Method for testing shear strength of ice body-HDPE-concrete interface

Abstract

The invention discloses a method for testing shear strength of an ice body-HDPE-concrete interface. The method comprises the following steps: step A, pouring a concrete test block; step B, polishing the pressure-bearing surface of the concrete test block; step C, fixing an HDPE plate on the polished and flattened pressure-bearing surface of the concrete test block to obtain an HDPE-concrete test block; step D, putting the HDPE-concrete test block into a detachable mold box, and adding liquid with the same components as the ice body in the to-be-tested ice body-HDPE-concrete structure into the detachable mold box; the liquid is in contact with the HDPE surface of the HDPE-concrete test block; step E, freezing the detachable mold box in a freezing environment to obtain an ice body-HDPE-concrete test block; f, the ice body-HDPE-concrete test block is placed in a direct shear box of a frozen soil direct shear tester to be subjected to a shear test; and calculating the shear strength according to a shear test result. According to the invention, a test result with high data trueness can be obtained, and the method is simple, rapid and low in cost.

Description

Technical Field

[0001] The invention relates to the technical field of interface shear strength testing, in particular to a method for testing the shear strength of an ice-HDPE-concrete interface. Background Art

[0002] In most areas, the municipal sewage main pump house is connected to the underground sewage pipe, and many vertical shafts along the line are connected to the underground sewage pipe. The sewage pipe is generally a concrete pipe segment with an inner lining structure. The inner surface of the lining is usually a HDPE (high-density polyethylene) material plate, and the vertical shaft is usually a concrete structure. When sewage in the sewage pipe is poured into the sewage main pump house for various reasons, it will affect the normal use of the equipment in the pump house or cause it to be damaged. In order to quickly restore the normal operation of the equipment in the pump house, it is necessary to use liquid nitrogen freezing method to form an ice plug at the intersection of the vertical shaft and the sewage pipe, and then pump water in the downstream main pump house to repair and restore the equipment in the pump house.

[0003] Due to the effect of the upstream and downstream water level difference, when the ice plug is subjected to high head pressure, the ice plug is subjected to shear force along the inner edge of the tunnel due to the effect of water pressure. In order to ensure the stability of the ice plug, it is necessary to obtain the shear strength of the ice plug. At present, the test of the shear strength of the ice plug is mostly in-situ testing. Although the data obtained through the in-situ shear test of the ice plug is more authentic, the cycle of the in-situ test is too long to meet the construction period requirements, and the economic cost required is also high. Therefore, it is necessary to improve the existing test method of the shear strength of the ice plug. Summary of the invention

[0004] Therefore, the technical problem to be solved by the present invention is to provide a simple, fast and low-cost method for testing the shear strength of the ice-HDPE-concrete interface, which method can obtain test results with high data authenticity.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] A method for testing the shear strength of an ice-HDPE-concrete interface comprises the following steps:

[0007] Step A, pouring a concrete test block, and the strength of the concrete test block is the same as the concrete strength in the ice body-HDPE-concrete structure to be tested;

[0008] Step B, grinding the pressure-bearing surface of the concrete test block;

[0009] Step C, fixing the HDPE plate on a flattened pressure-bearing surface of the concrete test block to obtain a HDPE-concrete test block;

[0010] Step D, placing the HDPE-concrete test block into a detachable mold box, and adding a liquid having the same composition as the ice body in the ice body-HDPE-concrete structure to be tested into the detachable mold box; the liquid is in contact with the HDPE surface of the HDPE-concrete test block;

[0011] Step E, placing the detachable mold box in a freezing environment and freezing it to obtain an ice body-HDPE-concrete test block;

[0012] Step F, placing the ice-HDPE-concrete test block in a direct shear box of a frozen soil direct shear tester capable of achieving high-precision temperature control;

[0013] Step G, controlling the internal temperature of the frozen soil direct shear tester according to the design temperature, and applying a vertical pressure consistent with the actual project to the ice body-HDPE-concrete test block;

[0014] Step H, shearing the ice-HDPE-concrete test block until it is damaged;

[0015] Step I: Analyze the interface shear test results of the ice-HDPE-concrete specimen and perform anti-slip calculation of the ice plug.

