Concrete creep device capable of adjusting confining pressure

Abstract

The confining pressure adjustable concrete creep device comprises a pressure chamber, the pressure chamber comprises an isolation sleeve, an upper pressure head and a lower pressure head are arranged at the upper end and the lower end of the pressure chamber in a sliding mode respectively, the upper pressure head and the lower pressure head both extend into the isolation sleeve to be matched with a concrete test piece, and an oil cavity is formed between the isolation sleeve and the inner wall of the pressure chamber; an inlet hole and an outlet hole are formed in the pressure chamber, the inlet hole is connected with an energy storage pressure tank through an oil supply pipe, and the energy storage pressure tank is connected with a hydraulic system. Compared with the prior art, axial load is applied through the upper pressure head and the lower pressure head, then the concrete test piece is isolated from hydraulic oil in the oil cavity by matching with the isolation sleeve, the moving upper pressure head and the moving lower pressure head are sealed, confining pressure is applied to the concrete test piece through the hydraulic oil, the overall structure is simple, the manufacturing cost is low, and the manufacturing difficulty is low; popularization and application are convenient. The pressure in the oil cavity can be kept stable for a long time through the hydraulic system and the energy storage pressure tank, and it is ensured that the measured long-term creep deformation of the concrete is more accurate.

Description

Technical Field

[0001] The invention relates to the technical field of concrete creep measurement, in particular to a concrete creep device capable of adjusting confining pressure. Background Art

[0002] Concrete creep is the slow plastic deformation of concrete structures under continuous load over time, which has an important impact on the long-term deformation, stress distribution and durability of engineering structures. Studying the creep behavior under confining pressure (lateral restraint stress) can reveal the changes in the mechanical properties and microscopic mechanisms of materials under triaxial stress states, and provide a basis for the design and safety assessment of actual structures such as underground projects and bridge piers. Existing test devices may have large pressure fluctuations during loading and the confining pressure is difficult to maintain for a long time. In addition, the existing test devices are complex in design and manufacturing, resulting in high costs and difficulty in widespread application. Summary of the invention

[0003] The invention provides a concrete creep device with adjustable confining pressure, which is used to solve the problems that the existing testing device has high cost, large pressure fluctuation during testing, and difficulty in maintaining the confining pressure for a long time.

[0004] The present invention provides a concrete creep device with adjustable confining pressure, comprising a pressure chamber, the pressure chamber comprising an isolation sleeve, upper and lower ends of the pressure chamber are respectively slidably provided with an upper pressure head and a lower pressure head, the upper pressure head and the lower pressure head both extend into the isolation sleeve and cooperate with a concrete test piece, an oil cavity is arranged between the isolation sleeve and the inner wall of the pressure chamber, an inlet hole and an outlet hole are arranged on the pressure chamber, the inlet hole is connected to an energy storage pressure tank through an oil supply pipe, and the energy storage pressure tank is connected to a hydraulic system; pressure edges are extended outwardly from the upper and lower ends of the isolation sleeve, and the two pressure edges are respectively fitted with the top and bottom of the oil cavity; the pressure chamber comprises: a cylinder, an upper end cover and a lower end cover, the upper end cover is threadedly connected to the cylinder, and the upper pressure head extends through the upper end cover into the isolation sleeve in the cylinder.

[0005] Preferably, the pressed edge is in contact with the inner wall of the cylinder.

[0006] Preferably, the lower end cover is threadably connected to the cylinder.

[0007] Preferably, it further comprises a bracket, on which an upper pressure plate and a lower pressure plate which can move up and down are provided, the upper pressure head is arranged below the upper pressure plate, and the lower pressure head is arranged above the lower pressure plate.

[0008] Preferably, a top plate is fixed to the upper end of the bracket, and a jack is provided between the top plate and the upper pressure plate.

[0009] Preferably, a bottom plate is fixed to the upper end of the bracket, and a spring is provided between the lower pressure plate and the bottom plate.

[0010] Preferably, the bracket includes a plurality of positioning screws, the upper pressure plate and the lower pressure plate are respectively slidably connected to the positioning screws, the positioning screws are threadedly connected with a locking nut above the upper pressure plate, and the spring is arranged on the positioning screw between the lower pressure plate and the bottom plate.

[0011] Preferably, the positioning screw is provided with a nut above the top plate.

[0012] Preferably, both the upper pressure head and the lower pressure head are connected with a holder, and a micrometer is provided between the two holders.

[0013] Preferably, the hydraulic system includes: a hydraulic pump, an oil tank and a reversing valve, the oil inlet of the hydraulic pump is connected to the oil tank, the oil outlet of the hydraulic pump is connected to the energy storage pressure tank through a first pipeline, the reversing valve is arranged on the oil supply pipe, and the reversing valve is connected to the oil tank through an oil return pipe.

