Test device and test method for simulating crack propagation of concrete test piece under impact disturbance

Abstract

The invention discloses a test device and a test method for simulating crack propagation of a concrete test piece under impact disturbance. The test device comprises a test main body, a sealing rubber strip, a water pressure applying assembly, an anti-bending moment balancing assembly and a load applying device. The test device and the test method have the following technical advantages: 1, the test device can simulate the water-force balance state of a concrete test piece, is more consistent with the actual engineering, and overcomes the defect that a crack hydraulic fracture test is carried out by only providing mechanical force; 2, the test precision is high, and an opening displacement measuring device and an acoustic emission detector are adopted to monitor the hydraulic fracture characteristics of the crack extending to the crack initiation stage so as to obtain the hydraulic fracture extension process of the concrete test piece under impact disturbance; and 3, the experimental device is simple to operate, accessories are simple and easy to replace, and the experimental device has popularization value in the technical field of hydraulic fracture tests of concrete structure cracks.

Description

Technical Field

[0001] The invention relates to the technical field of concrete structure crack testing, and in particular to a testing device and a testing method for simulating crack expansion of a concrete specimen under impact disturbance. Background Art

[0002] At present, dam construction technology is developing rapidly, and large concrete high dams are being built or put into operation. Due to the weak tensile properties of concrete materials and the large volume characteristics of concrete dams, it is inevitable that the completed concrete dams have microcracks. However, under the action of high-pressure water flow, the existing cracks in the concrete dam body will expand, which will affect the safety and durability of the overall structure. Therefore, it is very necessary to conduct experimental research on the damage, fracture and destruction process of concrete structures under the action of high-pressure water flow. However, the test models used in the existing research methods for concrete structure cracks simplify the test conditions, making the test results conservative. The existing test methods often cannot accurately simulate the complex loads that cracks are subjected to in the actual environment, especially the combined effects of high-pressure water flow and impact loads, so that the test conclusions are quite different from the actual crack expansion of concrete structures. In view of this, the existing problems are studied and improved. The present invention aims to provide a test device and a test method for simulating the crack expansion of concrete specimens under impact disturbance, so as to accurately simulate the actual working conditions, and the operation is simple, and the test cost is effectively reduced, which is of great significance for studying the crack expansion mechanism of concrete structures under impact disturbance. Summary of the invention

[0003] In order to overcome the technical problems described in the prior art, the purpose of the present invention is to provide a test device and a test method for simulating crack expansion of a concrete specimen under impact disturbance.

[0004] In a first aspect, the present invention provides a test device for simulating crack propagation of a concrete specimen under impact disturbance, comprising:

[0005] A test subject includes a concrete specimen, wherein the concrete specimen is provided with prefabricated cracks opening upward;

[0006] A sealing strip, used for covering the prefabricated crack for sealing;

[0007] A water pressure applying assembly, used to make the prefabricated cracks filled with water pressure and open;

[0008] a reverse bending moment balance assembly, used for applying a reverse bending moment to the concrete specimen; and

[0009] A load applying device is arranged above the prefabricated crack.

[0010] As a preferred technical solution, the concrete specimen also includes a connecting conduit, one end of which is connected to the prefabricated crack, and the other end of which extends out of the concrete specimen and is connected to the water pressure applying assembly; wherein the water pressure applying assembly includes a pressure pump for pressurized water supply and a water pressure sensor for obtaining a constant water pressure in the prefabricated crack.

[0011] As a preferred technical solution, the anti-bending moment balance assembly is used to accommodate the concrete specimen, and includes two groups of parallel and oppositely arranged combination rods, the top ends of the two groups of combination rods are threaded downward with a first pressure plate, and the bottom ends of the two groups of combination rods are threaded upward with a second pressure plate, wherein the first pressure plate and the second pressure plate are both provided with an arc surface on one side close to the concrete specimen.

[0012] As a preferred technical solution, the anti-bending moment balance assembly also includes a bending moment sensor arranged on the first connecting rod, so that the test personnel can adjust the height of the first pressure plate to achieve initial bending moment compensation.

[0013] As a preferred technical solution, a supporting seat is provided at the bottom edge of the concrete specimen, and at the same time, an assembly space is provided for two groups of the second pressing plates.

[0014] As a preferred technical solution, the load applying device includes a force applying seat arranged above the prefabricated crack, and the force applying seat is provided with a load measuring device for measuring the external load value.

