are typically used at the joints of precast components, allowing for butt jointing during assembly. Water-swellable rubber strips are also installed at the joints. To ensure effective impermeability at the joints, impermeability tests are required before actual assembly and construction.

[0003] During the actual installation of precast tunnel lining components, a certain gap is usually maintained between adjacent components to accommodate temperature deformation, concrete shrinkage and creep, and grouting requirements. Existing joint impermeability tests often focus on the performance of the sealing material under ideal installation conditions or simply increase water pressure to observe leakage. However, errors sometimes occur during the actual assembly of precast components, often leading to initial defects such as slight rotations or uneven joint opening after installation. Therefore, the impermeability of the joint depends not only on the water-swellable rubber strip but also on the initial defects caused by construction errors. If, in the impermeability test, a shim is inserted at the shear key to simulate this initial rotation, the actual contact path of the shear key will be disrupted. Since the shear key itself serves positioning and force transmission functions, the test results cannot accurately reflect the impermeability under the influence of actual construction errors. Summary of the Invention

[0004] The purpose of this invention is to address the above-mentioned problems by providing a test device and method for the impermeability of prefabricated tunnel secondary lining joints that takes into account initial defects. Under the premise of truly preserving the shear key structure, a quantifiable initial corner defect is formed, and impermeability testing is carried out under the condition of the initial defect.

[0005] This invention provides a prefabricated tunnel secondary lining joint impermeability test device considering initial defects, characterized by: two square specimens, one specimen having a shear key at one end and the other specimen having a slot at one end, the two specimens being joined together by the shear key and the slot; a water-swellable rubber strip being provided above the shear key in the joint between the two specimens; a rectangular water tank being provided in the middle of the top surface of the two specimens at the joint; supports being provided at the bottom of the two specimens to stably support them; a pad beam being provided on the outer side of the water tank of each specimen along a direction parallel to the joint; two pressure beams being erected on the two pad beams along a direction perpendicular to the joint; a screw rod being threaded through both ends of each pressure beam between the ends of the two specimens away from the joint; adjusting nuts being screwed to the top surface of the pad beam and the bottom surface of the specimen at both ends of each screw rod; a cover plate being provided on the water tank; a sealing strip being provided around the bottom perimeter of the cover plate; the cover plate being pressed onto the specimen by multiple bolts that penetrate vertically through the specimen; and a water injection hole, a vent hole, and a pressure gauge connection hole being provided on the cover plate.

[0006] Furthermore, the aforementioned test device for the impermeability of prefabricated tunnel secondary lining joints, which takes into account initial defects, has a specimen thickness of 50cm and a length and width of 1m. The joint between the two specimens is consistent with the joint structure of the actual prefabricated tunnel secondary lining.

[0007] Furthermore, in the aforementioned test device for the impermeability of prefabricated tunnel secondary lining joints that takes into account initial defects, the distance between the two pad beams and the joints of the two specimens can be equal or unequal.

[0008] The test method using the above-mentioned prefabricated tunnel secondary lining joint impermeability test device considering initial defects is characterized by comprising the following steps:

[0009] (1) Specimen assembly: The two specimens are spliced ​​together by shear keys and slots at the ends of the two specimens. When splicing, a certain gap is left at the joint between the two specimens to simulate the actual assembly state of the tunnel secondary lining prefabricated components; to ensure that the two specimens are stably supported on the support.

[0010] (2) Place pad beams and pressure beams on the two specimens in sequence, install the screw between the pressure beam and the specimen, and screw adjusting nuts at both ends of the screw. Do not tighten the adjusting nuts at first.

[0011] (3) Preset the initial defect angle value of the specimen according to the test target; gradually tighten the adjusting nut at the end of the pressure beam with a wrench so that the pressure beam applies an upward tension to the specimen, and at the same time the pressure beam applies a downward pressure to the specimen through the pad beam, so that the joint end of the two specimens will generate vertical displacement and form an angle; control the tightening amount of the adjusting nut so that the two specimens reach the preset initial angle defect value.

