Device and method for simulating influence of reciprocating flow of underground water on concrete crack propagation

Abstract

The invention discloses a device and method for simulating influence of reciprocating flow of underground water on concrete crack propagation, the device comprises a sample box, the sample box comprises a top plate, a bottom plate and two groups of coamings, the two coamings are symmetrically arranged between the top plate and the bottom plate, a sample is placed between the two coamings, and rubber pads are arranged between the coamings and the outer wall of the sample; the top plate and the bottom plate are fixedly connected with water pipes respectively; the output end of the muddy water preparation system is fixedly connected with the water pipe on the bottom plate; the seepage driving system is fixedly connected with the water pipe on the top plate; the seepage flow control system comprises a flow control unit and a controller; a first fixing assembly is arranged between the top plate and the bottom plate, and a second fixing assembly is arranged between the two surrounding plates. According to the method, research on influence of reciprocating scouring of underground water on crack extension of fragile materials such as concrete can be more accurately carried out, and guidance can be provided for content analysis of the evolution process of slurry and water spill diseases of the tunnel bottom structure and the like.

Description

Technical Field

[0001] The invention relates to the technical field of rock mass engineering, in particular to a device and a method for simulating the influence of reciprocating flow of groundwater on the expansion of concrete cracks. Background Art

[0002] Bottom structural diseases such as slurry and water seepage are an important factor affecting the service safety of tunnels. The deterioration of this disease is inseparable from the expansion of seepage channels such as cracks. After the construction of the tunnel, as the service time increases, groundwater will gradually seep to the bottom of the tunnel, forming a water-rich environment. After that, the deformation of the tunnel bottom structure caused by the train load will squeeze the water, causing the groundwater to flow in the rock mass and concrete. When groundwater flows in the cracks, some soluble substances in the concrete (or rock) (such as calcium hydroxide in concrete, soil in the surrounding rock, etc.) will dissolve in water and gradually migrate out of the cracks with the flow of water. In addition, water scouring may also cause the material on the surface of the seepage channel to peel off, and then migrate out of the cracks with the flow of water. The action of these two factors may cause the seepage channel to continue to expand, and then lead to the deterioration of the tunnel bottom structural disease. Accurately understanding the impact of water scouring under train load on the evolution of cracks is helpful to evaluate the service status of the tunnel bottom structure, thereby improving the level of tunnel operation and maintenance and reducing operation risks.

[0003] At present, some progress has been made in the study of the influence of water scouring on concrete (or rock). For example, Reference 1 (Wu Fufei, Shi Kebin, Dong Shuangkuai, et al. Long-term seepage dissolution stability test of plastic concrete [J]. Transactions of the Chinese Society of Agricultural Engineering, 2014, 30(22): 112-119.) used a constant water pressure method to conduct a long-term seepage test; Reference 2 (Zhou Ying, Mu Song, Pu Chunping, et al. Evaluation of anti-scouring dissolution technology and mechanism of action of tunnel primary support concrete [J]. Journal of Materials, 2022, 36(4): 93-100.) used a spraying method to study the calcium dissolution damage of tunnel primary support concrete. However, there is still a lack of research on concrete (or rock) cracks under reciprocating scouring, and there is a lack of relevant test equipment and methods. Although there are test devices for the effect of reciprocating motion of water flow on rock and soil (patents: dynamic water scouring instrument for asphalt mixture, CN102706760A; a high-frequency reciprocating and changing-direction pavement material scouring device and its use method, CN115452639A), it is still impossible to simulate the scouring of concrete (or rock) by the reciprocating flow of water flow, and thus it is impossible to effectively carry out research on the effect of reciprocating scouring of water flow on crack expansion, especially it is impossible to carry out research on the effect of reciprocating scouring of mud-water mixture on crack expansion.

[0004] Based on the above technical problems, the present invention provides a device and method for simulating the influence of reciprocating flow of groundwater on the expansion of concrete cracks. Summary of the invention

[0005] The object of the present invention is to provide a device and method for simulating the influence of reciprocating groundwater flow on the expansion of concrete cracks, so as to solve the problems existing in the prior art.