[0015] As a preferred technical solution, the test device includes an opening displacement measuring device to measure the opening change of the prefabricated crack expansion.

[0016] As a preferred technical solution, the test device further includes an acoustic emission detector to monitor the initiation of the prefabricated cracks.

[0017] In a second aspect, based on the above test device for simulating crack propagation of concrete specimens under impact disturbance, the present invention further provides a test method, comprising the following steps:

[0018] Preparation of concrete specimens: concrete specimens with prefabricated cracks are obtained by formwork casting;

[0019] Test device assembly: Use sealing strips to cover the prefabricated cracks for sealing, place the concrete specimens in the anti-bending moment balance assembly, and connect the concrete specimens to the water pressure application assembly;

[0020] Water pressure loading: Start the water pressure application component to simulate the water pressure effect under actual working conditions;

[0021] Anti-bending moment balance: the first pressing plate or the height of the first pressing plate is adjusted according to the bending moment sensor to achieve initial bending moment compensation, so as to keep the prefabricated crack in a water-force balance state;

[0022] Impact disturbance: start the load application device to apply external load above the prefabricated crack;

[0023] Data recording and analysis: Record parameters such as water pressure, bending moment and displacement when cracks initiate to evaluate the hydraulic fracturing performance of concrete specimen cracks.

[0024] As a preferred technical solution, the surface of the concrete specimen needs to be polished and smoothed to ensure that the sealing strip is in uniform contact with the surface of the concrete specimen; in addition, after the sealing strip covers the prefabricated crack, epoxy resin glue is evenly applied around the sealing strip.

[0025] In summary, the present invention has the following technical effects:

[0026] The test device and test method for simulating crack expansion of concrete specimens under impact disturbance of the present invention include a test body, a sealing strip, a water pressure application component, a reverse moment balance component and a load application device. The test device and test method of the present invention have the following technical advantages: 1. The test device of the present invention can simulate the water-force balance state of the concrete specimen, which is more consistent with the actual project, and overcomes the defect of hydraulic splitting test of cracks by providing mechanical force alone; 2. The test accuracy of the present invention is high. It adopts an opening displacement measurement device and an acoustic emission detector to monitor the hydraulic splitting characteristics of crack expansion to the crack initiation stage, so as to obtain the hydraulic splitting expansion process of the concrete specimen under impact disturbance; 3. The experimental device of the present invention is simple to operate, and its accessories are simple and easy to replace, which has promotion value in the field of hydraulic splitting test technology of concrete structure cracks. Therefore, compared with the existing research methods of concrete structure cracks, the test device and test method for simulating crack expansion of concrete specimens under impact disturbance provided by the present invention have obvious technical advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] 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.

[0028] Figure 1 Schematic diagram of the overall structure of a test device for simulating crack expansion of a concrete specimen under impact disturbance according to an embodiment of the present invention;

[0029] Figure 2It is a schematic diagram of the principle that the prefabricated cracks in the embodiment of the present invention are in a water-force balance state;

[0030] Figure 3 Schematic diagram of bending moment when prefabricated cracks expand in an embodiment of the present invention.

[0031] The meanings of the reference numerals are as follows:

[0032] 1-concrete specimen, 11-support seat, 12-precast crack;

[0033] 2-sealing strip, 21-clamp;

[0034] 31-connecting conduit, 32-water pressure sensor;

[0035] 4-combination rod, 41-first pressing plate, 42-second pressing plate;

[0036] 5-force applying seat, 51-load measuring device;

[0037] 6-opening displacement measuring device, 61-support;

[0038] 7-Acoustic emission detector. DETAILED DESCRIPTION

[0039] The following will be combined with the accompanying drawings in this embodiment to clearly and completely describe the technical solution in this embodiment. The present embodiment described herein is only for illustrative purposes and is not intended to limit the scope of protection of the present invention. Therefore, it should be understood that various modifications and changes can be made to this embodiment without departing from the scope of protection of the present invention.

[0040] In the description of the present invention, unless otherwise clearly specified and limited, the term "and / or" includes any and all combinations of one or more associated listed items. Unless otherwise specified or explained, the terms "connection", "fixed", etc. should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, an integral connection, an electrical connection, or a signal connection; "connection" can be a direct connection or an indirect connection through an intermediate medium. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0041] Further, in the description of the present invention, it should be understood that the directional words described in the present embodiment are described at the angles shown in the accompanying drawings and should not be understood as limiting the present embodiment. It should also be understood that in the context, when it is mentioned that an element or feature is connected to another element (one or more), it can not only be directly connected to the other (one or more) elements, but also indirectly connected to the other (one or more) elements through an intermediate element.