[0016] In the above method for testing the shear strength of the ice-HDPE-concrete interface, in step A, the concrete test block is a cubic structure with dimensions of 100 mm×100 mm×100 mm (length×width×height);

[0017] In step C, the HDPE board is a rectangular parallelepiped structure with dimensions of 100 mm×100 mm×2 mm (length×width×height). The height of the HDPE board can be adjusted according to different engineering practices. The HDPE board is anchored on a flattened pressure-bearing surface of the concrete test block using expansion screws.

[0018] In step D, the internal space of the detachable mold box is a rectangular parallelepiped structure with dimensions of 100 mm×100 mm×202 mm (length×width×height); the HDPE-concrete test block is placed close to one end of the detachable mold box.

[0019] In the above method for testing the shear strength of the ice-HDPE-concrete interface, in step F, the direct shear box includes an upper box and a lower box; a lower concrete pad is placed at the bottom of the lower box, and an ice-HDPE-concrete test block is placed on the lower concrete pad, and the concrete part of the ice-HDPE-concrete test block is in contact with the lower concrete pad; an upper concrete pad is placed on the ice part of the ice-HDPE-concrete test block, and then an iron pad is placed on the upper concrete pad; the minimum requirement for the strength of the upper concrete pad and the lower concrete pad is that they can withstand the vertical pressure applied in step G without being damaged;

[0020] The sum of the heights of the lower concrete pad and the concrete portion of the ice-HDPE-concrete test block is equal to the height of the lower box, and the sum of the heights of the iron pad, the upper concrete pad and the ice portion of the ice-HDPE-concrete test block is equal to the height of the upper box.

[0021] In the above method for testing the shear strength of the ice-HDPE-concrete interface, in step F, the size of the ice part of the ice-HDPE-concrete test block is 100mm×100mm×100mm (length×width×height), the size of the HDPE board is 100mm×100mm×2mm (length×width×height), the height of the HDPE board can be adjusted according to different engineering practices, and the size of the concrete part is 100mm×100mm×100mm (length×width×height); the size of the upper box is 100mm×100mm×260mm (length×width×height), and the size of the lower box is 100mm×100mm×202mm (length×width×height); the sizes of the upper concrete pad and the lower concrete pad are both 100mm×100mm×100mm (length×width×height), and the size of the iron pad is 100mm×100mm×60mm (length×width×height).

[0022] The present invention reasonably designs the sizes of the ice-HDPE-concrete test block, the upper concrete pad, the lower concrete pad and the iron pad, and controls the size of the ice body in the ice-HDPE-concrete test block, so that when the shear test is performed, the ice body can withstand the vertical pressure transmitted from the iron pad and the upper concrete pad. In addition, compared with the use of a larger upper concrete pad alone, the present invention uses a 100mm×100mm×100mm (length×width×height) upper concrete pad to directly contact the ice body, and uses a 100mm×100mm×60mm (length×width×height) iron pad to directly withstand the vertical pressure consistent with the actual project. The two are superimposed and used as an upper pad, and the flatness, parallelism, surface hardness and roughness are relatively ideal, which can ensure that the test block is slightly deformed and will not be damaged when subjected to axial pressure during the shear test, thereby obtaining a more accurate shear test result.

[0023] In the above method for testing the shear strength of the ice-HDPE-concrete interface, in step B, the pressure-bearing surface of the concrete test block is polished to a flatness tolerance of 0.0005d (d is the side length of the concrete test block). Grinding the pressure-bearing surface of the concrete test block to this flatness can ensure that the concrete test block is tightly attached and anchored to the HDPE board, and can reduce the test error, thereby providing a guarantee for obtaining test data that is closer to the actual situation.

