Device for testing failure permeability of concrete under combined action of load and water pressure

Abstract

The invention relates to a device for testing the failure permeability of concrete under the combined action of load-water pressure, which comprises a sample and a loading piece abutted against the sample, the loading piece is provided with a water delivery channel, one end of the water delivery channel is communicated with a water supply assembly, and the other end of the water delivery channel is communicated with the surface of the sample. The pressure applying mechanism is used for performing stress loading on the loading piece, and the stress loading direction of the pressure applying mechanism to the loading piece is the same as the water pressure bearing direction of the sample. According to the invention, the defects that in the prior art, only a compression test based on a single stress state can be carried out on concrete and the influence of seepage pressure cannot be considered synchronously with a triaxial compression penetration test are overcome, and a brand new test platform is provided for researching the anti-cracking and anti-seepage performance of the concrete; the mechanical property, the permeability and the damage characteristic of the concrete can be systematically researched under the coupling action of water pressure and stress, and the device has high applicability and wide engineering application prospects.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of concrete failure test, in particular to a concrete failure and permeability test device under the combined action of load and water pressure. BACKGROUND

[0002] With the rapid development of cities, the subway has become an important infrastructure to improve the efficiency of city operation and reduce traffic congestion. However, the land resources in the city center are scarce, and the environment of the subway station is becoming more and more complex. A large number of subway stations have frequent water leakage problems due to the water-rich stratum environment. Due to the characteristics of high groundwater level and strong permeability, the side wall of the subway station is subjected to the combined action of water pressure and ground stress for a long time. It is difficult to meet the long-term waterproofing requirements by relying solely on external waterproofing measures, and the impermeability of concrete under load needs to be considered.

[0003] At present, the related research of concrete is mostly focused on the influence of steel mesh, steel fiber, glass fiber, polypropylene fiber and admixture on its mechanical properties through conventional mechanical tests. However, such research is often based on a single stress state, and it is difficult to truly reflect the impermeability of concrete under the combined action of load and water pressure in a water-rich environment.

[0004] Some scholars use triaxial compression permeation tests to analyze the failure process and permeability evolution of concrete under different conditions. However, in existing tests, the water pressure loading direction is usually inconsistent with the stress loading direction, and the water pressure is only applied as a confining pressure condition, which fails to truly simulate the cracking and leakage behavior of concrete under the combined action of load and water pressure. In addition, due to the small size of the test block in the triaxial compression permeation test, the research scope is also limited. SUMMARY

[0005] The purpose of the present application is to overcome the shortcomings of the prior art and provide a concrete failure and permeability test device under the combined action of load and water pressure, which can systematically study the mechanical properties, permeability and failure characteristics of concrete under the combined action of water pressure and stress. The problem of the traditional test device that cannot truly reflect the impermeability of concrete under the combined action of load and water pressure in a water-rich environment is solved.

[0006] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows: A concrete failure and permeability test device under the combined action of load and water pressure, comprising a test sample and a loading piece abutting with the test sample, a water delivery channel is formed on the loading piece, one end of the water delivery channel is in communication with a water supply assembly, and the other end is in communication with the surface of the test sample. The water pressure loading to the test sample is realized through the water supply assembly. The device further comprises a pressure applying mechanism for stress loading to the loading piece, and the stress loading direction of the pressure applying mechanism to the loading piece is the same as the direction of the water pressure bearing of the test sample.

[0007] Further, the loading pieces are multiple and abut against each other in the water pressure loading direction, multiple holes are uniformly arranged on each loading piece, the holes on different loading pieces are communicated with each other to form a water delivery channel, the holes on the outer loading pieces are communicated with the water supply assembly, the hole density on different loading pieces gradually increases along the water pressure loading direction, and the stress loading mechanism loads stress on the outer loading pieces.

[0008] Further, the loading piece comprises an upper loading piece and a lower loading piece, and the lower loading piece is located between the upper loading piece and the sample; the upper loading piece comprises an upper loading plate, multiple blind holes are uniformly arranged on the upper loading plate, adjacent blind holes are communicated with each other, the blind holes are communicated with the water supply assembly, and the openings of the blind holes face the lower loading piece; and the lower loading piece comprises a lower loading plate, multiple through holes are uniformly arranged on the lower loading plate, and adjacent through holes are communicated with each other.

[0009] Further, the upper loading piece further comprises an upper sealing connecting net with a porous structure between the upper loading plate and the lower loading plate.