[0006] To achieve the above object, the present invention provides the following solution: The present invention provides a device for simulating the influence of reciprocating groundwater flow on the expansion of concrete cracks, including:

[0007] Specimen boxes, several groups of which are provided. Each specimen box includes a top plate, a bottom plate and two sets of side plates. The top plate and the bottom plate are arranged opposite to each other. The cross-sectional shape of the side plates is U-shaped. The two side plates are symmetrically arranged between the top plate and the bottom plate. There is a gap between the two side plates. The specimen is placed between the two side plates. A rubber pad is arranged between the side plate and the outer wall of the specimen. Water pipes are fixedly connected to the top plate and the bottom plate respectively;

[0008] A muddy water preparation system, the output end of which is fixedly connected to the water pipe on the bottom plate;

[0009] A seepage driving system, which is fixedly connected to the water pipe on the top plate;

[0010] A seepage flow control system, which includes a flow control unit and a controller. The controller is electrically connected to the flow control unit. The flow control unit is respectively installed on the water pipes of the top plate and the bottom plate;

[0011] Wherein, a first fixing component is arranged between the top plate and the bottom plate, and a second fixing component is arranged between the two side plates.

[0012] According to the device for simulating the influence of reciprocating groundwater flow on the expansion of concrete cracks provided by the present invention, the muddy water preparation system includes a water tank. An inlet is opened at the top of the water tank, and the inlet is connected to an external water source. A stirring system is installed at the bottom of the water tank. The top of the water tank is fixedly communicated with a first circulation pipe. One end of the first circulation pipe is connected to a diversion system, and several specimen boxes are all connected to the diversion system;

[0013] The diversion system includes a main pipe. A number of diversion pipes are fixedly connected to the main pipe. One end of the first circulation pipe is connected to the main pipe, and the water pipes on the bottom plate are respectively fixedly communicated with a number of the diversion pipes.

[0014] According to the device for simulating the effect of reciprocating flow of groundwater on the expansion of concrete cracks provided by the present invention, the seepage driving system comprises a cylinder body, a piston is slidably connected to the cylinder body, a second circulation pipe is fixedly connected to the top of the cylinder body, the second circulation pipe is connected to the water pipe on the top plate through the diversion system, a connecting rod is fixedly connected to the bottom of the piston, and the connecting rod is connected to the driving system;

[0015] The driving system comprises an active motor and a transmission, wherein the output shaft of the active motor is connected to the input shaft of the transmission, the output shaft of the transmission is fixedly connected to a crankshaft, one end of the connecting rod is fixedly connected to a connecting shaft, the connecting shaft is rotatably connected to the crankshaft, and the crankshaft and the connecting shaft are eccentrically matched;

[0016] Wherein, the second circulation pipe is connected to the main pipeline of the diversion system, and the diversion pipe is communicated with the water pipe on the top plate.

[0017] According to the device for simulating the influence of the reciprocating flow of groundwater on the expansion of concrete cracks provided by the present invention, the flow control unit includes a plurality of valves and a plurality of flow meters, the plurality of flow meters are respectively arranged between the water pipe and the diversion pipe on the bottom plate, the plurality of valves are respectively arranged between the water pipe and the diversion pipe on the top plate, and the valves and the flow meters are respectively connected to the controller.

[0018] According to the device for simulating the influence of the reciprocating flow of groundwater on the expansion of concrete cracks provided by the present invention, the second fixing component is provided with two groups, and the second fixing component includes two groups of rib plates and two groups of first screw rods. The two groups of rib plates are respectively arranged on the outer walls of the two groups of enclosure plates away from each other, and abut against the enclosure plates. The two groups of first screw rods and the two groups of rib plates are combined to form a rectangular structure, and the two ends of the first screw rod respectively pass through the two groups of rib plates, and one end of the first screw rod is threadedly connected with a nut.

[0019] According to the device for simulating the influence of the reciprocating flow of groundwater on the expansion of concrete cracks provided by the present invention, the first fixing component includes four groups of second screws, four corners of the top plate are respectively vertically provided with through holes, the four groups of second screws are respectively inserted into the through holes, and the bottom ends of the second screws pass through the bottom plate and are threadedly connected with the nuts.

[0020] According to the device for simulating the influence of the reciprocating flow of groundwater on the expansion of concrete cracks provided by the present invention, a positioning groove is provided on the outer wall of the enclosure, and the positioning groove is arranged along the width direction of the enclosure. The depth of the positioning groove is 1 mm and the width is 10 mm, and the rib plate is clamped in the positioning groove.

[0021] According to the device for simulating the effect of reciprocating flow of groundwater on the expansion of concrete cracks provided by the present invention, square grooves are respectively opened on the top plate and the bottom plate, and the two enclosure plates are both clamped in the square grooves.