[0024] In the above method for testing the shear strength of the ice-HDPE-concrete interface, in step E, the freezing temperature is -15°C, -20°C and -25°C, or the freezing temperature is other designed freezing wall temperatures; 3 ice-HDPE-concrete test blocks are prepared at each freezing temperature for parallel testing.

[0025] In the above method for testing the shear strength of the ice-HDPE-concrete interface, in step G, the vertical pressure is determined according to the tunnel burial depth and water level; the method for determining the vertical pressure F1 is: F1 = p × s; p is the hydrostatic pressure of the tunnel floor, and s is the area of ​​the pressure-bearing surface of the iron pad. Using this method to determine the vertical pressure of the shear test is not only simple and direct, but also the test results are relatively reliable.

[0026] In the above method for testing the shear strength of the ice-HDPE-concrete interface, in step H, a strain-controlled direct shear apparatus is used to perform shear failure in a quick shear manner with a shear rate of 1.0 mm / min; displacement control is used to determine the shear displacement according to the shear stress peak; when there is no peak, shear to a maximum displacement of 15 mm. The quick shear failure mode is used to simulate the "undrained" shear condition, and the results of the shear test are more consistent with the actual project, thereby ensuring the authenticity of the test data. The present invention selects a strain-controlled direct shear apparatus to obtain a more accurate stress-strain relationship.

[0027] In the above method for testing the shear strength of the ice-HDPE-concrete interface, in step I, the anti-slip calculation method of the ice plug is as follows: (1) Calculate the thrust F exerted on the ice plug on the high head pressure side and the surface area A of the ice plug. s , the calculation formula is: F = γH × A f ;

[0028] Where: γ is the severity; H is the water level difference between the upstream and downstream sides of the ice jam; A f is the cross-sectional area of ​​the tunnel where the ice jam is located;

[0029] (2) Calculate the bonding strength τ between the ice and the tunnel lining HDPE required to maintain the stability of the ice plug; the calculation formula is: τ = F / A s ;

[0030] (3) Calculate the safety factor k, which is the average shear strength τ obtained from the test t The ratio of the bonding strength τ.

[0031] In the above method for testing the shear strength of the ice-HDPE-concrete interface, in step A, the concrete test block is a cubic structure with dimensions of 100 mm×100 mm×100 mm (length×width×height);

[0032] In step B, the pressure-bearing surface of the concrete test block is polished until the flatness tolerance of the pressure-bearing surface is 0.0005d (d is the side length of the concrete test block);

[0033] In step C, the HDPE board is a rectangular parallelepiped structure with dimensions of 100 mm×100 mm×2 mm (length×width×height). The height of the HDPE board can be adjusted according to different engineering practices. The HDPE board is anchored on a flattened pressure-bearing surface of the concrete test block using expansion screws.

[0034] In step D, the internal space of the detachable mold box is a rectangular parallelepiped structure with dimensions of 100 mm×100 mm×202 mm (length×width×height); the HDPE-concrete test block is placed close to one end of the detachable mold box;

[0035] In step E, the freezing temperature is -15°C, -20°C and -25°C; or the freezing temperature is other designed freezing wall temperatures; three ice-HDPE-concrete test blocks are prepared at each freezing temperature for parallel testing;

[0036] In step F, the direct shear box includes an upper box and a lower box; a lower concrete pad is placed at the bottom of the lower box, an ice-HDPE-concrete test block is placed on the lower concrete pad, and the concrete part of the ice-HDPE-concrete test block is in contact with the lower concrete pad; an upper concrete pad is placed on the ice part of the ice-HDPE-concrete test block, and then an iron pad is placed on the upper concrete pad;

[0037] The minimum requirement for the strength of the upper concrete pad and the lower concrete pad is to be able to withstand the vertical pressure applied in step G without being damaged;

[0038] The size of the ice body part of the ice-HDPE-concrete test block is 100mm×100mm×100mm (length×width×height), the size of the HDPE board is 100mm×100mm×2mm (length×width×height), the height of the HDPE board can be adjusted according to the actual situation of different projects, and the size of the concrete part is 100mm×100mm×100mm (length×width×height); the size of the upper box is 100mm×100mm×260mm (length×width×height), and the size of the lower box is 100mm×100mm×202mm (length×width×height); the size of the upper concrete pad and the lower concrete pad are both 100mm×100mm×100mm (length×width×height), and the size of the iron pad is 100mm×100mm×60mm (length×width×height);