[0010] Further, the lower loading piece further comprises a lower sealing connecting net with a porous structure between the lower loading plate and the sample.

[0011] Further, the stress loading direction of the stress loading mechanism to the loading piece and the water pressure bearing direction of the sample are both vertical directions, and the water delivery channel on the loading piece is communicated with the water supply assembly in the horizontal direction.

[0012] Further, the stress loading mechanism is a press machine, and the press machine comprises an upper pressing plate for loading stress on the loading piece and a workbench for placing and supporting the sample.

[0013] Further, a water seepage collecting groove is further arranged at the lower part of the sample.

[0014] Further, the water supply assembly comprises a water supply pump and a water supply tank, and the water delivery channel on the loading piece is connected with the water supply pump and the water supply tank through a water delivery pipeline.

[0015] Further, a data acquisition and monitoring system for monitoring and recording test data in real time is further arranged.

[0016] Compared with the prior art, the present application has the following beneficial effects: The present application overcomes the problem that the prior art can only carry out compression test based on a single stress state and cannot consider the influence of seepage pressure simultaneously with triaxial compression seepage test, and provides a new test platform for studying the anti-seepage performance of concrete, and can systematically study the mechanical properties, seepage performance and failure characteristics of concrete under the coupling action of water pressure and stress, and has strong applicability and wide engineering application prospect.

[0017] The application can simultaneously perform stress loading and water pressure loading in the same direction on the sample by arranging two loading members above the sample and arranging water conveying channels in communication with the sample on the loading members, simulating the real working environment of the concrete under the combined action of load and water pressure, and gradually increasing the porosity of the two loading members to maximize the contact area between the water and the sample surface while ensuring smooth water conveying, thereby ensuring that the sample surface can uniformly bear stress loading and water pressure loading and improving the accuracy of the test. In addition, the sealing connection net can increase the central stress area while ensuring waterproof sealing effect on the periphery, thereby avoiding edge damage caused by stress mainly acting on the periphery. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 It is a schematic diagram of the overall structure of the application; Figure 2 It is a schematic diagram of the installation structure of the loading member, the sample and the water seepage collection groove in the application; Figure 3 It is an exploded view of the loading member, the sample and the water seepage collection groove in the application from the top; Figure 4 It is an exploded view of the loading member, the sample and the water seepage collection groove in the application from the bottom; Figure 5 It is a partial sectional view of the loading member and the sample in the application; Figure 6 It is a bottom view of the upper loading plate, i.e., a schematic diagram of the bottom surface structure of the upper loading plate in the application; Figure 7 It is a top view of the lower loading plate, i.e., a schematic diagram of the top surface structure of the lower loading plate in the application.

[0019] Among them, the reference signs are: 1, sample; 2, upper loading member; 21, upper loading plate; 211, blind hole; 212, connecting port; 22, upper sealing connection net; 3, lower loading member; 31, lower loading plate; 311, through hole; 32, lower sealing connection net; 4, water seepage collection groove; 5, press; 51, upper pressing plate; 52, workbench; 61, water conveying pipeline; 62, water supply pump; 63, water supply tank; 64, pressure gauge; 65, flow meter; 7, acoustic emission probe. DETAILED DESCRIPTION

[0020] In order for those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0021] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0022] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0023] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature.

[0024] For easier understanding, please refer to Figures 1 to 7 This embodiment provides a concrete deterioration and permeability testing device under combined load and water pressure. It includes a square concrete specimen 1 (300mm × 300mm × 300mm), a loading component that fits tightly against the specimen 1, and a pressure applying mechanism. The pressure applying mechanism applies stress to the loading component, thereby applying stress to the specimen 1. The loading component has a water supply channel connected to a water supply assembly, with the other end connected to the surface of the specimen 1. Water pressure is applied to the specimen 1 through the water supply assembly. Specifically, when water pressure is required, water is supplied to the water supply channel of the loading component and ultimately delivered to the surface of the specimen 1 along the water supply channel. The stress loading direction of the pressure applying mechanism on the specimen 1 is the same as the direction of water pressure on the specimen 1. By simultaneously and in the same direction applying stress and water pressure to the specimen 1 through the pressure applying mechanism and the water supply assembly, the cracking and leakage behavior of the concrete specimen 1 under combined load and water pressure is realistically simulated. Preferably, the stress loading direction of the pressure applying mechanism onto the loading member and the direction in which the sample 1 is subjected to water pressure are both vertical. The water delivery channel on the loading member has an L-shaped structure. Specifically, one end of the water delivery channel is connected to the surface of the sample 1 in the vertical direction, and the other end is connected to the water supply component in the horizontal direction.