[0012] (4) Install a cover plate on the water tank at the top of the specimen and tighten it with bolts;

[0013] (5) Seal the sides and top of the joint with adhesive strips or sealant; connect the water inlet on the cover plate to the pressurized water supply system, connect the pressure gauge connection hole to the pressure gauge or pressure sensor, and open the water outlet; inject water into the water tank at low pressure from the water inlet, and close the water outlet after the water outlet is continuously flowing out and there are no obvious bubbles.

[0014] (6) Gradually increase the water pressure, and stabilize the pressure for no less than 20 minutes at each level; during the pressure stabilization period, record the pressure, stabilization time, whether there are wet marks, water droplets, linear seepage or through seepage on the joint surface, and collect the leakage per unit time; when through seepage occurs, the leakage per unit time exceeds the preset threshold, the pressure cannot be maintained or the maximum water pressure set for the test is reached, stop water injection and end the test.

[0015] Furthermore, in the above method, the distance between the pad beams at the top of the two specimens and the joint can be changed to produce different vertical displacements at the joint ends of the two specimens.

[0016] Furthermore, in the above method, a displacement measuring point is set on each side of the joint. The initial rotation angle defect is quantified by the positional change of the two displacement measuring points. The arctangent value of the relative vertical displacement difference between the two displacement measuring points and the distance between the measuring points is taken as the initial rotation angle. Let the distance between the two displacement measuring points be L, and the vertical displacements of the two measuring points be u1 and u2, respectively. Then the initial rotation angle of the joint is calculated according to θ=arctan[(u1-u2) / L]. When θ is small, the ratio of the relative vertical displacement difference between the two measuring points to the distance between the measuring points is taken as the initial rotation angle, and it is calculated according to θ≈(u1-u2) / L.

[0017] Furthermore, in the above method, the adjusting nut is tightened in a graded and alternating manner. After each grade of tightening, the displacement value of the displacement measuring points on both sides of the joint is read, and the initial rotation angle θ is calculated.

[0018] Furthermore, in the above method, after the initial angle defect reaches the set value, a stability judgment is made. If the initial angle change rate is not greater than 5% within a holding time of not less than 10 minutes, or the vertical displacement difference between the two measuring points is not greater than 0.02 mm, the initial angle defect is determined to be stable. If the stability condition is not met, the tightening amount of the adjusting bolt is further fine-tuned.

[0019] Furthermore, in the above method, when gradually increasing the water pressure, the pressure is applied in increments of 0.05 MPa to 0.10 MPa.

[0020] The above method may further include the following steps:

[0021] (8) Set different initial corner defect values ​​according to the purpose of the test, and repeat the test according to the methods of steps (1) to (7).

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] First, by applying symmetrical self-balancing vertical forces to the two components to form an initial defect, there is no need to insert shims at the shear key, and the actual shear key contact path will not be destroyed.

[0024] Second, the initial corner defects can be directly quantified by the displacement difference between the two sides of the joint, which makes it easier to establish a quantitative relationship between the degree of defects and the impermeability.

[0025] Third, the steel cover plate is embedded in the non-continuous groove to form a local water pressure chamber, which can be used to focus on the leakage behavior in the key areas of the joint.

[0026] Fourth, the test device has a simple structure, is easy to manufacture and install, and is suitable for conducting multiple sets of repeated tests;

[0027] Fifth, the test method organically combines the formation of initial defects, determination of defect stability, sealing of cover plate and progressive water pressure loading, which is more conducive to evaluating the degradation law of the impermeability of prefabricated tunnel secondary lining joints under construction error conditions. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the elevation structure of the test device of the present invention;

[0029] Figure 2 This is a schematic diagram of the planar structure of the test apparatus of the present invention;

[0030] Figure 3 This is a schematic diagram of the specimen without a cover plate on its top surface.