[0039] In step G, the method for determining the vertical pressure F1 is: F1 = p × s; p is the hydrostatic pressure of the fluid on the tunnel floor, and s is the area of ​​the pressure-bearing surface of the iron pad;

[0040] In step H, a strain-controlled direct shear apparatus is used to perform shear failure in a rapid shearing manner at a shear rate of 1.0 mm / min; displacement control is used to determine the shear stress peak value, and when there is no peak value, shearing is performed to a maximum displacement of 15 mm;

[0041] In step I, the anti-slip calculation method of the ice plug is:

[0042] (1) Calculate the thrust F on the ice plug at the high head pressure side and the surface area A of the ice plug s , the calculation formula is: F = γH × A f ;

[0043] Where: γ is the severity; H is the water level difference between the upstream and downstream sides of the ice jam; A f is the cross-sectional area of ​​the tunnel where the ice jam is located;

[0044] (2) Calculate the bonding strength τ between the ice and the tunnel lining HDPE required to maintain the stability of the ice plug; the calculation formula is: τ = F / A s ;

[0045] (3) Calculate the safety factor k, which is the average shear strength τ obtained from the test t The ratio of the bonding strength τ.

[0046] The technical solution of the present invention achieves the following beneficial technical effects:

[0047] 1. The method for testing the shear strength of the ice-HDPE-concrete interface of the present invention is simple and easy to operate, requires less equipment, and has the technical advantages of short test time and low cost. It effectively solves the problem of accurately testing the shear strength of the ice-HDPE-concrete interface, reduces the major risks of liquid nitrogen plugging sewage construction, and ensures the safety of liquid nitrogen plugging sewage construction.

[0048] 2. The present invention designs a reasonable size of ice-HDPE-concrete test block, designs a reasonable vertical pressure, and uses direct shear, quick shear and displacement control to conduct shear failure tests on ice-HDPE-concrete test blocks. The test results obtained are relatively close to the results of the in-situ shear test. In addition, the anti-slip calculation method of the ice plug body in the present invention can obtain a more reliable safety factor, so that a reasonable ice plug freezing temperature can be obtained; engineering tests have proved that the freezing temperature finally determined by the method of the present invention for testing the shear strength of the ice-HDPE-concrete interface can fully meet the safety requirements of risk prediction during the construction of liquid nitrogen plugging sewage. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 A schematic diagram of the structure of the ice plug body and the HDPE liner in the pipeline and the shaft in the embodiment of the present invention;

[0050] Figure 2 Actual photos of the anchoring of HDPE and concrete in the embodiment of the present invention;

[0051] Figure 3 A real shot of the concrete-HDPE placed in the mold box after anchoring in the embodiment of the present invention;

[0052] Figure 4 Schematic diagram of the arrangement of ice-HDPE-concrete samples in an embodiment of the present invention;

[0053] Figure 5 Schematic diagram of loading method of ice-HDPE-concrete sample in an embodiment of the present invention. DETAILED DESCRIPTION

[0054] The method of testing the shear strength of the ice-HDPE-concrete interface of the present invention is used in engineering experiments. The specific engineering background is: due to continuous heavy rain, sewage in the municipal sewage pipe of a certain place is poured into the main pump room, causing damage to the equipment in the main pump room; currently, the water depth in the pump room is about 100m. The sewage pipe structure is a 350mm thick steel fiber reinforced concrete pipe segment lining, the inner lining is a 250mm thick concrete structure, a 2mm thick HDPE material is pasted on the inner lining concrete, and the vertical shaft is a 500mm thick concrete structure.