[0042] Before introducing the technical solution of the present invention, it is necessary to explain the background of the invention. Concrete has good durability and strength characteristics and is widely used in various buildings, bridges and road projects. When concrete structures are subjected to external loads, especially the combined action of water pressure and impact loads, cracks are prone to occur. The expansion and extension of cracks will seriously affect the safety and durability of the structure. Therefore, it is very necessary to conduct a comprehensive and systematic detection and evaluation of concrete structure cracks. However, the test models used in the existing research methods for concrete structure cracks simplify the test conditions, making the test results conservative. The existing test methods often cannot accurately simulate the complex loads that cracks are subjected to in the actual environment, especially the combined action of water pressure and impact loads, so that the test conclusions are quite different from the actual expansion of concrete structure cracks.

[0043] First, see Figure 1 and Figure 2 An exemplary embodiment of the present invention first provides a test device for simulating crack expansion of a concrete specimen 1 under impact disturbance, wherein the test device includes a test body, a sealing strip 2, a water pressure applying component, a reverse bending moment balance component, and a load applying device.

[0044] The components of the above experimental device are described below:

[0045] Test subject:

[0046] In some embodiments, see Figures 1 to 3 The test subject includes a concrete specimen 1, and the concrete specimen 1 is provided with a prefabricated crack 12 with an opening facing upward. It should be understood that the prefabricated crack 12 is opened upward in order to facilitate the installation of a load applying device above the concrete specimen to conduct an expansion study. A sealing device will be used to seal the prefabricated crack 12 in the future to simulate the existence of cracks in actual working conditions. Preferably, a supporting seat 11 is provided at the bottom edge of the concrete specimen 1, which not only supports the concrete specimen 1, but also reserves sufficient space at the bottom of the concrete specimen 1 to provide assembly space for the corresponding structure of the load applying device. It should be noted that the prefabricated crack 12 is located in the middle of the concrete specimen 1, so that the test personnel can operate the load applying device to maintain the water-mechanical balance state of the concrete specimen 1 in the future.

[0047] Sealing strip 2:

[0048] In some embodiments, see Figure 1The sealing strip 2 is used to cover the entire prefabricated crack 12 to achieve a sealing effect. It should be understood that the sealing strip 2 is transparent so that the test personnel can observe the crack expansion. Furthermore, the surface of the concrete specimen 1 needs to be polished and smooth to ensure that the sealing strip 2 is in uniform contact with the surface of the concrete specimen 1; further, after the sealing strip 2 covers the prefabricated crack 12, epoxy resin glue is evenly applied around the sealing strip 2 to enhance the sealing of the two sides of the gravity dam. In some embodiments, a clamp 21 is also configured at the edge of the sealing strip to further enhance the stability of the sealing strip 2.

[0049] Water pressure applying components:

[0050] In some embodiments, see Figure 1 The water pressure applying assembly is used to make the prefabricated crack 12 filled with water pressure and opened. Specifically, it should be noted that the concrete specimen 1 also includes a connecting conduit 31, one end of which is connected to the prefabricated crack 12, and the other end extends out of the concrete specimen 1 and is connected to the water pressure applying assembly; wherein the water pressure applying assembly includes a pressure pump for pressurized water supply, that is, applying water pressure to the prefabricated crack 12 to simulate the concrete structure containing water pressure in actual working conditions, and a water pressure sensor 32 for obtaining a constant water pressure in the prefabricated crack 12.

[0051] Anti-bending moment balance components:

[0052] In some embodiments, see Figure 1 and Figure 2 , the anti-bending moment balance assembly is used to apply an anti-bending moment to the concrete specimen 1. Specifically, the anti-bending moment balance assembly is used to accommodate the concrete specimen 1, and includes two sets of parallel and oppositely arranged combination rods 4, the top ends of the two sets of combination rods 4 are threaded downwardly with a first pressing plate 41, and the bottom ends of the two sets of combination rods 4 are threaded upwardly with a second pressing plate 42. It should be noted that the present invention does not specifically limit the specific connection structure of the combination rod 4, such as Figure 1 and Figure 2 A structure of a combined rod 4 is provided, and it is sufficient that the first pressing plate 41 and the second pressing plate 42 can be close to or away from the surface of the concrete specimen 1. It should be understood that the water pressure applying component will bring an initial bending moment M2 to the prefabricated crack 12, that is, the prefabricated crack 12 has a tendency to expand under the action of the water pressure applying component. In order to ensure the initial water-force balance state of the concrete specimen 1, the test personnel can adjust the height position of the first pressing plate 41 or the second pressing plate 42 of the anti-bending moment balance component according to the bending moment sensor, which is equivalent to making the anti-bending moment balance component provide the corresponding stress σ for balancing the water pressure, that is, generating the anti-bending moment M1 that balances the initial bending moment M2, and realizing the initial bending moment compensation; preferably, the first pressing plate 41 and the second pressing plate 42 are both provided with an arc surface on one side close to the concrete specimen 1.

[0053] Load application device:

[0054] In some embodiments, see Figure 1 The load applying device is arranged above the prefabricated crack 12, and includes a force applying seat 5 arranged above the prefabricated crack 12. The force applying seat 5 is provided with a load measuring device 51 for measuring the external load value. The specific method of load application can be to add a counterweight to the load measuring device 51 or to apply pressure by manpower to generate a load P, and cooperate with the supporting seat 11 to form a bending moment M3 to destroy the prefabricated crack in a water-mechanical balance state, and the maximum test load Pun applied is measured by the load measuring device. To improve the accuracy and reliability of the test, please refer to Figure 1 The test device for simulating hydraulic fracturing of cracks in a gravity dam under impact load of the present invention also includes a bracket 61 disposed on the surface of the concrete specimen 1 and close to the bottom of the crack, and the bracket 61 is used to install an opening displacement measuring device 6 for measuring the opening change of the expansion of the prefabricated crack 12. In addition, the test device also includes an acoustic emission detector 7 for monitoring the initiation of the prefabricated crack 12, so that the test personnel can record parameters such as water pressure, bending moment and displacement when the cracks are initiating. During the test, the acoustic emission detector 7 is used to monitor the initiation of the prefabricated crack 12 of the concrete specimen 1 and obtain the initiation load Pini, thereby evaluating the hydraulic fracturing performance of the cracks in the concrete specimen 1.

[0055] In a second aspect, based on the above-mentioned test device for simulating crack extension of a concrete specimen 1 under impact disturbance, the present invention further provides a test method, comprising the following steps:

[0056] Step 1, preparation of concrete specimen 1: formwork casting to obtain a concrete specimen 1 with prefabricated cracks 12;

[0057] Among them, after the concrete specimen 1 is prepared, its surface needs to be polished and smoothed to ensure that the subsequent sealing strip 2 is in uniform contact with the surface of the concrete specimen 1;

[0058] Step 2, assembling the test device: using the sealing strip 2 to cover the prefabricated crack 12 for sealing, placing the concrete specimen 1 into the reverse bending moment balance assembly, and connecting the concrete specimen 1 to the water pressure application assembly;

[0059] After the sealing strip 2 covers the prefabricated crack 12, epoxy resin glue is evenly applied around the sealing strip 2;

[0060] Step 3, water pressure loading: start the water pressure applying component to simulate the water pressure effect under actual working conditions;

[0061] Step 4, counter-bending moment balance: adjusting the first pressing plate 41 or the height of the first pressing plate 41 according to the bending moment sensor to achieve initial bending moment compensation, so as to keep the prefabricated crack 12 in a water-force balance state;

[0062] Step 5, impact disturbance: start the load applying device to apply an external load above the prefabricated crack 12;

[0063] Step 6: Data recording and analysis: Record parameters such as water pressure, bending moment and displacement when cracks are initiated to evaluate the hydraulic fracturing performance of the cracks in concrete specimen 1.

[0064] The present invention realizes the real simulation of hydraulic splitting of cracks in concrete structures, and overcomes the defects of the test model used in the traditional splitting test, which simplifies the test conditions, makes the test results conservative, has a large difference from the actual hydraulic splitting of cracks, and has a simple simulated stress state.