[0025] Multiple loading components are arranged vertically in pairs, each with a plurality of evenly distributed vertical holes. These holes on different loading components are interconnected to form a water supply channel. The pore density on different loading components gradually increases from top to bottom, with the bottommost loading component having the highest pore density. This maximizes the contact area between the water and the surface of sample 1, ensuring that the surface of sample 1 is uniformly subjected to water pressure and improving the accuracy of the test. The holes on the topmost (outer) loading component are horizontally connected to the water supply assembly, and the pressure applying mechanism applies stress to the topmost loading component. Furthermore, there are two loading components: an upper loading component 2 and a lower loading component 3. The lower loading component 3 is located between the upper loading component 2 and sample 1. The upper loading component 2 includes an upper loading plate 21, on which a plurality of evenly distributed vertical blind holes 211 are formed, with the openings of the blind holes 211 all facing the lower loading component 3. The blind ends of adjacent blind holes 211 are horizontally interconnected. The upper loading plate 21 has a connection port 212 on its side wall, and the blind end of a peripheral blind hole 211 is connected to the water supply component in the horizontal direction through the connection port 212. The lower loading component 3 includes a lower loading plate 31, on which a plurality of vertical through holes 311 are evenly distributed. Adjacent through holes 311 are interconnected on the top surface of the lower loading plate 31 (i.e., the contact surface with the upper loading component 2). The blind hole 211 of the upper loading plate 21 is connected to the through hole 311 of the lower loading plate 31 in the vertical direction.

[0026] The upper loading member 2 also includes an upper sealing connection mesh 22 with a porous structure located between the upper loading plate 21 and the lower loading plate 31. The upper sealing connection mesh 22 ensures the waterproof sealing effect between the upper loading plate 21 and the lower loading plate 31, thereby ensuring that the water supplied to the blind hole 211 of the upper loading plate 21 by the water supply component can flow smoothly downward into the through hole 311 of the lower loading plate 31, preventing leakage from the periphery of the connection between the upper loading plate 21 and the lower loading plate 31. At the same time, the upper sealing connection mesh 22 can increase the contact area between the upper loading member 2 and the middle of the lower loading plate 31 while ensuring waterproof sealing, so that the upper surface of the lower loading plate 31 is evenly stressed, preventing the stress applied by the upper loading member 2 from mainly acting on the periphery of the lower loading plate 31 and causing damage to the edge of the lower loading plate 31. The lower loading member 3 also includes a porous lower sealing connection mesh 32 located between the lower loading plate 31 and the sample 1. The lower sealing connection mesh 32 ensures a waterproof seal between the lower loading plate 31 and the surface of the sample 1, thereby ensuring that water delivered to the through holes 311 of the lower loading plate 31 can flow smoothly downwards to the surface of the sample 1 to apply water pressure, preventing seepage from the periphery of the connection between the lower loading plate 31 and the surface of the sample 1. Simultaneously, the lower sealing connection mesh 32 increases the contact area between the lower loading member 3 and the central surface of the sample 1 while ensuring a waterproof seal, allowing for uniform stress distribution on the surface of the sample 1 and preventing the stress applied by the lower loading member 3 from primarily acting on the periphery of the sample 1 surface, thus preventing edge damage. Furthermore, the hole spacing of the upper sealing connection mesh 22 is the same as the hole spacing of the blind holes 211 of the upper loading plate 21, and the hole spacing of the lower sealing connection mesh 32 is the same as the hole spacing of the through holes 311 of the lower loading plate 31, further ensuring uniform stress distribution and improving the overall stress loading effect. Preferably, the upper loading plate 21 is a 300mm×300mm×60mm square high-strength steel plate, and the lower loading plate 31 is a 300mm×300mm×30mm square high-strength steel plate, which matches the structure of the square concrete sample 1 and can completely cover the entire surface. The upper sealing connection mesh 22 and the lower sealing connection mesh 32 are both made of EPDM material, and the outer dimensions of the upper sealing connection mesh 22 and the lower sealing connection mesh 32 are also 300mm×300mm, which ensures the waterproof sealing effect of the perimeter under pressure.