[0055] The municipal sewage pipe plugging project in this area plans to use liquid nitrogen to freeze an ice plug at the intersection of a vertical shaft and a sewage pipe. The strength of the ice plug needs to resist the pressure caused by the water pressure difference between the upstream and downstream, so it is necessary to measure the interface shear strength of the structure formed by the ice plug, HDPE and concrete. After the pump room maintenance is completed, the water level on both sides of the ice plug is balanced, then the ice plug is thawed, and finally the freezer is removed. The structure of the ice plug is shown in Figure 1 .

[0056] The method for testing the shear strength of the ice-HDPE-concrete interface in this embodiment includes the following steps:

[0057] Step A: Cast and maintain a concrete test block with the same structural strength as the actual sewage pipe. The size of the test block is 100mm×100mm×100mm (length×width×height).

[0058] Step B: Grind the bottom of the cured concrete test block and measure its surface flatness to minimize the impact of the uneven concrete surface on the test results. In this embodiment, the pressure-bearing surface of the concrete test block is polished to a flatness tolerance of 0.0005d (d is the side length of the concrete test block); prepare a smooth HDPE plate without a plastic rivet structure, the size of which is 100mm×100mm×2mm (length×width×height).

[0059] Step C: Use expansion bolts to fix the HDPE plate on a flattened bearing surface of the concrete test block to obtain a HDPE-concrete test block (see Figure 2 ).

[0060] Step D: Place the HDPE-concrete test block into the removable mold box (see Figure 3 ), place the HDPE-concrete test block close to one end of the mold box, add liquid with the same composition as the ice body in the ice body-HDPE-concrete structure to be tested into the detachable mold box; the liquid is in contact with the HDPE surface of the HDPE-concrete test block; the internal space of the detachable mold box is a rectangular structure with dimensions of 100 mm×100 mm×202 mm (length×width×height).

[0061] Step E: placing the detachable mold box in a freezing environment of a specimen curing box to freeze, thereby obtaining an ice-HDPE-concrete specimen; the temperature of the curing box was set to -15°C, -20°C and -25°C, respectively, for a total of three temperature test groups, and 3 ice-HDPE-concrete specimens were prepared in each group, for a total of 9 ice-HDPE-concrete specimens.

[0062] Step F: placing the ice-HDPE-concrete test block frozen at the design temperature into a direct shear box of a frozen soil direct shear tester capable of achieving high-precision temperature control; the direct shear box has an outer dimension of 300 mm×300 mm×462 mm (length×width×height); the direct shear box includes a lower box with a dimension of 100 mm×100 mm×202 mm (length×width×height) and an upper box with a dimension of 100 mm×100 mm×260 mm (length×width×height); Place a concrete pad (size 100mm×100mm×100mm(length×width×height)) at the bottom of the direct shear box, then place an ice-HDPE-concrete test block (100mm×100mm×202mm(length×width×height)), with the ice part of the ice-HDPE-concrete test block facing upwards, then place a concrete pad (100mm×100mm×100mm(length×width×height)), and finally place an iron pad. Figure 4 As shown, this ensures that the shear surface of the sample is the bonding surface of ice-HDPE-concrete. The strength of the upper and lower concrete pads (100mm×100mm×100mm (length×width×height)) can withstand the vertical pressure applied in step G without damage.

[0063] Step G: Control the internal temperature of the direct shear apparatus according to the design temperature, apply the designed vertical pressure to the sample, and carry out three parallel tests at each temperature; the vertical pressure F1 is determined as follows: F1=p×s; p is the hydrostatic pressure of the fluid on the tunnel floor, and s is the area of ​​the pressure-bearing surface of the iron pad; the vertical pressure determined in this embodiment is 3.028 kN.