[0022] The method for simulating the effect of groundwater reciprocating flow on concrete crack expansion includes the following steps:

[0023] Step 1: Select a sample, record the data of the sample cracks in the initial state, arrange the sample in the sample box, ensure that the cracks of the sample are arranged vertically and correspond to the water pipes on the top plate and the bottom plate respectively, set a rubber pad between the enclosure and the sample, use the first fixing assembly to fix the top plate and the bottom plate, and use the second fixing assembly to fix the two sets of enclosures;

[0024] Step 2: Connect the water pipe on the top plate to the seepage driving system, connect the water pipe on the bottom plate to the mud water preparation system, and arrange the flow control unit between the water pipe on the top plate and the seepage driving system, and between the water pipe on the bottom plate and the mud water preparation system;

[0025] Step 3: The mud water preparation system prepares mud water of a preset concentration, the seepage driving system extracts mud water from the mud water preparation system into the sample box, and the flow control unit controls the flow;

[0026] Step 4: muddy water flows back and forth in the cracks of the sample to simulate the effect of the reciprocating flow of groundwater on the cracks of the sample;

[0027] Step 5: After the experiment, disassemble the sample box, take out the sample, obtain the sample crack data after the reciprocating flow of water, compare it with the initial crack data, analyze the two data, and complete the study on the impact of crack expansion.

[0028] The present invention discloses the following technical effects:

[0029] In the present invention, the mud water preparation system can prepare mud water of different concentrations according to different needs, and control the mud water to flush back and forth in the cracks of the sample through the seepage drive system, so as to simulate the influence of the reciprocating flushing of groundwater on the cracks of the sample.

[0030] The test device and the method of use thereof proposed in the present invention can more accurately carry out research on the influence of reciprocating scouring of groundwater on the crack expansion of brittle materials such as concrete (rock), and can provide guidance for the analysis of the evolution process of slurry and water seepage diseases at the bottom structure of tunnels. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required in the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0032] Figure 1 It is a schematic structural diagram of the device for simulating the influence of reciprocating groundwater flow on the expansion of concrete cracks in the present invention;

[0033] Figure 2 It is a schematic structural diagram of the sample box in the present invention;

[0034] Figure 3 It is a cross-sectional view of the sample box in the present invention.

[0035] Among them, 1. Top plate; 2. Bottom plate; 3. Enclosure plate; 4. Rubber pad; 5. Water pipe; 6. Controller; 7. Water tank; 8. Water inlet; 9. Stirring system; 10. First circulation pipe; 11. Main pipe; 12. Shunt pipe; 13. Cylinder block; 14. Piston; 15. Second circulation pipe; 16. Connecting rod; 17. Driving motor; 18. Transmission; 19. Crankshaft; 20. Connecting shaft; 21. Valve; 22. Flowmeter; 23. Rib plate; 24. First screw; 25. Second screw. Specific embodiments

[0036] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0037] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] Refer to Figure 1-3 , the present invention provides a device for simulating the influence of reciprocating groundwater flow on the expansion of concrete cracks, including:

[0039] A sample box, several groups of sample boxes are provided. The sample box includes a top plate 1, a bottom plate 2, and two groups of enclosure plates 3. The top plate 1 and the bottom plate 2 are arranged opposite to each other. The cross-sectional shape of the enclosure plate 3 is U-shaped. The two enclosure plates 3 are symmetrically arranged between the top plate 1 and the bottom plate 2. There is a gap between the two enclosure plates 3. The sample is placed between the two enclosure plates 3. A rubber pad 4 is provided between the enclosure plate 3 and the outer wall of the sample. Water pipes 5 are fixedly connected to the top plate 1 and the bottom plate 2 respectively;

[0040] A muddy water preparation system, the output end of which is fixedly connected to the water pipe 5 on the bottom plate 2;

[0041] A seepage driving system, the seepage driving system is fixedly connected to the water pipe 5 on the top plate 1;

[0042] A seepage control system, the seepage control system includes a flow control unit and a controller 6, the controller 6 is electrically connected to the flow control unit, and the flow control unit is respectively installed on the water pipes 5 of the top plate 1 and the bottom plate 2;

[0043] Among them, a first fixing component is arranged between the top plate 1 and the bottom plate 2 , and a second fixing component is arranged between the two surrounding plates 3 .