[0014] Preferably, the hydraulic system further comprises an overflow valve, wherein the overflow valve is arranged on the first pipeline, and the oil return pipe is connected to the overflow valve via a second pipeline.

[0015] Compared with the prior art, the present invention applies axial loads through the upper and lower pressure heads, and then cooperates with the isolation sleeve to form a sealed oil chamber, isolating the concrete specimen from the hydraulic oil in the oil chamber, and sealing the moving upper and lower pressure heads at the same time, so that the concrete specimen can be axially pressed while the hydraulic oil in the oil chamber can also apply confining pressure to the concrete specimen. The overall structure is simple, the design is ingenious, and the manufacturing cost is low. By unscrewing the upper end cover, the isolation sleeve and the concrete specimen can be disassembled and assembled, which reduces the difficulty of promotion and improves the test efficiency. The hydraulic system and the energy storage pressure tank can keep the pressure in the oil chamber stable for a long time, ensuring that the measured long-term creep deformation of the concrete is more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 It is a partial structural schematic diagram of the present invention;

[0018] Figure 2 for Figure 1 The main view;

[0019] Figure 3 for Figure 1 Schematic diagram of some structures;

[0020] Figure 4 for Figure 3 A cross-sectional schematic diagram of

[0021] Figure 5 It is a structural schematic diagram of the present invention;

[0022] Figure 6 It is a structural schematic diagram of the hydraulic system of the present invention.

[0023] Reference numerals:

[0024] 1. Isolation sleeve, 2. Upper pressure head, 3. Lower pressure head, 4. Concrete specimen, 5. Oil chamber, 6. Inlet hole, 7. Outlet hole, 8. Oil supply pipe, 9. Energy storage pressure tank, 10. Hydraulic system, 11. Pressure edge, 12. Cylinder, 13. Upper end cover, 14. Lower end cover, 15. Upper pressure plate, 16. Lower pressure plate, 17. Top plate, 18. Jack, 19. Bottom plate, 20. Spring, 21. Positioning screw, 22. Locking nut, 23. Card seat, 24. Micrometer, 25. Pressure sensor, 26. Hydraulic pump, 27. Oil tank, 100. Pressure chamber, 200. Bracket. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are 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.

[0026] Refer to the attached Figure 2 and attached Figure 4 The present embodiment provides a concrete creep device with adjustable confining pressure, including a pressure chamber 100, the pressure chamber 100 including an isolation sleeve 1, an upper pressure head 2 and a lower pressure head 3 are slidably arranged at the upper and lower ends of the pressure chamber 100, the upper pressure head 2 and the lower pressure head 3 are both extended into the isolation sleeve 1 to cooperate with the concrete specimen 4, the concrete specimen 4 is cylindrical, square or other shapes, an oil cavity 5 is arranged between the isolation sleeve 1 and the inner wall of the pressure chamber 100, the isolation sleeve 1, the upper pressure head 2 and the lower pressure head 3 are enclosed to form a sealed cavity to prevent the hydraulic oil in the oil cavity 5 from contacting the concrete specimen 4, and an inlet hole 6 and an outlet hole 7 are arranged on the pressure chamber 100, refer to the attached Figure 5, the inlet hole 6 is connected to the energy storage pressure tank 9 through the oil supply pipe 8, and the energy storage pressure tank 9 is connected to the hydraulic system 10. The upper and lower ends of the isolation sleeve 1 are extended outward with pressure edges 11, and the two pressure edges 11 are respectively fitted with the top and bottom of the oil chamber 5. The length of the isolation sleeve 1 is greater than the depth of the oil chamber 5. The pressure edges 11 at both ends of the isolation sleeve 1 will fit tightly with the top and bottom of the oil chamber 5. This structure is simple and can effectively prevent the hydraulic oil in the oil chamber 5 from entering the position where the concrete specimen 4 is located. At the same time, it can also effectively prevent the hydraulic oil in the oil chamber 5 from leaking from the upper pressure head 2 or the lower pressure head 3. An embodiment of the pressure chamber 100: refer to the attached Figure 1 The pressure chamber 100 includes a cylinder 12, an upper end cover 13 and a lower end cover 14. The upper end cover 13 and the cylinder 12 are threadedly connected. The upper pressure head 2 passes through the upper end cover 13 and extends into the isolation sleeve 1 in the cylinder 12. The length of the isolation sleeve 1 is greater than the length of the cylinder 12. This structural design facilitates the disassembly and assembly of the concrete specimen 4 and the isolation sleeve 1. The hydraulic system 10 sends the hydraulic oil into the energy storage pressure tank 9, and then the energy storage pressure tank 9 sends it into the oil chamber 5 through the oil supply pipe 8. The energy storage pressure tank 9 is used to buffer the hydraulic oil, thereby stabilizing the pressure in the oil chamber 5 to avoid violent fluctuations. In the present invention, the pressure chamber 100 axially pre-presses the concrete specimen 4 through the upper pressure head 2 and the lower pressure head 3 before applying the confining pressure, and then the hydraulic oil provided by the hydraulic system 10 enters the oil chamber 5 through the energy storage pressure tank 9. When the hydraulic oil comes out of the outlet 7, the valve at the outlet 7 is closed, and the hydraulic system 10 applies the confining pressure to the concrete specimen 4 through the hydraulic oil. When the confining pressure reaches the preset value, the hydraulic system is closed, and the oil pressure of the oil chamber 5 is maintained for a long time through the energy storage pressure tank 9. The overall structure of the present invention is simple and the design is ingenious. On the one hand, the upper pressure head 2 and the lower pressure head 3 apply axial pressure to the concrete specimen 4, and on the other hand, they cooperate with the isolation sleeve 1 to form a sealed oil chamber 5, which completes the isolation of the concrete specimen 4 while also sealing the movable upper pressure head 2 and the lower pressure head 3. While applying axial pressure to the concrete specimen 4, the hydraulic oil in the oil chamber 5 can also apply confining pressure to the concrete specimen 4. Secondly, the cooperation between the hydraulic system 10 and the energy storage pressure tank 9 is conducive to maintaining the stability of the pressure in the oil chamber 5. Third, it is easy to assemble. By unscrewing the upper end cover 13, the isolation sleeve 1 and the concrete test piece 4 can be disassembled and assembled, which reduces the difficulty of promotion and improves the test efficiency.