[0064] Step H: Shear the sample to failure: Use a strain-controlled direct shear apparatus to perform shear failure in a rapid shearing manner at a shear rate of 1.0 mm / min; Use displacement control to determine the shear displacement based on the shear stress peak value. When there is no peak value, shear to a maximum displacement of 15 mm;

[0065] Step I: Analyze the shear test results of the ice-HDPE-concrete interface at different temperatures and perform anti-slip calculation of the ice plug; the anti-slip calculation method of the ice plug is as follows: (1) calculate the thrust exerted on the ice plug on the high head pressure side and the surface area of ​​the ice plug; (2) calculate the bond strength between the ice and the tunnel lining HDPE required to maintain the stability of the ice plug; (3) calculate the safety factor, that is, the average shear strength obtained from the test compared with the bond strength.

[0066] In this embodiment, the water level difference between the upstream and downstream sides of the ice plug is 20.6m. After pumping water on one side of the main pump room, the calculation is performed based on the water level difference of 20.6m. At this time, the pressure surface on the upstream side of the ice plug is subjected to the force F:

[0067] F=γH×A f =γH×πr 2 = 9.8×20.6×3.14×2.75 2 =4793.89 kN (1)

[0068] In formula (1), F is the force on the pressure surface on the upstream side of the ice plug; γ is the gravity; H is the water level difference between the upstream and downstream sides of the ice plug, which is 20.6m in this embodiment; A f is the cross-sectional area of ​​the tunnel where the ice plug is located, and r is the radius of the tunnel, which is 2.75 m in this embodiment.

[0069] Surface area A of cylindrical ice plug s :

[0070] A s =2πrL=2×3.14×2.75×3.6=62.17 m 2 (2)

[0071] In formula (2), L is the length of the ice plug in the tunnel, which is 3.6 m in this embodiment.

[0072] The bonding strength τ between the ice body and the tunnel lining HDPE required to maintain the stability of the ice plug is:

[0073] τ=F / A s =77.11 kPa (3)

[0074] Safety factor k:

[0075] k = τt / τ=316 / 77.11=4.098 (4)

[0076] Where: τ t —The average shear strength of the ice-HDPE-concrete test block obtained at a test temperature of -20°C is 316 kPa in this embodiment;

[0077] The shear strength of the ice-HDPE-concrete interface measured by the method of this embodiment at -15°C, -20°C and -25°C is 232 kPa, 316 kPa and 337 kPa respectively. The safety factors calculated in step I are 2.996, 4.098 and 4.370 respectively; the pressure caused by the water pressure difference between the upstream and downstream of the ice plug in the municipal sewage pipeline is 4793.89 kN, and the surface area of ​​the cylindrical ice plug is 62.17 m 2 The bonding strength between the ice body and the tunnel lining HDPE required to maintain the stability of the ice plug is 77.11 kPa. When the average shear strength obtained at the test temperature of -20°C is used, the safety factor is 316 / 77.11=4.098, which is sufficient to meet the engineering requirements. After comprehensive consideration of other factors, it is finally determined that the average temperature of the design freezing wall is -20°C for the construction of the frozen ice plug. After the ice plug is frozen, the main pump room is pumped out for maintenance as planned. The ice plug shows good stability during the entire construction process, indicating that the method of this embodiment is highly reliable in testing the shear strength of the ice body-HDPE-concrete interface and can fully meet the engineering requirements.

[0078] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the claims of this patent application.

Claims

1. A method for testing the shear strength of the ice-HDPE-concrete interface, characterized in that: The steps include: Step A, pouring a concrete test block, and the strength of the concrete test block is the same as the concrete strength in the ice body-HDPE-concrete structure to be tested; Step B, grinding the pressure-bearing surface of the concrete test block; Step C, fixing the HDPE plate on a flattened pressure-bearing surface of the concrete test block to obtain a HDPE-concrete test block; Step D, placing the HDPE-concrete test block into a detachable mold box, and adding a liquid having the same composition as the ice body in the ice body-HDPE-concrete structure to be tested into the detachable mold box; the liquid is in contact with the HDPE surface of the HDPE-concrete test block; Step E, placing the detachable mold box in a freezing environment and freezing it to obtain an ice body-HDPE-concrete test block; Step F, placing the ice-HDPE-concrete test block in a direct shear box of a frozen soil direct shear tester capable of achieving high-precision temperature control; Step G, controlling the internal temperature of the frozen soil direct shear tester according to the design temperature, and applying a vertical pressure consistent with the actual project to the ice body-HDPE-concrete test block; Step H, shearing the ice-HDPE-concrete test block until it is damaged; Step I: Analyze the interface shear test results of the ice-HDPE-concrete specimen and perform anti-slip calculation of the ice plug.