[0027] The pressure-applying mechanism is a press 5, which includes an upper pressure plate 51 and a worktable 52. The upper pressure plate 51 is used to apply stress to the loading member, and the worktable 52 is used to place and support the sample 1. The worktable 52 is provided with a seepage collection tank 4, in which the sample 1 is placed. Water seeping from the sample 1 during the test is collected through the seepage collection tank 4. Furthermore, the seepage collection tank 4 can be connected to a wastewater tank for drainage through a drainage pipeline. Preferably, the seepage collection tank 4 is made of steel. The water supply assembly includes a water supply pump 62 and a water supply tank 63. The blind end of one of the blind holes 211 on the upper loading plate 21 is connected to the water supply pump 62 and the water supply tank 63 in the horizontal direction through a water supply pipeline 61. The water supply pump 62 pressurizes and delivers the water stored in the water supply tank 63 to the water supply pipeline 61, and the water enters the blind hole 211 of the upper loading plate 21 along the path of the water supply pipeline 61.

[0028] The testing apparatus also includes a data acquisition and monitoring system, which monitors and records test data in real time. Specifically, the data acquisition and monitoring system includes an acoustic emission monitoring system, a high-definition camera, colorimetric test paper, a flow meter 65 and a pressure gauge 64 on the water supply pipeline 61, and displacement and pressure sensors integrated into the press 5. The acoustic emission probe 7 of the acoustic emission monitoring system is installed on the side of the sample 1 to acquire the acoustic emission characteristics and dynamic evolution of the cracks during the load-permeability failure test, and then calculates the energy dissipation characteristics based on the acoustic emission characteristics. The flow meter 65 on the water supply pipeline 61 acquires the seepage volume at each moment, and the permeability coefficient is calculated. The pressure gauge 64 on the water supply pipeline 61 monitors the water pressure value in real time to ensure that the water pressure remains at a preset value during the load-permeability failure test. The colorimetric test paper is attached to the side of the sample 1 to monitor whether there is water seepage on the side of the sample 1 during the load-permeability failure test, ensuring the accuracy of the test results. A high-definition camera was mounted directly in front of specimen 1 to record the failure mode of specimen 1 in real time during the load-penetration failure test, facilitating subsequent observation and research. Displacement and stress data during the entire load-penetration failure test were acquired by the displacement sensor and pressure sensor built into the press 5, respectively, and stress-strain curves were plotted to calculate compressive strength and elastic modulus.

[0029] The testing steps of this invention are as follows: 1. Place a seepage collection tank 4 at the center of the workbench 52 of the press 5 to collect water seeping out from the bottom of the sample 1 and prevent water from contaminating the workbench 52. Apply MC421 transparent special high-flexibility non-permeable coating to the side of the prepared concrete sample 1 to be tested. The coating should be applied at 4-hour intervals and the total thickness should be greater than or equal to 1.2 mm. Then place the coated sample 1 in the seepage collection tank 4.

[0030] 2. Use 703 silicone rubber adhesive to fix the lower sealing connection mesh 32 to the bottom surface of the lower loading plate 31 (i.e. the surface that is in contact with the sample 1). Similarly, use adhesive to fix the lower loading plate 31 with the lower sealing connection mesh 32 to the top surface of the sample 1. After curing for 24 hours, use non-penetrating coating and waterproof tape to reinforce the joints around the lower loading part 3 and the sample 1.

[0031] 3. Use 703 silicone rubber adhesive to fix the upper sealing connection mesh 22 to the bottom surface of the upper loading plate 21 (i.e. the surface that is in contact with the lower loading plate 31). Similarly, use adhesive to fix the upper loading plate 21 with the upper sealing connection mesh 22 to the top surface of the lower loading plate 31. After curing for 24 hours, use non-penetrating coating and waterproof tape to reinforce the joints around the upper loading component 2 and the lower loading plate 31.

[0032] 4. Connect the water supply tank 63, water supply pump 62, pressure machine 5, flow meter 65 and the connection port 212 of the upper loading plate 21 in series through the water supply pipeline 61. Perform a pre-test using colorimetric test paper within 48 hours after the high-flexibility non-permeable coating is applied to check the integrity of the waterproof layer.

[0033] 5. Install the acoustic emission probe 7 on the side of the sample 1 to obtain the dynamic evolution of the cracks during the load-penetration failure process of the sample 1. Attach the colorimetric test paper to the other side of the sample 1 to ensure that there is no water seepage on the side of the sample 1 during the test and to maintain the accuracy of the test results. Set up a high-definition camera on the front of the sample 1 to observe the failure mode of the sample 1.