[0027] Specifically, the gas in the energy storage pressure tank 9 absorbs the oil pressure change by compression or expansion, thereby maintaining the oil pressure in the oil chamber 5 stable. The energy storage pressure tank 9 achieves pressure stability and buffering by compressing air, with a maximum pressure of 20Mpa, and can achieve position control with an accuracy of ±0.05Mpa.

[0028] Specifically, the pressing edge 11 is in contact with the inner wall of the cylinder 12 . This arrangement further improves the sealing performance of the pressure chamber 100 , thereby preventing the hydraulic oil from leaking from the upper pressure head 2 and the lower pressure head 3 and contacting the concrete specimen 4 .

[0029] As another embodiment of the present invention: the lower end cover 14 is threadedly connected to the cylinder 12 .

[0030] As another embodiment of the present invention: this embodiment further includes a bracket 200, on which an upper pressure plate 15 and a lower pressure plate 16 are provided, the upper pressure plate 15 and the lower pressure plate 16 move up and down along the bracket 200, the upper pressure head 2 is provided below the upper pressure plate 15, and the lower pressure head 3 is provided above the lower pressure plate 16. Axial pressure is applied to the concrete specimen 4 by moving the upper pressure plate 15 and the lower pressure plate 16.

[0031] As another embodiment of the present invention: a top plate 17 is fixed to the upper end of the bracket 200 , and a jack 18 is provided between the top plate 17 and the upper pressure plate 15 , and pressure is applied to the upper pressure plate 15 by the jack 18 , thereby applying a load to the concrete specimen 4 .

[0032] As another embodiment of the present invention: a bottom plate 19 is fixed to the upper end of the bracket 200, and a spring 20 is provided between the lower pressure plate 16 and the bottom plate 19. The spring 20 can buffer the load transmitted by the jack 18, thereby ensuring stable transmission of the load.

[0033] An embodiment of the bracket 200: the bracket 200 includes a plurality of positioning screws 21, the upper pressure plate 15 and the lower pressure plate 16 are respectively slidably connected to the positioning screws 21, the positioning screws 21 are threadedly connected with locking nuts 22 above the upper pressure plate 15, and the spring 20 is arranged on the positioning screws 21 between the lower pressure plate 16 and the bottom plate 19. The jack 18 applies a load to the upper pressure plate 15, and when the axial pressure reaches a preset value, the upper pressure plate 15 is tightened by the locking nuts 22 to stabilize the axial load size, and the jack 18 and the top plate 17 can be removed after the load is applied.

[0034] Specifically, the positioning screw 21 is provided with a nut above the top plate 17 , and the positioning screw 21 is provided with a nut below the bottom plate 19 . This structural design facilitates the disassembly and assembly of the top plate 17 and the jack 18 .

[0035] As another embodiment of the present invention: the upper pressure head 2 is connected to the upper pressure plate 15 through a ball joint, and the lower pressure head 3 is connected to the lower pressure plate 16 through a ball joint. In this structural design, the balance is adjusted by the ball joint to ensure that the concrete specimen 4 is evenly stressed during loading.

[0036] As another embodiment of the present invention: a holder 23 is connected to both the upper pressure head 2 and the lower pressure head 3, and the two holders 23 are detachably connected to the upper pressure head 2 and the lower pressure head 3 respectively, and a micrometer 24 is installed between the two holders 23, and the micrometer 24 is used to accurately record the creep data of the concrete specimen 4.