2. The method for testing the shear strength of the ice-HDPE-concrete interface according to claim 1, characterized in that: In step A, the concrete test block is a cubic structure with dimensions of 100 mm × 100 mm × 100 mm in length × width × height; In step C, the HDPE board is a rectangular parallelepiped structure, and the dimensions of length×width×height are 100 mm×100 mm×2 mm; Anchor the HDPE plate to a flattened bearing surface of the concrete test block using expansion screws; In step D, the internal space of the detachable mold box is a rectangular parallelepiped structure with dimensions of 100 mm×100 mm×202 mm in length×width×height; the HDPE-concrete test block is placed close to one end of the detachable mold box.

3. The method for testing the shear strength of the ice-HDPE-concrete interface according to claim 1, characterized in that: In step F, the direct shear box includes an upper box and a lower box; A lower concrete pad is placed at the bottom of the lower box, and an ice-HDPE-concrete test block is placed on the lower concrete pad, with the concrete part of the ice-HDPE-concrete test block in contact with the lower concrete pad; an upper concrete pad is placed on the ice part of the ice-HDPE-concrete test block, and then an iron pad is placed on the upper concrete pad; The minimum requirement for the strength of the upper concrete pad and the lower concrete pad is to be able to withstand the vertical pressure applied in step G without being damaged; The sum of the heights of the lower concrete pad and the concrete portion of the ice-HDPE-concrete test block is equal to the height of the lower box, and the sum of the heights of the iron pad, the upper concrete pad and the ice portion of the ice-HDPE-concrete test block is equal to the height of the upper box.

4. The method for testing the shear strength of the ice-HDPE-concrete interface according to claim 3, characterized in that: In step F, the length × width × height dimensions of the ice body part of the ice body-HDPE-concrete test block are 100 mm × 100 mm × 100 mm, the length × width × height dimensions of the HDPE board are 100 mm × 100 mm × 2 mm, and the length × width × height dimensions of the concrete part are 100 mm × 100 mm × 100 mm; The length × width × height of the upper box is 100mm × 100mm × 260mm, and the length × width × height of the lower box is 100mm × 100mm × 202mm; the length × width × height of the upper concrete pad and the lower concrete pad are both 100mm × 100mm × 100mm, and the length × width × height of the iron pad is 100mm × 100mm × 60mm.

5. The method for testing the shear strength of the ice-HDPE-concrete interface according to claim 1, characterized in that: In step B, the pressure-bearing surface of the concrete test block is polished until the flatness tolerance of the pressure-bearing surface is 0.0005d, where d is the side length of the concrete test block.

6. The method for testing the shear strength of the ice-HDPE-concrete interface according to claim 1, characterized in that: In step E, the freezing temperature is -15°C, -20°C and -25°C; or the freezing temperature is other designed freezing wall temperatures; three ice-HDPE-concrete test blocks are prepared at each freezing temperature for parallel testing.

7. The method for testing the shear strength of the ice-HDPE-concrete interface according to claim 3, characterized in that: In step G, the method for determining the vertical pressure F1 is: F1 = p × s; p is the hydrostatic pressure of the fluid on the tunnel floor, and s is the area of ​​the pressure-bearing surface of the iron pad.

8. The method for testing the shear strength of the ice-HDPE-concrete interface according to claim 1, characterized in that: In step H, a strain-controlled direct shear apparatus is used to perform shear failure in a rapid shearing manner at a shear rate of 1.0 mm / min. Displacement control is used to determine the shear displacement according to the shear stress peak value. When there is no peak value, shearing is performed to a maximum displacement of 15 mm.