[0034] 6. Start the data acquisition and monitoring system, and control the upper pressure plate 51 of the press 5 to fall to the top surface of the upper loading plate 21 until the upper pressure plate 51 contacts the top surface of the upper loading plate 21. When the feedback signal shows a slight pressure, stop the upper pressure plate 51. During this process, when the upper pressure plate 51 is at a suitable distance from the upper loading plate 21, start the water supply pump 62 and adjust the loading water pressure to the preset value.

[0035] 7. Clear the monitoring data and control the upper pressure plate 51 of the press 5 to continuously apply pressure to the upper loading plate 21, that is, start the uniaxial compression test. During the test, the water pressure is kept constant by the pressure stabilizing water supply pump 62.

[0036] 8. When the stress-strain curve drops sharply (indicating that sample 1 has already experienced peak failure), stop the test, turn off the press 5 and the water supply pump 62, remove sample 1, and plot the uniaxial compressive stress-strain curve, acoustic emission characteristic curve, and permeability coefficient evolution curve of the rock based on the test. Calculate the uniaxial compressive strength, elastic modulus (tangent modulus, secant modulus), energy dissipation characteristics, permeability coefficient, etc.

[0037] Although the present invention has been described using the above preferred embodiments, it is not intended to limit the scope of protection of the present invention. Any changes and modifications made by those skilled in the art to the above embodiments without departing from the spirit and scope of the present invention shall still fall within the scope of protection of the present invention.

Claims

1. A device for testing the permeability of concrete under combined load and water pressure, characterized in that, It includes a sample (1) and a loading member that fits and abuts against the sample (1). The loading member has a water supply channel. One end of the water supply channel is connected to the water supply component, and the other end is connected to the surface of the sample (1). Water pressure is applied to the sample (1) through the water supply component. It also includes a pressure applying mechanism for applying stress to the loading member. The stress applying direction of the pressure applying mechanism to the loading member is the same as the direction of water pressure on the sample (1). The loading components are multiple and abut against each other in pairs in the stress loading direction. Each loading component has multiple holes evenly opened on it. The holes on different loading components are interconnected to form a water conveying channel. The holes on the loading components located on the outer side are connected to the water supply component. The pore density on different loading components gradually increases along the stress loading direction. The pressure applying mechanism applies stress to the loading components located on the outer side.

2. The concrete deterioration permeability testing device under combined load and water pressure as described in claim 1, characterized in that, The loading element includes an upper loading element (2) and a lower loading element (3), with the lower loading element (3) located between the upper loading element (2) and the sample (1); The upper loading component (2) includes an upper loading plate (21), on which multiple blind holes (211) are evenly opened. Adjacent blind holes (211) are interconnected. The blind holes (211) are connected to the water supply component. The openings of the blind holes (211) face the lower loading component (3). The lower loading component (3) includes a lower loading plate (31), on which a plurality of through holes (311) are evenly provided, and adjacent through holes (311) are interconnected.

3. The concrete deterioration permeability testing device under combined load and water pressure as described in claim 2, characterized in that, The upper loading member (2) also includes an upper sealing connection mesh (22) with a porous structure located between the upper loading plate (21) and the lower loading plate (31).

4. The concrete deterioration and permeability testing device under combined load and water pressure as described in claim 2, characterized in that, The lower loading member (3) also includes a lower sealing connection mesh (32) with a porous structure located between the lower loading plate (31) and the sample (1).

5. The test device for concrete deterioration permeability under combined load and water pressure according to any one of claims 1 to 4, characterized in that, The stress loading direction of the pressure applying mechanism to the loading member and the direction of water pressure borne by the sample (1) are both vertical, and the water supply channel on the loading member is connected to the water supply component in the horizontal direction.

6. The concrete deterioration and permeability testing device under combined load and water pressure as described in claim 5, characterized in that, The pressure-applying mechanism is a press (5), which includes an upper pressure plate (51) for applying stress to the loading member and a worktable (52) for placing and supporting the sample (1).

7. The concrete deterioration permeability testing device under combined load and water pressure as described in claim 1, characterized in that, It also includes a seepage collection tank (4) located at the bottom of the sample (1).

8. The concrete deterioration and permeability testing device under combined load and water pressure as described in claim 1, characterized in that, The water supply assembly includes a water supply pump (62) and a water supply tank (63). The water delivery channel on the loading component is connected to the water supply pump (62) and the water supply tank (63) through a water delivery pipeline (61).

9. The concrete deterioration and permeability testing device under combined load and water pressure as described in claim 1, characterized in that, It also includes a data acquisition and monitoring system for real-time monitoring and recording of test data.

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