[0031] Reference numerals: 1. Specimen; 2. Shear key; 3. Joint; 4. Water-swellable rubber strip; 5. Water tank; 6. Support; 7. Pad beam; 8. Pressure beam; 9. Screw; 10. Adjusting nut; 11. Cover plate; 12. Bolt; 13. Water injection hole; 14. Vent hole; 15. Pressure gauge connection hole. Detailed Implementation

[0032] like Figure 1 , Figure 2 , Figure 3As shown, the present invention provides a test device for the impermeability of prefabricated tunnel secondary lining joints considering initial defects, comprising two square specimens 1, one specimen having a shear key 2 at one end and the other specimen having a slot at one end, the two specimens being joined together by the shear key and the slot, a water-swellable rubber strip 4 being provided above the shear key in the joint 3 of the two specimens, a rectangular water trough 5 being provided in the middle of the top surface of the two specimens at the joint, and supports 6 being provided at the bottom of the two specimens respectively to stably support the two specimens; the top surface of each specimen 1 is parallel to the two square specimens along the outer edge of the water trough. A pad beam 7 is provided in the direction of the joint of the specimen. Two pressure beams 8 are erected on the two pad beams 7 in the direction perpendicular to the joint. Each pressure beam 8 has a screw 9 inserted between its two ends and the ends of the two specimens away from the joint. Adjusting nuts 10 are screwed to the top surface of the pad beam and the bottom surface of the specimen at both ends of each screw 9. A cover plate 11 is provided on the top of the water tank 5. A sealing strip is provided around the bottom of the cover plate. The cover plate 11 is pressed onto the specimen by multiple bolts 12 that penetrate the specimen vertically. The cover plate has a water injection hole 13, a vent hole 14 and a pressure gauge connection hole 15.

[0033] In a specific implementation of the present invention, a U-shaped groove can be provided at the top of the joint end of the two test pieces respectively, and the rectangular water tank 5 is formed after the two test pieces are joined together.

[0034] The test specimens can be manufactured according to the actual dimensions of prefabricated blocks for prefabricated tunnel lining. Each specimen is 50cm thick, 1m long and 1m wide, and the joint between two specimens is consistent with the joint structure of the actual prefabricated tunnel lining. The water-swellable rubber strip above the shear key completely simulates the water-stopping structure of the actual lining joint.

[0035] The distance between the two pad beams 7 and the joints of the two specimens can be equal or unequal.

[0036] The method for conducting permeability tests using the prefabricated tunnel secondary lining joint permeability testing device that considers initial defects is as follows:

[0037] (1) Specimen assembly: Two specimens are spliced ​​together by shear keys and slots at the ends of the two specimens. When splicing, a certain gap is left between the two specimens to simulate the actual assembly state of the tunnel secondary lining prefabricated components; to ensure that the two specimens are stably supported on the support.

[0038] (2) Place pad beams and pressure beams on the two specimens in sequence. The two ends of the pressure beams extend to the top of one end of the joint of the specimen. The specimens have pre-set screw through holes. Screws are inserted between the two ends of the pressure beams and the specimens. Adjusting nuts are screwed to both ends of the screws. The adjusting nuts are not tightened at first.

[0039] (3) Preset the initial defect angle value of the specimen according to the test target; gradually tighten the adjusting nut at the end of the pressure beam with a wrench so that the pressure beam applies an upward tension to the end of the specimen away from the joint, and at the same time, the pressure beam applies a downward pressure to the joint end of the specimen through the pad beam, so that the joint ends of the two specimens produce vertical displacement and form an angle; control the tightening amount of the adjusting nut so that the two specimens reach the preset initial angle defect value. Alternatively, the distance between the pad beam at the top of the two specimens and the joint can be changed to produce different vertical displacements at the joint ends of the two specimens to form the test target angle.

[0040] When a corner is formed, a displacement measuring point can be set on each side of the joint. The initial corner defect is quantified by the positional changes of the two displacement measuring points. The specific method is as follows:

[0041] The initial rotation angle is taken as the arctangent of the relative vertical displacement difference between two displacement measuring points and the distance between the measuring points, or as the ratio of the relative vertical displacement difference between the two measuring points to the distance between the measuring points. Let the distance between the two displacement measuring points be L, and the measured vertical displacements of the two measuring points be u1 and u2, respectively. Then the initial rotation angle of the joint is calculated as θ=arctan[(u1-u2) / L]; when θ is small, it can be calculated as θ≈(u1-u2) / L.