9. The method for testing the shear strength of the ice-HDPE-concrete interface according to claim 1, characterized in that: In step I, the anti-slip calculation method of the ice plug is: (1) Calculate the thrust F on the ice plug at the high head pressure side and the surface area A of the ice plug s , the calculation formula is: F = γH × A f ; Where: γ is the severity; H is the water level difference between the upstream and downstream sides of the ice jam; A f is the cross-sectional area of ​​the tunnel where the ice jam is located; (2) Calculate the bonding strength τ between the ice and the tunnel lining HDPE required to maintain the stability of the ice plug; the calculation formula is: τ = F / A s ; (3) Calculate the safety factor k, which is the average shear strength τ obtained from the test t The ratio of the bonding strength τ.

10. The method for testing the shear strength of the ice-HDPE-concrete interface according to any one of claims 3 to 9, characterized in that: In step A, the concrete test block is a cubic structure with dimensions of 100 mm × 100 mm × 100 mm in length × width × height; In step B, the pressure-bearing surface of the concrete test block is polished until the flatness tolerance of the pressure-bearing surface is 0.0005d, where d is the side length of the concrete test block; In step C, the HDPE board is a rectangular parallelepiped structure, and the dimensions of length×width×height are 100 mm×100 mm×2 mm; Anchor the HDPE plate to a flattened bearing surface of the concrete test block using expansion screws; In step D, the internal space of the detachable mold box is a rectangular parallelepiped structure, and the dimensions of length×width×height are 100 mm×100 mm×202 mm; the HDPE-concrete test block is placed close to one end of the detachable mold box; In step E, the freezing temperature is -15°C, -20°C and -25°C; or the freezing temperature is other designed freezing wall temperatures; three ice-HDPE-concrete test blocks are prepared at each freezing temperature for parallel testing; In step F, the direct shear box includes an upper box and a lower box; A lower concrete pad is placed at the bottom of the lower box, and an ice-HDPE-concrete test block is placed on the lower concrete pad, with the concrete part of the ice-HDPE-concrete test block in contact with the lower concrete pad; an upper concrete pad is placed on the ice part of the ice-HDPE-concrete test block, and then an iron pad is placed on the upper concrete pad; The minimum requirement for the strength of the upper concrete pad and the lower concrete pad is to be able to withstand the vertical pressure applied in step G without being damaged; The length × width × height dimensions of the ice part of the ice-HDPE-concrete test block are 100 mm × 100 mm × 100 mm, the length × width × height dimensions of the HDPE board are 100 mm × 100 mm × 2 mm, and the length × width × height dimensions of the concrete part are 100 mm × 100 mm × 100 mm; The length × width × height of the upper box is 100mm × 100mm × 260mm, and the length × width × height of the lower box is 100mm × 100mm × 202mm; the length × width × height of the upper concrete pad and the lower concrete pad are both 100mm × 100mm × 100mm, and the length × width × height of the iron pad is 100mm × 100mm × 60mm; In step G, the method for determining the vertical pressure F1 is: F1 = p × s; p is the hydrostatic pressure of the fluid on the tunnel floor, and s is the area of ​​the pressure-bearing surface of the iron pad; In step H, a strain-controlled direct shear apparatus is used to perform shear failure in a rapid shearing manner at a shear rate of 1.0 mm / min; displacement control is used to determine the shear stress peak value, and when there is no peak value, shearing is performed to a maximum displacement of 15 mm; In step I, the anti-slip calculation method of the ice plug is: (1) Calculate the thrust F on the ice plug at the high head pressure side and the surface area A of the ice plug s , the calculation formula is: F = γH × A f ; Where: γ is the severity; H is the water level difference between the upstream and downstream sides of the ice jam; A f is the cross-sectional area of ​​the tunnel where the ice jam is located; (2) Calculate the bonding strength τ between the ice and the tunnel lining HDPE required to maintain the stability of the ice plug; the calculation formula is: τ = F / A s ; (3) Calculate the safety factor k, which is the average shear strength τ obtained from the test t The ratio of the bonding strength τ.

Images