[0044] In the present invention, the mud water preparation system can prepare mud water of different concentrations according to different needs, and control the mud water to flush back and forth in the cracks of the sample through the seepage drive system, so as to simulate the influence of the reciprocating flushing of groundwater on the cracks of the sample.

[0045] The test device and the method of use thereof proposed in the present invention can more accurately carry out research on the influence of reciprocating scouring of groundwater on the crack expansion of brittle materials such as concrete (rock), and can provide guidance for the analysis of the evolution process of slurry and water seepage diseases at the bottom structure of tunnels.

[0046] Further optimizing the scheme, the mud water preparation system includes a water tank 7, a water inlet 8 is opened on the top of the water tank 7, the water inlet 8 is connected to the external water source, a stirring system 9 is installed at the bottom of the water tank 7, and a first circulation pipe 10 is fixedly connected to the top of the water tank 7, one end of the first circulation pipe 10 is connected to the diversion system, and a plurality of sample boxes are connected to the diversion system;

[0047] The diversion system includes a main pipeline 11 , to which a plurality of diversion pipes 12 are fixedly connected. One end of the first circulation pipe 10 is connected to the main pipeline 11 , and the water pipes 5 on the bottom plate 2 are fixedly connected to the plurality of diversion pipes 12 .

[0048] Further optimization scheme, the seepage drive system includes a cylinder 13, a piston 14 is slidably connected in the cylinder 13, a second circulation pipe 15 is fixedly connected to the top of the cylinder 13, the second circulation pipe 15 is connected to the water pipe 5 on the top plate 1 through the diversion system, and a connecting rod 16 is fixedly connected to the bottom of the piston 14, and the connecting rod 16 is connected to the drive system;

[0049] The driving system includes an active motor 17 and a transmission 18. The output shaft of the active motor 17 is connected to the input shaft of the transmission 18. The output shaft of the transmission 18 is fixedly connected to a crankshaft 19. One end of the connecting rod 16 is fixedly connected to a connecting shaft 20. The connecting shaft 20 is rotatably connected to the crankshaft 19, and the crankshaft 19 and the connecting shaft 20 are eccentrically matched.

[0050] The second circulation pipe 15 is connected to the main pipeline 11 of the diversion system, and the diversion pipe 12 is communicated with the water pipe 5 on the top plate 1 .

[0051] The crankshaft 19 is driven to rotate by the active motor 17, and the crankshaft 19 rotates to pull the connecting rod 16, and the connecting rod 16 drives the piston 14 to move in the cylinder body 13. The cylinder body 13 is connected to the second circulation pipe 15. The second circulation pipe 15 is set with the first circulation pipe 10 and the two-group flow system to achieve reciprocating flow of muddy water in the cracks of the samples in the multiple groups of sample boxes, so as to carry out synchronous experiments on multiple groups of samples.

[0052] The stirring system 9 adopts existing technologies, such as a stirring motor in combination with a stirring rod, or a paddle wheel in combination with a motor, and is specifically configured according to actual needs.

[0053] Further optimizing the scheme, the flow control unit includes a plurality of valves 21 and a plurality of flow meters 22, the plurality of flow meters 22 are respectively arranged between the water pipe 5 and the diversion pipe 12 on the bottom plate 2, and the plurality of valves 21 are respectively arranged between the water pipe 5 and the diversion pipe 12 on the top plate 1, and the valves 21 and the flow meters 22 are respectively connected to the controller 6. The controller 6 adopts the existing technology, and the specific model is selected according to the actual needs, and this embodiment does not make a specific limitation.

[0054] A further optimized solution is provided with two groups of second fixing components, and the second fixing components include two groups of ribs 23 and two groups of first screws 24. The two groups of ribs 23 are respectively arranged on the outer walls of the two groups of enclosures 3 on the side away from each other, and abut against the enclosures 3. The two groups of first screws 24 and the two groups of ribs 23 are combined to form a rectangular structure, and the two ends of the first screw 24 pass through the two groups of ribs 23 respectively, and one end of the first screw 24 is threadedly connected with a nut.

[0055] A further optimized solution is that the first fixing assembly includes four groups of second screw rods 25, and through holes are vertically opened on the four corners of the top plate 1. The four groups of second screw rods 25 are respectively inserted into the through holes, and the bottom ends of the second screw rods 25 pass through the bottom plate 2 and are threadedly connected with nuts.