[0042] In practice, the adjusting nut can be tightened in stages and alternately. After each stage of tightening, the displacement value of the displacement measuring points on both sides of the joint is read, and the initial rotation angle θ is calculated.

[0043] In practice, after the initial angle defect reaches the set value, a stability judgment is made. If the rate of change of the initial angle is not greater than 5% within a holding time of not less than 10 minutes, or the difference in vertical displacement between the two measuring points is not greater than 0.02 mm, the initial angle defect is determined to be stable. If the stability condition is not met, the tightening amount of the adjusting bolt is further fine-tuned.

[0044] (4) After a stable experimental target angle is formed, a cover plate is installed on the water tank at the top of the specimen. A sealing strip is set around the bottom of the cover plate. Multiple pre-set vertical bolt holes are installed on the specimen. The cover plate is fastened to the specimen by bolts.

[0045] (5) Seal the sides and top of the joint with adhesive strips or sealant to prevent water from overflowing from the sides or top of the joint when filling the water tank. Connect the water inlet on the cover plate to the pressurized water supply system, connect the pressure gauge connection hole to the pressure gauge or pressure sensor, and open the water outlet. Fill the water tank with water at low pressure through the water inlet, and close the water outlet after water flows out continuously without obvious bubbles.

[0046] (6) Gradually increase the water pressure, specifically by applying pressure increments from 0.05 MPa to 0.10 MPa. Stabilize the pressure at each level for no less than 20 minutes. During the stabilization period, record the pressure, stabilization time, whether wet marks, water droplets, linear seepage, or through-flow appear on the joint surface, and collect the leakage per unit time. When through-flow occurs, the leakage per unit time exceeds the preset threshold, the pressure cannot be maintained, or the maximum water pressure set for the test is reached, stop water injection and end the test.

[0047] Furthermore, the above method can be further improved by setting different initial corner defect values ​​according to the purpose of the test, and repeating the test according to the methods of steps (1) to (7) above.

[0048] Finally, using leakage initiation pressure, stable leakage rate, maximum holding pressure, pressure decay rate, and final leakage morphology as evaluation indicators, the degradation relationship of joint impermeability under different initial corner defects was established.

Claims

1. A test device for the impermeability of prefabricated tunnel secondary lining joints considering initial defects, characterized in that: The test includes two square specimens. One specimen has a shear key at one end, and the other has a slot at one end. The two specimens are joined together by the shear key and the slot. A water-swellable rubber strip is installed above the shear key in the joint between the two specimens. A rectangular water tank is installed in the middle of the top surface of the two specimens at the joint. Supports are installed at the bottom of the two specimens to stably support them. A pad beam is installed on the outer side of the water tank of each specimen along the direction parallel to the joint. Two pressure beams are installed on the two pad beams along the direction perpendicular to the joint. A screw is inserted between the two ends of each pressure beam and the ends of the two specimens away from the joint. Adjusting nuts are screwed to the top surface of the pad beam and the bottom surface of the specimen at the two ends of each screw. A cover plate is installed on the water tank. A sealing strip is installed around the bottom of the cover plate. The cover plate is pressed onto the specimen by multiple bolts that penetrate the specimen vertically. The cover plate has a water injection hole, a vent hole, and a pressure gauge connection hole.

2. The prefabricated tunnel secondary lining joint impermeability test device considering initial defects according to claim 1, characterized in that: Each specimen is 50cm thick and 1m long and wide. The joint between the two specimens is consistent with the joint structure of the actual prefabricated tunnel lining.

3. The prefabricated tunnel secondary lining joint impermeability test device considering initial defects according to claim 1, characterized in that: The distances between the two pad beams and the joints of the two specimens may be equal or unequal.