[0065] In summary, the test device and test method for simulating crack extension of concrete specimens under impact disturbance of the present invention have the following technical advantages:

[0066] 1. The test device of the present invention can simulate the hydraulic-mechanical equilibrium state of a concrete specimen, which is more consistent with actual engineering and overcomes the defect of conducting a hydraulic splitting test of cracks by simply providing mechanical force; 2. The test of the present invention has high test accuracy. It adopts an opening displacement measuring device and an acoustic emission detector to monitor the hydraulic splitting characteristics of cracks from the expansion to the crack initiation stage, so as to obtain the hydraulic splitting expansion process of the concrete specimen under impact disturbance; 3. The experimental device of the present invention is simple to operate, and its accessories are simple and easy to replace, which has promotion value in the field of hydraulic splitting test technology of concrete structure cracks.

[0067] 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 test device for simulating crack expansion of concrete specimens under impact disturbance, characterized in that: include: The test subject comprises a concrete specimen, wherein the concrete specimen is provided with prefabricated cracks opening upward; A sealing strip, used for covering the prefabricated crack for sealing; A water pressure applying assembly, used to make the prefabricated cracks filled with water pressure and open; A reverse bending moment balance assembly, used for applying a reverse bending moment to the concrete specimen; as well as, A load applying device is arranged above the prefabricated crack.

2. The test device for simulating crack expansion of concrete specimens under impact disturbance according to claim 1, characterized in that: The concrete specimen also includes a connecting conduit, one end of which is connected to the prefabricated crack, and the other end of which extends out of the concrete specimen and is connected to the water pressure applying assembly; wherein the water pressure applying assembly includes a pressure pump for pressurized water supply and a water pressure sensor for obtaining a constant water pressure in the prefabricated crack.

3. The test device for simulating crack expansion of concrete specimens under impact disturbance according to claim 2, characterized in that: The anti-bending moment balance assembly is used to accommodate the concrete specimen, and includes two groups of parallel and oppositely arranged combination rods, the top ends of the two groups of combination rods are threaded downwardly with first pressing plates, and the bottom ends of the two groups of combination rods are threaded upwardly with second pressing plates, wherein the first pressing plate and the second pressing plate are both provided with an arc surface on one side close to the concrete specimen.

4. The test device for simulating crack expansion of concrete specimens under impact disturbance according to claim 3, characterized in that: The anti-bending moment balancing assembly further includes a bending moment sensor disposed on the first connecting rod, so that a tester can adjust the height of the first pressing plate to achieve initial bending moment compensation.

5. The test device for simulating crack expansion of concrete specimens under impact disturbance according to claim 4, characterized in that: A supporting seat is provided at the bottom edge of the concrete specimen, and at the same time provides assembly space for two groups of the second pressing plates.

6. The test device for simulating crack expansion of concrete specimens under impact disturbance according to claim 5, characterized in that: The load applying device comprises a force applying seat arranged above the prefabricated crack, and a load measuring device for measuring an external load value is arranged on the force applying seat.

7. The test device for simulating crack expansion of concrete specimens under impact disturbance according to claim 6, characterized in that: The test device comprises an opening displacement measuring device to measure the opening change of the prefabricated crack extension.

8. The test device for simulating crack expansion of concrete specimens under impact disturbance according to claim 7, characterized in that: The test device also includes an acoustic emission detector to monitor the occurrence of crack initiation events of the prefabricated cracks.

9. A test method based on the test device for simulating crack expansion of concrete specimens under impact disturbance according to any one of claims 1 to 8, characterized in that: The following steps are involved: Preparation of concrete specimens: concrete specimens with prefabricated cracks are obtained by formwork casting; Test device assembly: Use sealing strips to cover the prefabricated cracks for sealing, place the concrete specimens in the anti-bending moment balance assembly, and connect the concrete specimens to the water pressure application assembly; Water pressure loading: Start the water pressure application component to simulate the water pressure effect under actual working conditions; Anti-bending moment balance: the first pressing plate or the height of the first pressing plate is adjusted according to the bending moment sensor to achieve initial bending moment compensation, so as to keep the prefabricated crack in a water-force balance state; Impact disturbance: start the load application device to apply external load above the prefabricated crack; Data recording and analysis: Record parameters such as water pressure, bending moment and displacement when cracks initiate to evaluate the hydraulic fracturing performance of concrete specimen cracks.

10. The test method according to claim 9, characterized in that: The surface of the concrete specimen needs to be polished and smooth to ensure that the sealing strip is in uniform contact with the surface of the concrete specimen; in addition, after the sealing strip covers the prefabricated crack, epoxy resin glue is evenly applied around the sealing strip.

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