[0056] According to a further optimization scheme, a positioning groove is provided on the outer wall of the enclosure 3, and the positioning groove is arranged along the width direction of the enclosure 3. The depth of the positioning groove is 1 mm and the width is 10 mm. The rib plate 23 is clamped in the positioning groove.

[0057] According to a further optimized solution, square grooves are respectively provided on the top plate 1 and the bottom plate 2, and the two surrounding plates 3 are both snapped into the square grooves.

[0058] The method for simulating the effect of groundwater reciprocating flow on concrete crack expansion includes the following steps:

[0059] Step 1: Select a sample, record the data of the sample cracks in the initial state, arrange the sample in the sample box, ensure that the cracks of the sample are arranged vertically and correspond to the water pipes 5 on the top plate 1 and the bottom plate 2 respectively, arrange a rubber pad 4 between the enclosure 3 and the sample, use a first fixing assembly to fix the top plate 1 and the bottom plate 2, and use a second fixing assembly to fix the two sets of enclosures 3;

[0060] Step 2: Connect the water pipe 5 on the top plate 1 to the seepage driving system, connect the water pipe 5 on the bottom plate 2 to the mud water preparation system, and arrange the flow control unit between the water pipe 5 on the top plate 1 and the seepage driving system, and between the water pipe 5 on the bottom plate 2 and the mud water preparation system;

[0061] Step 3: The mud water preparation system prepares mud water of a preset concentration, the seepage driving system extracts mud water from the mud water preparation system into the sample box, and the flow control unit controls the flow;

[0062] Step 4: muddy water circulates in the cracks of the sample to simulate the effect of groundwater circulation on the cracks of the sample;

[0063] Step 5: After the experiment, disassemble the sample box, take out the sample, obtain the sample crack data after the reciprocating flow of water, compare it with the initial crack data, analyze the two data, and complete the study on the impact of crack expansion.

[0064] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0065] The above embodiments are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A device for simulating the effect of reciprocating groundwater flow on the expansion of concrete cracks, characterized in that: Comprising: Specimen boxes, several groups of which are provided. Each specimen box includes a top plate (1), a bottom plate (2) and two sets of side plates (3). The top plate (1) and the bottom plate (2) are arranged opposite to each other. The cross-sectional shape of the side plate (3) is U-shaped. The two side plates (3) are symmetrically arranged between the top plate (1) and the bottom plate (2). There is a gap between the two side plates (3). The specimen is placed between the two side plates (3). A rubber pad (4) is provided between the side plate (3) and the outer wall of the specimen. Water pipes (5) are fixedly connected to the top plate (1) and the bottom plate (2) respectively; A muddy water preparation system, the output end of which is fixedly connected to the water pipe (5) on the bottom plate (2); A seepage driving system, which is fixedly connected to the water pipe (5) on the top plate (1); A seepage flow control system, which includes a flow control unit and a controller (6). The controller (6) is electrically connected to the flow control unit. The flow control unit is respectively installed on the water pipes (5) of the top plate (1) and the bottom plate (2); Wherein, a first fixing component is provided between the top plate (1) and the bottom plate (2), and a second fixing component is provided between the two side plates (3).

2. The device for simulating the effect of reciprocating groundwater flow on concrete crack expansion according to claim 1, characterized in that: The muddy water preparation system includes a water tank (7). An inlet (8) is opened at the top of the water tank (7), and the inlet (8) is connected to an external water source. A stirring system (9) is installed at the bottom of the water tank (7). The top end of the water tank (7) is fixedly communicated with a first circulation pipe (10). One end of the first circulation pipe (10) is connected to a diversion system, and several specimen boxes are all connected to the diversion system; The diversion system includes a main pipeline (11). A plurality of diversion pipes (12) are fixedly connected to the main pipeline (11). One end of the first circulation pipe (10) is connected to the main pipeline (11), and the water pipes (5) on the bottom plate (2) are respectively fixedly communicated with several diversion pipes (12).