4. A test method for the impermeability of prefabricated tunnel secondary lining joints considering initial defects, using the test apparatus described in any one of claims 1 to 3, characterized in that, Includes the following steps: (1) Specimen assembly: The two specimens are spliced ​​together by shear keys and slots at the ends of the two specimens. When splicing, a certain gap is left at the joint between the two specimens to simulate the actual assembly state of the tunnel secondary lining prefabricated components; to ensure that the two specimens are stably supported on the support. (2) Place pad beams and pressure beams on the two specimens in sequence, install the screw between the pressure beam and the specimen, and screw adjusting nuts at both ends of the screw. Do not tighten the adjusting nuts at first. (3) Preset the initial defect angle value of the specimen according to the test target; gradually tighten the adjusting nut at the end of the pressure beam with a wrench so that the pressure beam applies an upward tension to the specimen, and at the same time the pressure beam applies a downward pressure to the specimen through the pad beam, so that the joint end of the two specimens will generate vertical displacement and form an angle; control the tightening amount of the adjusting nut so that the two specimens reach the preset initial angle defect value. (4) Install a cover plate on the water tank at the top of the specimen and tighten it with bolts; (5) Seal the sides and top of the joint with adhesive strips or sealant; connect the water inlet on the cover plate to the pressurized water supply system, connect the pressure gauge connection hole to the pressure gauge or pressure sensor, and open the water outlet; inject water into the water tank at low pressure from the water inlet, and close the water outlet after the water outlet is continuously flowing out and there are no obvious bubbles. (6) Gradually increase the water pressure, and stabilize the pressure for no less than 20 minutes at each level; during the pressure stabilization period, record the pressure, stabilization time, whether there are wet marks, water droplets, linear seepage or through seepage on the joint surface, and collect the leakage per unit time; when through seepage occurs, the leakage per unit time exceeds the preset threshold, the pressure cannot be maintained or the maximum water pressure set for the test is reached, stop water injection and end the test.

5. The test method for impermeability of prefabricated tunnel secondary lining joints considering initial defects according to claim 4, characterized in that: By changing the distance between the pad beams at the top of the two specimens and the joint, different vertical displacements are generated at the joint ends of the two specimens.

6. The test method for impermeability of prefabricated tunnel secondary lining joints considering initial defects according to claim 4, characterized in that: A displacement measuring point is set on each side of the joint. The initial rotation angle defect is quantified by the position change of the two displacement measuring points. The arctangent value of the relative vertical displacement difference between the two displacement measuring points and the distance between the measuring points is taken as the initial rotation angle. Let the distance between the two displacement measuring points be L, and the vertical displacements of the two measuring points be u1 and u2, respectively. Then the initial rotation angle of the joint is calculated according to θ=arctan[(u1-u2) / L]. When θ is small, the ratio of the vertical displacement difference between the two measuring points to the distance between the measuring points is taken as the initial rotation angle, and it is calculated according to θ≈(u1-u2) / L.

7. The test method for impermeability of prefabricated tunnel secondary lining joints considering initial defects according to claim 6, characterized in that: The adjusting nut is tightened in stages and alternately. After each stage of tightening, the displacement value of the displacement measuring points on both sides of the joint is read, and the initial rotation angle θ is calculated.

8. The test method for impermeability of prefabricated tunnel secondary lining joints considering initial defects according to claim 6, characterized in that: After the initial angle defect reaches the set value, a stability judgment is made. If the rate of change of the initial angle is not greater than 5% within a holding time of not less than 10 minutes, or the difference in vertical displacement between the two measuring points is not greater than 0.02 mm, the initial angle defect is determined to be stable. If the stability condition is not met, the tightening amount of the adjusting bolt is further fine-tuned.

9. The test method for impermeability of prefabricated tunnel secondary lining joints considering initial defects according to claim 4, characterized in that: When gradually increasing the water pressure, apply pressure increments ranging from 0.05 MPa to 0.10 MPa.

10. The test method for impermeability of prefabricated tunnel secondary lining joints considering initial defects according to claim 4, characterized in that, Further steps include: (8) Set different initial corner defect values ​​according to the purpose of the test, and repeat the test according to the methods of steps (1) to (7).

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