[0037] As another embodiment of the present invention: a first through hole compatible with the upper pressure head 2 is provided on the base 23, one base 23 is sleeved on the upper pressure head 2 through the first through hole, and the other base 23 is sleeved on the lower pressure head 3 through the first through hole; a first locking screw is threadedly connected to the first through hole, and the upper pressure head 2 or the lower pressure head 3 is tightened by the first locking screw, and a second through hole compatible with the micrometer 24 is provided on the base 23, and a second locking screw is threadedly connected to the second through hole, and the second locking screw locks the two ends of the micrometer 24 in the second through hole.

[0038] Specifically, the isolation sleeve 1 is made of a flexible material.

[0039] As another embodiment of the present invention: Figure 6 The hydraulic system 10 includes: a hydraulic pump 26, an oil tank 27 and a reversing valve. The oil inlet of the hydraulic pump 26 is connected to the oil tank 27, and the oil outlet of the hydraulic pump 26 is connected to the energy storage pressure tank 9 through a first pipeline. The reversing valve is arranged on the oil supply pipe 8, and the reversing valve is connected to the oil tank 27 through an oil return pipe.

[0040] As another embodiment of the present invention: the hydraulic system 10 also includes an overflow valve, which is arranged on the first pipeline. The oil return pipe is connected to the overflow valve through the second pipeline. By setting the overflow valve, the oil pressure in the first pipeline is prevented from being too high.

[0041] As another embodiment of the present invention: Figure 3 A pressure sensor 25 is provided between the lower pressure plate 16 and the lower pressure head 3, and the pressure sensor 25 is used to detect the magnitude of the axial load.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A concrete creep device with adjustable confining pressure, characterized in that: It includes a pressure chamber, which includes an isolation sleeve, and an upper pressure head and a lower pressure head are slidably provided at the upper and lower ends of the pressure chamber, respectively, and the upper pressure head and the lower pressure head are both extended into the isolation sleeve to cooperate with the concrete specimen, and an oil cavity is provided between the isolation sleeve and the inner wall of the pressure chamber, and an inlet hole and an outlet hole are provided on the pressure chamber, and the inlet hole is connected to the energy storage pressure tank through an oil supply pipe, and the energy storage pressure tank is connected to the hydraulic system; the upper and lower ends of the isolation sleeve are both extended outward with pressure edges, and the two pressure edges are respectively fitted with the top and bottom of the oil cavity; the pressure chamber includes: a cylinder, an upper end cover and a lower end cover, the upper end cover and the cylinder are threadedly connected, and the upper pressure head passes through the upper end cover and extends into the isolation sleeve in the cylinder.

2. The concrete creep device with adjustable confining pressure according to claim 1, characterized in that: The pressed edge is in contact with the inner wall of the cylinder.

3. The concrete creep device with adjustable confining pressure according to claim 2, characterized in that: The lower end cover is threadedly connected to the cylinder.

4. The concrete creep device with adjustable confining pressure according to claim 3, characterized in that: It also includes a bracket, on which an upper pressure plate and a lower pressure plate that can move up and down are provided, the upper pressure head is arranged below the upper pressure plate, and the lower pressure head is arranged above the lower pressure plate.

5. The concrete creep device with adjustable confining pressure according to claim 4, characterized in that: A top plate is fixed to the upper end of the bracket, and a jack is arranged between the top plate and the upper pressure plate.

6. The concrete creep device with adjustable confining pressure according to claim 5, characterized in that: A bottom plate is fixed to the upper end of the bracket, and a spring is arranged between the lower pressure plate and the bottom plate.

7. The concrete creep device with adjustable confining pressure according to claim 6, characterized in that: The bracket includes a plurality of positioning screws, the upper pressure plate and the lower pressure plate are slidably connected to the positioning screws respectively, the positioning screws are threadedly connected with locking nuts above the upper pressure plate, and the spring is arranged on the positioning screws between the lower pressure plate and the bottom plate.

8. The concrete creep device with adjustable confining pressure according to claim 7, characterized in that: The positioning screw is provided with a nut above the top plate.

9. The concrete creep device with adjustable confining pressure according to claim 8, characterized in that: The upper pressure head and the lower pressure head are both connected with a holder, and a micrometer is arranged between the two holders.

10. The concrete creep device with adjustable confining pressure according to claim 1, characterized in that: The hydraulic system includes: a hydraulic pump, an oil tank and a reversing valve, the oil inlet of the hydraulic pump is connected to the oil tank, the oil outlet of the hydraulic pump is connected to the energy storage pressure tank through a first pipeline, the reversing valve is arranged on the oil supply pipe, and the reversing valve is connected to the oil tank through an oil return pipe.

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