3. The device for simulating the effect of reciprocating groundwater flow on concrete crack expansion according to claim 2, characterized in that: The seepage driving system includes a cylinder block (13). A piston (14) is slidably connected in the cylinder block (13). A second circulation pipe (15) is fixedly connected to the top of the cylinder block (13). The second circulation pipe (15) is communicated with the water pipe (5) on the top plate (1) through the diversion system. A connecting rod (16) is fixedly connected to the bottom of the piston (14), and the connecting rod (16) is connected to a driving system; The driving system includes a driving motor (17) and a transmission (18). The output shaft of the driving motor (17) is connected to the input shaft of the transmission (18). The output shaft of the transmission (18) is fixedly connected to a crankshaft (19). One end of the connecting rod (16) is fixedly connected to a connecting shaft (20). The connecting shaft (20) is rotatably connected to the crankshaft (19), and the crankshaft (19) and the connecting shaft (20) are eccentrically matched; The second circulation pipe (15) is connected to the main pipe (11) of the diversion system, and the diversion pipe (12) is connected to the water pipe (5) on the top plate (1).

4. The device for simulating the effect of reciprocating groundwater flow on concrete crack expansion according to claim 3, characterized in that: The flow control unit comprises a plurality of valves (21) and a plurality of flow meters (22); the plurality of flow meters (22) are respectively arranged between the water pipe (5) and the diversion pipe (12) on the bottom plate (2); the plurality of valves (21) are respectively arranged between the water pipe (5) and the diversion pipe (12) on the top plate (1); and the valves (21) and the flow meters (22) are respectively connected to the controller (6).

5. The device for simulating the effect of reciprocating groundwater flow on concrete crack expansion according to claim 1, characterized in that: The second fixing assembly is provided with two groups, and the second fixing assembly includes two groups of rib plates (23) and two groups of first screw rods (24). The two groups of rib plates (23) are respectively arranged on the outer walls of the two groups of enclosure plates (3) on the side away from each other, and are in contact with the enclosure plates (3). The two groups of first screw rods (24) and the two groups of rib plates (23) are combined to form a rectangular structure, and the two ends of the first screw rod (24) respectively pass through the two groups of rib plates (23), and one end of the first screw rod (24) is threadedly connected with a nut.

6. The device for simulating the effect of reciprocating groundwater flow on concrete crack expansion according to claim 5, characterized in that: The first fixing assembly comprises four groups of second screw rods (25), four corners of the top plate (1) are respectively provided with vertical through holes, the four groups of second screw rods (25) are respectively inserted into the through holes, and the bottom ends of the second screw rods (25) pass through the bottom plate (2) and are threadedly connected to the nuts.

7. The device for simulating the effect of reciprocating groundwater flow on concrete crack expansion according to claim 5, characterized in that: The outer wall of the enclosure (3) is provided with a positioning groove, which is arranged along the width direction of the enclosure (3), has a depth of 1 mm and a width of 10 mm, and the rib plate (23) is clamped in the positioning groove.

8. The device for simulating the effect of reciprocating groundwater flow on concrete crack expansion according to claim 1, characterized in that: The top plate (1) and the bottom plate (2) are respectively provided with square grooves, and the two enclosure plates (3) are both snap-fitted into the square grooves.

9. A method for simulating the effect of reciprocating groundwater flow on the expansion of concrete cracks, based on the device for simulating the effect of reciprocating groundwater flow on the expansion of concrete cracks according to any one of claims 1 to 8, characterized in that: The steps include: Step 1, selecting a sample, recording data of cracks of the sample in an initial state, arranging the sample in a sample box, ensuring that the cracks of the sample are arranged vertically and correspond to the water pipes (5) on the top plate (1) and the bottom plate (2), respectively, arranging a rubber pad (4) between the enclosure plate (3) and the sample, fixing the top plate (1) and the bottom plate (2) with a first fixing assembly, and fixing the two sets of enclosure plates (3) with a second fixing assembly; Step 2: Connect the water pipe (5) on the top plate (1) to the seepage driving system, connect the water pipe (5) on the bottom plate (2) to the mud water preparation system, and arrange the flow control unit between the water pipe (5) on the top plate (1) and the seepage driving system, and between the water pipe (5) on the bottom plate (2) and the mud water preparation system; Step 3: The mud water preparation system prepares mud water of a preset concentration, the seepage driving system extracts mud water from the mud water preparation system into the sample box, and the flow control unit controls the flow; Step 4: muddy water flows back and forth in the cracks of the sample to simulate the effect of the reciprocating flow of groundwater on the cracks of the sample; Step 5: After the experiment, disassemble the sample box, take out the sample, obtain the sample crack data after the reciprocating flow of water, compare it with the initial crack data, analyze the two data, and complete the study on the impact of crack expansion.

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